refactor: handle layer plans outside of buffer (CURA-3339)

allocation is handled outside buffer
writing gcode is handled outside buffer
buffer processing is handled separately from adding to the buffer

.gitignore

@@ -7,8 +7,14 @@
 NUL
 *.gcode
 
+## Directories used for other stuff
+Trash/*
+output/*
+callgrind/*
+
 ## Building result.
 build/*
+debug_build/*
 *.pyc
 *.exe
 *.a

CMakeLists.txt

@@ -42,6 +42,16 @@ if(NOT APPLE AND NOT WIN32)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static-libstdc++")
 endif()
 
+option (ENABLE_OPENMP
+    "Use OpenMP for parallel code" ON)
+
+if (ENABLE_OPENMP)
+    FIND_PACKAGE( OpenMP )
+    if( OPENMP_FOUND )
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}" )
+    endif()
+endif()
+
 include_directories(${CMAKE_CURRENT_BINARY_DIR} libs)
 
 add_library(clipper STATIC libs/clipper/clipper.cpp)
@@ -96,6 +106,7 @@ set(engine_SRCS # Except main.cpp.
     src/progress/Progress.cpp
     src/progress/ProgressStageEstimator.cpp
 
+    src/settings/PathConfigStorage.cpp
     src/settings/SettingConfig.cpp
     src/settings/SettingContainer.cpp
     src/settings/SettingRegistry.cpp

src/FffGcodeWriter.cpp

@@ -25,11 +25,11 @@ void FffGcodeWriter::writeGCode(SliceDataStorage& storage, TimeKeeper& time_keep
     // set the initial extruder of this meshgroup
     if (FffProcessor::getInstance()->getMeshgroupNr() == 0)
     { // first meshgroup
-        current_extruder_planned = getStartExtruder(storage);
+        planner_state.current_extruder = getStartExtruder(storage);
     }
     else
     {
-        current_extruder_planned = gcode.getExtruderNr();
+        planner_state.current_extruder = gcode.getExtruderNr();
     }
 
     if (CommandSocket::isInstantiated())
@@ -42,12 +42,9 @@ void FffGcodeWriter::writeGCode(SliceDataStorage& storage, TimeKeeper& time_keep
     setConfigCoasting(storage);
 
     setConfigRetraction(storage);
-    
-    initConfigs(storage);
-    
+
     for (int extruder = 0; extruder < storage.meshgroup->getExtruderCount(); extruder++)
     { //Skirt and brim.
-        storage.skirt_brim_config[extruder].setLayerHeight(getSettingInMicrons("layer_height_0"));
         skirt_brim_is_processed[extruder] = false;
     }
 
@@ -71,17 +68,6 @@ void FffGcodeWriter::writeGCode(SliceDataStorage& storage, TimeKeeper& time_keep
     
     gcode.writeLayerCountComment(total_layers);
 
-    bool has_raft = getSettingAsPlatformAdhesion("adhesion_type") == EPlatformAdhesion::RAFT;
-    if (has_raft)
-    {
-        processRaft(storage, total_layers);
-        // process filler layers to fill the airgap with helper object (support etc) so that they stick better to the raft.
-        for (int layer_nr = -Raft::getFillerLayerCount(storage); layer_nr < 0; layer_nr++)
-        {
-            processLayer(storage, layer_nr, total_layers);
-        }
-    }
-
     { // calculate the mesh order for each extruder
         int extruder_count = storage.meshgroup->getExtruderCount();
         mesh_order_per_extruder.reserve(extruder_count);
@@ -91,9 +77,26 @@ void FffGcodeWriter::writeGCode(SliceDataStorage& storage, TimeKeeper& time_keep
         }
     }
 
-    for(unsigned int layer_nr=0; layer_nr<total_layers; layer_nr++)
+    int process_layer_starting_layer_nr = 0;
+    bool has_raft = getSettingAsPlatformAdhesion("adhesion_type") == EPlatformAdhesion::RAFT;
+    if (has_raft)
     {
-        processLayer(storage, layer_nr, total_layers);
+        processRaft(storage, total_layers);
+        // process filler layers to fill the airgap with helper object (support etc) so that they stick better to the raft.
+        process_layer_starting_layer_nr = -Raft::getFillerLayerCount(storage);
+    }
+
+    for (unsigned int layer_nr = process_layer_starting_layer_nr; layer_nr < total_layers; layer_nr++)
+    {
+        GCodePlanner& gcode_layer = processLayer(storage, layer_nr, total_layers);
+        layer_plan_buffer.push(gcode_layer);
+        planner_state = gcode_layer.getPlanningState();
+        GCodePlanner* to_be_written = layer_plan_buffer.processBuffer();
+        if (to_be_written)
+        {
+            to_be_written->writeGCode(gcode);
+            delete to_be_written;
+        }
     }
     
     Progress::messageProgressStage(Progress::Stage::FINISH, &time_keeper);
@@ -172,39 +175,7 @@ void FffGcodeWriter::setConfigRetraction(SliceDataStorage& storage)
     }
 }
 
-void FffGcodeWriter::initConfigs(SliceDataStorage& storage)
-{
-    for (int extruder = 0; extruder < storage.meshgroup->getExtruderCount(); extruder++)
-    { //Skirt and brim.
-        SettingsBase* train = storage.meshgroup->getExtruderTrain(extruder);
-        storage.skirt_brim_config[extruder].init(train->getSettingInMillimetersPerSecond("skirt_brim_speed"), train->getSettingInMillimetersPerSecond("acceleration_skirt_brim"), train->getSettingInMillimetersPerSecond("jerk_skirt_brim"), train->getSettingInMicrons("skirt_brim_line_width"), train->getSettingInPercentage("material_flow"));
-        storage.travel_config_per_extruder[extruder].init(train->getSettingInMillimetersPerSecond("speed_travel"), train->getSettingInMillimetersPerSecond("acceleration_travel"), train->getSettingInMillimetersPerSecond("jerk_travel"), 0, 0);
-    }
-
-    { // support 
-        SettingsBase* infill_train = storage.meshgroup->getExtruderTrain(getSettingAsIndex("support_infill_extruder_nr"));
-        storage.support_config.init(infill_train->getSettingInMillimetersPerSecond("speed_support_infill"), infill_train->getSettingInMillimetersPerSecond("acceleration_support_infill"), infill_train->getSettingInMillimetersPerSecond("jerk_support_infill"), infill_train->getSettingInMicrons("support_line_width"), infill_train->getSettingInPercentage("material_flow"));
-    
-        SettingsBase* interface_train = storage.meshgroup->getExtruderTrain(getSettingAsIndex("support_interface_extruder_nr"));
-        storage.support_skin_config.init(interface_train->getSettingInMillimetersPerSecond("speed_support_interface"), interface_train->getSettingInMillimetersPerSecond("acceleration_support_interface"), interface_train->getSettingInMillimetersPerSecond("jerk_support_interface"), interface_train->getSettingInMicrons("support_interface_line_width"), interface_train->getSettingInPercentage("material_flow"));
-    }
-    
-    for (SliceMeshStorage& mesh : storage.meshes)
-    {
-        mesh.inset0_config.init(mesh.getSettingInMillimetersPerSecond("speed_wall_0"), mesh.getSettingInMillimetersPerSecond("acceleration_wall_0"), mesh.getSettingInMillimetersPerSecond("jerk_wall_0"), mesh.getSettingInMicrons("wall_line_width_0"), mesh.getSettingInPercentage("material_flow"));
-        mesh.insetX_config.init(mesh.getSettingInMillimetersPerSecond("speed_wall_x"), mesh.getSettingInMillimetersPerSecond("acceleration_wall_x"), mesh.getSettingInMillimetersPerSecond("jerk_wall_x"), mesh.getSettingInMicrons("wall_line_width_x"), mesh.getSettingInPercentage("material_flow"));
-        mesh.skin_config.init(mesh.getSettingInMillimetersPerSecond("speed_topbottom"), mesh.getSettingInMillimetersPerSecond("acceleration_topbottom"), mesh.getSettingInMillimetersPerSecond("jerk_topbottom"), mesh.getSettingInMicrons("skin_line_width"), mesh.getSettingInPercentage("material_flow"));
-    
-        for (unsigned int idx = 0; idx < MAX_INFILL_COMBINE; idx++)
-        {
-            mesh.infill_config[idx].init(mesh.getSettingInMillimetersPerSecond("speed_infill"), mesh.getSettingInMillimetersPerSecond("acceleration_infill"), mesh.getSettingInMillimetersPerSecond("jerk_infill"), mesh.getSettingInMicrons("infill_line_width") * (idx + 1), mesh.getSettingInPercentage("material_flow"));
-        }
-    }
-    
-    storage.primeTower.initConfigs(storage.meshgroup);
-}
-
-unsigned int FffGcodeWriter::getStartExtruder(SliceDataStorage& storage)
+unsigned int FffGcodeWriter::getStartExtruder(const SliceDataStorage& storage)
 {
     int start_extruder_nr = getSettingAsIndex("adhesion_extruder_nr");
     if (getSettingAsPlatformAdhesion("adhesion_type") == EPlatformAdhesion::NONE)
@@ -223,7 +194,7 @@ unsigned int FffGcodeWriter::getStartExtruder(SliceDataStorage& storage)
     return start_extruder_nr;
 }
 
-void FffGcodeWriter::processStartingCode(SliceDataStorage& storage, const unsigned int start_extruder_nr)
+void FffGcodeWriter::processStartingCode(const SliceDataStorage& storage, const unsigned int start_extruder_nr)
 {
     if (!CommandSocket::isInstantiated())
     {
@@ -286,12 +257,12 @@ void FffGcodeWriter::processStartingCode(SliceDataStorage& storage, const unsign
         gcode.writeTemperatureCommand(start_extruder_nr, print_temp_here, wait);
         gcode.writePrimeTrain(train.getSettingInMillimetersPerSecond("speed_travel"));
         extruder_prime_is_planned[start_extruder_nr] = true;
-        RetractionConfig& retraction_config = storage.retraction_config_per_extruder[start_extruder_nr];
+        const RetractionConfig& retraction_config = storage.retraction_config_per_extruder[start_extruder_nr];
         gcode.writeRetraction(retraction_config);
     }
 }
 
-void FffGcodeWriter::processNextMeshGroupCode(SliceDataStorage& storage)
+void FffGcodeWriter::processNextMeshGroupCode(const SliceDataStorage& storage)
 {
     gcode.writeFanCommand(0);
 
@@ -303,11 +274,11 @@ void FffGcodeWriter::processNextMeshGroupCode(SliceDataStorage& storage)
 
     gcode.setZ(max_object_height + 5000);
     gcode.writeMove(gcode.getPositionXY(), storage.meshgroup->getExtruderTrain(gcode.getExtruderNr())->getSettingInMillimetersPerSecond("speed_travel"), 0);
-    last_position_planned = Point(storage.model_min.x, storage.model_min.y);
-    gcode.writeMove(last_position_planned, storage.meshgroup->getExtruderTrain(gcode.getExtruderNr())->getSettingInMillimetersPerSecond("speed_travel"), 0);
+    planner_state.last_position = Point(storage.model_min.x, storage.model_min.y);
+    gcode.writeMove(planner_state.last_position, storage.meshgroup->getExtruderTrain(gcode.getExtruderNr())->getSettingInMillimetersPerSecond("speed_travel"), 0);
 }
     
-void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_layers)
+void FffGcodeWriter::processRaft(const SliceDataStorage& storage, unsigned int total_layers)
 {
     int extruder_nr = getSettingAsIndex("adhesion_extruder_nr");
     ExtruderTrain* train = storage.meshgroup->getExtruderTrain(extruder_nr);
@@ -316,16 +287,7 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
 
     int z = 0;
     
-    { // set configs 
-        storage.raft_base_config.init(train->getSettingInMillimetersPerSecond("raft_base_speed"), train->getSettingInMillimetersPerSecond("raft_base_acceleration"), train->getSettingInMillimetersPerSecond("raft_base_jerk"), train->getSettingInMicrons("raft_base_line_width"), train->getSettingInPercentage("material_flow"));
-        storage.raft_base_config.setLayerHeight(train->getSettingInMicrons("raft_base_thickness"));
-        
-        storage.raft_interface_config.init(train->getSettingInMillimetersPerSecond("raft_interface_speed"), train->getSettingInMillimetersPerSecond("raft_interface_acceleration"), train->getSettingInMillimetersPerSecond("raft_interface_jerk"), train->getSettingInMicrons("raft_interface_line_width"), train->getSettingInPercentage("material_flow"));
-        storage.raft_interface_config.setLayerHeight(train->getSettingInMicrons("raft_interface_thickness"));
 
-        storage.raft_surface_config.init(train->getSettingInMillimetersPerSecond("raft_surface_speed"), train->getSettingInMillimetersPerSecond("raft_surface_acceleration"), train->getSettingInMillimetersPerSecond("raft_surface_jerk"), train->getSettingInMicrons("raft_surface_line_width"), train->getSettingInPercentage("material_flow"));
-        storage.raft_surface_config.setLayerHeight(train->getSettingInMicrons("raft_surface_thickness"));
-    }
 
     const int initial_raft_layer_nr = -Raft::getTotalExtraLayers(storage);
 
@@ -341,7 +303,7 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
         int layer_height = train->getSettingInMicrons("raft_base_thickness");
         z += layer_height;
         int64_t comb_offset = train->getSettingInMicrons("raft_base_line_spacing");
-        GCodePlanner& gcode_layer = layer_plan_buffer.emplace_back(storage, layer_nr, z, layer_height, last_position_planned, current_extruder_planned, is_inside_mesh_layer_part, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
+        GCodePlanner& gcode_layer = *new GCodePlanner(storage, layer_nr, z, layer_height, planner_state, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
         gcode_layer.setIsInside(true);
 
         gcode_layer.setExtruder(extruder_nr);
@@ -351,26 +313,31 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
             CommandSocket::getInstance()->sendOptimizedLayerInfo(layer_nr, z, layer_height);
         }
 
-        Polygons wall = storage.raftOutline.offset(-storage.raft_base_config.getLineWidth() / 2);
-        gcode_layer.addPolygonsByOptimizer(wall, &storage.raft_base_config);
+        Polygons wall = storage.raftOutline.offset(-gcode_layer.configs_storage.raft_base_config.getLineWidth() / 2);
+        gcode_layer.addPolygonsByOptimizer(wall, &gcode_layer.configs_storage.raft_base_config);
 
         Polygons raftLines;
         double fill_angle = 0;
-        Infill infill_comp(EFillMethod::LINES, wall, offset_from_poly_outline, storage.raft_base_config.getLineWidth(), train->getSettingInMicrons("raft_base_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
+        Infill infill_comp(EFillMethod::LINES, wall, offset_from_poly_outline, gcode_layer.configs_storage.raft_base_config.getLineWidth(), train->getSettingInMicrons("raft_base_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
         infill_comp.generate(raft_polygons, raftLines);
-        gcode_layer.addLinesByOptimizer(raftLines, &storage.raft_base_config, SpaceFillType::Lines);
+        gcode_layer.addLinesByOptimizer(raftLines, &gcode_layer.configs_storage.raft_base_config, SpaceFillType::Lines);
 
         if (getExtrudersNeedPrimeDuringFirstLayer())
         {
             ensureAllExtrudersArePrimed(storage, gcode_layer, layer_nr);
         }
 
-        last_position_planned = gcode_layer.getLastPosition();
-        current_extruder_planned = gcode_layer.getExtruder();
-        is_inside_mesh_layer_part = gcode_layer.getIsInsideMesh();
-
         gcode_layer.processFanSpeedAndMinimalLayerTime();
         gcode_layer.overrideFanSpeeds(train->getSettingInPercentage("raft_base_fan_speed"));
+
+        layer_plan_buffer.push(gcode_layer);
+        planner_state = gcode_layer.getPlanningState();
+        GCodePlanner* to_be_written = layer_plan_buffer.processBuffer();
+        if (to_be_written)
+        {
+            to_be_written->writeGCode(gcode);
+            delete to_be_written;
+        }
     }
 
     { // raft interface layer
@@ -378,7 +345,7 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
         int layer_height = train->getSettingInMicrons("raft_interface_thickness");
         z += layer_height;
         int64_t comb_offset = train->getSettingInMicrons("raft_interface_line_spacing");
-        GCodePlanner& gcode_layer = layer_plan_buffer.emplace_back(storage, layer_nr, z, layer_height, last_position_planned, current_extruder_planned, is_inside_mesh_layer_part, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
+        GCodePlanner& gcode_layer = *new GCodePlanner(storage, layer_nr, z, layer_height, planner_state, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
         gcode_layer.setIsInside(true);
 
         gcode_layer.setExtruder(extruder_nr); // reset to extruder number, because we might have primed in the last layer
@@ -391,16 +358,21 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
         Polygons raftLines;
         int offset_from_poly_outline = 0;
         double fill_angle = train->getSettingAsCount("raft_surface_layers") > 0 ? 45 : 90;
-        Infill infill_comp(EFillMethod::ZIG_ZAG, storage.raftOutline, offset_from_poly_outline, storage.raft_interface_config.getLineWidth(), train->getSettingInMicrons("raft_interface_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
+        Infill infill_comp(EFillMethod::ZIG_ZAG, storage.raftOutline, offset_from_poly_outline, gcode_layer.configs_storage.raft_interface_config.getLineWidth(), train->getSettingInMicrons("raft_interface_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
         infill_comp.generate(raft_polygons, raftLines);
-        gcode_layer.addLinesByOptimizer(raftLines, &storage.raft_interface_config, SpaceFillType::Lines);
-        
-        last_position_planned = gcode_layer.getLastPosition();
-        current_extruder_planned = gcode_layer.getExtruder();
-        is_inside_mesh_layer_part = gcode_layer.getIsInsideMesh();
+        gcode_layer.addLinesByOptimizer(raftLines, &gcode_layer.configs_storage.raft_interface_config, SpaceFillType::Lines);
 
         gcode_layer.processFanSpeedAndMinimalLayerTime();
         gcode_layer.overrideFanSpeeds(train->getSettingInPercentage("raft_interface_fan_speed"));
+
+        layer_plan_buffer.push(gcode_layer);
+        planner_state = gcode_layer.getPlanningState();
+        GCodePlanner* to_be_written = layer_plan_buffer.processBuffer();
+        if (to_be_written)
+        {
+            to_be_written->writeGCode(gcode);
+            delete to_be_written;
+        }
     }
     
     int layer_height = train->getSettingInMicrons("raft_surface_thickness");
@@ -410,7 +382,7 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
         const int layer_nr = initial_raft_layer_nr + 2 + raftSurfaceLayer - 1; // 2: 1 base layer, 1 interface layer
         z += layer_height;
         const int64_t comb_offset = train->getSettingInMicrons("raft_surface_line_spacing");
-        GCodePlanner& gcode_layer = layer_plan_buffer.emplace_back(storage, layer_nr, z, layer_height, last_position_planned, current_extruder_planned, is_inside_mesh_layer_part, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
+        GCodePlanner& gcode_layer = *new GCodePlanner(storage, layer_nr, z, layer_height, planner_state, fan_speed_layer_time_settings_per_extruder, combing_mode, comb_offset, train->getSettingBoolean("travel_avoid_other_parts"), train->getSettingInMicrons("travel_avoid_distance"));
         gcode_layer.setIsInside(true);
 
         if (CommandSocket::isInstantiated())
@@ -421,20 +393,25 @@ void FffGcodeWriter::processRaft(SliceDataStorage& storage, unsigned int total_l
         Polygons raft_lines;
         int offset_from_poly_outline = 0;
         double fill_angle = 90 * raftSurfaceLayer;
-        Infill infill_comp(EFillMethod::ZIG_ZAG, storage.raftOutline, offset_from_poly_outline, storage.raft_surface_config.getLineWidth(), train->getSettingInMicrons("raft_surface_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
+        Infill infill_comp(EFillMethod::ZIG_ZAG, storage.raftOutline, offset_from_poly_outline, gcode_layer.configs_storage.raft_surface_config.getLineWidth(), train->getSettingInMicrons("raft_surface_line_spacing"), fill_overlap, fill_angle, z, extra_infill_shift);
         infill_comp.generate(raft_polygons, raft_lines);
-        gcode_layer.addLinesByOptimizer(raft_lines, &storage.raft_surface_config, SpaceFillType::Lines);
+        gcode_layer.addLinesByOptimizer(raft_lines, &gcode_layer.configs_storage.raft_surface_config, SpaceFillType::Lines);
 
-        last_position_planned = gcode_layer.getLastPosition();
-        current_extruder_planned = gcode_layer.getExtruder();
-        is_inside_mesh_layer_part = gcode_layer.getIsInsideMesh();
-        
         gcode_layer.processFanSpeedAndMinimalLayerTime();
         gcode_layer.overrideFanSpeeds(train->getSettingInPercentage("raft_surface_fan_speed"));
+
+        layer_plan_buffer.push(gcode_layer);
+        planner_state = gcode_layer.getPlanningState();
+        GCodePlanner* to_be_written = layer_plan_buffer.processBuffer();
+        if (to_be_written)
+        {
+            to_be_written->writeGCode(gcode);
+            delete to_be_written;
+        }
     }
 }
 
-void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsigned int total_layers)
+GCodePlanner& FffGcodeWriter::processLayer(const SliceDataStorage& storage, int layer_nr, unsigned int total_layers) const
 {
     Progress::messageProgress(Progress::Stage::EXPORT, std::max(0, layer_nr) + 1, total_layers);
     logDebug("GcodeWriter processing layer %i of %i\n", layer_nr, total_layers);
@@ -486,15 +463,14 @@ void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsig
     }
 
     coord_t max_inner_wall_width = 0;
-    for (SettingsBaseVirtual& mesh_settings : storage.meshes)
+    for (const SettingsBaseVirtual& mesh_settings : storage.meshes)
     {
         max_inner_wall_width = std::max(max_inner_wall_width, mesh_settings.getSettingInMicrons((mesh_settings.getSettingAsCount("wall_line_count") > 1) ? "wall_line_width_x" : "wall_line_width_0")); 
     }
     int64_t comb_offset_from_outlines = max_inner_wall_width * 2;
 
 
-
-    GCodePlanner& gcode_layer = layer_plan_buffer.emplace_back(storage, layer_nr, z, layer_thickness, last_position_planned, current_extruder_planned, is_inside_mesh_layer_part, fan_speed_layer_time_settings_per_extruder, getSettingAsCombingMode("retraction_combing"), comb_offset_from_outlines, avoid_other_parts, avoid_distance);
+    GCodePlanner& gcode_layer = *new GCodePlanner(storage, layer_nr, z, layer_thickness, planner_state, fan_speed_layer_time_settings_per_extruder, getSettingAsCombingMode("retraction_combing"), comb_offset_from_outlines, avoid_other_parts, avoid_distance);
 
     if (include_helper_parts && layer_nr == 0)
     { // process the skirt or the brim of the starting extruder.
@@ -525,10 +501,10 @@ void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsig
 
         if (layer_nr >= 0)
         {
-            std::vector<unsigned int>& mesh_order = mesh_order_per_extruder[extruder_nr];
+            const std::vector<unsigned int>& mesh_order = mesh_order_per_extruder[extruder_nr];
             unsigned int mesh_order_idx_starting_mesh = 0;
             { // calculate mesh_order_idx_starting_mesh
-                Point layer_start_position = last_position_planned;
+                Point layer_start_position = planner_state.last_position;
                 if (storage.getSettingBoolean("start_layers_at_same_position"))
                 {
                     layer_start_position = Point(storage.getSettingInMicrons("layer_start_x"), storage.getSettingInMicrons("layer_start_y"));
@@ -536,12 +512,12 @@ void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsig
                 coord_t best_dist2 = std::numeric_limits<coord_t>::max();
                 for (unsigned int mesh_order_idx = 0; mesh_order_idx < mesh_order.size(); mesh_order_idx++)
                 {
-                    unsigned int mesh_idx = mesh_order[mesh_order_idx];
-                    SliceMeshStorage& mesh = storage.meshes[mesh_idx];
-                    for (SliceLayerPart& part : mesh.layers[layer_nr].parts)
+                    const unsigned int mesh_idx = mesh_order[mesh_order_idx];
+                    const SliceMeshStorage& mesh = storage.meshes[mesh_idx];
+                    for (const SliceLayerPart& part : mesh.layers[layer_nr].parts)
                     {
-                        Point middle = (part.boundaryBox.min + part.boundaryBox.max) / 2;
-                        coord_t dist2 = vSize2(middle - layer_start_position);
+                        const Point middle = (part.boundaryBox.min + part.boundaryBox.max) / 2;
+                        const coord_t dist2 = vSize2(middle - layer_start_position);
                         if (dist2 < best_dist2)
                         {
                             best_dist2 = dist2;
@@ -555,14 +531,15 @@ void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsig
             {
                 unsigned int mesh_order_idx = (mesh_iterator_idx + mesh_order_idx_starting_mesh) % mesh_order.size();
                 unsigned int mesh_idx = mesh_order[mesh_order_idx];
-                SliceMeshStorage* mesh = &storage.meshes[mesh_idx];
+                const SliceMeshStorage* mesh = &storage.meshes[mesh_idx];
+                const PathConfigStorage::MeshPathConfigs& mesh_config = gcode_layer.configs_storage.mesh_configs[mesh_idx];
                 if (mesh->getSettingAsSurfaceMode("magic_mesh_surface_mode") == ESurfaceMode::SURFACE)
                 {
-                    addMeshLayerToGCode_meshSurfaceMode(storage, mesh, gcode_layer, layer_nr);
+                    addMeshLayerToGCode_meshSurfaceMode(storage, mesh, mesh_config, gcode_layer, layer_nr);
                 }
                 else
                 {
-                    addMeshLayerToGCode(storage, mesh, gcode_layer, layer_nr);
+                    addMeshLayerToGCode(storage, mesh, mesh_config, gcode_layer, layer_nr);
                 }
             }
         }
@@ -579,15 +556,13 @@ void FffGcodeWriter::processLayer(SliceDataStorage& storage, int layer_nr, unsig
         int prev_extruder = gcode_layer.getExtruder(); // most likely the same extruder as we are extruding with now
         addPrimeTower(storage, gcode_layer, layer_nr, prev_extruder);
     }
-    
-    last_position_planned = gcode_layer.getLastPosition();
-    current_extruder_planned = gcode_layer.getExtruder();
-    is_inside_mesh_layer_part = gcode_layer.getIsInsideMesh();
-    
+
     gcode_layer.processFanSpeedAndMinimalLayerTime();
+
+    return gcode_layer;
 }
 
-bool FffGcodeWriter::getExtrudersNeedPrimeDuringFirstLayer()
+bool FffGcodeWriter::getExtrudersNeedPrimeDuringFirstLayer() const
 {
     switch(gcode.getFlavor())
     {
@@ -598,7 +573,7 @@ bool FffGcodeWriter::getExtrudersNeedPrimeDuringFirstLayer()
     }
 }
 
-void FffGcodeWriter::ensureAllExtrudersArePrimed(SliceDataStorage& storage, GCodePlanner& gcode_layer, const int layer_nr)
+void FffGcodeWriter::ensureAllExtrudersArePrimed(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const int layer_nr) const
 {
     // Add prime for all extruders which haven't primed yet.
 
@@ -612,23 +587,23 @@ void FffGcodeWriter::ensureAllExtrudersArePrimed(SliceDataStorage& storage, GCod
     }
 }
 
-void FffGcodeWriter::processSkirtBrim(SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int extruder_nr)
+void FffGcodeWriter::processSkirtBrim(const SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int extruder_nr) const
 {
     if (skirt_brim_is_processed[extruder_nr])
     {
         return;
     }
-    Polygons& skirt_brim = storage.skirt_brim[extruder_nr];
-    skirt_brim_is_processed[extruder_nr] = true;
+    const Polygons& skirt_brim = storage.skirt_brim[extruder_nr];
+    const_cast<bool&>(skirt_brim_is_processed[extruder_nr]) = true; // TODO: resolve const cast!
     if (skirt_brim.size() == 0)
     {
         return;
     }
     gcode_layer.addTravel(skirt_brim.back().closestPointTo(gcode_layer.getLastPosition()));
-    gcode_layer.addPolygonsByOptimizer(skirt_brim, &storage.skirt_brim_config[extruder_nr]);
+    gcode_layer.addPolygonsByOptimizer(skirt_brim, &gcode_layer.configs_storage.skirt_brim_config[extruder_nr]);
 }
 
-void FffGcodeWriter::processOozeShield(SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int layer_nr)
+void FffGcodeWriter::processOozeShield(const SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int layer_nr) const
 {
     if (layer_nr == 0 && storage.getSettingAsPlatformAdhesion("adhesion_type") == EPlatformAdhesion::BRIM)
     {
@@ -636,11 +611,11 @@ void FffGcodeWriter::processOozeShield(SliceDataStorage& storage, GCodePlanner&
     }
     if (storage.oozeShield.size() > 0 && layer_nr < storage.oozeShield.size())
     {
-        gcode_layer.addPolygonsByOptimizer(storage.oozeShield[layer_nr], &storage.skirt_brim_config[0]); //TODO: Skirt and brim configuration index should correspond to draft shield extruder number.
+        gcode_layer.addPolygonsByOptimizer(storage.oozeShield[layer_nr], &gcode_layer.configs_storage.skirt_brim_config[0]); //TODO: Skirt and brim configuration index should correspond to draft shield extruder number.
     }
 }
 
-void FffGcodeWriter::processDraftShield(SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int layer_nr)
+void FffGcodeWriter::processDraftShield(const SliceDataStorage& storage, GCodePlanner& gcode_layer, unsigned int layer_nr) const
 {
     if (storage.draft_protection_shield.size() == 0)
     {
@@ -667,10 +642,10 @@ void FffGcodeWriter::processDraftShield(SliceDataStorage& storage, GCodePlanner&
         }
     }
 
-    gcode_layer.addPolygonsByOptimizer(storage.draft_protection_shield, &storage.skirt_brim_config[0]); //TODO: Skirt and brim configuration index should correspond to draft shield extruder number.
+    gcode_layer.addPolygonsByOptimizer(storage.draft_protection_shield, &gcode_layer.configs_storage.skirt_brim_config[0]); //TODO: Skirt and brim configuration index should correspond to draft shield extruder number.
 }
 
-std::vector<int> FffGcodeWriter::calculateExtruderOrder(SliceDataStorage& storage, int current_extruder)
+std::vector<int> FffGcodeWriter::calculateExtruderOrder(const SliceDataStorage& storage, int current_extruder) const
 {
     int extruder_count = storage.getSettingAsCount("machine_extruder_count");
     std::vector<int> ret;
@@ -687,17 +662,17 @@ std::vector<int> FffGcodeWriter::calculateExtruderOrder(SliceDataStorage& storag
     return ret;
 }
 
-std::vector<unsigned int> FffGcodeWriter::calculateMeshOrder(SliceDataStorage& storage, int extruder_nr)
+std::vector<unsigned int> FffGcodeWriter::calculateMeshOrder(const SliceDataStorage& storage, int extruder_nr) const
 {
     OrderOptimizer<unsigned int> mesh_idx_order_optimizer;
 
     for (unsigned int mesh_idx = 0; mesh_idx < storage.meshes.size(); mesh_idx++)
     {
-        SliceMeshStorage& mesh = storage.meshes[mesh_idx];
+        const SliceMeshStorage& mesh = storage.meshes[mesh_idx];
         if (mesh.getSettingAsIndex("extruder_nr") == extruder_nr)
         {
-            Mesh& mesh_data = storage.meshgroup->meshes[mesh_idx];
-            Point3 middle = (mesh_data.getAABB().min + mesh_data.getAABB().max) / 2;
+            const Mesh& mesh_data = storage.meshgroup->meshes[mesh_idx];
+            const Point3 middle = (mesh_data.getAABB().min + mesh_data.getAABB().max) / 2;
             mesh_idx_order_optimizer.addItem(Point(middle.x, middle.y), mesh_idx);
         }
     }
@@ -712,7 +687,7 @@ std::vector<unsigned int> FffGcodeWriter::calculateMeshOrder(SliceDataStorage& s
     return ret;
 }
 
-void FffGcodeWriter::addMeshLayerToGCode_meshSurfaceMode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcode_layer, int layer_nr)
+void FffGcodeWriter::addMeshLayerToGCode_meshSurfaceMode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcode_layer, int layer_nr) const
 {
     if (layer_nr > mesh->layer_nr_max_filled_layer)
     {
@@ -728,7 +703,7 @@ void FffGcodeWriter::addMeshLayerToGCode_meshSurfaceMode(SliceDataStorage& stora
 
     setExtruder_addPrime(storage, gcode_layer, layer_nr, mesh->getSettingAsIndex("extruder_nr"));
 
-    SliceLayer* layer = &mesh->layers[layer_nr];
+    const SliceLayer* layer = &mesh->layers[layer_nr];
 
 
     Polygons polygons;
@@ -739,17 +714,17 @@ void FffGcodeWriter::addMeshLayerToGCode_meshSurfaceMode(SliceDataStorage& stora
 
     EZSeamType z_seam_type = mesh->getSettingAsZSeamType("z_seam_type");
     Point z_seam_pos(mesh->getSettingInMicrons("z_seam_x"), mesh->getSettingInMicrons("z_seam_y"));
-    gcode_layer.addPolygonsByOptimizer(polygons, &mesh->inset0_config, nullptr, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), mesh->getSettingBoolean("magic_spiralize"));
+    gcode_layer.addPolygonsByOptimizer(polygons, &mesh_config.inset0_config, nullptr, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), mesh->getSettingBoolean("magic_spiralize"));
 
-    addMeshOpenPolyLinesToGCode(storage, mesh, gcode_layer, layer_nr);
+    addMeshOpenPolyLinesToGCode(storage, mesh, mesh_config, gcode_layer, layer_nr);
 }
 
-void FffGcodeWriter::addMeshOpenPolyLinesToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcode_layer, int layer_nr)
+void FffGcodeWriter::addMeshOpenPolyLinesToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcode_layer, int layer_nr) const
 {
-    SliceLayer* layer = &mesh->layers[layer_nr];
+    const SliceLayer* layer = &mesh->layers[layer_nr];
     
     Polygons lines;
-    for(PolygonRef polyline : layer->openPolyLines)
+    for(ConstPolygonRef polyline : layer->openPolyLines)
     {
         for(unsigned int point_idx = 1; point_idx<polyline.size(); point_idx++)
         {
@@ -759,11 +734,11 @@ void FffGcodeWriter::addMeshOpenPolyLinesToGCode(SliceDataStorage& storage, Slic
             lines.add(p);
         }
     }
-    gcode_layer.addLinesByOptimizer(lines, &mesh->inset0_config, SpaceFillType::PolyLines);
+    gcode_layer.addLinesByOptimizer(lines, &mesh_config.inset0_config, SpaceFillType::PolyLines);
     
 }
 
-void FffGcodeWriter::addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcode_layer, int layer_nr)
+void FffGcodeWriter::addMeshLayerToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcode_layer, int layer_nr) const
 {
     if (layer_nr > mesh->layer_nr_max_filled_layer)
     {
@@ -777,7 +752,7 @@ void FffGcodeWriter::addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshSto
         return;
     }
 
-    SliceLayer* layer = &mesh->layers[layer_nr];
+    const SliceLayer* layer = &mesh->layers[layer_nr];
 
     if (layer->parts.size() == 0)
     {
@@ -787,7 +762,7 @@ void FffGcodeWriter::addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshSto
     if (mesh->getSettingAsCount("wall_line_count") > 0)
     { // don't switch extruder if there's nothing to print
         bool empty = true;
-        for (SliceLayerPart& part : layer->parts)
+        for (const SliceLayerPart& part : layer->parts)
         {
             if (part.insets.size() > 0)
             {
@@ -805,7 +780,7 @@ void FffGcodeWriter::addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshSto
 
     EZSeamType z_seam_type = mesh->getSettingAsZSeamType("z_seam_type");
     Point z_seam_pos(mesh->getSettingInMicrons("z_seam_x"), mesh->getSettingInMicrons("z_seam_y"));
-    Point layer_start_position = last_position_planned;
+    Point layer_start_position = planner_state.last_position;
     if (storage.getSettingBoolean("start_layers_at_same_position"))
     {
         layer_start_position = Point(storage.getSettingInMicrons("layer_start_x"), storage.getSettingInMicrons("layer_start_y"));
@@ -819,16 +794,16 @@ void FffGcodeWriter::addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshSto
 
     for (int part_idx : part_order_optimizer.polyOrder)
     {
-        SliceLayerPart& part = layer->parts[part_idx];
-        addMeshPartToGCode(storage, mesh, part, gcode_layer, layer_nr);
+        const SliceLayerPart& part = layer->parts[part_idx];
+        addMeshPartToGCode(storage, mesh, mesh_config, part, gcode_layer, layer_nr);
     }
     if (mesh->getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL)
     {
-        addMeshOpenPolyLinesToGCode(storage, mesh, gcode_layer, layer_nr);
+        addMeshOpenPolyLinesToGCode(storage, mesh, mesh_config, gcode_layer, layer_nr);
     }
 }
 
-void FffGcodeWriter::addMeshPartToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, SliceLayerPart& part, GCodePlanner& gcode_layer, int layer_nr)
+void FffGcodeWriter::addMeshPartToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, GCodePlanner& gcode_layer, int layer_nr) const
 {
     bool skin_alternate_rotation = mesh->getSettingBoolean("skin_alternate_rotation") && ( mesh->getSettingAsCount("top_layers") >= 4 || mesh->getSettingAsCount("bottom_layers") >= 4 );
 
@@ -850,21 +825,23 @@ void FffGcodeWriter::addMeshPartToGCode(SliceDataStorage& storage, SliceMeshStor
     
     if (mesh->getSettingBoolean("infill_before_walls"))
     {
-        processMultiLayerInfill(gcode_layer, mesh, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
-        processSingleLayerInfill(gcode_layer, mesh, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
+        processMultiLayerInfill(gcode_layer, mesh, mesh_config, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
+        processSingleLayerInfill(gcode_layer, mesh, mesh_config, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
     }
 
     EZSeamType z_seam_type = mesh->getSettingAsZSeamType("z_seam_type");
     Point z_seam_pos(mesh->getSettingInMicrons("z_seam_x"), mesh->getSettingInMicrons("z_seam_y"));
-    processInsets(gcode_layer, mesh, part, layer_nr, z_seam_type, z_seam_pos);
+    processInsets(gcode_layer, mesh, mesh_config, part, layer_nr, z_seam_type, z_seam_pos);
 
     if (!mesh->getSettingBoolean("infill_before_walls"))
     {
-        processMultiLayerInfill(gcode_layer, mesh, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
-        processSingleLayerInfill(gcode_layer, mesh, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
+        processMultiLayerInfill(gcode_layer, mesh, mesh_config, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
+        processSingleLayerInfill(gcode_layer, mesh, mesh_config, part, layer_nr, infill_line_distance, infill_overlap, infill_angle);
     }
 
-    EFillMethod skin_pattern = mesh->getSettingAsFillMethod("top_bottom_pattern");
+    EFillMethod skin_pattern = (layer_nr == 0)?
+        mesh->getSettingAsFillMethod("top_bottom_pattern_0") :
+        mesh->getSettingAsFillMethod("top_bottom_pattern");
     int skin_angle = 45;
     if ((skin_pattern == EFillMethod::LINES || skin_pattern == EFillMethod::ZIG_ZAG) && layer_nr & 1)
     {
@@ -874,7 +851,7 @@ void FffGcodeWriter::addMeshPartToGCode(SliceDataStorage& storage, SliceMeshStor
         skin_angle -= 45;
 
     int64_t skin_overlap = mesh->getSettingInMicrons("skin_overlap_mm");
-    processSkinAndPerimeterGaps(gcode_layer, mesh, part, layer_nr, skin_overlap, skin_angle);
+    processSkinAndPerimeterGaps(gcode_layer, mesh, mesh_config, part, layer_nr, skin_overlap, skin_angle);
 
     //After a layer part, make sure the nozzle is inside the comb boundary, so we do not retract on the perimeter.
     if (!mesh->getSettingBoolean("magic_spiralize") || static_cast<int>(layer_nr) < mesh->getSettingAsCount("bottom_layers"))
@@ -888,7 +865,7 @@ void FffGcodeWriter::addMeshPartToGCode(SliceDataStorage& storage, SliceMeshStor
             
 
 
-void FffGcodeWriter::processMultiLayerInfill(GCodePlanner& gcode_layer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int infill_angle)
+void FffGcodeWriter::processMultiLayerInfill(GCodePlanner& gcode_layer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int infill_angle) const
 {
     int64_t z = layer_nr * getSettingInMicrons("layer_height");
     if (infill_line_distance > 0)
@@ -896,7 +873,7 @@ void FffGcodeWriter::processMultiLayerInfill(GCodePlanner& gcode_layer, SliceMes
         //Print the thicker infill lines first. (double or more layer thickness, infill combined with previous layers)
         for(unsigned int combine_idx = 1; combine_idx < part.infill_area_per_combine_per_density[0].size(); combine_idx++)
         {
-            const unsigned int infill_line_width = mesh->infill_config[combine_idx].getLineWidth();
+            const unsigned int infill_line_width = mesh_config.infill_config[combine_idx].getLineWidth();
             EFillMethod infill_pattern = mesh->getSettingAsFillMethod("infill_pattern");
             Polygons infill_polygons;
             Polygons infill_lines;
@@ -913,19 +890,19 @@ void FffGcodeWriter::processMultiLayerInfill(GCodePlanner& gcode_layer, SliceMes
                 Infill infill_comp(infill_pattern, part.infill_area_per_combine_per_density[density_idx][combine_idx], 0, infill_line_width, infill_line_distance_here, infill_overlap, infill_angle, z, infill_shift);
                 infill_comp.generate(infill_polygons, infill_lines, mesh);
             }
-            gcode_layer.addPolygonsByOptimizer(infill_polygons, &mesh->infill_config[combine_idx]);
-            gcode_layer.addLinesByOptimizer(infill_lines, &mesh->infill_config[combine_idx], (infill_pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
+            gcode_layer.addPolygonsByOptimizer(infill_polygons, &mesh_config.infill_config[combine_idx]);
+            gcode_layer.addLinesByOptimizer(infill_lines, &mesh_config.infill_config[combine_idx], (infill_pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
         }
     }
 }
 
-void FffGcodeWriter::processSingleLayerInfill(GCodePlanner& gcode_layer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int infill_angle)
+void FffGcodeWriter::processSingleLayerInfill(GCodePlanner& gcode_layer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int infill_angle) const
 {
     if (infill_line_distance == 0 || part.infill_area_per_combine_per_density[0].size() == 0)
     {
         return;
     }
-    const unsigned int infill_line_width = mesh->infill_config[0].getLineWidth();
+    const unsigned int infill_line_width = mesh_config.infill_config[0].getLineWidth();
         
     //Combine the 1 layer thick infill with the top/bottom skin and print that as one thing.
     Polygons infill_polygons;
@@ -969,18 +946,18 @@ void FffGcodeWriter::processSingleLayerInfill(GCodePlanner& gcode_layer, SliceMe
         Infill infill_comp(pattern, part.infill_area_per_combine_per_density[density_idx][0], 0, infill_line_width, infill_line_distance_here, infill_overlap, infill_angle, z, infill_shift);
         infill_comp.generate(infill_polygons, infill_lines, mesh);
     }
-    gcode_layer.addPolygonsByOptimizer(infill_polygons, &mesh->infill_config[0]);
+    gcode_layer.addPolygonsByOptimizer(infill_polygons, &mesh_config.infill_config[0]);
     if (pattern == EFillMethod::GRID || pattern == EFillMethod::LINES || pattern == EFillMethod::TRIANGLES)
     {
-        gcode_layer.addLinesByOptimizer(infill_lines, &mesh->infill_config[0], SpaceFillType::Lines, mesh->getSettingInMicrons("infill_wipe_dist")); 
+        gcode_layer.addLinesByOptimizer(infill_lines, &mesh_config.infill_config[0], SpaceFillType::Lines, mesh->getSettingInMicrons("infill_wipe_dist")); 
     }
     else 
     {
-        gcode_layer.addLinesByOptimizer(infill_lines, &mesh->infill_config[0], (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines); 
+        gcode_layer.addLinesByOptimizer(infill_lines, &mesh_config.infill_config[0], (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
     }
 }
 
-void FffGcodeWriter::processInsets(GCodePlanner& gcode_layer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, EZSeamType z_seam_type, Point z_seam_pos)
+void FffGcodeWriter::processInsets(GCodePlanner& gcode_layer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, EZSeamType z_seam_type, Point z_seam_pos) const
 {
     bool compensate_overlap_0 = mesh->getSettingBoolean("travel_compensate_overlapping_walls_0_enabled");
     bool compensate_overlap_x = mesh->getSettingBoolean("travel_compensate_overlapping_walls_x_enabled");
@@ -997,7 +974,7 @@ void FffGcodeWriter::processInsets(GCodePlanner& gcode_layer, SliceMeshStorage*
             { // on the last normal layer first make the outer wall normally and then start a second outer wall from the same hight, but gradually moving upward
                 WallOverlapComputation* wall_overlap_computation(nullptr);
                 int wall_0_wipe_dist(0);
-                gcode_layer.addPolygonsByOptimizer(part.insets[0], &mesh->insetX_config, wall_overlap_computation, EZSeamType::SHORTEST, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), wall_0_wipe_dist);
+                gcode_layer.addPolygonsByOptimizer(part.insets[0], &mesh_config.insetX_config, wall_overlap_computation, EZSeamType::SHORTEST, z_seam_pos, wall_0_wipe_dist, spiralize);
             }
         }
         int processed_inset_number = -1;
@@ -1013,26 +990,26 @@ void FffGcodeWriter::processInsets(GCodePlanner& gcode_layer, SliceMeshStorage*
                 if (!compensate_overlap_0)
                 {
                     WallOverlapComputation* wall_overlap_computation(nullptr);
-                    gcode_layer.addPolygonsByOptimizer(part.insets[0], &mesh->inset0_config, wall_overlap_computation, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), spiralize);
+                    gcode_layer.addPolygonsByOptimizer(part.insets[0], &mesh_config.inset0_config, wall_overlap_computation, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), spiralize);
                 }
                 else
                 {
-                    Polygons& outer_wall = part.insets[0];
+                    Polygons outer_wall = part.insets[0];
                     WallOverlapComputation wall_overlap_computation(outer_wall, mesh->getSettingInMicrons("wall_line_width_0"));
-                    gcode_layer.addPolygonsByOptimizer(outer_wall, &mesh->inset0_config, &wall_overlap_computation, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), spiralize);
+                    gcode_layer.addPolygonsByOptimizer(outer_wall, &mesh_config.inset0_config, &wall_overlap_computation, z_seam_type, z_seam_pos, mesh->getSettingInMicrons("wall_0_wipe_dist"), spiralize);
                 }
             }
             else
             {
                 if (!compensate_overlap_x)
                 {
-                    gcode_layer.addPolygonsByOptimizer(part.insets[processed_inset_number], &mesh->insetX_config);
+                    gcode_layer.addPolygonsByOptimizer(part.insets[processed_inset_number], &mesh_config.insetX_config);
                 }
                 else
                 {
-                    Polygons& outer_wall = part.insets[processed_inset_number];
+                    Polygons outer_wall = part.insets[processed_inset_number];
                     WallOverlapComputation wall_overlap_computation(outer_wall, mesh->getSettingInMicrons("wall_line_width_x"));
-                    gcode_layer.addPolygonsByOptimizer(outer_wall, &mesh->insetX_config, &wall_overlap_computation);
+                    gcode_layer.addPolygonsByOptimizer(outer_wall, &mesh_config.insetX_config, &wall_overlap_computation);
                 }
             }
         }
@@ -1040,31 +1017,35 @@ void FffGcodeWriter::processInsets(GCodePlanner& gcode_layer, SliceMeshStorage*
 }
 
 
-void FffGcodeWriter::processSkinAndPerimeterGaps(GCodePlanner& gcode_layer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, int skin_overlap, int skin_angle)
+void FffGcodeWriter::processSkinAndPerimeterGaps(GCodePlanner& gcode_layer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int skin_overlap, int skin_angle) const
 {
     int64_t z = layer_nr * getSettingInMicrons("layer_height");
-    const unsigned int skin_line_width = mesh->skin_config.getLineWidth();
+    const unsigned int skin_line_width = mesh_config.skin_config.getLineWidth();
+    const unsigned int perimeter_gaps_line_width = mesh_config.perimeter_gap_config.getLineWidth();
 
     constexpr int perimeter_gaps_extra_offset = 15; // extra offset so that the perimeter gaps aren't created everywhere due to rounding errors
-    bool fill_perimeter_gaps = mesh->getSettingAsFillPerimeterGapMode("fill_perimeter_gaps") != FillPerimeterGapMode::NOWHERE;
+    bool fill_perimeter_gaps = mesh->getSettingAsFillPerimeterGapMode("fill_perimeter_gaps") != FillPerimeterGapMode::NOWHERE
+                            && !mesh->getSettingBoolean("magic_spiralize");
 
     Point z_seam_pos(0, 0); // not used
     PathOrderOptimizer part_order_optimizer(gcode_layer.getLastPosition(), z_seam_pos, EZSeamType::SHORTEST);
     for (unsigned int skin_part_idx = 0; skin_part_idx < part.skin_parts.size(); skin_part_idx++)
     {
-        PolygonsPart& outline = part.skin_parts[skin_part_idx].outline;
+        const PolygonsPart& outline = part.skin_parts[skin_part_idx].outline;
         part_order_optimizer.addPolygon(outline.outerPolygon());
     }
     part_order_optimizer.optimize();
 
     for (int ordered_skin_part_idx : part_order_optimizer.polyOrder)
     {
-        SkinPart& skin_part = part.skin_parts[ordered_skin_part_idx];
+        const SkinPart& skin_part = part.skin_parts[ordered_skin_part_idx];
 
         Polygons skin_polygons;
         Polygons skin_lines;
         
-        EFillMethod pattern = mesh->getSettingAsFillMethod("top_bottom_pattern");
+        EFillMethod pattern = (layer_nr == 0)?
+            mesh->getSettingAsFillMethod("top_bottom_pattern_0") :
+            mesh->getSettingAsFillMethod("top_bottom_pattern");
         int bridge = -1;
         if (layer_nr > 0)
             bridge = bridgeAngle(skin_part.outline, &mesh->layers[layer_nr-1]);
@@ -1076,30 +1057,30 @@ void FffGcodeWriter::processSkinAndPerimeterGaps(GCodePlanner& gcode_layer, Slic
 
         Polygons perimeter_gaps; // the perimeter gaps of the insets of this skin part
 
-        Polygons* inner_skin_outline = nullptr;
+        const Polygons* inner_skin_outline = nullptr;
         int offset_from_inner_skin_outline = 0;
         if (pattern != EFillMethod::CONCENTRIC)
         {
-            for (Polygons& skin_perimeter : skin_part.insets)
+            for (const Polygons& skin_perimeter : skin_part.insets)
             {
-                gcode_layer.addPolygonsByOptimizer(skin_perimeter, &mesh->insetX_config); // add polygons to gcode in inward order
+                gcode_layer.addPolygonsByOptimizer(skin_perimeter, &mesh_config.insetX_config); // add polygons to gcode in inward order
             }
             if (skin_part.insets.size() > 0)
             {
                 inner_skin_outline = &skin_part.insets.back();
-                offset_from_inner_skin_outline = -mesh->insetX_config.getLineWidth() / 2;
+                offset_from_inner_skin_outline = -mesh_config.insetX_config.getLineWidth() / 2;
 
                 if (fill_perimeter_gaps)
                 {
                     // add perimeter gaps between the outer skin inset and the innermost wall
                     const Polygons outer = skin_part.outline;
-                    const Polygons inner = skin_part.insets[0].offset(mesh->insetX_config.getLineWidth() / 2 + perimeter_gaps_extra_offset);
+                    const Polygons inner = skin_part.insets[0].offset(mesh_config.insetX_config.getLineWidth() / 2 + perimeter_gaps_extra_offset);
                     perimeter_gaps.add(outer.difference(inner));
 
                     for (unsigned int inset_idx = 1; inset_idx < skin_part.insets.size(); inset_idx++)
                     { // add perimeter gaps between consecutive skin walls
-                        const Polygons outer = skin_part.insets[inset_idx - 1].offset(-1 * mesh->insetX_config.getLineWidth() / 2 - perimeter_gaps_extra_offset);
-                        const Polygons inner = skin_part.insets[inset_idx].offset(mesh->insetX_config.getLineWidth() / 2);
+                        const Polygons outer = skin_part.insets[inset_idx - 1].offset(-1 * mesh_config.insetX_config.getLineWidth() / 2 - perimeter_gaps_extra_offset);
+                        const Polygons inner = skin_part.insets[inset_idx].offset(mesh_config.insetX_config.getLineWidth() / 2);
                         perimeter_gaps.add(outer.difference(inner));
                     }
                 }
@@ -1116,63 +1097,70 @@ void FffGcodeWriter::processSkinAndPerimeterGaps(GCodePlanner& gcode_layer, Slic
         Infill infill_comp(pattern, *inner_skin_outline, offset_from_inner_skin_outline, skin_line_width, skin_line_width, skin_overlap, skin_angle, z, extra_infill_shift, perimeter_gaps_output);
         infill_comp.generate(skin_polygons, skin_lines);
 
-        if (fill_perimeter_gaps)
-        { // handle perimeter_gaps of skin insets
-            int offset = 0;
-            Infill infill_comp(EFillMethod::LINES, perimeter_gaps, offset, skin_line_width, skin_line_width, skin_overlap, skin_angle, z, extra_infill_shift);
-            infill_comp.generate(skin_polygons, skin_lines);
-        }
-
-        gcode_layer.addPolygonsByOptimizer(skin_polygons, &mesh->skin_config);
+        gcode_layer.addPolygonsByOptimizer(skin_polygons, &mesh_config.skin_config);
 
         if (pattern == EFillMethod::GRID || pattern == EFillMethod::LINES || pattern == EFillMethod::TRIANGLES)
         {
-            gcode_layer.addLinesByOptimizer(skin_lines, &mesh->skin_config, SpaceFillType::Lines, mesh->getSettingInMicrons("infill_wipe_dist"));
+            gcode_layer.addLinesByOptimizer(skin_lines, &mesh_config.skin_config, SpaceFillType::Lines, mesh->getSettingInMicrons("infill_wipe_dist"));
         }
         else
         {
-            gcode_layer.addLinesByOptimizer(skin_lines, &mesh->skin_config, (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
+            gcode_layer.addLinesByOptimizer(skin_lines, &mesh_config.skin_config, (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
+        }
+
+        if (fill_perimeter_gaps)
+        { // handle perimeter_gaps of skin insets
+            Polygons gap_polygons; // will remain empty
+            Polygons gap_lines;
+            int offset = 0;
+            Infill infill_comp(EFillMethod::LINES, perimeter_gaps, offset, perimeter_gaps_line_width, perimeter_gaps_line_width, skin_overlap, skin_angle, z, extra_infill_shift);
+            infill_comp.generate(gap_polygons, gap_lines);
+            gcode_layer.addLinesByOptimizer(gap_lines, &mesh_config.perimeter_gap_config, SpaceFillType::Lines);
         }
     }
 
     if (fill_perimeter_gaps)
     { // handle perimeter gaps of normal insets
         Polygons perimeter_gaps;
-        int line_width = mesh->inset0_config.getLineWidth();
+        int line_width = mesh_config.inset0_config.getLineWidth();
         for (unsigned int inset_idx = 0; inset_idx < part.insets.size() - 1; inset_idx++)
         {
             const Polygons outer = part.insets[inset_idx].offset(-1 * line_width / 2 - perimeter_gaps_extra_offset);
-            line_width = mesh->insetX_config.getLineWidth();
+            line_width = mesh_config.insetX_config.getLineWidth();
 
             Polygons inner = part.insets[inset_idx + 1].offset(line_width / 2);
             perimeter_gaps.add(outer.difference(inner));
         }
         { // gap between inner wall and skin/infill
-            if (mesh->getSettingInMicrons("infill_line_distance") > 0 && !mesh->getSettingBoolean("infill_hollow"))
+            if (mesh->getSettingInMicrons("infill_line_distance") > 0
+                && !mesh->getSettingBoolean("infill_hollow")
+                && mesh->getSettingInMicrons("infill_overlap_mm") >= 0
+            )
             {
                 const Polygons outer = part.insets.back().offset(-1 * line_width / 2 - perimeter_gaps_extra_offset);
 
                 Polygons inner = part.infill_area;
-                for (SkinPart& skin_part : part.skin_parts)
+                for (const SkinPart& skin_part : part.skin_parts)
                 {
                     inner.add(skin_part.outline);
                 }
+                inner = inner.unionPolygons();
                 perimeter_gaps.add(outer.difference(inner));
             }
         }
 
-        Polygons skin_polygons; // unused
-        Polygons skin_lines; // soon to be generated gap filler lines
+        Polygons gap_polygons; // unused
+        Polygons gap_lines; // soon to be generated gap filler lines
         int offset = 0;
         int extra_infill_shift = 0;
-        Infill infill_comp(EFillMethod::LINES, perimeter_gaps, offset, skin_line_width, skin_line_width, skin_overlap, skin_angle, z, extra_infill_shift);
-        infill_comp.generate(skin_polygons, skin_lines);
+        Infill infill_comp(EFillMethod::LINES, perimeter_gaps, offset, perimeter_gaps_line_width, perimeter_gaps_line_width, skin_overlap, skin_angle, z, extra_infill_shift);
+        infill_comp.generate(gap_polygons, gap_lines);
 
-        gcode_layer.addLinesByOptimizer(skin_lines, &mesh->skin_config, SpaceFillType::Lines);
+        gcode_layer.addLinesByOptimizer(gap_lines, &mesh_config.perimeter_gap_config, SpaceFillType::Lines);
     }
 }
 
-bool FffGcodeWriter::addSupportToGCode(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr)
+bool FffGcodeWriter::addSupportToGCode(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr) const
 {
     bool support_added = false;
     if (!storage.support.generated || layer_nr > storage.support.layer_nr_max_filled_layer)
@@ -1183,7 +1171,7 @@ bool FffGcodeWriter::addSupportToGCode(SliceDataStorage& storage, GCodePlanner&
     int support_interface_extruder_nr = getSettingAsIndex("support_interface_extruder_nr");
     int support_infill_extruder_nr = (layer_nr <= 0)? getSettingAsIndex("support_extruder_nr_layer_0") : getSettingAsIndex("support_infill_extruder_nr");
 
-    SupportLayer& support_layer = storage.support.supportLayers[layer_nr];
+    const SupportLayer& support_layer = storage.support.supportLayers[layer_nr];
     if (support_layer.skin.size() == 0 && support_layer.supportAreas.size() == 0)
     {
         return support_added;
@@ -1201,12 +1189,14 @@ bool FffGcodeWriter::addSupportToGCode(SliceDataStorage& storage, GCodePlanner&
     return support_added;
 }
 
-bool FffGcodeWriter::addSupportInfillToGCode(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr)
+bool FffGcodeWriter::addSupportInfillToGCode(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr) const
 {
+    const SupportLayer& support_layer = storage.support.supportLayers[std::max(0, layer_nr)]; // account for negative layer numbers for raft filler layers
+
     bool added = false;
     if (!storage.support.generated 
         || layer_nr > storage.support.layer_nr_max_filled_layer 
-        || storage.support.supportLayers[layer_nr].supportAreas.size() == 0)
+        || support_layer.supportAreas.size() == 0)
     {
         return added;
     }
@@ -1215,14 +1205,14 @@ bool FffGcodeWriter::addSupportInfillToGCode(SliceDataStorage& storage, GCodePla
 
     const ExtruderTrain& infill_extr = *storage.meshgroup->getExtruderTrain(getSettingAsIndex("support_infill_extruder_nr"));
     int support_line_distance = infill_extr.getSettingInMicrons("support_line_distance"); // first layer line distance must be the same as the second layer line distance
-    const int support_line_width = storage.support_config.getLineWidth();
+    const int support_line_width = gcode_layer.configs_storage.support_infill_config.getLineWidth();
     EFillMethod support_pattern = infill_extr.getSettingAsFillMethod("support_pattern"); // first layer pattern must be same as other layers
     if (layer_nr <= 0 && (support_pattern == EFillMethod::LINES || support_pattern == EFillMethod::ZIG_ZAG)) { support_pattern = EFillMethod::GRID; }
 
     int infill_extruder_nr_here = (layer_nr <= 0)? getSettingAsIndex("support_extruder_nr_layer_0") : getSettingAsIndex("support_infill_extruder_nr");
     const ExtruderTrain& infill_extr_here = *storage.meshgroup->getExtruderTrain(infill_extruder_nr_here);
 
-    Polygons& support = storage.support.supportLayers[std::max(0, layer_nr)].supportAreas;
+    const Polygons& support = support_layer.supportAreas;
 
     std::vector<PolygonsPart> support_islands = support.splitIntoParts();
 
@@ -1246,7 +1236,7 @@ bool FffGcodeWriter::addSupportInfillToGCode(SliceDataStorage& storage, GCodePla
             if (boundary.size() > 0)
             {
                 setExtruder_addPrime(storage, gcode_layer, layer_nr, infill_extruder_nr_here); // only switch extruder if we're sure we're going to switch
-                gcode_layer.addPolygonsByOptimizer(boundary, &storage.support_config);
+                gcode_layer.addPolygonsByOptimizer(boundary, &gcode_layer.configs_storage.support_infill_config);
             }
             offset_from_outline = -support_line_width;
             support_infill_overlap = infill_extr_here.getSettingInMicrons("infill_overlap_mm"); // support lines area should be expanded outward to overlap with the boundary polygon
@@ -1263,20 +1253,22 @@ bool FffGcodeWriter::addSupportInfillToGCode(SliceDataStorage& storage, GCodePla
         if (support_lines.size() > 0 || support_polygons.size() > 0)
         {
             setExtruder_addPrime(storage, gcode_layer, layer_nr, infill_extruder_nr_here); // only switch extruder if we're sure we're going to switch
-            gcode_layer.addPolygonsByOptimizer(support_polygons, &storage.support_config);
-            gcode_layer.addLinesByOptimizer(support_lines, &storage.support_config, (support_pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
+            gcode_layer.addPolygonsByOptimizer(support_polygons, &gcode_layer.configs_storage.support_infill_config);
+            gcode_layer.addLinesByOptimizer(support_lines, &gcode_layer.configs_storage.support_infill_config, (support_pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
             added = true;
         }
     }
     return added;
 }
 
-bool FffGcodeWriter::addSupportRoofsToGCode(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr)
+bool FffGcodeWriter::addSupportRoofsToGCode(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr) const
 {
+    const SupportLayer& support_layer = storage.support.supportLayers[std::max(0, layer_nr)];
+
     bool added = false;
     if (!storage.support.generated 
         || layer_nr > storage.support.layer_nr_max_filled_layer 
-        || storage.support.supportLayers[std::max(0, layer_nr)].skin.size() == 0)
+        || support_layer.skin.size() == 0)
     {
         return added;
     }
@@ -1291,7 +1283,7 @@ bool FffGcodeWriter::addSupportRoofsToGCode(SliceDataStorage& storage, GCodePlan
     
     
     bool all_roofs_are_low = true;
-    for (SliceMeshStorage& mesh : storage.meshes)
+    for (const SliceMeshStorage& mesh : storage.meshes)
     {
         if (mesh.getSettingInMicrons("support_roof_height") >= 2 * getSettingInMicrons("layer_height"))
         {
@@ -1320,7 +1312,7 @@ bool FffGcodeWriter::addSupportRoofsToGCode(SliceDataStorage& storage, GCodePlan
     Polygons* perimeter_gaps = nullptr;
     bool use_endpieces = true;
     bool connected_zigzags = false;
-    Infill infill_comp(pattern, storage.support.supportLayers[std::max(0, layer_nr)].skin, outline_offset, storage.support_skin_config.getLineWidth(), support_line_distance, support_skin_overlap, fillAngle, z, extra_infill_shift, perimeter_gaps, connected_zigzags, use_endpieces);
+    Infill infill_comp(pattern, support_layer.skin, outline_offset, gcode_layer.configs_storage.support_interface_config.getLineWidth(), support_line_distance, support_skin_overlap, fillAngle, z, extra_infill_shift, perimeter_gaps, connected_zigzags, use_endpieces);
     Polygons support_polygons;
     Polygons support_lines;
     infill_comp.generate(support_polygons, support_lines);
@@ -1328,14 +1320,14 @@ bool FffGcodeWriter::addSupportRoofsToGCode(SliceDataStorage& storage, GCodePlan
     if (support_lines.size() > 0 || support_polygons.size() > 0)
     {
         setExtruder_addPrime(storage, gcode_layer, layer_nr, skin_extruder_nr);
-        gcode_layer.addPolygonsByOptimizer(support_polygons, &storage.support_skin_config);
-        gcode_layer.addLinesByOptimizer(support_lines, &storage.support_skin_config, (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
+        gcode_layer.addPolygonsByOptimizer(support_polygons, &gcode_layer.configs_storage.support_interface_config);
+        gcode_layer.addLinesByOptimizer(support_lines, &gcode_layer.configs_storage.support_interface_config, (pattern == EFillMethod::ZIG_ZAG)? SpaceFillType::PolyLines : SpaceFillType::Lines);
         added = true;
     }
     return added;
 }
 
-void FffGcodeWriter::setExtruder_addPrime(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr)
+void FffGcodeWriter::setExtruder_addPrime(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr) const
 {
     if (extruder_nr == -1) // an object with extruder_nr==-1 means it will be printed with any current nozzle
         return;
@@ -1346,7 +1338,7 @@ void FffGcodeWriter::setExtruder_addPrime(SliceDataStorage& storage, GCodePlanne
     
     if (extruder_changed)
     {
-        if (!extruder_prime_is_planned[extruder_nr])
+        if (!const_cast<bool&>(extruder_prime_is_planned[extruder_nr])) // TODO: const cast!
         {
             ExtruderTrain* train = storage.meshgroup->getExtruderTrain(extruder_nr);
 
@@ -1357,7 +1349,7 @@ void FffGcodeWriter::setExtruder_addPrime(SliceDataStorage& storage, GCodePlanne
 
             gcode_layer.planPrime();
 
-            extruder_prime_is_planned[extruder_nr] = true;
+            const_cast<bool&>(extruder_prime_is_planned[extruder_nr]) = true; // TODO: const cast!
         }
 
         assert(extruder_prime_is_planned[extruder_nr] && "extruders should be primed before they are used!");
@@ -1372,7 +1364,7 @@ void FffGcodeWriter::setExtruder_addPrime(SliceDataStorage& storage, GCodePlanne
     }
 }
 
-void FffGcodeWriter::addPrimeTower(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int prev_extruder)
+void FffGcodeWriter::addPrimeTower(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int prev_extruder) const
 {
     if (!getSettingBoolean("prime_tower_enable"))
     {

src/FffGcodeWriter.h

@@ -74,18 +74,19 @@ private:
 
     std::vector<FanSpeedLayerTimeSettings> fan_speed_layer_time_settings_per_extruder; //!< The settings used relating to minimal layer time and fan speeds. Configured for each extruder.
 
-    Point last_position_planned; //!< The position of the head before planning the next layer
-    int current_extruder_planned; //!< The extruder train in use before planning the next layer
-    bool is_inside_mesh_layer_part; //!< Whether the last position was inside a layer part (used in combing)
+
+    GCodePlanner::PlanningState planner_state;
+
 public:
     FffGcodeWriter(SettingsBase* settings_)
     : SettingsMessenger(settings_)
     , max_object_height(0)
     , layer_plan_buffer(this, gcode)
     , extruder_prime_is_planned {} // initialize all values in array with [false]
-    , last_position_planned(no_point)
-    , current_extruder_planned(0) // changed somewhere early in FffGcodeWriter::writeGCode
-    , is_inside_mesh_layer_part(false)
+    , planner_state{ no_point
+                    , 0 // changed somewhere early in FffGcodeWriter::writeGCode
+                    , false
+                    }
     {
     }
 
@@ -172,17 +173,6 @@ private:
      * \param[out] storage The data storage to which to save the configurations
      */
     void setConfigRetraction(SliceDataStorage& storage);
-    
-    /*!
-     * Initialize the GcodePathConfig config parameters which don't change over
-     * all layers, for each feature.
-     * 
-     * The features are: skirt or brim, support and for each mesh: outer wall,
-     * inner walls, skin, infill (and combined infill).
-     * 
-     * \param[out] storage The data storage to which to save the configurations.
-     */
-    void initConfigs(SliceDataStorage& storage);
 
     /*!
      * Get the extruder with which to start the print.
@@ -192,7 +182,7 @@ private:
      * 
      * \param[in] storage where to get settings from.
      */
-    unsigned int getStartExtruder(SliceDataStorage& storage);
+    unsigned int getStartExtruder(const SliceDataStorage& storage);
 
     /*!
      * Set temperatures and perform initial priming.
@@ -202,14 +192,14 @@ private:
      * \param[in] storage where the slice data is stored.
      * \param[in] start_extruder_nr The extruder with which to start the print.
      */
-    void processStartingCode(SliceDataStorage& storage, const unsigned int start_extruder_nr);
+    void processStartingCode(const SliceDataStorage& storage, const unsigned int start_extruder_nr);
 
     /*!
      * Move up and over the already printed meshgroups to print the next meshgroup.
      * 
      * \param[in] storage where the slice data is stored.
      */
-    void processNextMeshGroupCode(SliceDataStorage& storage);
+    void processNextMeshGroupCode(const SliceDataStorage& storage);
     
     /*!
      * Add raft layer plans onto the FffGcodeWriter::layer_plan_buffer
@@ -217,7 +207,7 @@ private:
      * \param[in,out] storage where the slice data is stored.
      * \param total_layers The total number of layers.
      */
-    void processRaft(SliceDataStorage& storage, unsigned int total_layers);
+    void processRaft(const SliceDataStorage& storage, unsigned int total_layers);
 
     /*!
      * Convert the polygon data of a layer into a layer plan on the FffGcodeWriter::layer_plan_buffer
@@ -228,15 +218,16 @@ private:
      * \param[in] storage where the slice data is stored.
      * \param layer_nr The index of the layer to write the gcode of.
      * \param total_layers The total number of layers.
+     * \return The layer plans
      */
-    void processLayer(SliceDataStorage& storage, int layer_nr, unsigned int total_layers);
+    GCodePlanner& processLayer(const SliceDataStorage& storage, int layer_nr, unsigned int total_layers) const;
 
     /*!
      * Whether the extruders need to be primed separately just before they are used.
      * 
      * \return whether the extruders need to be primed separately just before they are used
      */
-    bool getExtrudersNeedPrimeDuringFirstLayer();
+    bool getExtrudersNeedPrimeDuringFirstLayer() const;
 
     /*!
      * Plan priming of all used extruders which haven't been primed yet
@@ -244,7 +235,7 @@ private:
      * \param layer_plan The initial planning of the g-code of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      */
-    void ensureAllExtrudersArePrimed(SliceDataStorage& storage, GCodePlanner& layer_plan, const int layer_nr);
+    void ensureAllExtrudersArePrimed(const SliceDataStorage& storage, GCodePlanner& layer_plan, const int layer_nr) const;
 
     /*!
      * Add the skirt or the brim to the layer plan \p gcodeLayer.
@@ -254,7 +245,7 @@ private:
      * \param extruder_nr The extruder train for which to process the skirt or
      * brim.
      */
-    void processSkirtBrim(SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int extruder_nr);
+    void processSkirtBrim(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int extruder_nr) const;
     
     /*!
      * Adds the ooze shield to the layer plan \p gcodeLayer.
@@ -263,7 +254,7 @@ private:
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      */
-    void processOozeShield(SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int layer_nr);
+    void processOozeShield(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int layer_nr) const;
     
     /*!
      * Adds the draft protection screen to the layer plan \p gcodeLayer.
@@ -272,7 +263,7 @@ private:
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      */
-    void processDraftShield(SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int layer_nr);
+    void processDraftShield(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, unsigned int layer_nr) const;
 
     /*!
      * Calculate in which order to plan the extruders
@@ -281,7 +272,7 @@ private:
      * \param current_extruder The current extruder with which we last printed
      * \return A vector of pairs of extruder numbers coupled with the mesh indices ordered on print order for that extruder.
      */
-    std::vector<int> calculateExtruderOrder(SliceDataStorage& storage, int current_extruder);
+    std::vector<int> calculateExtruderOrder(const SliceDataStorage& storage, int current_extruder) const;
 
     /*!
      * Calculate in which order to plan the meshes of a specific extruder
@@ -290,88 +281,95 @@ private:
      * \param extruder_nr The extruder for which to determine the order
      * \return A vector of pairs of extruder numbers coupled with the mesh indices ordered on print order for that extruder.
      */
-    std::vector<unsigned int> calculateMeshOrder(SliceDataStorage& storage, int extruder_nr);
+    std::vector<unsigned int> calculateMeshOrder(const SliceDataStorage& storage, int extruder_nr) const;
 
     /*!
      * Add a single layer from a single mesh-volume to the layer plan \p gcodeLayer in mesh surface mode.
      * 
      * \param[in] storage where the slice data is stored.
      * \param mesh The mesh to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      * 
      */
-    void addMeshLayerToGCode_meshSurfaceMode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcodeLayer, int layer_nr);
+    void addMeshLayerToGCode_meshSurfaceMode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcodeLayer, int layer_nr) const;
     
     /*!
      * Add the open polylines from a single layer from a single mesh-volume to the layer plan \p gcodeLayer for mesh the surface modes.
      * 
      * \param[in] storage where the slice data is stored.
      * \param mesh The mesh for which to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      * 
      */
-    void addMeshOpenPolyLinesToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcode_layer, int layer_nr);
+    void addMeshOpenPolyLinesToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcode_layer, int layer_nr) const;
     
     /*!
      * Add a single layer from a single mesh-volume to the layer plan \p gcode_layer.
      * 
      * \param[in] storage where the slice data is stored.
      * \param mesh The mesh to add to the layer plan \p gcode_layer.
+     * \param mesh_config the line config with which to print a print feature
      * \param gcode_layer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      * 
      */
-    void addMeshLayerToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, GCodePlanner& gcode_layer, int layer_nr);
+    void addMeshLayerToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, GCodePlanner& gcode_layer, int layer_nr) const;
 
     /*!
      * Add a single part from a given layer of a mesh-volume to the layer plan \p gcode_layer.
      * 
      * \param[in] storage where the slice data is stored.
      * \param mesh The mesh to add to the layer plan \p gcode_layer.
+     * \param mesh_config the line config with which to print a print feature
      * \param part The part to add
      * \param gcode_layer The initial planning of the gcode of the layer.
      * \param layer_nr The index of the layer to write the gcode of.
      * 
      */
-    void addMeshPartToGCode(SliceDataStorage& storage, SliceMeshStorage* mesh, SliceLayerPart& part, GCodePlanner& gcode_layer, int layer_nr);
+    void addMeshPartToGCode(const SliceDataStorage& storage, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, GCodePlanner& gcode_layer, int layer_nr) const;
     
     /*!
      * Add thicker (multiple layers) sparse infill for a given part in a layer plan.
      * 
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param mesh The mesh for which to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param part The part for which to create gcode
      * \param layer_nr The current layer number.
      * \param infill_line_distance The distance between the infill lines
      * \param infill_overlap The distance by which the infill overlaps with the wall insets.
      * \param fillAngle The angle in the XY plane at which the infill is generated.
      */
-    void processMultiLayerInfill(GCodePlanner& gcodeLayer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int fillAngle); 
+    void processMultiLayerInfill(GCodePlanner& gcodeLayer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int fillAngle) const;
     
     /*!
      * Add normal sparse infill for a given part in a layer.
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param mesh The mesh for which to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param part The part for which to create gcode
      * \param layer_nr The current layer number.
      * \param infill_line_distance The distance between the infill lines
      * \param infill_overlap The distance by which the infill overlaps with the wall insets.
      * \param fillAngle The angle in the XY plane at which the infill is generated.
      */
-    void processSingleLayerInfill(GCodePlanner& gcodeLayer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int fillAngle);
+    void processSingleLayerInfill(GCodePlanner& gcodeLayer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int infill_line_distance, int infill_overlap, int fillAngle) const;
     
     /*!
      * Generate the insets for the walls of a given layer part.
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param mesh The mesh for which to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param part The part for which to create gcode
      * \param layer_nr The current layer number.
      * \param z_seam_type dir3ective for where to start the outer paerimeter of a part
      * \param z_seam_pos The location near where to start the outer inset in case \p z_seam_type is 'back'
      */
-    void processInsets(GCodePlanner& gcodeLayer, SliceMeshStorage* mesh, SliceLayerPart& part, unsigned int layer_nr, EZSeamType z_seam_type, Point z_seam_pos);
+    void processInsets(GCodePlanner& gcodeLayer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, EZSeamType z_seam_type, Point z_seam_pos) const;
     
     
     /*!
@@ -382,12 +380,13 @@ private:
      * 
      * \param gcodeLayer The initial planning of the gcode of the layer.
      * \param mesh The mesh for which to add to the layer plan \p gcodeLayer.
+     * \param mesh_config the line config with which to print a print feature
      * \param part The part for which to create gcode
      * \param layer_nr The current layer number.
      * \param skin_overlap The distance by which the skin overlaps with the wall insets and the distance by which the perimeter gaps overlap with adjacent print features.
      * \param fillAngle The angle in the XY plane at which the infill is generated.
      */
-    void processSkinAndPerimeterGaps(cura::GCodePlanner& gcode_layer, cura::SliceMeshStorage* mesh, cura::SliceLayerPart& part, unsigned int layer_nr, int skin_overlap, int infill_angle);
+    void processSkinAndPerimeterGaps(GCodePlanner& gcode_layer, const SliceMeshStorage* mesh, const PathConfigStorage::MeshPathConfigs& mesh_config, const SliceLayerPart& part, unsigned int layer_nr, int skin_overlap, int infill_angle) const;
 
     /*!
      * Add the support to the layer plan \p gcodeLayer of the current layer for all support parts with the given \p extruder_nr.
@@ -396,7 +395,7 @@ private:
      * \param layer_nr The index of the layer to write the gcode of.
      * \return whether any support was added to the layer plan
      */
-    bool addSupportToGCode(SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr, int extruder_nr);
+    bool addSupportToGCode(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr, int extruder_nr) const;
     /*!
      * Add the support lines/walls to the layer plan \p gcodeLayer of the current layer.
      * \param[in] storage where the slice data is stored.
@@ -404,7 +403,7 @@ private:
      * \param layer_nr The index of the layer to write the gcode of.
      * \return whether any support infill was added to the layer plan
      */
-    bool addSupportInfillToGCode(SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr);
+    bool addSupportInfillToGCode(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr) const;
     /*!
      * Add the support skins to the layer plan \p gcodeLayer of the current layer.
      * \param[in] storage where the slice data is stored.
@@ -412,7 +411,7 @@ private:
      * \param layer_nr The index of the layer to write the gcode of.
      * \return whether any support skin was added to the layer plan
      */
-    bool addSupportRoofsToGCode(SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr);
+    bool addSupportRoofsToGCode(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr) const;
     
     /*!
      * Change to a new extruder, and add the prime tower instructions if the new extruder is different from the last.
@@ -424,7 +423,7 @@ private:
      * \param layer_nr The index of the layer to write the gcode of.
      * \param extruder_nr The extruder to which to switch
      */
-    void setExtruder_addPrime(SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr);
+    void setExtruder_addPrime(const SliceDataStorage& storage, GCodePlanner& gcode_layer, int layer_nr, int extruder_nr) const;
     
     /*!
      * Add the prime tower gcode for the current layer.
@@ -433,7 +432,7 @@ private:
      * \param layer_nr The index of the layer to write the gcode of.
      * \param prev_extruder The current extruder with which we last printed.
      */
-    void addPrimeTower(SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr, int prev_extruder);
+    void addPrimeTower(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, int layer_nr, int prev_extruder) const;
     
     /*!
      * Add the end gcode and set all temperatures to zero.

src/FffPolygonGenerator.cpp

@@ -2,6 +2,7 @@
 
 #include <algorithm>
 #include <map> // multimap (ordered map allowing duplicate keys)
+#include <omp.h>
 
 #include "utils/math.h"
 #include "utils/algorithm.h"
@@ -151,6 +152,10 @@ bool FffPolygonGenerator::sliceModel(MeshGroup* meshgroup, TimeKeeper& timeKeepe
                 SupportLayer& support_layer = storage.support.supportLayers[layer_nr];
                 SlicerLayer& slicer_layer = slicer->layers[layer_nr];
                 support_layer.anti_overhang = support_layer.anti_overhang.unionPolygons(slicer_layer.polygons);
+                meshStorage.layers[layer_nr].printZ =
+                    slicer_layer.z
+                    + getSettingInMicrons("layer_height_0")
+                    - initial_slice_z;
             }
             continue;
         }
@@ -161,6 +166,10 @@ bool FffPolygonGenerator::sliceModel(MeshGroup* meshgroup, TimeKeeper& timeKeepe
                 SupportLayer& support_layer = storage.support.supportLayers[layer_nr];
                 SlicerLayer& slicer_layer = slicer->layers[layer_nr];
                 support_layer.support_mesh.add(slicer_layer.polygons);
+                meshStorage.layers[layer_nr].printZ =
+                    slicer_layer.z
+                    + getSettingInMicrons("layer_height_0")
+                    - initial_slice_z;
             }
             continue;
         }
@@ -337,12 +346,24 @@ void FffPolygonGenerator::processBasicWallsSkinInfill(SliceDataStorage& storage,
     
     
     // walls
+    unsigned int processed_layer_count = 0;
+#pragma omp parallel for default(none) shared(mesh_layer_count, mesh, inset_skin_progress_estimate, processed_layer_count) schedule(dynamic)
     for (unsigned int layer_number = 0; layer_number < mesh.layers.size(); layer_number++)
     {
         logDebug("Processing insets for layer %i of %i\n", layer_number, mesh_layer_count);
         processInsets(mesh, layer_number);
-        double progress = inset_skin_progress_estimate.progress(layer_number);
-        Progress::messageProgress(Progress::Stage::INSET_SKIN, progress * 100, 100);
+#ifdef _OPENMP
+        if (omp_get_thread_num() == 0)
+#endif
+        { // progress estimation is done only in one thread so that no two threads message progress at the same time
+            int _processed_layer_count;
+#pragma omp atomic read
+                _processed_layer_count = processed_layer_count;
+            double progress = inset_skin_progress_estimate.progress(_processed_layer_count);
+            Progress::messageProgress(Progress::Stage::INSET_SKIN, progress * 100, 100);
+        }
+#pragma omp atomic
+        processed_layer_count++;
     }
 
     ProgressEstimatorLinear* skin_estimator = new ProgressEstimatorLinear(mesh_layer_count);
@@ -373,16 +394,33 @@ void FffPolygonGenerator::processBasicWallsSkinInfill(SliceDataStorage& storage,
     {
         mesh_max_bottom_layer_count = std::max(mesh_max_bottom_layer_count, mesh.getSettingAsCount("bottom_layers"));
     }
-    for (unsigned int layer_number = 0; layer_number < mesh.layers.size(); layer_number++)
+
+    processed_layer_count = 0;
+#pragma omp parallel default(none) shared(mesh_layer_count, mesh, mesh_max_bottom_layer_count, process_infill, inset_skin_progress_estimate, processed_layer_count)
     {
-        logDebug("Processing skins and infill layer %i of %i\n", layer_number, mesh_layer_count);
-        if (!mesh.getSettingBoolean("magic_spiralize") || static_cast<int>(layer_number) < mesh_max_bottom_layer_count)    //Only generate up/downskin and infill for the first X layers when spiralize is choosen.
+
+#pragma omp for schedule(dynamic)
+        for (unsigned int layer_number = 0; layer_number < mesh.layers.size(); layer_number++)
         {
-            processSkinsAndInfill(mesh, layer_number, process_infill);
+            logDebug("Processing skins and infill layer %i of %i\n", layer_number, mesh_layer_count);
+            if (!mesh.getSettingBoolean("magic_spiralize") || static_cast<int>(layer_number) < mesh_max_bottom_layer_count)    //Only generate up/downskin and infill for the first X layers when spiralize is choosen.
+            {
+                processSkinsAndInfill(mesh, layer_number, process_infill);
+            }
+#ifdef _OPENMP
+            if (omp_get_thread_num() == 0)
+#endif
+            { // progress estimation is done only in one thread so that no two threads message progress at the same time
+                int _processed_layer_count;
+#pragma omp atomic read
+                    _processed_layer_count = processed_layer_count;
+                double progress = inset_skin_progress_estimate.progress(_processed_layer_count);
+                Progress::messageProgress(Progress::Stage::INSET_SKIN, progress * 100, 100);
+            }
+#pragma omp atomic
+                processed_layer_count++;
+        }
         }
-        double progress = inset_skin_progress_estimate.progress(layer_number);
-        Progress::messageProgress(Progress::Stage::INSET_SKIN, progress * 100, 100);
-    }
 }
 
 void FffPolygonGenerator::processInfillMesh(SliceDataStorage& storage, unsigned int mesh_order_idx, std::vector<unsigned int>& mesh_order)
@@ -478,6 +516,12 @@ void FffPolygonGenerator::processDerivedWallsSkinInfill(SliceMeshStorage& mesh)
     }
 }
 
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * processInsets only reads and writes data for the current layer
+ */
 void FffPolygonGenerator::processInsets(SliceMeshStorage& mesh, unsigned int layer_nr) 
 {
     SliceLayer* layer = &mesh.layers[layer_nr];
@@ -516,11 +560,19 @@ void FffPolygonGenerator::removeEmptyFirstLayers(SliceDataStorage& storage, cons
         for (SliceMeshStorage& mesh : storage.meshes)
         {
             SliceLayer& layer = mesh.layers[layer_idx];
-            if (layer.parts.size() > 0 || (mesh.getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL && layer.openPolyLines.size() > 0) )
+            if (mesh.getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL && layer.openPolyLines.size() > 0)
             {
                 layer_is_empty = false;
                 break;
             }
+            for (const SliceLayerPart& part : layer.parts)
+            {
+                if (part.print_outline.size() > 0)
+                {
+                    layer_is_empty = false;
+                    break;
+                }
+            }
         }
         
         if (layer_is_empty) 
@@ -551,8 +603,18 @@ void FffPolygonGenerator::removeEmptyFirstLayers(SliceDataStorage& storage, cons
         support_layers.erase(support_layers.begin(), support_layers.begin() + n_empty_first_layers);
     }
 }
-  
-void FffPolygonGenerator::processSkinsAndInfill(SliceMeshStorage& mesh, unsigned int layer_nr, bool process_infill) 
+
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateSkins read (depend on) data from mesh.layers[*].parts[*].insets and write mesh.layers[n].parts[*].skin_parts
+ * generateInfill read mesh.layers[n].parts[*].{insets,skin_parts,boundingBox} and write mesh.layers[n].parts[*].infill_area
+ *
+ * processSkinsAndInfill read (depend on) mesh.layers[*].parts[*].{insets,boundingBox}.
+ *                       write mesh.layers[n].parts[*].{skin_parts,infill_area}.
+ */
+void FffPolygonGenerator::processSkinsAndInfill(SliceMeshStorage& mesh, unsigned int layer_nr, bool process_infill)
 {
     if (mesh.getSettingAsSurfaceMode("magic_mesh_surface_mode") == ESurfaceMode::SURFACE) 
     { 

src/GCodePathConfig.cpp

@@ -6,105 +6,74 @@
 namespace cura 
 {
 
-GCodePathConfig::BasicConfig::BasicConfig()
-: speed(0)
-, acceleration(0)
-, jerk(0)
-, line_width(0)
-, flow(100)
+GCodePathConfig::GCodePathConfig(const GCodePathConfig& other)
+: type(other.type)
+, speed_derivatives(other.speed_derivatives)
+, line_width(other.line_width)
+, layer_thickness(other.layer_thickness)
+, flow(other.flow)
+, extrusion_mm3_per_mm(other.extrusion_mm3_per_mm)
 {
 }
 
 
-GCodePathConfig::BasicConfig::BasicConfig(double speed, double acceleration, double jerk, int line_width, double flow)
-: speed(speed)
-, acceleration(acceleration)
-, jerk(jerk)
+
+GCodePathConfig::GCodePathConfig(PrintFeatureType type, int line_width, int layer_height, double flow, GCodePathConfig::SpeedDerivatives speed_derivatives)
+: type(type)
+, speed_derivatives(speed_derivatives)
 , line_width(line_width)
+, layer_thickness(layer_height)
 , flow(flow)
+, extrusion_mm3_per_mm(calculateExtrusion())
 {
 }
 
-void GCodePathConfig::BasicConfig::set(double speed, double acceleration, double jerk, int line_width, double flow)
+void GCodePathConfig::smoothSpeed(GCodePathConfig::SpeedDerivatives first_layer_config, int layer_nr, int max_speed_layer_nr) 
 {
-    this->speed = speed;
-    this->acceleration = acceleration;
-    this->jerk = jerk;
-    this->line_width = line_width;
-    this->flow = flow;
+    double max_speed_layer = max_speed_layer_nr;
+    speed_derivatives.speed = (speed_derivatives.speed * layer_nr) / max_speed_layer + (first_layer_config.speed * (max_speed_layer - layer_nr) / max_speed_layer);
+    speed_derivatives.acceleration = (speed_derivatives.acceleration * layer_nr) / max_speed_layer + (first_layer_config.acceleration * (max_speed_layer - layer_nr) / max_speed_layer);
+    speed_derivatives.jerk = (speed_derivatives.jerk * layer_nr) / max_speed_layer + (first_layer_config.jerk * (max_speed_layer - layer_nr) / max_speed_layer);
 }
 
-
-GCodePathConfig::GCodePathConfig(PrintFeatureType type)
-: extrusion_mm3_per_mm(0.0)
-, type(type)
-{
-}
-
-void GCodePathConfig::init(double speed, double acceleration, double jerk, int line_width, double flow)
-{
-    iconic_config.set(speed, acceleration, jerk, line_width, flow);
-    current_config = iconic_config;
-}
-
-void GCodePathConfig::setLayerHeight(int layer_height)
-{
-    this->layer_thickness = layer_height;
-    calculateExtrusion();
-}
-
-void GCodePathConfig::smoothSpeed(GCodePathConfig::BasicConfig first_layer_config, int layer_nr, double max_speed_layer) 
-{
-    current_config.speed = (iconic_config.speed * layer_nr) / max_speed_layer + (first_layer_config.speed * (max_speed_layer - layer_nr) / max_speed_layer);
-    current_config.acceleration = (iconic_config.acceleration * layer_nr) / max_speed_layer + (first_layer_config.acceleration * (max_speed_layer - layer_nr) / max_speed_layer);
-    current_config.jerk = (iconic_config.jerk * layer_nr) / max_speed_layer + (first_layer_config.jerk * (max_speed_layer - layer_nr) / max_speed_layer);
-}
-
-void GCodePathConfig::setSpeedIconic()
-{
-    current_config.speed = iconic_config.speed;
-    current_config.acceleration = iconic_config.acceleration;
-    current_config.jerk = iconic_config.jerk;
-}
-
-double GCodePathConfig::getExtrusionMM3perMM()
+double GCodePathConfig::getExtrusionMM3perMM() const
 {
     return extrusion_mm3_per_mm;
 }
 
-double GCodePathConfig::getSpeed()
+double GCodePathConfig::getSpeed() const
 {
-    return current_config.speed;
+    return speed_derivatives.speed;
 }
 
-double GCodePathConfig::getAcceleration()
+double GCodePathConfig::getAcceleration() const
 {
-    return current_config.acceleration;
+    return speed_derivatives.acceleration;
 }
 
-double GCodePathConfig::getJerk()
+double GCodePathConfig::getJerk() const
 {
-    return current_config.jerk;
+    return speed_derivatives.jerk;
 }
 
-int GCodePathConfig::getLineWidth()
+int GCodePathConfig::getLineWidth() const
 {
-    return current_config.line_width;
+    return line_width;
 }
 
-bool GCodePathConfig::isTravelPath()
+bool GCodePathConfig::isTravelPath() const
 {
-    return current_config.line_width == 0;
+    return line_width == 0;
 }
 
-double GCodePathConfig::getFlowPercentage()
+double GCodePathConfig::getFlowPercentage() const
 {
-    return current_config.flow;
+    return flow;
 }
 
-void GCodePathConfig::calculateExtrusion()
+double GCodePathConfig::calculateExtrusion() const
 {
-    extrusion_mm3_per_mm = INT2MM(current_config.line_width) * INT2MM(layer_thickness) * double(current_config.flow) / 100.0;
+    return INT2MM(line_width) * INT2MM(layer_thickness) * double(flow) / 100.0;
 }
 
 

src/GCodePathConfig.h

@@ -16,94 +16,70 @@ class GCodePathConfig
     friend class GCodePlannerTest;
 public:
     /*!
-     * The path config settings which may change from layer to layer
+     * A simple wrapper class for all derivatives of position which are used when printing a line
      */
-    struct BasicConfig
+    struct SpeedDerivatives
     {
         double speed; //!< movement speed (mm/s)
         double acceleration; //!< acceleration of head movement (mm/s^2)
-        double jerk; //!< jerk of the head movement (around stand still) (mm/s^3)
-        int line_width; //!< width of the line extruded
-        double flow; //!< extrusion flow modifier in %
-        BasicConfig(); //!< basic contructor initializing with inaccurate values
-        BasicConfig(double speed, double acceleration, double jerk, int line_width, double flow); //!< basic contructor initializing all values
-        void set(double speed, double acceleration, double jerk, int line_width, double flow); //!< Set all config values
+        double jerk; //!< jerk of the head movement (around stand still) as instantaneous speed change (mm/s)
     };
-private:
-    BasicConfig iconic_config; //!< The basic path configuration iconic to this print feature type
-    BasicConfig current_config; //!< The current path configuration for the current layer
-    int layer_thickness; //!< current layer height in micron
-    double extrusion_mm3_per_mm;//!< current mm^3 filament moved per mm line traversed
-public:
     const PrintFeatureType type; //!< name of the feature type
+private:
+    SpeedDerivatives speed_derivatives; //!< The speed settings (and acceleration and jerk) of the extruded line. May be changed when smoothSpeed is called.
+    const int line_width; //!< width of the line extruded
+    const int layer_thickness; //!< current layer height in micron
+    const double flow; //!< extrusion flow modifier in %
+    const double extrusion_mm3_per_mm;//!< current mm^3 filament moved per mm line traversed
+public:
+    GCodePathConfig(PrintFeatureType type, int line_width, int layer_height, double flow, SpeedDerivatives speed_derivatives); // , SpeedDerivatives slowdown_speed_derivatives, int layer_nr, int max_speed_layer_nr);
 
     /*!
-     * Basic constructor.
+     * copy constructor
      */
-    GCodePathConfig(PrintFeatureType type);
-    
-    /*!
-     * Initialize some of the member variables.
-     * 
-     * \warning GCodePathConfig::setLayerHeight still has to be called before this object can be used.
-     * 
-     * \param speed The regular speed with which to print this feature
-     * \param line_width The line width for this feature
-     * \param flow The flow modifier to apply to the extruded filament when printing this feature
-     */
-    void init(double speed, double acceleration, double jerk, int line_width, double flow);
-
-    /*!
-     * Set the layer height and (re)compute the extrusion_per_mm
-     */
-    void setLayerHeight(int layer_height);
+    GCodePathConfig(const GCodePathConfig& other);
 
     /*!
      * Set the speed to somewhere between the speed of @p first_layer_config and the iconic speed.
      * 
      * \warning This functions should not be called with @p layer_nr > @p max_speed_layer !
      * 
+     * \warning Calling this function twice will smooth the speed more toward \p first_layer_config
+     * 
      * \param first_layer_config The speed settings at layer zero
      * \param layer_nr The layer number 
      * \param max_speed_layer The layer number for which the speed_iconic should be used.
      */
-    void smoothSpeed(BasicConfig first_layer_config, int layer_nr, double max_speed_layer);
-
-    /*!
-     * Set the speed config to the iconic speed config, i.e. the normal speed of the feature type for which this is a config.
-     * 
-     * Does the same for acceleration and jerk.
-     */
-    void setSpeedIconic();
+    void smoothSpeed(SpeedDerivatives first_layer_config, int layer_nr, int max_speed_layer);
 
     /*!
      * Can only be called after the layer height has been set (which is done while writing the gcode!)
      */
-    double getExtrusionMM3perMM();
+    double getExtrusionMM3perMM() const;
 
     /*!
      * Get the movement speed in mm/s
      */
-    double getSpeed();
+    double getSpeed() const;
 
     /*!
      * Get the current acceleration of this config
      */
-    double getAcceleration();
+    double getAcceleration() const;
 
     /*!
      * Get the current jerk of this config
      */
-    double getJerk();
+    double getJerk() const;
 
-    int getLineWidth();
+    int getLineWidth() const;
 
-    bool isTravelPath();
+    bool isTravelPath() const;
 
-    double getFlowPercentage();
+    double getFlowPercentage() const;
 
 private:
-    void calculateExtrusion();
+    double calculateExtrusion() const;
 };
 
 

src/LayerPlanBuffer.cpp

@@ -17,7 +17,7 @@ void LayerPlanBuffer::flush()
     }
     while (!buffer.empty())
     {
-        buffer.front().writeGCode(gcode);
+        buffer.front()->writeGCode(gcode);
         if (CommandSocket::isInstantiated())
         {
             CommandSocket::getInstance()->flushGcode();
@@ -324,7 +324,7 @@ void LayerPlanBuffer::insertFinalPrintTempCommand(std::vector<ExtruderPlan*>& ex
 
 void LayerPlanBuffer::insertTempCommands()
 {
-    if (buffer.back().extruder_plans.size() == 0 || (buffer.back().extruder_plans.size() == 1 && buffer.back().extruder_plans[0].paths.size() == 0))
+    if (buffer.back()->extruder_plans.size() == 0 || (buffer.back()->extruder_plans.size() == 1 && buffer.back()->extruder_plans[0].paths.size() == 0))
     { // disregard empty layer
         buffer.pop_back();
         return;
@@ -332,9 +332,9 @@ void LayerPlanBuffer::insertTempCommands()
 
     std::vector<ExtruderPlan*> extruder_plans;
     extruder_plans.reserve(buffer.size() * 2);
-    for (GCodePlanner& layer_plan : buffer)
+    for (GCodePlanner* layer_plan : buffer)
     {
-        for (ExtruderPlan& extr_plan : layer_plan.extruder_plans)
+        for (ExtruderPlan& extr_plan : layer_plan->extruder_plans)
         {
             extruder_plans.push_back(&extr_plan);
         }
@@ -342,7 +342,7 @@ void LayerPlanBuffer::insertTempCommands()
 
 
     // insert commands for all extruder plans on this layer
-    GCodePlanner& layer_plan = buffer.back();
+    GCodePlanner& layer_plan = *buffer.back();
     for (unsigned int extruder_plan_idx = 0; extruder_plan_idx < layer_plan.extruder_plans.size(); extruder_plan_idx++)
     {
         unsigned int overall_extruder_plan_idx = extruder_plans.size() - layer_plan.extruder_plans.size() + extruder_plan_idx;

src/LayerPlanBuffer.h

@@ -42,7 +42,7 @@ class LayerPlanBuffer : SettingsMessenger
 
     std::vector<bool> extruder_used_in_meshgroup; //!< For each extruder whether it has already been planned once in this meshgroup. This is used to see whether we should heat to the initial_print_temp or to the printing_temperature
 public:
-    std::list<GCodePlanner> buffer; //!< The buffer containing several layer plans (GCodePlanner) before writing them to gcode.
+    std::list<GCodePlanner*> buffer; //!< The buffer containing several layer plans (GCodePlanner) before writing them to gcode.
     
     LayerPlanBuffer(SettingsBaseVirtual* settings, GCodeExport& gcode)
     : SettingsMessenger(settings)
@@ -54,29 +54,39 @@ public:
     {
         preheat_config.setConfig(settings);
     }
-    
+
     /*!
-     * Place a new layer plan (GcodePlanner) by constructing it with the given arguments.
-     * Pop back the oldest layer plan is it exceeds the buffer size and write it to gcode.
+     * Push a new layer plan into the buffer
      */
-    template<typename... Args>
-    GCodePlanner& emplace_back(Args&&... constructor_args)
+    void push(GCodePlanner& layer_plan)
+    {
+        buffer.push_back(&layer_plan);
+    }
+
+    /*!
+     * Process all layers in the buffer
+     * This inserts the temperature commands to start warming for a given layer in earlier layers
+     * 
+     * Pop out the earliest layer in the buffer if the buffer size is exceeded
+     * \return A nullptr or the popped gcode_layer
+     */
+    GCodePlanner* processBuffer()
     {
         if (buffer.size() > 0)
         {
             insertTempCommands(); // insert preheat commands of the just completed layer plan (not the newly emplaced one)
         }
-        buffer.emplace_back(constructor_args...);
         if (buffer.size() > buffer_size)
         {
-            buffer.front().writeGCode(gcode);
+            GCodePlanner* ret = buffer.front();
             if (CommandSocket::isInstantiated())
             {
                 CommandSocket::getInstance()->flushGcode();
             }
             buffer.pop_front();
+            return ret;
         }
-        return buffer.back();
+        return nullptr;
     }
     
     /*!

src/MergeInfillLines.h

@@ -17,7 +17,7 @@ class MergeInfillLines
     std::vector<GCodePath>& paths; //!< The paths currently under consideration
     ExtruderPlan& extruder_plan; //!< The extruder plan of the paths currently under consideration
     
-    GCodePathConfig& travelConfig; //!< The travel settings used to see whether a path is a travel path or an extrusion path
+    const GCodePathConfig& travelConfig; //!< The travel settings used to see whether a path is a travel path or an extrusion path
     int64_t nozzle_size; //!< The diameter of the hole in the nozzle
     bool speed_equalize_flow_enabled; //!< Should the speed be varied with extrusion width
     double speed_equalize_flow_max; //!< Maximum speed when adjusting speed for flow
@@ -64,9 +64,18 @@ public:
     /*!
      * Simple constructor only used by MergeInfillLines::isConvertible to easily convey the environment
      */
-    MergeInfillLines(GCodeExport& gcode, int layer_nr, std::vector<GCodePath>& paths, ExtruderPlan& extruder_plan, GCodePathConfig& travelConfig, int64_t nozzle_size, bool speed_equalize_flow_enabled, double speed_equalize_flow_max) 
-    : gcode(gcode), layer_nr(layer_nr), paths(paths), extruder_plan(extruder_plan), travelConfig(travelConfig), nozzle_size(nozzle_size), speed_equalize_flow_enabled(speed_equalize_flow_enabled), speed_equalize_flow_max(speed_equalize_flow_max) { }
-    
+    MergeInfillLines(GCodeExport& gcode, int layer_nr, std::vector<GCodePath>& paths, ExtruderPlan& extruder_plan, const GCodePathConfig& travelConfig, int64_t nozzle_size, bool speed_equalize_flow_enabled, double speed_equalize_flow_max)
+    : gcode(gcode)
+    , layer_nr(layer_nr)
+    , paths(paths)
+    , extruder_plan(extruder_plan)
+    , travelConfig(travelConfig)
+    , nozzle_size(nozzle_size)
+    , speed_equalize_flow_enabled(speed_equalize_flow_enabled)
+    , speed_equalize_flow_max(speed_equalize_flow_max)
+    {
+    }
+
     /*!
      * Check for lots of small moves and combine them into one large line.
      * Updates \p path_idx to the next path which is not combined.

src/PrimeTower.cpp

@@ -15,12 +15,7 @@ namespace cura
 PrimeTower::PrimeTower(const SliceDataStorage& storage)
 : is_hollow(false)
 , wipe_from_middle(false)
-, current_pre_wipe_location_idx(0)
 {
-    for (int extruder_nr = 0; extruder_nr < MAX_EXTRUDERS; extruder_nr++)
-    {
-        last_prime_tower_poly_printed[extruder_nr] = -1;
-    }
     enabled = storage.getSettingBoolean("prime_tower_enable")
            && storage.getSettingInMicrons("prime_tower_wall_thickness") > 10
            && storage.getSettingInMicrons("prime_tower_size") > 10;
@@ -30,34 +25,6 @@ PrimeTower::PrimeTower(const SliceDataStorage& storage)
     }
 }
 
-
-
-void PrimeTower::initConfigs(const MeshGroup* meshgroup)
-{
-    extruder_count = meshgroup->getExtruderCount();
-
-    for (int extr = 0; extr < extruder_count; extr++)
-    {
-        config_per_extruder.emplace_back(PrintFeatureType::Support);// so that visualization in the old Cura still works (TODO)
-    }
-    for (int extr = 0; extr < extruder_count; extr++)
-    {
-        const ExtruderTrain* train = meshgroup->getExtruderTrain(extr);
-        config_per_extruder[extr].init(train->getSettingInMillimetersPerSecond("speed_prime_tower"), train->getSettingInMillimetersPerSecond("acceleration_prime_tower"), train->getSettingInMillimetersPerSecond("jerk_prime_tower"), train->getSettingInMicrons("prime_tower_line_width"), train->getSettingInPercentage("prime_tower_flow"));
-    }
-}
-
-void PrimeTower::setConfigs(const MeshGroup* meshgroup, const int layer_thickness)
-{
-    extruder_count = meshgroup->getExtruderCount();
-
-    for (int extr = 0; extr < extruder_count; extr++)
-    {
-        GCodePathConfig& conf = config_per_extruder[extr];
-        conf.setLayerHeight(layer_thickness);
-    }
-}
-
 void PrimeTower::generateGroundpoly(const SliceDataStorage& storage)
 {
     extruder_count = storage.meshgroup->getExtruderCount();
@@ -127,18 +94,13 @@ void PrimeTower::generatePaths_denseInfill(const SliceDataStorage& storage)
 }
 
 
-void PrimeTower::addToGcode(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, const GCodeExport& gcode, const int layer_nr, const int prev_extruder, const int new_extruder)
+void PrimeTower::addToGcode(const SliceDataStorage& storage, GCodePlanner& gcodeLayer, const GCodeExport& gcode, const int layer_nr, const int prev_extruder, const int new_extruder) const
 {
     if (!enabled)
     {
         return;
     }
-    bool prime_tower_added = false;
-    for (int extruder = 0; extruder <  storage.meshgroup->getExtruderCount() && !prime_tower_added; extruder++)
-    {
-        prime_tower_added = last_prime_tower_poly_printed[extruder] == int(layer_nr);
-    }
-    if (prime_tower_added)
+    if (gcodeLayer.getPrimeTowerIsPlanned())
     { // don't print the prime tower if it has been printed already
         return;
     }
@@ -159,7 +121,7 @@ void PrimeTower::addToGcode(const SliceDataStorage& storage, GCodePlanner& gcode
     // pre-wipe:
     if (pre_wipe)
     {
-        preWipe(storage, gcodeLayer, new_extruder);
+        preWipe(storage, gcodeLayer, layer_nr, new_extruder);
     }
 
     addToGcode_denseInfill(gcodeLayer, layer_nr, new_extruder);
@@ -169,21 +131,21 @@ void PrimeTower::addToGcode(const SliceDataStorage& storage, GCodePlanner& gcode
     { //Make sure we wipe the old extruder on the prime tower.
         gcodeLayer.addTravel(post_wipe_point - gcode.getExtruderOffset(prev_extruder) + gcode.getExtruderOffset(new_extruder));
     }
+
+    gcodeLayer.setPrimeTowerIsPlanned();
 }
 
-void PrimeTower::addToGcode_denseInfill(GCodePlanner& gcodeLayer, const int layer_nr, const int extruder)
+void PrimeTower::addToGcode_denseInfill(GCodePlanner& gcode_layer, const int layer_nr, const int extruder_nr) const
 {
-    ExtrusionMoves& pattern = patterns_per_extruder[extruder][((layer_nr % 2) + 2) % 2]; // +2) %2 to handle negative layer numbers
+    const ExtrusionMoves& pattern = patterns_per_extruder[extruder_nr][((layer_nr % 2) + 2) % 2]; // +2) %2 to handle negative layer numbers
 
-    GCodePathConfig& config = config_per_extruder[extruder];
+    const GCodePathConfig& config = gcode_layer.configs_storage.prime_tower_config_per_extruder[extruder_nr];
 
-    gcodeLayer.addPolygonsByOptimizer(pattern.polygons, &config);
-    gcodeLayer.addLinesByOptimizer(pattern.lines, &config, SpaceFillType::Lines);
-
-    last_prime_tower_poly_printed[extruder] = layer_nr;
+    gcode_layer.addPolygonsByOptimizer(pattern.polygons, &config);
+    gcode_layer.addLinesByOptimizer(pattern.lines, &config, SpaceFillType::Lines);
 }
 
-Point PrimeTower::getLocationBeforePrimeTower(const SliceDataStorage& storage)
+Point PrimeTower::getLocationBeforePrimeTower(const SliceDataStorage& storage) const
 {
     Point ret(0, 0);
     int absolute_starting_points = 0;
@@ -263,10 +225,10 @@ void PrimeTower::generateWipeLocations(const SliceDataStorage& storage)
     PolygonUtils::spreadDots(segment_start, segment_end, number_of_pre_wipe_locations, pre_wipe_locations);
 }
 
-void PrimeTower::preWipe(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const int extruder_nr)
+void PrimeTower::preWipe(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const int layer_nr, const int extruder_nr) const
 {
+    int current_pre_wipe_location_idx = (pre_wipe_location_skip * layer_nr) % number_of_pre_wipe_locations;
     const ClosestPolygonPoint wipe_location = pre_wipe_locations[current_pre_wipe_location_idx];
-    current_pre_wipe_location_idx = (current_pre_wipe_location_idx + pre_wipe_location_skip) % number_of_pre_wipe_locations;
 
     ExtruderTrain& train = *storage.meshgroup->getExtruderTrain(extruder_nr);
     const int inward_dist = train.getSettingInMicrons("machine_nozzle_size") * 3 / 2 ;
@@ -294,7 +256,7 @@ void PrimeTower::preWipe(const SliceDataStorage& storage, GCodePlanner& gcode_la
         gcode_layer.addTravel(start);
     }
     float flow = 0.0001; // force this path being interpreted as an extrusion path, so that no Z hop will occur (TODO: really separately handle travel and extrusion moves)
-    gcode_layer.addExtrusionMove(end, &config_per_extruder[extruder_nr], SpaceFillType::None, flow);
+    gcode_layer.addExtrusionMove(end, &gcode_layer.configs_storage.prime_tower_config_per_extruder[extruder_nr], SpaceFillType::None, flow);
 }
 
 void PrimeTower::subtractFromSupport(SliceDataStorage& storage)

src/PrimeTower.h

@@ -34,7 +34,6 @@ private:
         Polygons lines;
     };
     int extruder_count; //!< number of extruders
-    std::vector<GCodePathConfig> config_per_extruder; //!< Path config for prime tower for each extruder
 
     bool is_hollow; //!< Whether the prime tower is hollow
 
@@ -47,7 +46,6 @@ private:
     const unsigned int pre_wipe_location_skip = 13; //!< How big the steps are when stepping through \ref PrimeTower::wipe_locations
     const unsigned int number_of_pre_wipe_locations = 21; //!< The required size of \ref PrimeTower::wipe_locations
     // note that the above are two consecutive numbers in the Fibonacci sequence
-    int current_pre_wipe_location_idx; //!< Index into \ref PrimeTower::wipe_locations of where to pre-wipe the nozzle
 
 public:
     bool enabled; //!< Whether the prime tower is enabled.
@@ -63,21 +61,6 @@ public:
      */
     PrimeTower(const SliceDataStorage& storage);
 
-    /*!
-     * Initialize \ref PrimeTower::config_per_extruder with speed and line width settings.
-     * 
-     * \param meshgroup Where to retrieve the setttings for each extruder
-     */
-    void initConfigs(const MeshGroup* meshgroup);
-
-    /*!
-     * Complete the \ref PrimeTower::config_per_extruder by settings the layer height.
-     * 
-     * \param meshgroup Where to retrieve the setttings for each extruder
-     * \param layer_thickness The current layer thickness
-     */
-    void setConfigs(const MeshGroup* meshgroup, const int layer_thickness);
-
     /*!
      * Generate the prime tower area to be used on each layer
      * 
@@ -104,7 +87,7 @@ public:
      * \param prev_extruder The previous extruder with which paths were planned; from which extruder a switch was made
      * \param new_extruder The switched to extruder with which the prime tower paths should be generated.
      */
-    void addToGcode(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const GCodeExport& gcode, const int layer_nr, const int prev_extruder, const int new_extruder);
+    void addToGcode(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const GCodeExport& gcode, const int layer_nr, const int prev_extruder, const int new_extruder) const;
 
     /*!
      * \brief Subtract the prime tower from the support areas in storage.
@@ -115,12 +98,6 @@ public:
     void subtractFromSupport(SliceDataStorage& storage);
 
 private:
-    /*!
-     * Layer number of the last layer in which a prime tower has been printed per extruder train.  
-     * 
-     * This is recorded per extruder to account for a prime tower per extruder, instead of the mixed prime tower.
-     */
-    int last_prime_tower_poly_printed[MAX_EXTRUDERS];
 
     /*!
      * Find an approriate representation for the point representing the location before going to the prime tower
@@ -130,7 +107,7 @@ private:
      * \param storage where to get settings from
      * \return that location
      */
-    Point getLocationBeforePrimeTower(const SliceDataStorage& storage);
+    Point getLocationBeforePrimeTower(const SliceDataStorage& storage) const;
 
     /*!
      * \param storage where to get settings from
@@ -159,16 +136,17 @@ private:
      * \param extruder The extruder we just switched to, with which the prime
      * tower paths should be drawn.
      */
-    void addToGcode_denseInfill(GCodePlanner& gcode_layer, const int layer_nr, const int extruder);
+    void addToGcode_denseInfill(GCodePlanner& gcode_layer, const int layer_nr, const int extruder) const;
 
     /*!
      * Plan the moves for wiping the current nozzles oozed material before starting to print the prime tower.
      * 
      * \param storage where to get settings from
      * \param[out] gcode_layer where to add the planned paths for wiping
+     * \param layer_nr The layer number of the \p gcode_layer
      * \param extruder_nr The current extruder
      */
-    void preWipe(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const int extruder_nr);
+    void preWipe(const SliceDataStorage& storage, GCodePlanner& gcode_layer, const int layer_nr, const int extruder_nr) const;
 };
 
 

src/SkirtBrim.cpp

@@ -58,6 +58,10 @@ void SkirtBrim::getFirstLayerOutline(SliceDataStorage& storage, const unsigned i
     constexpr int smallest_line_length = 200;
     constexpr int largest_error_of_removed_point = 50;
     first_layer_outline.simplify(smallest_line_length, largest_error_of_removed_point); // simplify for faster processing of the brim lines
+    if (first_layer_outline.size() == 0)
+    {
+        logError("Couldn't generate skirt / brim! No polygons on first layer.");
+    }
 }
 
 int SkirtBrim::generatePrimarySkirtBrimLines(SliceDataStorage& storage, int start_distance, unsigned int primary_line_count, const int primary_extruder_skirt_brim_line_width, const int64_t primary_extruder_minimal_length, const Polygons& first_layer_outline, Polygons& skirt_brim_primary_extruder)

src/WallsComputation.cpp

@@ -12,6 +12,12 @@ WallsComputation::WallsComputation(int wall_0_inset, int line_width_0, int line_
 {
 }
 
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateInsets only reads and writes data for the current layer
+ */
 void WallsComputation::generateInsets(SliceLayerPart* part)
 {
     if (insetCount == 0)
@@ -58,6 +64,12 @@ void WallsComputation::generateInsets(SliceLayerPart* part)
     }
 }
 
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateInsets only reads and writes data for the current layer
+ */
 void WallsComputation::generateInsets(SliceLayer* layer)
 {
     for(unsigned int partNr = 0; partNr < layer->parts.size(); partNr++)

src/Weaver.cpp

@@ -389,7 +389,7 @@ void Weaver::chainify_polygons(Polygons& parts1, Point start_close_to, Polygons&
 {
     for (unsigned int prt = 0 ; prt < parts1.size(); prt++)
     {
-        const PolygonRef upperPart = parts1[prt];
+        ConstPolygonRef upperPart = parts1[prt];
         
         ClosestPolygonPoint closestInPoly = PolygonUtils::findClosest(start_close_to, upperPart);
 
@@ -439,7 +439,7 @@ void Weaver::connect_polygons(Polygons& supporting, int z0, Polygons& supported,
     for (unsigned int prt = 0 ; prt < supported.size(); prt++)
     {
         
-        const PolygonRef upperPart = supported[prt];
+        ConstPolygonRef upperPart(supported[prt]);
         
         
         parts.emplace_back(prt);

src/bridge.cpp

@@ -5,7 +5,7 @@
 
 namespace cura {
 
-int bridgeAngle(Polygons outline, SliceLayer* prevLayer)
+int bridgeAngle(Polygons outline, const SliceLayer* prevLayer)
 {
     AABB boundaryBox(outline);
     //To detect if we have a bridge, first calculate the intersection of the current layer with the previous layer.

src/bridge.h

@@ -6,7 +6,7 @@ namespace cura {
     class Polygons;
     class SliceLayer;
 
-int bridgeAngle(Polygons outline, SliceLayer* prevLayer);
+int bridgeAngle(Polygons outline, const SliceLayer* prevLayer);
 
 }//namespace cura
 

src/commandSocket.cpp

@@ -215,7 +215,7 @@ public:
     /*!
      * Adds closed polygon to the current path
      */
-    void sendPolygon(PrintFeatureType print_feature_type, Polygon poly, int width);
+    void sendPolygon(PrintFeatureType print_feature_type, ConstPolygonRef poly, int width);
 private:
     /*!
      * Convert and add a point to the points buffer, each point being represented as two consecutive floats. All members adding a 2D point to the data should use this function.
@@ -522,7 +522,7 @@ void CommandSocket::sendPolygons(PrintFeatureType type, const Polygons& polygons
 #endif
 }
 
-void CommandSocket::sendPolygon(PrintFeatureType type, Polygon& polygon, int line_width)
+void CommandSocket::sendPolygon(PrintFeatureType type, ConstPolygonRef polygon, int line_width)
 {
 #ifdef ARCUS
     if (CommandSocket::isInstantiated())
@@ -642,6 +642,7 @@ void CommandSocket::sendLayerData()
     {
         for (std::pair<const int, std::shared_ptr<cura::proto::Layer>> entry : data.slice_data) //Note: This is in no particular order!
         {
+            logDebug("Sending layer data for layer %i of %i.\n", entry.first, data.slice_data.size());
             private_data->socket->sendMessage(entry.second); //Send the actual layers.
         }
         data.sliced_objects = 0;
@@ -667,6 +668,7 @@ void CommandSocket::sendOptimizedLayerData()
     {
         for (std::pair<const int, std::shared_ptr<cura::proto::LayerOptimized>> entry : data.slice_data) //Note: This is in no particular order!
         {
+            logDebug("Sending layer data for layer %i of %i.\n", entry.first, data.slice_data.size());
             private_data->socket->sendMessage(entry.second); //Send the actual layers.
         }
         data.sliced_objects = 0;
@@ -797,7 +799,7 @@ void CommandSocket::PathCompiler::sendLineTo(PrintFeatureType print_feature_type
     }
 }
 
-void CommandSocket::PathCompiler::sendPolygon(PrintFeatureType print_feature_type, Polygon polygon, int width)
+void CommandSocket::PathCompiler::sendPolygon(PrintFeatureType print_feature_type, ConstPolygonRef polygon, int width)
 {
     if (polygon.size() < 2)
     {

src/commandSocket.h

@@ -64,7 +64,7 @@ public:
     /*! 
      * Send a polygon to the front-end. This is used for the layerview in the GUI
      */
-    static void sendPolygon(cura::PrintFeatureType type, Polygon& polygon, int line_width);
+    static void sendPolygon(cura::PrintFeatureType type, ConstPolygonRef polygon, int line_width);
 
     /*!
      * Send a line to the front-end. This is used for the layerview in the GUI

src/gcodeExport.cpp

@@ -270,7 +270,7 @@ void GCodeExport::setFlavor(EGCodeFlavor flavor)
     }
 }
 
-EGCodeFlavor GCodeExport::getFlavor()
+EGCodeFlavor GCodeExport::getFlavor() const
 {
     return this->flavor;
 }
@@ -556,8 +556,6 @@ void GCodeExport::writeMove(int x, int y, int z, double speed, double extrusion_
     assert((Point3(x,y,z) - currentPosition).vSize() < MM2INT(300)); // no crazy positions (this code should not be compiled for release)
 #endif //ASSERT_INSANE_OUTPUT
 
-    total_bounding_box.include(Point3(x, y, z));
-
     if (extrusion_mm3_per_mm < 0)
         logWarning("Warning! Negative extrusion move!");
 
@@ -570,6 +568,7 @@ void GCodeExport::writeMove(int x, int y, int z, double speed, double extrusion_
     double extrusion_per_mm = mm3ToE(extrusion_mm3_per_mm);
 
     Point gcode_pos = getGcodePos(x,y, current_extruder);
+    total_bounding_box.include(Point3(gcode_pos.X, gcode_pos.Y, z));
 
     if (extrusion_mm3_per_mm > 0.000001)
     {
@@ -729,7 +728,7 @@ void GCodeExport::writeZhopStart(int hop_height)
     {
         isZHopped = hop_height;
         *output_stream << "G1 Z" << MMtoStream{currentPosition.z + isZHopped} << new_line;
-        total_bounding_box.include(currentPosition + Point3(0, 0, isZHopped));
+        total_bounding_box.includeZ(currentPosition.z + isZHopped);
     }
 }
 
@@ -776,7 +775,7 @@ void GCodeExport::switchExtruder(int new_extruder, const RetractionConfig& retra
 
     bool force = true;
     bool extruder_switch = true;
-    writeRetraction(const_cast<RetractionConfig&>(retraction_config_old_extruder), force, extruder_switch);
+    writeRetraction(retraction_config_old_extruder, force, extruder_switch);
 
     resetExtrusionValue(); // zero the E value on the old extruder, so that the current_e_value is registered on the old extruder
 
@@ -923,7 +922,7 @@ void GCodeExport::finalize(const char* endCode)
 {
     writeFanCommand(0);
     writeCode(endCode);
-    long print_time = getTotalPrintTime();
+    int64_t print_time = getTotalPrintTime();
     int mat_0 = getTotalFilamentUsed(0);
     log("Print time: %d\n", print_time);
     log("Print time (readable): %dh %dm %ds\n", print_time / 60 / 60, (print_time / 60) % 60, print_time % 60);

src/gcodeExport.h

@@ -188,7 +188,7 @@ public:
     Point getGcodePos(const int64_t x, const int64_t y, const int extruder_train) const;
     
     void setFlavor(EGCodeFlavor flavor);
-    EGCodeFlavor getFlavor();
+    EGCodeFlavor getFlavor() const;
     
     void setZ(int z);
     

src/gcodePlanner.cpp

@@ -10,7 +10,7 @@
 namespace cura {
 
 
-ExtruderPlan::ExtruderPlan(int extruder, Point start_position, int layer_nr, bool is_initial_layer, int layer_thickness, FanSpeedLayerTimeSettings& fan_speed_layer_time_settings, const RetractionConfig& retraction_config)
+ExtruderPlan::ExtruderPlan(int extruder, Point start_position, int layer_nr, bool is_initial_layer, int layer_thickness, const FanSpeedLayerTimeSettings& fan_speed_layer_time_settings, const RetractionConfig& retraction_config)
 : extruder(extruder)
 , heated_pre_travel_time(0)
 , initial_printing_temperature(-1)
@@ -56,7 +56,7 @@ double ExtruderPlan::getFanSpeed()
 }
 
 
-GCodePath* GCodePlanner::getLatestPathWithConfig(GCodePathConfig* config, SpaceFillType space_fill_type, float flow, bool spiralize)
+GCodePath* GCodePlanner::getLatestPathWithConfig(const GCodePathConfig* config, SpaceFillType space_fill_type, float flow, bool spiralize)
 {
     std::vector<GCodePath>& paths = extruder_plans.back().paths;
     if (paths.size() > 0 && paths.back().config == config && !paths.back().done && paths.back().flow == flow) // spiralize can only change when a travel path is in between
@@ -81,23 +81,26 @@ void GCodePlanner::forceNewPathStart()
         paths[paths.size()-1].done = true;
 }
 
-GCodePlanner::GCodePlanner(SliceDataStorage& storage, int layer_nr, int z, int layer_thickness, Point last_position, int current_extruder, bool is_inside_mesh, std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder, CombingMode combing_mode, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance)
+GCodePlanner::GCodePlanner(const SliceDataStorage& storage, int layer_nr, int z, int layer_thickness, PlanningState last_planned_state, const std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder, CombingMode combing_mode, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance)
 : storage(storage)
+, configs_storage(storage, layer_nr, layer_thickness)
 , layer_nr(layer_nr)
 , is_initial_layer(layer_nr == 0 - Raft::getTotalExtraLayers(storage))
 , z(z)
 , layer_thickness(layer_thickness)
-, start_position(last_position)
-, lastPosition(last_position)
-, last_extruder_previous_layer(current_extruder)
-, last_planned_extruder_setting_base(storage.meshgroup->getExtruderTrain(current_extruder))
+, start_position(last_planned_state.last_position)
+, lastPosition(last_planned_state.last_position)
+, has_prime_tower_planned(false)
+, last_extruder_previous_layer(last_planned_state.current_extruder)
+, last_planned_extruder_setting_base(storage.meshgroup->getExtruderTrain(last_planned_state.current_extruder))
 , comb_boundary_inside(computeCombBoundaryInside(combing_mode))
 , fan_speed_layer_time_settings_per_extruder(fan_speed_layer_time_settings_per_extruder)
 {
+    int current_extruder = last_planned_state.current_extruder;
     extruder_plans.reserve(storage.meshgroup->getExtruderCount());
     extruder_plans.emplace_back(current_extruder, start_position, layer_nr, is_initial_layer, layer_thickness, fan_speed_layer_time_settings_per_extruder[current_extruder], storage.retraction_config_per_extruder[current_extruder]);
     comb = nullptr;
-    was_inside = is_inside_mesh; 
+    was_inside = last_planned_state.is_inside_mesh_layer_part;
     is_inside = false; // assumes the next move will not be to inside a layer part (overwritten just before going into a layer part)
     if (combing_mode != CombingMode::OFF)
     {
@@ -139,12 +142,12 @@ Polygons GCodePlanner::computeCombBoundaryInside(CombingMode combing_mode)
     else 
     {
         Polygons comb_boundary;
-        for (SliceMeshStorage& mesh : storage.meshes)
+        for (const SliceMeshStorage& mesh : storage.meshes)
         {
-            SliceLayer& layer = mesh.layers[layer_nr];
+            const SliceLayer& layer = mesh.layers[layer_nr];
             if (mesh.getSettingAsCombingMode("retraction_combing") == CombingMode::NO_SKIN)
             {
-                for (SliceLayerPart& part : layer.parts)
+                for (const SliceLayerPart& part : layer.parts)
                 {
                     comb_boundary.add(part.infill_area);
                 }
@@ -241,12 +244,12 @@ void GCodePlanner::moveInsideCombBoundary(int distance)
 GCodePath& GCodePlanner::addTravel(Point p)
 {
     GCodePath* path = nullptr;
-    GCodePathConfig& travel_config = storage.travel_config_per_extruder[getExtruder()];
-    RetractionConfig& retraction_config = storage.retraction_config_per_extruder[getExtruder()];
+    const GCodePathConfig& travel_config = configs_storage.travel_config_per_extruder[getExtruder()];
+    const RetractionConfig& retraction_config = storage.retraction_config_per_extruder[getExtruder()];
     
     bool combed = false;
 
-    SettingsBaseVirtual* extr = getLastPlannedExtruderTrainSettings();
+    const SettingsBaseVirtual* extr = getLastPlannedExtruderTrainSettings();
 
     const bool perform_z_hops = extr->getSettingBoolean("retraction_hop_enabled");
 
@@ -333,7 +336,7 @@ GCodePath& GCodePlanner::addTravel_simple(Point p, GCodePath* path)
 {
     if (path == nullptr)
     {
-        path = getLatestPathWithConfig(&storage.travel_config_per_extruder[getExtruder()], SpaceFillType::None);
+        path = getLatestPathWithConfig(&configs_storage.travel_config_per_extruder[getExtruder()], SpaceFillType::None);
     }
     path->points.push_back(p);
     lastPosition = p;
@@ -349,13 +352,13 @@ void GCodePlanner::planPrime()
     forceNewPathStart();
 }
 
-void GCodePlanner::addExtrusionMove(Point p, GCodePathConfig* config, SpaceFillType space_fill_type, float flow, bool spiralize)
+void GCodePlanner::addExtrusionMove(Point p, const GCodePathConfig* config, SpaceFillType space_fill_type, float flow, bool spiralize)
 {
     getLatestPathWithConfig(config, space_fill_type, flow, spiralize)->points.push_back(p);
     lastPosition = p;
 }
 
-void GCodePlanner::addPolygon(PolygonRef polygon, int start_idx, GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation, coord_t wall_0_wipe_dist, bool spiralize)
+void GCodePlanner::addPolygon(ConstPolygonRef polygon, int start_idx, const GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation, coord_t wall_0_wipe_dist, bool spiralize)
 {
     Point p0 = polygon[start_idx];
     addTravel(p0);
@@ -368,7 +371,7 @@ void GCodePlanner::addPolygon(PolygonRef polygon, int start_idx, GCodePathConfig
     }
     if (polygon.size() > 2)
     {
-        Point& p1 = polygon[start_idx];
+        const Point& p1 = polygon[start_idx];
         float flow = (wall_overlap_computation)? wall_overlap_computation->getFlow(p0, p1) : 1.0;
         addExtrusionMove(p1, config, SpaceFillType::Polygons, flow, spiralize);
 
@@ -403,7 +406,7 @@ void GCodePlanner::addPolygon(PolygonRef polygon, int start_idx, GCodePathConfig
     }
 }
 
-void GCodePlanner::addPolygonsByOptimizer(Polygons& polygons, GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation, EZSeamType z_seam_type, Point z_seam_pos, coord_t wall_0_wipe_dist, bool spiralize)
+void GCodePlanner::addPolygonsByOptimizer(const Polygons& polygons, const GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation, EZSeamType z_seam_type, Point z_seam_pos, coord_t wall_0_wipe_dist, bool spiralize)
 {
     if (polygons.size() == 0)
     {
@@ -420,7 +423,7 @@ void GCodePlanner::addPolygonsByOptimizer(Polygons& polygons, GCodePathConfig* c
         addPolygon(polygons[poly_idx], orderOptimizer.polyStart[poly_idx], config, wall_overlap_computation, wall_0_wipe_dist, spiralize);
     }
 }
-void GCodePlanner::addLinesByOptimizer(Polygons& polygons, GCodePathConfig* config, SpaceFillType space_fill_type, int wipe_dist)
+void GCodePlanner::addLinesByOptimizer(const Polygons& polygons, const GCodePathConfig* config, SpaceFillType space_fill_type, int wipe_dist)
 {
     LineOrderOptimizer orderOptimizer(lastPosition);
     for (unsigned int line_idx = 0; line_idx < polygons.size(); line_idx++)
@@ -430,12 +433,12 @@ void GCodePlanner::addLinesByOptimizer(Polygons& polygons, GCodePathConfig* conf
     orderOptimizer.optimize();
     for (int poly_idx : orderOptimizer.polyOrder)
     {
-        PolygonRef polygon = polygons[poly_idx];
+        ConstPolygonRef polygon = polygons[poly_idx];
         int start = orderOptimizer.polyStart[poly_idx];
         int end = 1 - start;
-        Point& p0 = polygon[start];
+        const Point& p0 = polygon[start];
         addTravel(p0);
-        Point& p1 = polygon[end];
+        const Point& p1 = polygon[end];
         addExtrusionMove(p1, config, space_fill_type);
         if (wipe_dist != 0)
         {
@@ -553,7 +556,7 @@ TimeMaterialEstimates ExtruderPlan::computeNaiveTimeEstimates()
 
 void ExtruderPlan::processFanSpeedAndMinimalLayerTime(bool force_minimal_layer_time)
 {
-    FanSpeedLayerTimeSettings& fsml = fan_speed_layer_time_settings;
+    const FanSpeedLayerTimeSettings& fsml = fan_speed_layer_time_settings;
     TimeMaterialEstimates estimates = computeNaiveTimeEstimates();
     totalPrintTime = estimates.getTotalTime();
     if (force_minimal_layer_time)
@@ -636,8 +639,6 @@ void GCodePlanner::processFanSpeedAndMinimalLayerTime()
 
 void GCodePlanner::writeGCode(GCodeExport& gcode)
 {
-    completeConfigs();
-    
     CommandSocket::setLayerForSend(layer_nr);
     CommandSocket::setSendCurrentPosition( gcode.getPositionXY() );
     gcode.setLayerNr(layer_nr);
@@ -653,7 +654,7 @@ void GCodePlanner::writeGCode(GCodeExport& gcode)
     gcode.setZ(z);
     
     
-    GCodePathConfig* last_extrusion_config = nullptr; // used to check whether we need to insert a TYPE comment in the gcode.
+    const GCodePathConfig* last_extrusion_config = nullptr; // used to check whether we need to insert a TYPE comment in the gcode.
 
     int extruder = gcode.getExtruderNr();
     bool acceleration_enabled = storage.getSettingBoolean("acceleration_enabled");
@@ -662,7 +663,7 @@ void GCodePlanner::writeGCode(GCodeExport& gcode)
     for(unsigned int extruder_plan_idx = 0; extruder_plan_idx < extruder_plans.size(); extruder_plan_idx++)
     {
         ExtruderPlan& extruder_plan = extruder_plans[extruder_plan_idx];
-        RetractionConfig& retraction_config = storage.retraction_config_per_extruder[extruder_plan.extruder];
+        const RetractionConfig& retraction_config = storage.retraction_config_per_extruder[extruder_plan.extruder];
 
         if (extruder != extruder_plan.extruder)
         {
@@ -764,7 +765,7 @@ void GCodePlanner::writeGCode(GCodeExport& gcode)
             else
                 speed *= extruder_plan.getExtrudeSpeedFactor();
 
-            if (MergeInfillLines(gcode, layer_nr, paths, extruder_plan, storage.travel_config_per_extruder[extruder], nozzle_size, speed_equalize_flow_enabled, speed_equalize_flow_max).mergeInfillLines(path_idx)) // !! has effect on path_idx !!
+            if (MergeInfillLines(gcode, layer_nr, paths, extruder_plan, configs_storage.travel_config_per_extruder[extruder], nozzle_size, speed_equalize_flow_enabled, speed_equalize_flow_max).mergeInfillLines(path_idx)) // !! has effect on path_idx !!
             { // !! has effect on path_idx !!
                 // works when path_idx is the index of the travel move BEFORE the infill lines to be merged
                 continue;
@@ -787,7 +788,7 @@ void GCodePlanner::writeGCode(GCodeExport& gcode)
             bool spiralize = path.spiralize;
             if (!spiralize) // normal (extrusion) move (with coasting
             {
-                CoastingConfig& coasting_config = storage.coasting_config[extruder];
+                const CoastingConfig& coasting_config = storage.coasting_config[extruder];
                 bool coasting = coasting_config.coasting_enable; 
                 if (coasting)
                 {
@@ -858,15 +859,15 @@ void GCodePlanner::writeGCode(GCodeExport& gcode)
         if (train->getSettingBoolean("cool_lift_head") && extruder_plan.extraTime > 0.0)
         {
             gcode.writeComment("Small layer, adding delay");
-            RetractionConfig& retraction_config = storage.retraction_config_per_extruder[gcode.getExtruderNr()];
+            const RetractionConfig& retraction_config = storage.retraction_config_per_extruder[gcode.getExtruderNr()];
             gcode.writeRetraction(retraction_config);
             if (extruder_plan_idx == extruder_plans.size() - 1 || !train->getSettingBoolean("machine_extruder_end_pos_abs"))
             { // only move the head if it's the last extruder plan; otherwise it's already at the switching bay area 
                 // or do it anyway when we switch extruder in-place
                 gcode.setZ(gcode.getPositionZ() + MM2INT(3.0));
-                gcode.writeMove(gcode.getPositionXY(), storage.travel_config_per_extruder[extruder].getSpeed(), 0);
+                gcode.writeMove(gcode.getPositionXY(), configs_storage.travel_config_per_extruder[extruder].getSpeed(), 0);
                 // TODO: is this safe?! wouldn't the head move into the sides then?!
-                gcode.writeMove(gcode.getPositionXY() - Point(-MM2INT(20.0), 0), storage.travel_config_per_extruder[extruder].getSpeed(), 0);
+                gcode.writeMove(gcode.getPositionXY() - Point(-MM2INT(20.0), 0), configs_storage.travel_config_per_extruder[extruder].getSpeed(), 0);
             }
             gcode.writeDelay(extruder_plan.extraTime);
         }
@@ -886,106 +887,6 @@ void GCodePlanner::overrideFanSpeeds(double speed)
 }
 
 
-void GCodePlanner::completeConfigs()
-{
-    storage.support_config.setLayerHeight(layer_thickness);
-    storage.support_skin_config.setLayerHeight(layer_thickness);
-    
-    for (SliceMeshStorage& mesh : storage.meshes)
-    {
-        mesh.inset0_config.setLayerHeight(layer_thickness);
-
-        mesh.insetX_config.setLayerHeight(layer_thickness);
-        mesh.skin_config.setLayerHeight(layer_thickness);
-        for(unsigned int idx=0; idx<MAX_INFILL_COMBINE; idx++)
-        {
-            mesh.infill_config[idx].setLayerHeight(layer_thickness);
-        }
-    }
-    
-    storage.primeTower.setConfigs(storage.meshgroup, layer_thickness);
-    
-    processInitialLayersSpeedup();
-}
-
-
-void GCodePlanner::processInitialLayersSpeedup()
-{
-    int initial_speedup_layers = storage.getSettingAsCount("speed_slowdown_layers");
-    if (layer_nr >= 0 && layer_nr < initial_speedup_layers)
-    {
-        GCodePathConfig::BasicConfig initial_layer_speed_config;
-        int extruder_nr_support_infill = storage.getSettingAsIndex((layer_nr == 0)? "support_extruder_nr_layer_0" : "support_infill_extruder_nr");
-        initial_layer_speed_config.speed = storage.meshgroup->getExtruderTrain(extruder_nr_support_infill)->getSettingInMillimetersPerSecond("speed_print_layer_0");
-        initial_layer_speed_config.acceleration = storage.meshgroup->getExtruderTrain(extruder_nr_support_infill)->getSettingInMillimetersPerSecond("acceleration_print_layer_0");
-        initial_layer_speed_config.jerk = storage.meshgroup->getExtruderTrain(extruder_nr_support_infill)->getSettingInMillimetersPerSecond("jerk_print_layer_0");
-
-        //Support (global).
-        storage.support_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-
-        //Support roof (global).
-        int extruder_nr_support_skin = storage.getSettingAsIndex("support_interface_extruder_nr");
-        initial_layer_speed_config.speed = storage.meshgroup->getExtruderTrain(extruder_nr_support_skin)->getSettingInMillimetersPerSecond("speed_print_layer_0");
-        initial_layer_speed_config.acceleration = storage.meshgroup->getExtruderTrain(extruder_nr_support_skin)->getSettingInMillimetersPerSecond("acceleration_print_layer_0");
-        initial_layer_speed_config.jerk = storage.meshgroup->getExtruderTrain(extruder_nr_support_skin)->getSettingInMillimetersPerSecond("jerk_print_layer_0");
-        storage.support_skin_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-
-        for (int extruder_nr = 0; extruder_nr < storage.meshgroup->getExtruderCount(); ++extruder_nr)
-        {
-            const ExtruderTrain* extruder_train = storage.meshgroup->getExtruderTrain(extruder_nr);
-            initial_layer_speed_config.speed = extruder_train->getSettingInMillimetersPerSecond("speed_travel_layer_0");
-            initial_layer_speed_config.acceleration = extruder_train->getSettingInMillimetersPerSecond("acceleration_travel_layer_0");
-            initial_layer_speed_config.jerk = extruder_train->getSettingInMillimetersPerSecond("jerk_travel_layer_0");
-
-            //Travel speed (per extruder).
-            storage.travel_config_per_extruder[extruder_nr].smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-        }
-
-        for (SliceMeshStorage& mesh : storage.meshes)
-        {
-            initial_layer_speed_config.speed = mesh.getSettingInMillimetersPerSecond("speed_print_layer_0");
-            initial_layer_speed_config.acceleration = mesh.getSettingInMillimetersPerSecond("acceleration_print_layer_0");
-            initial_layer_speed_config.jerk = mesh.getSettingInMillimetersPerSecond("jerk_print_layer_0");
-
-            //Outer wall speed (per mesh).
-            mesh.inset0_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-
-            //Inner wall speed (per mesh).
-            mesh.insetX_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-
-            //Skin speed (per mesh).
-            mesh.skin_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-
-            for (unsigned int idx = 0; idx < MAX_INFILL_COMBINE; idx++)
-            {
-                //Infill speed (per combine part per mesh).
-                mesh.infill_config[idx].smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layers);
-            }
-        }
-    }
-    else if (layer_nr == initial_speedup_layers) //At the topmost layer of the gradient, reset all speeds to the typical speeds.
-    {
-        storage.support_config.setSpeedIconic();
-        storage.support_skin_config.setSpeedIconic();
-        for (int extruder_nr = 0; extruder_nr < storage.meshgroup->getExtruderCount(); ++extruder_nr)
-        {
-            storage.travel_config_per_extruder[extruder_nr].setSpeedIconic();
-        }
-        for (SliceMeshStorage& mesh : storage.meshes)
-        {
-            mesh.inset0_config.setSpeedIconic();
-            mesh.insetX_config.setSpeedIconic();
-            mesh.skin_config.setSpeedIconic();
-            for (unsigned int idx = 0; idx < MAX_INFILL_COMBINE; idx++)
-            {
-                mesh.infill_config[idx].setSpeedIconic();
-            }
-        }
-    }
-}
-
-
-
 bool GCodePlanner::makeRetractSwitchRetract(GCodeExport& gcode, unsigned int extruder_plan_idx, unsigned int path_idx)
 {
     std::vector<GCodePath>& paths = extruder_plans[extruder_plan_idx].paths;

src/gcodePlanner.h

@@ -16,6 +16,7 @@
 #include "FanSpeedLayerTime.h"
 #include "SpaceFillType.h"
 #include "GCodePathConfig.h"
+#include "settings/PathConfigStorage.h"
 
 #include "utils/optional.h"
 
@@ -57,7 +58,7 @@ public:
      * \param extruder The extruder number for which this object is a plan.
      * \param start_position The position the head is when this extruder plan starts
      */
-    ExtruderPlan(int extruder, Point start_position, int layer_nr, bool is_initial_layer, int layer_thickness, FanSpeedLayerTimeSettings& fan_speed_layer_time_settings, const RetractionConfig& retraction_config);
+    ExtruderPlan(int extruder, Point start_position, int layer_nr, bool is_initial_layer, int layer_thickness, const FanSpeedLayerTimeSettings& fan_speed_layer_time_settings, const RetractionConfig& retraction_config);
 
     /*!
      * Add a new Insert, constructed with the given arguments
@@ -165,7 +166,7 @@ protected:
 
     int layer_thickness; //!< The thickness of this layer in Z-direction
 
-    FanSpeedLayerTimeSettings& fan_speed_layer_time_settings; //!< The fan speed and layer time settings used to limit this extruder plan
+    const FanSpeedLayerTimeSettings& fan_speed_layer_time_settings; //!< The fan speed and layer time settings used to limit this extruder plan
 
     const RetractionConfig& retraction_config; //!< The retraction settings for the extruder of this plan
 
@@ -215,9 +216,25 @@ class GCodePlanner : public NoCopy
 {
     friend class LayerPlanBuffer;
     friend class GCodePlannerTest;
+public:
+    /*!
+     * The state which is passed along between layer plans.
+     * This is what a \ref GCodePlanner delivers to further computation in \ref FffGcodeWriter
+     * This is the state which is currently planned, not which is written to gcode.
+     */
+    struct PlanningState
+    {
+        Point last_position; //!< The position of the head before planning the next layer
+        int current_extruder; //!< The extruder train in use before planning the next layer
+        bool is_inside_mesh_layer_part; //!< Whether the last position was inside a layer part (used in combing)
+    };
 private:
-    SliceDataStorage& storage; //!< The polygon data obtained from FffPolygonProcessor
+    const SliceDataStorage& storage; //!< The polygon data obtained from FffPolygonProcessor
 
+public:
+    const PathConfigStorage configs_storage; //!< The line configs for this layer for each feature type
+
+private:
     int layer_nr; //!< The layer number of this layer plan
     int is_initial_layer; //!< Whether this is the first layer (which might be raft)
     
@@ -227,7 +244,9 @@ private:
     
     Point start_position;
     Point lastPosition;
-    
+
+    bool has_prime_tower_planned;
+
     std::vector<ExtruderPlan> extruder_plans; //!< should always contain at least one ExtruderPlan
 
     int last_extruder_previous_layer; //!< The last id of the extruder with which was printed in the previous layer
@@ -238,7 +257,7 @@ private:
     Comb* comb;
 
 
-    std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder;
+    const std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder;
     
 private:
     /*!
@@ -251,7 +270,7 @@ private:
      * \param spiralize Whether to gradually increase the z while printing. (Note that this path may be part of a sequence of spiralized paths, forming one polygon)
      * \return A path with the given config which is now the last path in GCodePlanner::paths
      */
-    GCodePath* getLatestPathWithConfig(GCodePathConfig* config, SpaceFillType space_fill_type, float flow = 1.0, bool spiralize = false);
+    GCodePath* getLatestPathWithConfig(const GCodePathConfig* config, SpaceFillType space_fill_type, float flow = 1.0, bool spiralize = false);
 
 public:
     /*!
@@ -274,7 +293,7 @@ public:
      * \param last_position The position of the head at the start of this gcode layer
      * \param combing_mode Whether combing is enabled and full or within infill only.
      */
-    GCodePlanner(SliceDataStorage& storage, int layer_nr, int z, int layer_height, Point last_position, int current_extruder, bool is_inside_mesh, std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder, CombingMode combing_mode, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance);
+    GCodePlanner(const SliceDataStorage& storage, int layer_nr, int z, int layer_height, PlanningState last_planned_state, const std::vector<FanSpeedLayerTimeSettings>& fan_speed_layer_time_settings_per_extruder, CombingMode combing_mode, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance);
     ~GCodePlanner();
 
     void overrideFanSpeeds(double speed);
@@ -292,12 +311,21 @@ private:
     Polygons computeCombBoundaryInside(CombingMode combing_mode);
 
 public:
-    int getLayerNr()
+    int getLayerNr() const
     {
         return layer_nr;
     }
-    
-    Point getLastPosition()
+
+    PlanningState getPlanningState() const
+    {
+        PlanningState ret;
+        ret.last_position = lastPosition;
+        ret.current_extruder = getExtruder();
+        ret.is_inside_mesh_layer_part = was_inside;
+        return ret;
+    }
+
+    Point getLastPosition() const
     {
         return lastPosition;
     }
@@ -305,14 +333,25 @@ public:
     /*!
      * return whether the last position planned was inside the mesh (used in combing)
      */
-    bool getIsInsideMesh()
+    bool getIsInsideMesh() const
     {
         return was_inside;
     }
+
+    bool getPrimeTowerIsPlanned() const
+    {
+        return has_prime_tower_planned;
+    }
+
+    void setPrimeTowerIsPlanned()
+    {
+        has_prime_tower_planned = true;
+    }
+
     /*!
      * send a line segment through the command socket from the previous point to the given point \p to
      */
-    void sendLineTo(PrintFeatureType print_feature_type, Point to, int line_width)
+    void sendLineTo(PrintFeatureType print_feature_type, Point to, int line_width) const
     {
         CommandSocket::sendLineTo(print_feature_type, to, line_width);
     }
@@ -336,7 +375,7 @@ public:
     /*!
      * Get the last planned extruder.
      */
-    int getExtruder()
+    int getExtruder() const
     {
         return extruder_plans.back().extruder;
     }
@@ -377,7 +416,7 @@ public:
      * \param flow A modifier of the extrusion width which would follow from the \p config
      * \param spiralize Whether to gradually increase the z while printing. (Note that this path may be part of a sequence of spiralized paths, forming one polygon)
      */
-    void addExtrusionMove(Point p, GCodePathConfig* config, SpaceFillType space_fill_type, float flow = 1.0, bool spiralize = false);
+    void addExtrusionMove(Point p, const GCodePathConfig* config, SpaceFillType space_fill_type, float flow = 1.0, bool spiralize = false);
 
     /*!
      * Add polygon to the gcode starting at vertex \p startIdx
@@ -388,7 +427,7 @@ public:
      * \param wall_0_wipe_dist The distance to travel along the polygon after it has been laid down, in order to wipe the start and end of the wall together
      * \param spiralize Whether to gradually increase the z height from the normal layer height to the height of the next layer over this polygon
      */
-    void addPolygon(PolygonRef polygon, int startIdx, GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation = nullptr, coord_t wall_0_wipe_dist = 0, bool spiralize = false);
+    void addPolygon(ConstPolygonRef polygon, int startIdx, const GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation = nullptr, coord_t wall_0_wipe_dist = 0, bool spiralize = false);
 
     /*!
      * Add polygons to the gcode with optimized order.
@@ -407,7 +446,7 @@ public:
      * \param wall_0_wipe_dist The distance to travel along each polygon after it has been laid down, in order to wipe the start and end of the wall together
      * \param spiralize Whether to gradually increase the z height from the normal layer height to the height of the next layer over each polygon printed
      */
-    void addPolygonsByOptimizer(Polygons& polygons, GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation = nullptr, EZSeamType z_seam_type = EZSeamType::SHORTEST, Point z_seam_pos = Point(0, 0), coord_t wall_0_wipe_dist = 0, bool spiralize = false);
+    void addPolygonsByOptimizer(const Polygons& polygons, const GCodePathConfig* config, WallOverlapComputation* wall_overlap_computation = nullptr, EZSeamType z_seam_type = EZSeamType::SHORTEST, Point z_seam_pos = Point(0, 0), coord_t wall_0_wipe_dist = 0, bool spiralize = false);
 
     /*!
      * Add lines to the gcode with optimized order.
@@ -416,7 +455,7 @@ public:
      * \param space_fill_type The type of space filling used to generate the line segments (should be either Lines or PolyLines!)
      * \param wipe_dist (optional) the distance wiped without extruding after laying down a line.
      */
-    void addLinesByOptimizer(Polygons& polygons, GCodePathConfig* config, SpaceFillType space_fill_type, int wipe_dist = 0);
+    void addLinesByOptimizer(const Polygons& polygons, const GCodePathConfig* config, SpaceFillType space_fill_type, int wipe_dist = 0);
 
     /*!
      * Compute naive time estimates (without accounting for slow down at corners etc.) and naive material estimates (without accounting for MergeInfillLines)
@@ -434,20 +473,7 @@ public:
      * \param gcode The gcode to write the planned paths to
      */
     void writeGCode(GCodeExport& gcode);
-    
-    /*!
-     * Complete all GcodePathConfigs by
-     * - altering speeds to conform to speed_print_layer_0 and
-     *   speed_travel_layer_0
-     * - setting the layer_height (and thereby computing the extrusionMM3perMM)
-     */
-    void completeConfigs();
-    
-    /*!
-     * Interpolate between the initial layer speeds and the eventual speeds.
-     */
-    void processInitialLayersSpeedup();
-    
+
     /*!
      * Whether the current retracted path is to be an extruder switch retraction.
      * This function is used to avoid a G10 S1 after a G10.

src/infill.cpp

@@ -17,7 +17,7 @@ int Infill::computeScanSegmentIdx(int x, int line_width)
     return x / line_width;
 }
 
-void Infill::generate(Polygons& result_polygons, Polygons& result_lines, SliceMeshStorage* mesh)
+void Infill::generate(Polygons& result_polygons, Polygons& result_lines, const SliceMeshStorage* mesh)
 {
     if (in_outline.size() == 0) return;
     if (line_distance == 0) return;
@@ -144,7 +144,7 @@ void Infill::generateTriangleInfill(Polygons& result)
     generateLineInfill(result, line_distance, fill_angle + 120, 0);
 }
 
-void Infill::generateCubicSubDivInfill(Polygons& result, SliceMeshStorage& mesh)
+void Infill::generateCubicSubDivInfill(Polygons& result, const SliceMeshStorage& mesh)
 {
     Polygons uncropped;
     mesh.base_subdiv_cube->generateSubdivisionLines(z, uncropped);

src/infill.h

@@ -80,7 +80,7 @@ public:
      * \param result_lines (output) The resulting line segments (from linear infill types)
      * \param mesh The mesh for which to geenrate infill (should only be used for non-helper objects)
      */
-    void generate(Polygons& result_polygons, Polygons& result_lines, SliceMeshStorage* mesh = nullptr);
+    void generate(Polygons& result_polygons, Polygons& result_lines, const SliceMeshStorage* mesh = nullptr);
 
 private:
     /*!
@@ -148,8 +148,8 @@ private:
      * \param[out] result The resulting lines
      * \param[in] mesh Where the Cubic Subdivision Infill precomputation is stored
      */
-    void generateCubicSubDivInfill(Polygons& result, SliceMeshStorage& mesh);
-    
+    void generateCubicSubDivInfill(Polygons& result, const SliceMeshStorage& mesh);
+
     /*!
      * Convert a mapping from scanline to line_segment-scanline-intersections (\p cut_list) into line segments, using the even-odd rule
      * \param result (output) The resulting lines

src/infill/SubDivCube.cpp

@@ -186,15 +186,15 @@ SubDivCube::SubDivCube(SliceMeshStorage& mesh, Point3& center, unsigned int dept
 bool SubDivCube::isValidSubdivision(SliceMeshStorage& mesh, Point3& center, int64_t radius)
 {
     int64_t distance2;
-    long int sphere_slice_radius2;//!< squared radius of bounding sphere slice on target layer
+    coord_t sphere_slice_radius2;//!< squared radius of bounding sphere slice on target layer
     bool inside_somewhere = false;
     bool outside_somewhere = false;
     int inside;
     double part_dist;//what percentage of the radius the target layer is away from the center along the z axis. 0 - 1
-    const long int layer_height = mesh.getSettingInMicrons("layer_height");
-    long int bottom_layer = (center.z - radius) / layer_height;
-    long int top_layer = (center.z + radius) / layer_height;
-    for (long int test_layer = bottom_layer; test_layer <= top_layer; test_layer += 3) // steps of three. Low-hanging speed gain.
+    const coord_t layer_height = mesh.getSettingInMicrons("layer_height");
+    int bottom_layer = (center.z - radius) / layer_height;
+    int top_layer = (center.z + radius) / layer_height;
+    for (int test_layer = bottom_layer; test_layer <= top_layer; test_layer += 3) // steps of three. Low-hanging speed gain.
     {
         part_dist = (double)(test_layer * layer_height - center.z) / radius;
         sphere_slice_radius2 = radius * radius * (1.0 - (part_dist * part_dist));
@@ -221,9 +221,9 @@ bool SubDivCube::isValidSubdivision(SliceMeshStorage& mesh, Point3& center, int6
     return false;
 }
 
-int SubDivCube::distanceFromPointToMesh(SliceMeshStorage& mesh, long int layer_nr, Point& location, int64_t* distance2)
+int SubDivCube::distanceFromPointToMesh(SliceMeshStorage& mesh, int layer_nr, Point& location, int64_t* distance2)
 {
-    if (layer_nr < 0 || (unsigned long int)layer_nr >= mesh.layers.size()) //!< this layer is outside of valid range
+    if (layer_nr < 0 || (unsigned int)layer_nr >= mesh.layers.size()) //!< this layer is outside of valid range
     {
         return 2;
     }

src/infill/SubDivCube.h

@@ -74,7 +74,7 @@ private:
      * \param[out] distance2 the squared distance to the infill border
      * \return Code 0: outside, 1: inside, 2: boundary does not exist at specified layer
      */
-    static int distanceFromPointToMesh(SliceMeshStorage& mesh, long int layer_nr, Point& location, int64_t* distance2);
+    static int distanceFromPointToMesh(SliceMeshStorage& mesh, int layer_nr, Point& location, int64_t* distance2);
 
     /*!
      * Adds the defined line to the specified polygons. It assumes that the specified polygons are all parallel lines. Combines line segments with touching ends closer than epsilon.

src/layerPart.cpp

@@ -44,7 +44,10 @@ void createLayerWithParts(SliceLayer& storageLayer, SlicerLayer* layer, bool uni
 }
 void createLayerParts(SliceMeshStorage& mesh, Slicer* slicer, bool union_layers, bool union_all_remove_holes)
 {
-    for(unsigned int layer_nr = 0; layer_nr < slicer->layers.size(); layer_nr++)
+    const auto total_layers = slicer->layers.size();
+    assert(mesh.layers.size() == total_layers);
+#pragma omp parallel for default(none) shared(mesh,slicer) firstprivate(union_layers,union_all_remove_holes) schedule(dynamic)
+    for(unsigned int layer_nr = 0; layer_nr < total_layers; layer_nr++)
     {
         mesh.layers[layer_nr].sliceZ = slicer->layers[layer_nr].z;
         mesh.layers[layer_nr].printZ = slicer->layers[layer_nr].z;

src/main.cpp

@@ -20,6 +20,8 @@
 
 #include "settings/SettingsToGV.h"
 
+#include <omp.h> // omp_get_num_threads
+
 namespace cura
 {
     
@@ -328,7 +330,19 @@ int main(int argc, char **argv)
         print_usage();
         exit(1);
     }
-    
+
+#pragma omp parallel
+    {
+#pragma omp master
+        {
+#ifdef _OPENMP
+            log("OpenMP multithreading enabled, likely number of threads to be used: %u\n", omp_get_num_threads());
+#else
+            log("OpenMP multithreading disabled\n");
+#endif
+        }
+    }
+
     if (stringcasecompare(argv[1], "connect") == 0)
     {
         connect(argc, argv);

src/pathOrderOptimizer.cpp

@@ -16,7 +16,7 @@ void PathOrderOptimizer::optimize()
     bool picked[polygons.size()];
     memset(picked, false, sizeof(bool) * polygons.size());/// initialized as falses
     
-    for (PolygonRef poly : polygons) /// find closest point to initial starting point within each polygon +initialize picked
+    for (ConstPolygonRef poly : polygons) /// find closest point to initial starting point within each polygon +initialize picked
     {
         int best = -1;
         float bestDist = std::numeric_limits<float>::infinity();
@@ -102,15 +102,15 @@ int PathOrderOptimizer::getPolyStart(Point prev_point, int poly_idx)
 
 int PathOrderOptimizer::getClosestPointInPolygon(Point prev_point, int poly_idx)
 {
-    PolygonRef poly = polygons[poly_idx];
+    ConstPolygonRef poly = polygons[poly_idx];
 
     int best_point_idx = -1;
     float best_point_score = std::numeric_limits<float>::infinity();
     Point p0 = poly.back();
     for (unsigned int point_idx = 0; point_idx < poly.size(); point_idx++)
     {
-        Point& p1 = poly[point_idx];
-        Point& p2 = poly[(point_idx + 1) % poly.size()];
+        const Point& p1 = poly[point_idx];
+        const Point& p2 = poly[(point_idx + 1) % poly.size()];
         int64_t dist = vSize2(p1 - prev_point);
         float is_on_inside_corner_score = -LinearAlg2D::getAngleLeft(p0, p1, p2) / M_PI * 5000 * 5000; // prefer inside corners
         // this score is in the order of 5 mm
@@ -143,7 +143,7 @@ void LineOrderOptimizer::optimize()
     {
         int best_point_idx = -1;
         float best_point_dist = std::numeric_limits<float>::infinity();
-        PolygonRef poly = polygons[poly_idx];
+        ConstPolygonRef poly = polygons[poly_idx];
         for (unsigned int point_idx = 0; point_idx < poly.size(); point_idx++) /// get closest point from polygon
         {
             float dist = vSize2f(poly[point_idx] - startPoint);
@@ -199,13 +199,13 @@ void LineOrderOptimizer::optimize()
 
         if (best_line_idx > -1) /// should always be true; we should have been able to identify the best next polygon
         {
-            PolygonRef best_line = polygons[best_line_idx];
+            ConstPolygonRef best_line = polygons[best_line_idx];
             assert(best_line.size() == 2);
 
             int line_start_point_idx = polyStart[best_line_idx];
             int line_end_point_idx = line_start_point_idx * -1 + 1; /// 1 -> 0 , 0 -> 1
-            Point& line_start = best_line[line_start_point_idx];
-            Point& line_end = best_line[line_end_point_idx];
+            const Point& line_start = best_line[line_start_point_idx];
+            const Point& line_end = best_line[line_end_point_idx];
             prev_point = line_end;
             incoming_perpundicular_normal = turn90CCW(normal(line_end - line_start, 1000));
 
@@ -221,8 +221,8 @@ void LineOrderOptimizer::optimize()
 
 inline void LineOrderOptimizer::updateBestLine(unsigned int poly_idx, int& best, float& best_score, Point prev_point, Point incoming_perpundicular_normal)
 {
-    Point& p0 = polygons[poly_idx][0];
-    Point& p1 = polygons[poly_idx][1];
+    const Point& p0 = polygons[poly_idx][0];
+    const Point& p1 = polygons[poly_idx][1];
     float dot_score = getAngleScore(incoming_perpundicular_normal, p0, p1);
     { /// check distance to first point on line (0)
         float score = vSize2f(p0 - prev_point) + dot_score; // prefer 90 degree corners

src/pathOrderOptimizer.h

@@ -20,7 +20,7 @@ public:
     EZSeamType type;
     Point startPoint; //!< A location near the prefered start location
     Point z_seam_pos; //!< The position near where to create the z_seam (if \ref PathOrderOptimizer::type == 'back')
-    std::vector<PolygonRef> polygons; //!< the parts of the layer (in arbitrary order)
+    std::vector<ConstPolygonRef> polygons; //!< the parts of the layer (in arbitrary order)
     std::vector<int> polyStart; //!< polygons[i][polyStart[i]] = point of polygon i which is to be the starting point in printing the polygon
     std::vector<int> polyOrder; //!< the optimized order as indices in #polygons
 
@@ -33,10 +33,15 @@ public:
 
     void addPolygon(PolygonRef polygon)
     {
-        this->polygons.push_back(polygon);
+        this->polygons.emplace_back(polygon);
     }
 
-    void addPolygons(Polygons& polygons)
+    void addPolygon(ConstPolygonRef polygon)
+    {
+        this->polygons.emplace_back(polygon);
+    }
+
+    void addPolygons(const Polygons& polygons)
     {
         for(unsigned int i=0;i<polygons.size(); i++)
             this->polygons.push_back(polygons[i]);
@@ -66,7 +71,7 @@ class LineOrderOptimizer
 {
 public:
     Point startPoint; //!< The location of the nozzle before starting to print the current layer
-    std::vector<PolygonRef> polygons; //!< the parts of the layer (in arbitrary order)
+    std::vector<ConstPolygonRef> polygons; //!< the parts of the layer (in arbitrary order)
     std::vector<int> polyStart; //!< polygons[i][polyStart[i]] = point of polygon i which is to be the starting point in printing the polygon
     std::vector<int> polyOrder; //!< the optimized order as indices in #polygons
 
@@ -80,6 +85,11 @@ public:
         this->polygons.push_back(polygon);
     }
 
+    void addPolygon(ConstPolygonRef polygon)
+    {
+        this->polygons.push_back(polygon);
+    }
+
     void addPolygons(Polygons& polygons)
     {
         for(unsigned int i=0;i<polygons.size(); i++)

src/pathPlanning/Comb.cpp

@@ -6,6 +6,7 @@
 #include <unordered_set>
 
 #include "../utils/polygonUtils.h"
+#include "../utils/linearAlg2D.h"
 #include "../utils/PolygonsPointIndex.h"
 #include "../sliceDataStorage.h"
 #include "../utils/SVG.h"
@@ -22,7 +23,7 @@ Polygons& Comb::getBoundaryOutside()
     return *boundary_outside;
 }
   
-Comb::Comb(SliceDataStorage& storage, int layer_nr, Polygons& comb_boundary_inside, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance)
+Comb::Comb(const SliceDataStorage& storage, int layer_nr, const Polygons& comb_boundary_inside, int64_t comb_boundary_offset, bool travel_avoid_other_parts, int64_t travel_avoid_distance)
 : storage(storage)
 , layer_nr(layer_nr)
 , offset_from_outlines(comb_boundary_offset) // between second wall and infill / other walls
@@ -31,7 +32,7 @@ Comb::Comb(SliceDataStorage& storage, int layer_nr, Polygons& comb_boundary_insi
 , offset_from_inside_to_outside(offset_from_outlines + offset_from_outlines_outside)
 , max_crossing_dist2(offset_from_inside_to_outside * offset_from_inside_to_outside * 2) // so max_crossing_dist = offset_from_inside_to_outside * sqrt(2) =approx 1.5 to allow for slightly diagonal crossings and slightly inaccurate crossing computation
 , avoid_other_parts(travel_avoid_other_parts)
-, boundary_inside( comb_boundary_inside )
+, boundary_inside( comb_boundary_inside ) // copy the boundary, because the partsView_inside will reorder the polygons
 , partsView_inside( boundary_inside.splitIntoPartsView() ) // WARNING !! changes the order of boundary_inside !!
 , inside_loc_to_line(PolygonUtils::createLocToLineGrid(boundary_inside, comb_boundary_offset))
 , boundary_outside(
@@ -213,7 +214,7 @@ Comb::Crossing::Crossing(const Point& dest_point, const bool dest_is_inside, con
 {
     if (dest_is_inside)
     {
-        dest_crossing_poly = boundary_inside[dest_part_boundary_crossing_poly_idx]; // initialize with most obvious poly, cause mostly a combing move will move outside the part, rather than inside a hole in the part
+        dest_crossing_poly.emplace(boundary_inside[dest_part_boundary_crossing_poly_idx]); // initialize with most obvious poly, cause mostly a combing move will move outside the part, rather than inside a hole in the part
     }
 }
 
@@ -332,7 +333,7 @@ bool Comb::Crossing::findOutside(const Polygons& outside, const Point close_to,
 }
 
 
-std::shared_ptr<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> Comb::Crossing::findBestCrossing(const Polygons& outside, const PolygonRef from, const Point estimated_start, const Point estimated_end, Comb& comber)
+std::shared_ptr<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> Comb::Crossing::findBestCrossing(const Polygons& outside, ConstPolygonRef from, const Point estimated_start, const Point estimated_end, Comb& comber)
 {
     ClosestPolygonPoint* best_in = nullptr;
     ClosestPolygonPoint* best_out = nullptr;

src/pathPlanning/Comb.h

@@ -48,7 +48,7 @@ private:
         Point in_or_mid; //!< The point on the inside boundary, or in between the inside and outside boundary if the start/end point isn't inside the inside boudary
         Point out; //!< The point on the outside boundary
         PolygonsPart dest_part; //!< The assembled inside-boundary PolygonsPart in which the dest_point lies. (will only be initialized when Crossing::dest_is_inside holds)
-        std::optional<PolygonRef> dest_crossing_poly; //!< The polygon of the part in which dest_point lies, which will be crossed (often will be the outside polygon)
+        std::optional<ConstPolygonRef> dest_crossing_poly; //!< The polygon of the part in which dest_point lies, which will be crossed (often will be the outside polygon)
         const Polygons& boundary_inside; //!< The inside boundary as in \ref Comb::boundary_inside
         const LocToLineGrid* inside_loc_to_line; //!< The loc to line grid \ref Comb::inside_loc_to_line
 
@@ -97,11 +97,11 @@ private:
          * \param comber[in] The combing calculator which has references to the offsets and boundaries to use in combing.
          * \return A pair of which the first is the crossing point on the inside boundary and the second the crossing point on the outside boundary
          */
-        std::shared_ptr<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> findBestCrossing(const Polygons& outside, const PolygonRef from, Point estimated_start, Point estimated_end, Comb& comber);
+        std::shared_ptr<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> findBestCrossing(const Polygons& outside, ConstPolygonRef from, Point estimated_start, Point estimated_end, Comb& comber);
     };
 
 
-    SliceDataStorage& storage; //!< The storage from which to compute the outside boundary, when needed.
+    const SliceDataStorage& storage; //!< The storage from which to compute the outside boundary, when needed.
     const int layer_nr; //!< The layer number for the layer for which to compute the outside boundary, when needed.
     
     const int64_t offset_from_outlines; //!< Offset from the boundary of a part to the comb path. (nozzle width / 2)
@@ -115,8 +115,8 @@ private:
 
     const bool avoid_other_parts; //!< Whether to perform inverse combing a.k.a. avoid parts.
     
-    Polygons& boundary_inside; //!< The boundary within which to comb.
-    PartsView partsView_inside; //!< Structured indices onto boundary_inside which shows which polygons belong to which part. 
+    Polygons boundary_inside; //!< The boundary within which to comb. (Will be reordered by the partsView_inside)
+    const PartsView partsView_inside; //!< Structured indices onto boundary_inside which shows which polygons belong to which part. 
     LocToLineGrid* inside_loc_to_line; //!< The SparsePointGridInclusive mapping locations to line segments of the inner boundary.
     LazyInitialization<Polygons> boundary_outside; //!< The boundary outside of which to stay to avoid collision with other layer parts. This is a pointer cause we only compute it when we move outside the boundary (so not when there is only a single part in the layer)
     LazyInitialization<LocToLineGrid, Comb*, const int64_t> outside_loc_to_line; //!< The SparsePointGridInclusive mapping locations to line segments of the outside boundary.
@@ -153,7 +153,7 @@ public:
      * \param travel_avoid_other_parts Whether to avoid other layer parts when traveling through air.
      * \param travel_avoid_distance The distance by which to avoid other layer parts when traveling through air.
      */
-    Comb(SliceDataStorage& storage, int layer_nr, Polygons& comb_boundary_inside, int64_t offset_from_outlines, bool travel_avoid_other_parts, int64_t travel_avoid_distance);
+    Comb(const SliceDataStorage& storage, int layer_nr, const Polygons& comb_boundary_inside, int64_t offset_from_outlines, bool travel_avoid_other_parts, int64_t travel_avoid_distance);
 
     ~Comb();
 

src/pathPlanning/GCodePath.h

@@ -23,7 +23,7 @@ namespace cura
 class GCodePath
 {
 public:
-    GCodePathConfig* config; //!< The configuration settings of the path.
+    const GCodePathConfig* config; //!< The configuration settings of the path.
     SpaceFillType space_fill_type; //!< The type of space filling of which this path is a part
     float flow; //!< A type-independent flow configuration (used for wall overlap compensation)
     bool retract; //!< Whether the path is a move path preceded by a retraction move; whether the path is a retracted move path. 

src/settings/PathConfigStorage.cpp

@@ -0,0 +1,235 @@
+/** Copyright (C) 2017 Ultimaker - Released under terms of the AGPLv3 License */
+#include "PathConfigStorage.h"
+
+#include "settings.h" // MAX_INFILL_COMBINE
+#include "../sliceDataStorage.h" // SliceDataStorage
+
+
+namespace cura
+{
+
+GCodePathConfig getPerimeterGapConfig(const SliceMeshStorage& mesh, int layer_thickness)
+{
+    // The perimeter gap config follows the skin config, but has a different line width:
+    // wall_line_width_x divided by two because the gaps are between 0 and 1 times the wall line width
+    const int perimeter_gaps_line_width = mesh.getSettingInMicrons("wall_line_width_x") / 2;
+    double perimeter_gaps_speed = mesh.getSettingInMillimetersPerSecond("speed_topbottom");
+    if (mesh.getSettingBoolean("speed_equalize_flow_enabled"))
+    {
+        perimeter_gaps_speed = perimeter_gaps_speed * mesh.getSettingInMicrons("skin_line_width") / perimeter_gaps_line_width;
+    }
+    return GCodePathConfig(
+            PrintFeatureType::Skin
+            , perimeter_gaps_line_width
+            , layer_thickness
+            , mesh.getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{perimeter_gaps_speed, mesh.getSettingInMillimetersPerSecond("acceleration_topbottom"), mesh.getSettingInMillimetersPerSecond("jerk_topbottom")}
+        );
+}
+
+PathConfigStorage::MeshPathConfigs::MeshPathConfigs(const SliceMeshStorage& mesh, int layer_thickness)
+: inset0_config(
+    PrintFeatureType::OuterWall
+    , mesh.getSettingInMicrons("wall_line_width_0")
+    , layer_thickness
+    , mesh.getSettingInPercentage("material_flow")
+    , GCodePathConfig::SpeedDerivatives{mesh.getSettingInMillimetersPerSecond("speed_wall_0"), mesh.getSettingInMillimetersPerSecond("acceleration_wall_0"), mesh.getSettingInMillimetersPerSecond("jerk_wall_0")}
+)
+, insetX_config(
+    PrintFeatureType::InnerWall
+    , mesh.getSettingInMicrons("wall_line_width_x")
+    , layer_thickness
+    , mesh.getSettingInPercentage("material_flow")
+    , GCodePathConfig::SpeedDerivatives{mesh.getSettingInMillimetersPerSecond("speed_wall_x"), mesh.getSettingInMillimetersPerSecond("acceleration_wall_x"), mesh.getSettingInMillimetersPerSecond("jerk_wall_x")}
+)
+, skin_config(
+    PrintFeatureType::Skin
+    , mesh.getSettingInMicrons("skin_line_width")
+    , layer_thickness
+    , mesh.getSettingInPercentage("material_flow")
+    , GCodePathConfig::SpeedDerivatives{mesh.getSettingInMillimetersPerSecond("speed_topbottom"), mesh.getSettingInMillimetersPerSecond("acceleration_topbottom"), mesh.getSettingInMillimetersPerSecond("jerk_topbottom")}
+)
+
+, perimeter_gap_config(getPerimeterGapConfig(mesh, layer_thickness))
+{
+    infill_config.reserve(MAX_INFILL_COMBINE);
+    for (int combine_idx = 0; combine_idx < MAX_INFILL_COMBINE; combine_idx++)
+    {
+        infill_config.emplace_back(
+                PrintFeatureType::Infill
+                , mesh.getSettingInMicrons("infill_line_width") * (combine_idx + 1)
+                , layer_thickness
+                , mesh.getSettingInPercentage("material_flow")
+                , GCodePathConfig::SpeedDerivatives{mesh.getSettingInMillimetersPerSecond("speed_infill"), mesh.getSettingInMillimetersPerSecond("acceleration_infill"), mesh.getSettingInMillimetersPerSecond("jerk_infill")}
+            );
+    }
+}
+
+PathConfigStorage::PathConfigStorage(const SliceDataStorage& storage, int layer_nr, int layer_thickness)
+: adhesion_extruder_train(storage.meshgroup->getExtruderTrain(storage.getSettingAsIndex("adhesion_extruder_nr")))
+, support_infill_train(storage.meshgroup->getExtruderTrain(storage.getSettingAsIndex("support_infill_extruder_nr")))
+, support_interface_train(storage.meshgroup->getExtruderTrain(storage.getSettingAsIndex("support_interface_extruder_nr")))
+, raft_base_config(
+            PrintFeatureType::SupportInterface
+            , adhesion_extruder_train->getSettingInMicrons("raft_base_line_width")
+            , adhesion_extruder_train->getSettingInMicrons("raft_base_thickness")
+            , adhesion_extruder_train->getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_base_speed"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_base_acceleration"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_base_jerk")}
+        )
+, raft_interface_config(
+            PrintFeatureType::Support
+            , adhesion_extruder_train->getSettingInMicrons("raft_interface_line_width")
+            , adhesion_extruder_train->getSettingInMicrons("raft_interface_thickness")
+            , adhesion_extruder_train->getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_interface_speed"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_interface_acceleration"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_interface_jerk")}
+        )
+, raft_surface_config(
+            PrintFeatureType::SupportInterface
+            , adhesion_extruder_train->getSettingInMicrons("raft_surface_line_width")
+            , adhesion_extruder_train->getSettingInMicrons("raft_surface_thickness")
+            , adhesion_extruder_train->getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_surface_speed"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_surface_acceleration"), adhesion_extruder_train->getSettingInMillimetersPerSecond("raft_surface_jerk")}
+        )
+, support_infill_config(
+            PrintFeatureType::Support
+            , support_infill_train->getSettingInMicrons("support_line_width")
+            , layer_thickness
+            , support_infill_train->getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{support_infill_train->getSettingInMillimetersPerSecond("speed_support_infill"), support_infill_train->getSettingInMillimetersPerSecond("acceleration_support_infill"), support_infill_train->getSettingInMillimetersPerSecond("jerk_support_infill")}
+        )
+, support_interface_config(
+            PrintFeatureType::SupportInterface
+            , support_interface_train->getSettingInMicrons("support_interface_line_width")
+            , layer_thickness
+            , support_interface_train->getSettingInPercentage("material_flow")
+            , GCodePathConfig::SpeedDerivatives{support_interface_train->getSettingInMillimetersPerSecond("speed_support_interface"), support_interface_train->getSettingInMillimetersPerSecond("acceleration_support_interface"), support_interface_train->getSettingInMillimetersPerSecond("jerk_support_interface")}
+        )
+{
+    int extruder_count = storage.meshgroup->getExtruderCount();
+    travel_config_per_extruder.reserve(extruder_count);
+    skirt_brim_config.reserve(extruder_count);
+    prime_tower_config_per_extruder.reserve(extruder_count);
+    for (int extruder_nr = 0; extruder_nr < extruder_count; extruder_nr++)
+    {
+        const ExtruderTrain* train = storage.meshgroup->getExtruderTrain(extruder_nr);
+        travel_config_per_extruder.emplace_back(
+                PrintFeatureType::MoveCombing
+                , 0
+                , 0
+                , 0.0
+                , GCodePathConfig::SpeedDerivatives{train->getSettingInMillimetersPerSecond("speed_travel"), train->getSettingInMillimetersPerSecond("acceleration_travel"), train->getSettingInMillimetersPerSecond("jerk_travel")}
+            );
+        skirt_brim_config.emplace_back(
+                PrintFeatureType::SkirtBrim
+                , train->getSettingInMicrons("skirt_brim_line_width")
+                , layer_thickness
+                , train->getSettingInPercentage("material_flow")
+                , GCodePathConfig::SpeedDerivatives{train->getSettingInMillimetersPerSecond("skirt_brim_speed"), train->getSettingInMillimetersPerSecond("acceleration_skirt_brim"), train->getSettingInMillimetersPerSecond("jerk_skirt_brim")}
+            );
+        prime_tower_config_per_extruder.emplace_back(
+                PrintFeatureType::SupportInfill
+                , train->getSettingInMicrons("prime_tower_line_width")
+                , layer_thickness
+                , train->getSettingInPercentage("prime_tower_flow")
+                , GCodePathConfig::SpeedDerivatives{train->getSettingInMillimetersPerSecond("speed_prime_tower"), train->getSettingInMillimetersPerSecond("acceleration_prime_tower"), train->getSettingInMillimetersPerSecond("jerk_prime_tower")}
+            );
+    }
+
+    mesh_configs.reserve(storage.meshes.size());
+    for (const SliceMeshStorage& mesh_storage : storage.meshes)
+    {
+        mesh_configs.emplace_back(mesh_storage, layer_thickness);
+    }
+
+    int initial_speedup_layer_count = storage.getSettingAsCount("speed_slowdown_layers");
+    if (layer_nr < initial_speedup_layer_count)
+    {
+        handleInitialLayerSpeedup(storage, layer_nr, initial_speedup_layer_count);
+    }
+}
+
+void cura::PathConfigStorage::handleInitialLayerSpeedup(const SliceDataStorage& storage, int layer_nr, int initial_speedup_layer_count)
+{
+    std::vector<GCodePathConfig::SpeedDerivatives> global_first_layer_config_per_extruder;
+    global_first_layer_config_per_extruder.reserve(storage.meshgroup->getExtruderCount());
+    for (int extruder_nr = 0; extruder_nr < storage.meshgroup->getExtruderCount(); extruder_nr++)
+    {
+        const ExtruderTrain* extruder = storage.meshgroup->getExtruderTrain(extruder_nr);
+        global_first_layer_config_per_extruder.emplace_back(
+            GCodePathConfig::SpeedDerivatives{
+                extruder->getSettingInMillimetersPerSecond("speed_print_layer_0")
+                , extruder->getSettingInMillimetersPerSecond("acceleration_print_layer_0")
+                , extruder->getSettingInMillimetersPerSecond("jerk_print_layer_0")
+            });
+    }
+
+    { // support
+        if (layer_nr < initial_speedup_layer_count)
+        {
+            int extruder_nr_support_infill = storage.getSettingAsIndex((layer_nr <= 0)? "support_extruder_nr_layer_0" : "support_infill_extruder_nr");
+            GCodePathConfig::SpeedDerivatives& first_layer_config_infill = global_first_layer_config_per_extruder[extruder_nr_support_infill];
+            support_infill_config.smoothSpeed(first_layer_config_infill, std::max(0, layer_nr), initial_speedup_layer_count);
+
+            int extruder_nr_support_interface = storage.getSettingAsIndex("support_interface_extruder_nr");
+            GCodePathConfig::SpeedDerivatives& first_layer_config_interface = global_first_layer_config_per_extruder[extruder_nr_support_interface];
+            support_interface_config.smoothSpeed(first_layer_config_interface, std::max(0, layer_nr), initial_speedup_layer_count);
+        }
+    }
+
+    { // extruder configs: travel, skirt/brim (= shield)
+        for (int extruder_nr = 0; extruder_nr < storage.meshgroup->getExtruderCount(); ++extruder_nr)
+        {
+            const ExtruderTrain* train = storage.meshgroup->getExtruderTrain(extruder_nr);
+            GCodePathConfig::SpeedDerivatives initial_layer_speed_config{
+                    train->getSettingInMillimetersPerSecond("speed_travel_layer_0")
+                    , train->getSettingInMillimetersPerSecond("acceleration_travel_layer_0")
+                    , train->getSettingInMillimetersPerSecond("jerk_travel_layer_0")
+            };
+            GCodePathConfig& travel = travel_config_per_extruder[extruder_nr];
+
+            travel.smoothSpeed(initial_layer_speed_config, std::max(0, layer_nr), initial_speedup_layer_count);
+
+            // don't smooth speed for the skirt/brim!
+            // NOTE: not smoothing skirt/brim means the speeds are also not smoothed for the draft/ooze shield
+
+            GCodePathConfig& prime_tower = prime_tower_config_per_extruder[extruder_nr];
+
+            prime_tower.smoothSpeed(initial_layer_speed_config, std::max(0, layer_nr), initial_speedup_layer_count);
+        }
+
+    }
+
+    { // meshes
+        for (unsigned int mesh_idx = 0; mesh_idx < storage.meshes.size(); mesh_idx++)
+        {
+            const SliceMeshStorage& mesh = storage.meshes[mesh_idx];
+
+
+            GCodePathConfig::SpeedDerivatives initial_layer_speed_config{
+                    mesh.getSettingInMillimetersPerSecond("speed_print_layer_0")
+                    , mesh.getSettingInMillimetersPerSecond("acceleration_print_layer_0")
+                    , mesh.getSettingInMillimetersPerSecond("jerk_print_layer_0")
+            };
+
+            MeshPathConfigs& mesh_config = mesh_configs[mesh_idx];
+            //Outer wall speed (per mesh).
+            mesh_config.inset0_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layer_count);
+
+            //Inner wall speed (per mesh).
+            mesh_config.insetX_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layer_count);
+
+            //Skin speed (per mesh).
+            mesh_config.skin_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layer_count);
+            mesh_config.perimeter_gap_config.smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layer_count);
+
+            for (unsigned int idx = 0; idx < MAX_INFILL_COMBINE; idx++)
+            {
+                //Infill speed (per combine part per mesh).
+                mesh_config.infill_config[idx].smoothSpeed(initial_layer_speed_config, layer_nr, initial_speedup_layer_count);
+            }
+        }
+    }
+}
+
+
+}//namespace cura

src/settings/PathConfigStorage.h

@@ -0,0 +1,63 @@
+/** Copyright (C) 2017 Ultimaker - Released under terms of the AGPLv3 License */
+#ifndef SETTINGS_PATH_CONFIGS_H
+#define SETTINGS_PATH_CONFIGS_H
+
+#include <vector>
+
+#include "../utils/intpoint.h" // coord_t
+#include "../GCodePathConfig.h"
+
+namespace cura
+{
+
+class SliceDataStorage; // forward decl for SliceDataStorage
+class SliceMeshStorage; // forward decl for SliceDataStorage
+class ExtruderTrain; // forward decl for SliceDataStorage
+
+/*!
+ * A class to represent all configurations for all features types of printed lines in a meshgroup.
+ */
+class PathConfigStorage
+{
+private:
+    const ExtruderTrain* adhesion_extruder_train;
+    const ExtruderTrain* support_infill_train;
+    const ExtruderTrain* support_interface_train;
+public:
+    class MeshPathConfigs
+    {
+    public:
+        GCodePathConfig inset0_config;
+        GCodePathConfig insetX_config;
+        GCodePathConfig skin_config;
+        GCodePathConfig perimeter_gap_config;
+        std::vector<GCodePathConfig> infill_config;
+
+        MeshPathConfigs(const SliceMeshStorage& mesh, int layer_thickness);
+    };
+    
+    GCodePathConfig raft_base_config;
+    GCodePathConfig raft_interface_config;
+    GCodePathConfig raft_surface_config;
+
+    std::vector<GCodePathConfig> travel_config_per_extruder; //!< The config used for travel moves (only speed is set!)
+    std::vector<GCodePathConfig> skirt_brim_config; //!< Configuration for skirt and brim per extruder.
+    std::vector<GCodePathConfig> prime_tower_config_per_extruder; //!< Configuration for the prime tower per extruder.
+
+    GCodePathConfig support_infill_config; //!< The config used to print the normal support, rather than the support interface
+    GCodePathConfig support_interface_config; //!< The config to use to print the dense roofs and bottoms of support
+
+    std::vector<MeshPathConfigs> mesh_configs; //!< For each meash the config for all its feature types
+    
+    /*!
+     * \warning Note that the layer_nr might be below zero for raft (filler) layers
+     */
+    PathConfigStorage(const SliceDataStorage& storage, int layer_nr, int layer_thickness);
+
+private:
+    void handleInitialLayerSpeedup(const SliceDataStorage& storage, int layer_nr, int initial_speedup_layer_count);
+};
+
+}; // namespace cura
+
+#endif // SETTINGS_PATH_CONFIGS_H

src/settings/SettingRegistry.cpp

@@ -125,7 +125,7 @@ bool SettingRegistry::getDefinitionFile(const std::string machine_id, std::strin
 
 int SettingRegistry::loadExtruderJSONsettings(unsigned int extruder_nr, SettingsBase* settings_base)
 {
-    if (extruder_train_ids.empty()) //... Tough luck, buddy.
+    if (extruder_train_ids.empty())
     {
         logError("Couldn't find any extruder trains!\n");
         return -1;

src/settings/settings.cpp

@@ -93,21 +93,23 @@ void SettingsBase::setSettingInheritBase(std::string key, const SettingsBaseVirt
 
 std::string SettingsBase::getSettingString(std::string key) const
 {
-    if (setting_values.find(key) != setting_values.end())
+    auto value_it = setting_values.find(key);
+    if (value_it != setting_values.end())
     {
-        return setting_values.at(key);
+        return value_it->second;
     }
-    if (setting_inherit_base.find(key) != setting_inherit_base.end())
+    auto inherit_override_it = setting_inherit_base.find(key);
+    if (inherit_override_it != setting_inherit_base.end())
     {
-        return setting_inherit_base.at(key)->getSettingString(key);
+        return inherit_override_it->second->getSettingString(key);
     }
     if (parent)
     {
         return parent->getSettingString(key);
     }
 
-    const_cast<SettingsBase&>(*this).setting_values[key] = "";
-    cura::logWarning("Unregistered setting %s\n", key.c_str());
+    cura::logError("Trying to retrieve unregistered setting with no value given: '%s'\n", key.c_str());
+    std::exit(-1);
     return "";
 }
 
@@ -426,7 +428,7 @@ FillPerimeterGapMode SettingsBaseVirtual::getSettingAsFillPerimeterGapMode(std::
     return FillPerimeterGapMode::NOWHERE;
 }
 
-CombingMode SettingsBaseVirtual::getSettingAsCombingMode(std::string key)
+CombingMode SettingsBaseVirtual::getSettingAsCombingMode(std::string key) const
 {
     std::string value = getSettingString(key);
     if (value == "off")
@@ -444,7 +446,7 @@ CombingMode SettingsBaseVirtual::getSettingAsCombingMode(std::string key)
     return CombingMode::ALL;
 }
 
-SupportDistPriority SettingsBaseVirtual::getSettingAsSupportDistPriority(std::string key)
+SupportDistPriority SettingsBaseVirtual::getSettingAsSupportDistPriority(std::string key) const
 {
     std::string value = getSettingString(key);
     if (value == "xy_overrides_z")

src/settings/settings.h

@@ -251,8 +251,8 @@ public:
     EZSeamType getSettingAsZSeamType(std::string key) const;
     ESurfaceMode getSettingAsSurfaceMode(std::string key) const;
     FillPerimeterGapMode getSettingAsFillPerimeterGapMode(std::string key) const;
-    CombingMode getSettingAsCombingMode(std::string key);
-    SupportDistPriority getSettingAsSupportDistPriority(std::string key);
+    CombingMode getSettingAsCombingMode(std::string key) const;
+    SupportDistPriority getSettingAsSupportDistPriority(std::string key) const;
 };
 
 class SettingRegistry;

src/skin.cpp

@@ -10,7 +10,16 @@
 namespace cura 
 {
 
-        
+
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateSkinAreas reads data from mesh.layers.parts[*].insets and writes to mesh.layers[n].parts[*].skin_parts
+ * generateSkinInsets only read/writes the skin_parts from the current layer.
+ *
+ * generateSkins therefore reads (depends on) data from mesh.layers[*].parts[*].insets and writes mesh.layers[n].parts[*].skin_parts
+ */
 void generateSkins(int layerNr, SliceMeshStorage& mesh, int downSkinCount, int upSkinCount, int wall_line_count, int innermost_wall_line_width, int insetCount, bool no_small_gaps_heuristic)
 {
     generateSkinAreas(layerNr, mesh, innermost_wall_line_width, downSkinCount, upSkinCount, wall_line_count, no_small_gaps_heuristic);
@@ -23,6 +32,12 @@ void generateSkins(int layerNr, SliceMeshStorage& mesh, int downSkinCount, int u
     }
 }
 
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateSkinAreas reads data from mesh.layers[*].parts[*].insets and writes to mesh.layers[n].parts[*].skin_parts
+ */
 void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost_wall_line_width, int downSkinCount, int upSkinCount, int wall_line_count, bool no_small_gaps_heuristic)
 {
     SliceLayer& layer = mesh.layers[layer_nr];
@@ -31,7 +46,7 @@ void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost
     {
         return;
     }
-    
+    int min_infill_area = mesh.getSettingInMillimeters("min_infill_area");
     for(unsigned int partNr = 0; partNr < layer.parts.size(); partNr++)
     {
         SliceLayerPart& part = layer.parts[partNr];
@@ -63,12 +78,22 @@ void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost
         {
             if (static_cast<int>(layer_nr - downSkinCount) >= 0)
             {
-                downskin = downskin.difference(getInsidePolygons(mesh.layers[layer_nr - downSkinCount])); // skin overlaps with the walls
+                Polygons not_air = getInsidePolygons(mesh.layers[layer_nr - downSkinCount]);
+                if (min_infill_area > 0)
+                {
+                    not_air.removeSmallAreas(min_infill_area);
+                }
+                downskin = downskin.difference(not_air); // skin overlaps with the walls
             }
             
             if (static_cast<int>(layer_nr + upSkinCount) < static_cast<int>(mesh.layers.size()))
             {
-                upskin = upskin.difference(getInsidePolygons(mesh.layers[layer_nr + upSkinCount])); // skin overlaps with the walls
+                Polygons not_air = getInsidePolygons(mesh.layers[layer_nr + upSkinCount]);
+                if (min_infill_area > 0)
+                {
+                    not_air.removeSmallAreas(min_infill_area);
+                }
+                upskin = upskin.difference(not_air); // skin overlaps with the walls
             }
         }
         else 
@@ -80,6 +105,10 @@ void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost
                 {
                     not_air = not_air.intersection(getInsidePolygons(mesh.layers[downskin_layer_nr]));
                 }
+                if (min_infill_area > 0)
+                {
+                    not_air.removeSmallAreas(min_infill_area);
+                }
                 downskin = downskin.difference(not_air); // skin overlaps with the walls
             }
             
@@ -90,6 +119,10 @@ void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost
                 {
                     not_air = not_air.intersection(getInsidePolygons(mesh.layers[upskin_layer_nr]));
                 }
+                if (min_infill_area > 0)
+                {
+                    not_air.removeSmallAreas(min_infill_area);
+                }
                 upskin = upskin.difference(not_air); // skin overlaps with the walls
             }
         }
@@ -106,7 +139,12 @@ void generateSkinAreas(int layer_nr, SliceMeshStorage& mesh, const int innermost
     }
 }
 
-
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateSkinInsets only read/writes the skin_parts from the current layer.
+ */
 void generateSkinInsets(SliceLayerPart* part, const int wall_line_width, int insetCount)
 {
     if (insetCount == 0)
@@ -139,6 +177,12 @@ void generateSkinInsets(SliceLayerPart* part, const int wall_line_width, int ins
     }
 }
 
+/*
+ * This function is executed in a parallel region based on layer_nr.
+ * When modifying make sure any changes does not introduce data races.
+ *
+ * generateInfill read mesh.layers[n].parts[*].{insets,skin_parts,boundingBox} and write mesh.layers[n].parts[*].infill_area
+ */
 void generateInfill(int layerNr, SliceMeshStorage& mesh, const int innermost_wall_line_width, int infill_skin_overlap, int wall_line_count)
 {
     SliceLayer& layer = mesh.layers[layerNr];

src/sliceDataStorage.cpp

@@ -35,7 +35,7 @@ void SliceLayer::getOutlines(Polygons& result, bool external_polys_only) const
     {
         if (external_polys_only)
         {
-            result.add(const_cast<SliceLayerPart&>(part).outline.outerPolygon()); // TODO: make a const version of outerPolygon()
+            result.add(part.outline.outerPolygon());
         }
         else 
         {
@@ -57,12 +57,12 @@ void SliceLayer::getSecondOrInnermostWalls(Polygons& layer_walls) const
     {
         // we want the 2nd inner walls
         if (part.insets.size() >= 2) {
-            layer_walls.add(const_cast<SliceLayerPart&>(part).insets[1]); // TODO const cast!
+            layer_walls.add(part.insets[1]);
             continue;
         }
         // but we'll also take the inner wall if the 2nd doesn't exist
         if (part.insets.size() == 1) {
-            layer_walls.add(const_cast<SliceLayerPart&>(part).insets[0]); // TODO const cast!
+            layer_walls.add(part.insets[0]);
             continue;
         }
         // offset_from_outlines was so large that it completely destroyed our isle,
@@ -87,38 +87,11 @@ std::vector<RetractionConfig> SliceDataStorage::initializeRetractionConfigs()
     return ret;
 }
 
-std::vector<GCodePathConfig> SliceDataStorage::initializeTravelConfigs()
-{
-    std::vector<GCodePathConfig> ret;
-    for (int extruder = 0; extruder < meshgroup->getExtruderCount(); extruder++)
-    {
-        travel_config_per_extruder.emplace_back(PrintFeatureType::MoveCombing);
-    }
-    return ret;
-}
-
-std::vector<GCodePathConfig> SliceDataStorage::initializeSkirtBrimConfigs()
-{
-    std::vector<GCodePathConfig> ret;
-    for (int extruder = 0; extruder < meshgroup->getExtruderCount(); extruder++)
-    {
-        skirt_brim_config.emplace_back(PrintFeatureType::SkirtBrim);
-    }
-    return ret;
-}
-
 SliceDataStorage::SliceDataStorage(MeshGroup* meshgroup) : SettingsMessenger(meshgroup),
     meshgroup(meshgroup != nullptr ? meshgroup : new MeshGroup(FffProcessor::getInstance())), //If no mesh group is provided, we roll our own.
     print_layer_count(0),
     retraction_config_per_extruder(initializeRetractionConfigs()),
     extruder_switch_retraction_config_per_extruder(initializeRetractionConfigs()),
-    travel_config_per_extruder(initializeTravelConfigs()),
-    skirt_brim_config(initializeSkirtBrimConfigs()),
-    raft_base_config(PrintFeatureType::SupportInterface),
-    raft_interface_config(PrintFeatureType::Support),
-    raft_surface_config(PrintFeatureType::SupportInterface),
-    support_config(PrintFeatureType::Support),
-    support_skin_config(PrintFeatureType::SupportInterface),
     max_print_height_second_to_last_extruder(-1),
     primeTower(*this)
 {
@@ -163,7 +136,7 @@ Polygons SliceDataStorage::getLayerOutlines(int layer_nr, bool include_helper_pa
                 }
                 const SliceLayer& layer = mesh.layers[layer_nr];
                 layer.getOutlines(total, external_polys_only);
-                if (const_cast<SliceMeshStorage&>(mesh).getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL) // TODO: make all getSetting functions const??
+                if (mesh.getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL)
                 {
                     total = total.unionPolygons(layer.openPolyLines.offsetPolyLine(100));
                 }
@@ -207,7 +180,7 @@ Polygons SliceDataStorage::getLayerSecondOrInnermostWalls(int layer_nr, bool inc
             {
                 const SliceLayer& layer = mesh.layers[layer_nr];
                 layer.getSecondOrInnermostWalls(total);
-                if (const_cast<SliceMeshStorage&>(mesh).getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL) // TODO: make getSetting const? make settings.setting_values mapping mutable??
+                if (mesh.getSettingAsSurfaceMode("magic_mesh_surface_mode") != ESurfaceMode::NORMAL)
                 {
                     total = total.unionPolygons(layer.openPolyLines.offsetPolyLine(100));
                 }

src/sliceDataStorage.h

@@ -8,10 +8,9 @@
 #include "utils/NoCopy.h"
 #include "utils/AABB.h"
 #include "mesh.h"
-#include "gcodePlanner.h"
 #include "MeshGroup.h"
 #include "PrimeTower.h"
-#include "GCodePathConfig.h"
+#include "gcodeExport.h" // CoastingConfig
 
 namespace cura 
 {
@@ -138,7 +137,11 @@ public:
 
     std::vector<SupportLayer> supportLayers;
 
-    SupportStorage() : generated(false), layer_nr_max_filled_layer(-1) { }
+    SupportStorage()
+    : generated(false)
+    , layer_nr_max_filled_layer(-1)
+    {
+    }
     ~SupportStorage(){ supportLayers.clear(); }
 };
 /******************/
@@ -152,25 +155,14 @@ public:
 
     int layer_nr_max_filled_layer; //!< the layer number of the uppermost layer with content (modified while infill meshes are processed)
 
-    GCodePathConfig inset0_config;
-    GCodePathConfig insetX_config;
-    GCodePathConfig skin_config;
-    std::vector<GCodePathConfig> infill_config;
-
     SubDivCube* base_subdiv_cube;
 
     SliceMeshStorage(SettingsBaseVirtual* settings, unsigned int slice_layer_count)
     : SettingsMessenger(settings)
     , layer_nr_max_filled_layer(0)
-    , inset0_config(PrintFeatureType::OuterWall)
-    , insetX_config(PrintFeatureType::InnerWall)
-    , skin_config(PrintFeatureType::Skin)
     , base_subdiv_cube(nullptr)
     {
         layers.resize(slice_layer_count);
-        infill_config.reserve(MAX_INFILL_COMBINE);
-        for(int n=0; n<MAX_INFILL_COMBINE; n++)
-            infill_config.emplace_back(PrintFeatureType::Infill);
     }
 
     virtual ~SliceMeshStorage();
@@ -189,18 +181,8 @@ public:
     std::vector<RetractionConfig> retraction_config_per_extruder; //!< Retraction config per extruder.
     std::vector<RetractionConfig> extruder_switch_retraction_config_per_extruder; //!< Retraction config per extruder for when performing an extruder switch
 
-    std::vector<GCodePathConfig> travel_config_per_extruder; //!< The config used for travel moves (only speed is set!)
-
-    std::vector<GCodePathConfig> skirt_brim_config; //!< Configuration for skirt and brim per extruder.
     std::vector<CoastingConfig> coasting_config; //!< coasting config per extruder
 
-    GCodePathConfig raft_base_config;
-    GCodePathConfig raft_interface_config;
-    GCodePathConfig raft_surface_config;
-
-    GCodePathConfig support_config;
-    GCodePathConfig support_skin_config; //!< The config to use to print the dense roofs and bottoms of support
-
     SupportStorage support;
 
     Polygons skirt_brim[MAX_EXTRUDERS]; //!< Skirt and brim polygons per extruder, ordered from inner to outer polygons.
@@ -215,21 +197,6 @@ public:
     std::vector<Polygons> oozeShield;        //oozeShield per layer
     Polygons draft_protection_shield; //!< The polygons for a heightened skirt which protects from warping by gusts of wind and acts as a heated chamber.
 
-    /*!
-     * Construct the initial retraction_config_per_extruder
-     */
-    std::vector<RetractionConfig> initializeRetractionConfigs();
-
-    /*!
-     * Construct the initial travel_config_per_extruder
-     */
-    std::vector<GCodePathConfig> initializeTravelConfigs();
-
-    /*!
-     * Construct the initial skirt & brim configurations for each extruder.
-     */
-    std::vector<GCodePathConfig> initializeSkirtBrimConfigs();
-
     /*!
      * \brief Creates a new slice data storage that stores the slice data of the
      * specified mesh group.
@@ -279,6 +246,12 @@ public:
      * \return a vector of bools indicating whether the extruder with corresponding index is used in this layer.
      */
     std::vector<bool> getExtrudersUsed(int layer_nr) const;
+
+private:
+    /*!
+     * Construct the retraction_config_per_extruder
+     */
+    std::vector<RetractionConfig> initializeRetractionConfigs();
 };
 
 }//namespace cura

src/slicer.cpp

@@ -216,7 +216,7 @@ SlicerLayer::findPossibleStitches(
     //   insert the starts of the polylines).
     for(unsigned int polyline_0_idx = 0; polyline_0_idx < open_polylines.size(); polyline_0_idx++)
     {
-        const PolygonRef polyline_0 = open_polylines[polyline_0_idx];
+        ConstPolygonRef polyline_0 = open_polylines[polyline_0_idx];
 
         if (polyline_0.size() < 1) continue;
 
@@ -231,7 +231,7 @@ SlicerLayer::findPossibleStitches(
     {
         for(unsigned int polyline_0_idx = 0; polyline_0_idx < open_polylines.size(); polyline_0_idx++)
         {
-            const PolygonRef polyline_0 = open_polylines[polyline_0_idx];
+            ConstPolygonRef polyline_0 = open_polylines[polyline_0_idx];
 
             if (polyline_0.size() < 1) continue;
 
@@ -245,7 +245,7 @@ SlicerLayer::findPossibleStitches(
     // search for nearby end points
     for(unsigned int polyline_1_idx = 0; polyline_1_idx < open_polylines.size(); polyline_1_idx++)
     {
-        const PolygonRef polyline_1 = open_polylines[polyline_1_idx];
+        ConstPolygonRef polyline_1 = open_polylines[polyline_1_idx];
 
         if (polyline_1.size() < 1) continue;
 
@@ -887,10 +887,14 @@ Slicer::Slicer(Mesh* mesh, int initial, int thickness, int slice_layer_count, bo
         }
     }
     log("slice of mesh took %.3f seconds\n",slice_timer.restart());
-    for(unsigned int layer_nr=0; layer_nr<layers.size(); layer_nr++)
+
+    std::vector<SlicerLayer>& layers_ref = layers; // force layers not to be copied into the threads
+#pragma omp parallel for default(none) shared(mesh,layers_ref) firstprivate(keep_none_closed, extensive_stitching)
+    for(unsigned int layer_nr=0; layer_nr<layers_ref.size(); layer_nr++)
     {
-        layers[layer_nr].makePolygons(mesh, keep_none_closed, extensive_stitching);
+        layers_ref[layer_nr].makePolygons(mesh, keep_none_closed, extensive_stitching);
     }
+
     mesh->expandXY(mesh->getSettingInMicrons("xy_offset"));
     log("slice make polygons took %.3f seconds\n",slice_timer.restart());
 }

src/support.cpp

@@ -90,6 +90,7 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int l
         storage.support.supportLayers.resize(layer_count);
     }
 
+    // generate support areas
     for (unsigned int mesh_idx = 0; mesh_idx < storage.meshes.size(); mesh_idx++)
     {
         SliceMeshStorage& mesh = storage.meshes[mesh_idx];
@@ -100,25 +101,33 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int l
         std::vector<Polygons> supportAreas;
         supportAreas.resize(layer_count, Polygons());
         generateSupportAreas(storage, mesh_idx, layer_count, supportAreas);
-        
-        if (mesh.getSettingBoolean("support_interface_enable"))
+
+        for (unsigned int layer_idx = 0; layer_idx < layer_count; layer_idx++)
         {
-            generateSupportInterface(storage, mesh, supportAreas, layer_count);
-        }
-        else 
-        {
-            for (unsigned int layer_idx = 0; layer_idx < layer_count ; layer_idx++)
-            {
-                storage.support.supportLayers[layer_idx].supportAreas.add(supportAreas[layer_idx]);
-            }
+            storage.support.supportLayers[layer_idx].supportAreas.add(supportAreas[layer_idx]);
         }
     }
-    
+
     for (unsigned int layer_idx = 0; layer_idx < layer_count ; layer_idx++)
     {
         Polygons& support_areas = storage.support.supportLayers[layer_idx].supportAreas;
         support_areas = support_areas.unionPolygons();
     }
+
+    // handle support interface
+    for (unsigned int mesh_idx = 0; mesh_idx < storage.meshes.size(); mesh_idx++)
+    {
+        SliceMeshStorage& mesh = storage.meshes[mesh_idx];
+        if (mesh.getSettingBoolean("infill_mesh") || mesh.getSettingBoolean("anti_overhang_mesh"))
+        {
+            continue;
+        }
+
+        if (mesh.getSettingBoolean("support_interface_enable"))
+        {
+            generateSupportInterface(storage, mesh, layer_count);
+        }
+    }
 }
 
 /* 
@@ -156,6 +165,7 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int m
     const int supportTowerDiameter = mesh.getSettingInMicrons("support_tower_diameter");
     const int supportMinAreaSqrt = mesh.getSettingInMicrons("support_minimal_diameter");
     const double supportTowerRoofAngle = mesh.getSettingInAngleRadians("support_tower_roof_angle");
+    const bool use_towers = mesh.getSettingBoolean("support_use_towers") && supportMinAreaSqrt > 0;
 
     const int layerThickness = storage.getSettingInMicrons("layer_height");
     const int supportXYDistance = mesh.getSettingInMicrons("support_xy_distance");
@@ -225,7 +235,10 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int m
         
     
     std::vector<std::pair<int, std::vector<Polygons>>> overhang_points; // stores overhang_points along with the layer index at which the overhang point occurs
-    AreaSupport::detectOverhangPoints(storage, mesh, overhang_points, layer_count, supportMinAreaSqrt);
+    if (use_towers)
+    {
+        AreaSupport::detectOverhangPoints(storage, mesh, overhang_points, layer_count, supportMinAreaSqrt);
+    }
 
     std::deque<std::pair<Polygons, Polygons>> basic_and_full_overhang_above;
     for (unsigned int layer_idx = support_layer_count - 1; layer_idx != support_layer_count - 1 - layerZdistanceTop ; layer_idx--)
@@ -255,7 +268,7 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int m
             supportLayer_this = supportLayer_this.offset(extension_offset);
         }
 
-        if (supportMinAreaSqrt > 0)
+        if (use_towers)
         {
             // handle straight walls
             AreaSupport::handleWallStruts(supportLayer_this, supportMinAreaSqrt, supportTowerDiameter);
@@ -342,14 +355,14 @@ void AreaSupport::generateSupportAreas(SliceDataStorage& storage, unsigned int m
     }
 
     //Enforce top Z distance.
-    if (layerZdistanceTop > 0)
+    if (layerZdistanceTop > 1)
     {
         // this is performed after the main support generation loop above, because it affects the joining of polygons
         // if this would be performed in the main loop then some support would not have been generated under the overhangs and consequently no support is generated for that,
         // meaning almost no support would be generated in some cases which definitely need support.
-        for (size_t layer_idx = 0; layer_idx < storage.support.supportLayers.size() && layer_idx < support_layer_count - layerZdistanceTop; layer_idx++)
+        for (size_t layer_idx = 0; layer_idx < storage.support.supportLayers.size() && layer_idx < support_layer_count - (layerZdistanceTop - 1); layer_idx++)
         {
-            supportAreas[layer_idx] = supportAreas[layer_idx].difference(storage.getLayerOutlines(layer_idx + layerZdistanceTop, false));
+            supportAreas[layer_idx] = supportAreas[layer_idx].difference(storage.getLayerOutlines(layer_idx + layerZdistanceTop - 1, false));
         }
     }
 
@@ -559,7 +572,7 @@ void AreaSupport::handleWallStruts(
 }
 
 
-void AreaSupport::generateSupportInterface(SliceDataStorage& storage, const SliceMeshStorage& mesh, std::vector<Polygons>& support_areas, const unsigned int layer_count)
+void AreaSupport::generateSupportInterface(SliceDataStorage& storage, const SliceMeshStorage& mesh, const unsigned int layer_count)
 {
     const unsigned int roof_layer_count = round_divide(mesh.getSettingInMicrons("support_roof_height"), storage.getSettingInMicrons("layer_height"));
     const unsigned int bottom_layer_count = round_divide(mesh.getSettingInMicrons("support_bottom_height"), storage.getSettingInMicrons("layer_height"));
@@ -576,44 +589,41 @@ void AreaSupport::generateSupportInterface(SliceDataStorage& storage, const Slic
 
         const unsigned int top_layer_idx_above = layer_idx + roof_layer_count + z_distance_top;
         const unsigned int bottom_layer_idx_below = std::max(0, int(layer_idx) - int(bottom_layer_count) - int(z_distance_bottom));
-        if (top_layer_idx_above < supportLayers.size())
+        if (top_layer_idx_above >= supportLayers.size())
         {
-            Polygons roofs;
-            if (roof_layer_count > 0)
-            {
-                Polygons model;
-                const unsigned int n_scans = std::max(1u, (roof_layer_count - 1) / skip_layer_count);
-                const float z_skip = std::max(1.0f, float(roof_layer_count - 1) / float(n_scans));
-                for (float layer_idx_above = top_layer_idx_above; layer_idx_above > layer_idx + z_distance_top; layer_idx_above -= z_skip)
-                {
-                    const Polygons outlines_above = mesh.layers[std::round(layer_idx_above)].getOutlines();
-                    model = model.unionPolygons(outlines_above);
-                }
-                roofs = support_areas[layer_idx].intersection(model);
-            }
-            Polygons bottoms;
-            if (bottom_layer_count > 0)
-            {
-                Polygons model;
-                const unsigned int n_scans = std::max(1u, (bottom_layer_count - 1) / skip_layer_count);
-                const float z_skip = std::max(1.0f, float(bottom_layer_count - 1) / float(n_scans));
-                for (float layer_idx_below = bottom_layer_idx_below; std::round(layer_idx_below) < (int)(layer_idx - z_distance_bottom); layer_idx_below += z_skip)
-                {
-                    const Polygons outlines_below = mesh.layers[std::round(layer_idx_below)].getOutlines();
-                    model = model.unionPolygons(outlines_below);
-                }
-                bottoms = support_areas[layer_idx].intersection(model);
-            }
-            // expand skin a bit so that we're sure it's not too thin to be printed.
-            Polygons skin = roofs.unionPolygons(bottoms).offset(interface_line_width).intersection(support_areas[layer_idx]);
-            skin.removeSmallAreas(1.0);
-            layer.skin.add(skin);
-            layer.supportAreas.add(support_areas[layer_idx].difference(layer.skin));
+            continue;
         }
-        else 
+        Polygons roofs;
+        if (roof_layer_count > 0)
         {
-            layer.skin.add(support_areas[layer_idx]);
+            Polygons model;
+            const unsigned int n_scans = std::max(1u, (roof_layer_count - 1) / skip_layer_count);
+            const float z_skip = std::max(1.0f, float(roof_layer_count - 1) / float(n_scans));
+            for (float layer_idx_above = top_layer_idx_above; layer_idx_above > layer_idx + z_distance_top; layer_idx_above -= z_skip)
+            {
+                const Polygons outlines_above = mesh.layers[std::round(layer_idx_above)].getOutlines();
+                model = model.unionPolygons(outlines_above);
+            }
+            roofs = layer.supportAreas.intersection(model);
         }
+        Polygons bottoms;
+        if (bottom_layer_count > 0)
+        {
+            Polygons model;
+            const unsigned int n_scans = std::max(1u, (bottom_layer_count - 1) / skip_layer_count);
+            const float z_skip = std::max(1.0f, float(bottom_layer_count - 1) / float(n_scans));
+            for (float layer_idx_below = bottom_layer_idx_below; std::round(layer_idx_below) < (int)(layer_idx - z_distance_bottom); layer_idx_below += z_skip)
+            {
+                const Polygons outlines_below = mesh.layers[std::round(layer_idx_below)].getOutlines();
+                model = model.unionPolygons(outlines_below);
+            }
+            bottoms = layer.supportAreas.intersection(model);
+        }
+        // expand skin a bit so that we're sure it's not too thin to be printed.
+        Polygons skin = roofs.unionPolygons(bottoms).offset(interface_line_width).intersection(layer.supportAreas);
+        skin.removeSmallAreas(1.0);
+        layer.skin.add(skin);
+        layer.supportAreas = layer.supportAreas.difference(layer.skin);
     }
 }
 

src/support.h

@@ -36,10 +36,9 @@ private:
      * 
      * \param storage Output storage: support area + support skin area output
      * \param mesh The mesh to generate support skins for.
-     * \param support_areas The basic support areas for the current mesh
      * \param layer_count The number of layers in this mesh group.
      */
-    static void generateSupportInterface(SliceDataStorage& storage, const SliceMeshStorage& mesh, std::vector<Polygons>& support_areas, const unsigned int layer_count);
+    static void generateSupportInterface(SliceDataStorage& storage, const SliceMeshStorage& mesh, const unsigned int layer_count);
 
     /*!
      * Join current support layer with the support of the layer above, (make support conical) and perform smoothing etc operations.

src/utils/AABB.cpp

@@ -24,7 +24,7 @@ AABB::AABB(const Polygons& polys)
     calculate(polys);
 }
 
-AABB::AABB(const PolygonRef poly)
+AABB::AABB(ConstPolygonRef poly)
 : min(POINT_MAX, POINT_MAX), max(POINT_MIN, POINT_MIN)
 {
     calculate(poly);
@@ -43,7 +43,7 @@ void AABB::calculate(const Polygons& polys)
     }
 }
 
-void AABB::calculate(const PolygonRef poly)
+void AABB::calculate(ConstPolygonRef poly)
 {
     min = Point(POINT_MAX, POINT_MAX);
     max = Point(POINT_MIN, POINT_MIN);

src/utils/AABB.h

@@ -20,10 +20,10 @@ public:
     AABB(); //!< initializes with invalid min and max
     AABB(Point& min, Point& max); //!< initializes with given min and max
     AABB(const Polygons& polys); //!< Computes the boundary box for the given polygons
-    AABB(const PolygonRef poly); //!< Computes the boundary box for the given polygons
+    AABB(ConstPolygonRef poly); //!< Computes the boundary box for the given polygons
 
     void calculate(const Polygons& polys); //!< Calculates the aabb for the given polygons (throws away old min and max data of this aabb)
-    void calculate(const PolygonRef poly); //!< Calculates the aabb for the given polygon (throws away old min and max data of this aabb)
+    void calculate(ConstPolygonRef poly); //!< Calculates the aabb for the given polygon (throws away old min and max data of this aabb)
 
     /*!
      * Check whether this aabb overlaps with another.

src/utils/AABB3D.cpp

@@ -37,6 +37,12 @@ void AABB3D::include(Point3 p)
     max.z = std::max(max.z, p.z);   
 }
 
+void AABB3D::includeZ(int32_t z)
+{
+    min.z = std::min(min.z, z);
+    max.z = std::max(max.z, z);
+}
+
 void AABB3D::offset(Point3 offset)
 {
     min += offset;

src/utils/AABB3D.h

@@ -38,6 +38,14 @@ struct AABB3D
      */
     void include(Point3 p);
 
+    /*!
+     * Expand the AABB3D to include a z-coordinate.
+     *
+     * This is for including a point of which the X and Y coordinates are
+     * unknown but known to already be included in the bounding box.
+     */
+    void includeZ(int32_t z);
+
     /*!
      * Offset the coordinates of the bounding box.
      * \param offset The offset with which to offset the AABB3D.

src/utils/ListPolyIt.cpp

@@ -10,21 +10,21 @@ namespace cura
 {
 
 
-void ListPolyIt::convertPolygonsToLists(Polygons& polys, ListPolygons& result)
+void ListPolyIt::convertPolygonsToLists(const Polygons& polys, ListPolygons& result)
 {
-    for (PolygonRef poly : polys)
+    for (ConstPolygonRef poly : polys)
     {
         result.emplace_back();
         convertPolygonToList(poly, result.back());
     }
 }
 
-void ListPolyIt::convertPolygonToList(PolygonRef poly, ListPolygon& result)
+void ListPolyIt::convertPolygonToList(ConstPolygonRef poly, ListPolygon& result)
 {
 #ifdef DEBUG
     Point last = poly.back();
 #endif // DEBUG
-    for (Point& p : poly) 
+    for (const Point& p : poly)
     {
         result.push_back(p);
 #ifdef DEBUG
@@ -39,7 +39,7 @@ void ListPolyIt::convertPolygonToList(PolygonRef poly, ListPolygon& result)
 }
 
 
-void ListPolyIt::convertListPolygonsToPolygons(ListPolygons& list_polygons, Polygons& polygons)
+void ListPolyIt::convertListPolygonsToPolygons(const ListPolygons& list_polygons, Polygons& polygons)
 {
     for (unsigned int poly_idx = 0; poly_idx < polygons.size(); poly_idx++)
     {
@@ -48,9 +48,9 @@ void ListPolyIt::convertListPolygonsToPolygons(ListPolygons& list_polygons, Poly
     }
 }
 
-void ListPolyIt::convertListPolygonToPolygon(ListPolygon& list_polygon, PolygonRef polygon)
+void ListPolyIt::convertListPolygonToPolygon(const ListPolygon& list_polygon, PolygonRef polygon)
 {
-    for (Point& p : list_polygon)
+    for (const Point& p : list_polygon)
     {
         polygon.add(p);
     }

src/utils/ListPolyIt.h

@@ -94,28 +94,28 @@ public:
      * \param polys The polygons to convert
      * \param result The converted polygons
      */
-    static void convertPolygonsToLists(Polygons& polys, ListPolygons& result);
+    static void convertPolygonsToLists(const Polygons& polys, ListPolygons& result);
     /*!
      * Convert Polygons to ListPolygons
      * 
      * \param polys The polygons to convert
      * \param result The converted polygons
      */
-    static void convertPolygonToList(PolygonRef poly, ListPolygon& result);
+    static void convertPolygonToList(ConstPolygonRef poly, ListPolygon& result);
     /*!
      * Convert ListPolygons to Polygons
      * 
      * \param list_polygons The polygons to convert
      * \param polygons The converted polygons
      */
-    static void convertListPolygonsToPolygons(ListPolygons& list_polygons, Polygons& polygons);
+    static void convertListPolygonsToPolygons(const ListPolygons& list_polygons, Polygons& polygons);
     /*!
      * Convert ListPolygons to Polygons
      * 
      * \param list_polygons The polygons to convert
      * \param polygons The converted polygons
      */
-    static void convertListPolygonToPolygon(ListPolygon& list_polygon, PolygonRef polygon);
+    static void convertListPolygonToPolygon(const ListPolygon& list_polygon, PolygonRef polygon);
 
     /*!
      * Insert a point into a ListPolygon if it's not a duplicate of the point before or the point after.

src/utils/PolygonsPointIndex.h

@@ -46,7 +46,7 @@ public:
     /*!
      * Get the polygon to which this PolygonsPointIndex refers
      */
-    const PolygonRef getPolygon() const
+    ConstPolygonRef getPolygon() const
     {
         return (*polygons)[poly_idx];
     }

src/utils/SVG.h

@@ -93,9 +93,8 @@ public:
         {
             for(unsigned int j=0;j<parts.size();j++)
             {
-                Polygon poly = parts[j];
                 fprintf(out, "<polygon points=\"");
-                for(Point& p : poly)
+                for (Point& p : parts[j])
                 {
                     Point fp = transform(p);
                     fprintf(out, "%lli,%lli ", fp.X, fp.Y);
@@ -130,9 +129,9 @@ public:
         }
     }
 
-    void writePoints(PolygonRef poly, bool write_coords=false, int size = 5, Color color = Color::BLACK)
+    void writePoints(ConstPolygonRef poly, bool write_coords=false, int size = 5, Color color = Color::BLACK)
     {
-        for (Point& p : poly)
+        for (const Point& p : poly)
         {
             writePoint(p, write_coords, size, color);
         }
@@ -209,12 +208,12 @@ public:
     }
     void writePolygons(const Polygons& polys, Color color = Color::BLACK)
     {
-        for (const PolygonRef poly : const_cast<Polygons&>(polys))
+        for (ConstPolygonRef poly : polys)
         {
             writePolygon(poly, color);
         }
     }
-    void writePolygon(const PolygonRef poly, Color color = Color::BLACK)
+    void writePolygon(ConstPolygonRef poly, Color color = Color::BLACK)
     {
         Point p0 = poly.back();
         for (Point p1 : poly)

src/utils/polygon.cpp

@@ -8,9 +8,9 @@
 namespace cura 
 {
 
-bool PolygonRef::shorterThan(int64_t check_length) const
+bool ConstPolygonRef::shorterThan(int64_t check_length) const
 {
-    const PolygonRef& polygon = *this;
+    const ConstPolygonRef& polygon = *this;
     const Point* p0 = &polygon.back();
     int64_t length = 0;
     for (const Point& p1 : polygon)
@@ -25,9 +25,9 @@ bool PolygonRef::shorterThan(int64_t check_length) const
     return true;
 }
 
-bool PolygonRef::_inside(Point p, bool border_result) const
+bool ConstPolygonRef::_inside(Point p, bool border_result) const
 {
-    PolygonRef thiss = *this;
+    const ConstPolygonRef thiss = *this;
     if (size() < 1)
     {
         return false;
@@ -200,11 +200,11 @@ Polygons Polygons::offset(int distance, ClipperLib::JoinType join_type, double m
     return ret;
 }
 
-Polygons PolygonRef::offset(int distance, ClipperLib::JoinType joinType, double miter_limit) const
+Polygons ConstPolygonRef::offset(int distance, ClipperLib::JoinType join_type, double miter_limit) const
 {
     Polygons ret;
     ClipperLib::ClipperOffset clipper(miter_limit, 10.0);
-    clipper.AddPath(*path, joinType, ClipperLib::etClosedPolygon);
+    clipper.AddPath(*path, join_type, ClipperLib::etClosedPolygon);
     clipper.MiterLimit = miter_limit;
     clipper.Execute(ret.paths, distance);
     return ret;
@@ -521,7 +521,7 @@ void Polygons::removeEmptyHoles_processPolyTreeNode(const ClipperLib::PolyNode&
     }
 }
 
-bool PolygonRef::smooth_corner_complex(ListPolygon& poly, const Point p1, ListPolyIt& p0_it, ListPolyIt& p2_it, const int64_t shortcut_length)
+bool ConstPolygonRef::smooth_corner_complex(ListPolygon& poly, const Point p1, ListPolyIt& p0_it, ListPolyIt& p2_it, const int64_t shortcut_length)
 {
     // walk away from the corner until the shortcut > shortcut_length or it would smooth a piece inward
     // - walk in both directions untill shortcut > shortcut_length 
@@ -703,7 +703,7 @@ bool PolygonRef::smooth_corner_complex(ListPolygon& poly, const Point p1, ListPo
     return false;
 }
 
-void PolygonRef::smooth_outward_step(const Point p1, const int64_t shortcut_length2, ListPolyIt& p0_it, ListPolyIt& p2_it, bool& forward_is_blocked, bool& backward_is_blocked, bool& forward_is_too_far, bool& backward_is_too_far)
+void ConstPolygonRef::smooth_outward_step(const Point p1, const int64_t shortcut_length2, ListPolyIt& p0_it, ListPolyIt& p2_it, bool& forward_is_blocked, bool& backward_is_blocked, bool& forward_is_too_far, bool& backward_is_too_far)
 {
     const bool forward_has_converged = forward_is_blocked || forward_is_too_far;
     const bool backward_has_converged = backward_is_blocked || backward_is_too_far;
@@ -759,7 +759,7 @@ void PolygonRef::smooth_outward_step(const Point p1, const int64_t shortcut_leng
     }
 }
 
-void PolygonRef::smooth_corner_simple(ListPolygon& poly, const Point p0, const Point p1, const Point p2, const ListPolyIt p0_it, const ListPolyIt p1_it, const ListPolyIt p2_it, const Point v10, const Point v12, const Point v02, const int64_t shortcut_length, float cos_angle)
+void ConstPolygonRef::smooth_corner_simple(ListPolygon& poly, const Point p0, const Point p1, const Point p2, const ListPolyIt p0_it, const ListPolyIt p1_it, const ListPolyIt p2_it, const Point v10, const Point v12, const Point v02, const int64_t shortcut_length, float cos_angle)
 {
     //  1----b---->2
     //  ^   /
@@ -837,7 +837,6 @@ void PolygonRef::smooth_corner_simple(ListPolygon& poly, const Point p0, const P
             Point b;
             bool success = LinearAlg2D::getPointOnLineWithDist(a, p1, p2, shortcut_length, b);
             // v02 has to be longer than ab!
-            p1_it.remove();
             if (success)
             { // if not success then assume b is negligibly close to 2, but rounding errors caused a problem
 #ifdef ASSERT_INSANE_OUTPUT
@@ -845,11 +844,12 @@ void PolygonRef::smooth_corner_simple(ListPolygon& poly, const Point p0, const P
 #endif // #ifdef ASSERT_INSANE_OUTPUT
                 ListPolyIt::insertPointNonDuplicate(p1_it, p2_it, b);
             }
+            p1_it.remove();
         }
     }
 }
 
-void PolygonRef::smooth_outward(float min_angle, int shortcut_length, PolygonRef result) const
+void ConstPolygonRef::smooth_outward(float min_angle, int shortcut_length, PolygonRef result) const
 {
 // example of smoothed out corner:
 //
@@ -952,7 +952,8 @@ Polygons Polygons::smooth_outward(float max_angle, int shortcut_length)
     return ret;
 }
 
-void PolygonRef::smooth(int remove_length, PolygonRef result)
+
+void ConstPolygonRef::smooth(int remove_length, PolygonRef result) const
 {
 // a typical zigzag with the middle part to be removed by removing (1) :
 //
@@ -967,7 +968,7 @@ void PolygonRef::smooth(int remove_length, PolygonRef result)
 //          |
 //          |
 //          0
-    PolygonRef& thiss = *this;
+    const ConstPolygonRef& thiss = *path;
     ClipperLib::Path* poly = result.path;
     if (size() > 0)
     {
@@ -1036,12 +1037,12 @@ void PolygonRef::smooth(int remove_length, PolygonRef result)
     }
 }
 
-Polygons Polygons::smooth(int remove_length)
+Polygons Polygons::smooth(int remove_length) const
 {
     Polygons ret;
     for (unsigned int p = 0; p < size(); p++)
     {
-        PolygonRef poly(paths[p]);
+        ConstPolygonRef poly(paths[p]);
         if (poly.size() < 3)
         {
             continue;
@@ -1061,23 +1062,23 @@ Polygons Polygons::smooth(int remove_length)
     return ret;
 }
 
-void PolygonRef::smooth2(int remove_length, PolygonRef result)
+void ConstPolygonRef::smooth2(int remove_length, PolygonRef result) const
 {
-    PolygonRef& thiss = *this;
+    const ConstPolygonRef& thiss = *this;
     ClipperLib::Path* poly = result.path;
-    if (size() > 0)
+    if (thiss.size() > 0)
     {
         poly->push_back(thiss[0]);
     }
-    for (unsigned int poly_idx = 1; poly_idx < size(); poly_idx++)
+    for (unsigned int poly_idx = 1; poly_idx < thiss.size(); poly_idx++)
     {
-        Point& last = thiss[poly_idx - 1];
-        Point& now = thiss[poly_idx];
-        Point& next = thiss[(poly_idx + 1) % size()];
-        if (shorterThen(last - now, remove_length) && shorterThen(now - next, remove_length)) 
+        const Point& last = thiss[poly_idx - 1];
+        const Point& now = thiss[poly_idx];
+        const Point& next = thiss[(poly_idx + 1) % thiss.size()];
+        if (shorterThen(last - now, remove_length) && shorterThen(now - next, remove_length))
         {
             poly_idx++; // skip the next line piece (dont escalate the removal of edges)
-            if (poly_idx < size())
+            if (poly_idx < thiss.size())
             {
                 poly->push_back(thiss[poly_idx]);
             }
@@ -1089,12 +1090,12 @@ void PolygonRef::smooth2(int remove_length, PolygonRef result)
     }
 }
 
-Polygons Polygons::smooth2(int remove_length, int min_area)
+Polygons Polygons::smooth2(int remove_length, int min_area) const
 {
     Polygons ret;
     for (unsigned int p = 0; p < size(); p++)
     {
-        PolygonRef poly(paths[p]);
+        ConstPolygonRef poly(paths[p]);
         if (poly.size() == 0)
         {
             continue;
@@ -1147,14 +1148,14 @@ void Polygons::splitIntoParts_processPolyTreeNode(ClipperLib::PolyNode* node, st
     }
 }
 
-unsigned int PartsView::getPartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx) 
+unsigned int PartsView::getPartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx) const
 {
-    PartsView& partsView = *this;
+    const PartsView& partsView = *this;
     for (unsigned int part_idx_now = 0; part_idx_now < partsView.size(); part_idx_now++)
     {
-        std::vector<unsigned int>& partView = partsView[part_idx_now];
+        const std::vector<unsigned int>& partView = partsView[part_idx_now];
         if (partView.size() == 0) { continue; }
-        std::vector<unsigned int>::iterator result = std::find(partView.begin(), partView.end(), poly_idx);
+        std::vector<unsigned int>::const_iterator result = std::find(partView.begin(), partView.end(), poly_idx);
         if (result != partView.end()) 
         { 
             if (boundary_poly_idx) { *boundary_poly_idx = partView[0]; }
@@ -1178,7 +1179,7 @@ PolygonsPart PartsView::assemblePart(unsigned int part_idx) const
     return ret;
 }
 
-PolygonsPart PartsView::assemblePartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx) 
+PolygonsPart PartsView::assemblePartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx) const
 {
     PolygonsPart ret;
     unsigned int part_idx = getPartContaining(poly_idx, boundary_poly_idx);
@@ -1215,7 +1216,7 @@ void Polygons::splitIntoPartsView_processPolyTreeNode(PartsView& partsView, Poly
         partsView.emplace_back();
         unsigned int pos = partsView.size() - 1;
         partsView[pos].push_back(reordered.size());
-        reordered.add(child->Contour);
+        reordered.add(child->Contour); //TODO: should this steal the internal representation for speed?
         for(int i = 0; i < child->ChildCount(); i++)
         {
             partsView[pos].push_back(reordered.size());

src/utils/polygon.h

@@ -27,6 +27,8 @@ namespace cura {
 
 class PartsView;
 class Polygons;
+class Polygon;
+class PolygonRef;
 
 class ListPolyIt;
 
@@ -36,31 +38,60 @@ typedef std::vector<ListPolygon> ListPolygons; //!< Polygons represented by a ve
 const static int clipper_init = (0);
 #define NO_INDEX (std::numeric_limits<unsigned int>::max())
 
-class PolygonRef
+class ConstPolygonRef
 {
+    friend class Polygons;
+    friend class Polygon;
+    friend class PolygonRef;
+protected:
     ClipperLib::Path* path;
-    PolygonRef()
+    ConstPolygonRef()
     : path(nullptr)
     {}
 public:
-    PolygonRef(ClipperLib::Path& polygon)
-    : path(&polygon)
+    ConstPolygonRef(const ClipperLib::Path& polygon)
+    : path(const_cast<ClipperLib::Path*>(&polygon))
     {}
-    
+
+    bool operator==(ConstPolygonRef& other) const =delete;
+
+// needed in std::optional<ConstPolygonRef>
+//     ConstPolygonRef& operator=(const ConstPolygonRef& other) =delete;
+    ConstPolygonRef& operator=(const ConstPolygonRef& other)
+    {
+        path = other.path;
+        return *this;
+    }
+
     unsigned int size() const
     {
         return path->size();
     }
 
-    Point& operator[] (unsigned int index) const
+    const Point& operator[] (unsigned int index) const
     {
-        POLY_ASSERT(index < size() && index <= std::numeric_limits<int>::max());
+        POLY_ASSERT(index < size());
         return (*path)[index];
     }
 
-    void* data()
+    const ClipperLib::Path& operator*() const
     {
-        return path->data();
+        return *path;
+    }
+
+    ClipperLib::Path::const_iterator begin() const
+    {
+        return path->begin();
+    }
+
+    ClipperLib::Path::const_iterator end() const
+    {
+        return path->end();
+    }
+
+    ClipperLib::Path::const_reference back() const
+    {
+        return path->back();
     }
 
     const void* data() const
@@ -68,37 +99,10 @@ public:
         return path->data();
     }
 
-    void add(const Point p)
-    {
-        path->push_back(p);
-    }
-
-    PolygonRef& operator=(const PolygonRef& other) { path = other.path; return *this; }
-
-    bool operator==(const PolygonRef& other) const =delete;
-
-    ClipperLib::Path& operator*() { return *path; }
-    
-    template <typename... Args>
-    void emplace_back(Args&&... args)
-    {
-        path->emplace_back(args...);
-    }
-
-    void remove(unsigned int index)
-    {
-        POLY_ASSERT(index < size() && index <= std::numeric_limits<int>::max());
-        path->erase(path->begin() + index);
-    }
-
-    void clear()
-    {
-        path->clear();
-    }
 
     /*!
      * On Y-axis positive upward displays, Orientation will return true if the polygon's orientation is counter-clockwise.
-     * 
+     *
      * from http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Functions/Orientation.htm
      */
     bool orientation() const
@@ -106,11 +110,6 @@ public:
         return ClipperLib::Orientation(*path);
     }
 
-    void reverse()
-    {
-        ClipperLib::ReversePath(*path);
-    }
-
     Polygons offset(int distance, ClipperLib::JoinType joinType = ClipperLib::jtMiter, double miter_limit = 1.2) const;
 
     int64_t polygonLength() const
@@ -125,7 +124,7 @@ public:
         }
         return length;
     }
-    
+
     bool shorterThan(int64_t check_length) const;
 
     Point min() const
@@ -138,7 +137,7 @@ public:
         }
         return ret;
     }
-    
+
     Point max() const
     {
         Point ret = Point(POINT_MIN, POINT_MIN);
@@ -154,19 +153,6 @@ public:
     {
         return ClipperLib::Area(*path);
     }
-    
-    /*!
-     * Translate the whole polygon in some direction.
-     * 
-     * \param translation The direction in which to move the polygon
-     */
-    void translate(Point translation)
-    {
-        for (Point& p : *this)
-        {
-            p += translation;
-        }
-    }
 
     Point centerOfMass() const
     {
@@ -183,14 +169,14 @@ public:
         }
 
         double area = Area(*path);
-        
+
         x = x / 6 / area;
         y = y / 6 / area;
 
         return Point(x, y);
     }
 
-    Point closestPointTo(Point p)
+    Point closestPointTo(Point p) const
     {
         Point ret = p;
         float bestDist = FLT_MAX;
@@ -205,7 +191,7 @@ public:
         }
         return ret;
     }
-    
+
     /*!
      * Check if we are inside the polygon. We do this by tracing from the point towards the positive X direction,
      * every line we cross increments the crossings counter. If we have an even number of crossings then we are not inside the polygon.
@@ -241,7 +227,7 @@ public:
         }
         return res == 1;
     }
-    
+
     /*!
      * Smooth out small perpendicular segments and store the result in \p result.
      * Smoothing is performed by removing the inner most vertex of a line segment smaller than \p remove_length
@@ -253,7 +239,7 @@ public:
      * \param remove_length The length of the largest segment removed
      * \param result (output) The result polygon, assumed to be empty
      */
-    void smooth(int remove_length, PolygonRef result);
+    void smooth(int remove_length, PolygonRef result) const;
 
     /*!
      * Smooth out sharp inner corners, by taking a shortcut which bypasses the corner
@@ -271,51 +257,8 @@ public:
      * \param remove_length The length of the largest segment removed
      * \param result (output) The result polygon, assumed to be empty
      */
-    void smooth2(int remove_length, PolygonRef result);
+    void smooth2(int remove_length, PolygonRef result) const;
 
-    /*! 
-     * Removes consecutive line segments with same orientation and changes this polygon.
-     * 
-     * Removes verts which are connected to line segments which are both too small.
-     * Removes verts which detour from a direct line from the previous and next vert by a too small amount.
-     * 
-     * \param smallest_line_segment_squared maximal squared length of removed line segments
-     * \param allowed_error_distance_squared The square of the distance of the middle point to the line segment of the consecutive and previous point for which the middle point is removed
-     */
-    void simplify(int smallest_line_segment_squared = 100, int allowed_error_distance_squared = 25);
-
-    void pop_back()
-    { 
-        path->pop_back();
-    }
-    
-    ClipperLib::Path::reference back() const
-    {
-        return path->back();
-    }
-    
-    ClipperLib::Path::iterator begin()
-    {
-        return path->begin();
-    }
-
-    ClipperLib::Path::iterator end()
-    {
-        return path->end();
-    }
-
-    ClipperLib::Path::const_iterator begin() const
-    {
-        return path->begin();
-    }
-
-    ClipperLib::Path::const_iterator end() const
-    {
-        return path->end();
-    }
-
-    friend class Polygons;
-    friend class Polygon;
 
 private:
     /*!
@@ -375,6 +318,113 @@ private:
     static void smooth_outward_step(const Point p1, const int64_t shortcut_length2, ListPolyIt& p0_it, ListPolyIt& p2_it, bool& forward_is_blocked, bool& backward_is_blocked, bool& forward_is_too_far, bool& backward_is_too_far);
 };
 
+
+class PolygonRef : public ConstPolygonRef
+{
+    PolygonRef()
+    : ConstPolygonRef()
+    {}
+public:
+    PolygonRef(ClipperLib::Path& polygon)
+    : ConstPolygonRef(polygon)
+    {}
+
+    PolygonRef& operator=(const PolygonRef& other)
+    {
+        path = other.path;
+        return *this;
+    }
+
+    Point& operator[] (unsigned int index)
+    {
+        POLY_ASSERT(index < size());
+        return (*path)[index];
+    }
+
+    ClipperLib::Path::iterator begin()
+    {
+        return path->begin();
+    }
+
+    ClipperLib::Path::iterator end()
+    {
+        return path->end();
+    }
+
+    ClipperLib::Path::reference back()
+    {
+        return path->back();
+    }
+
+    void* data()
+    {
+        return path->data();
+    }
+
+    void add(const Point p)
+    {
+        path->push_back(p);
+    }
+
+    PolygonRef& operator=(ConstPolygonRef& other) { path = other.path; return *this; }
+
+    ClipperLib::Path& operator*()
+    {
+        return *path;
+    }
+
+    template <typename... Args>
+    void emplace_back(Args&&... args)
+    {
+        path->emplace_back(args...);
+    }
+
+    void remove(unsigned int index)
+    {
+        POLY_ASSERT(index < size() && index <= std::numeric_limits<int>::max());
+        path->erase(path->begin() + index);
+    }
+
+    void clear()
+    {
+        path->clear();
+    }
+
+    void reverse()
+    {
+        ClipperLib::ReversePath(*path);
+    }
+
+    /*!
+     * Translate the whole polygon in some direction.
+     * 
+     * \param translation The direction in which to move the polygon
+     */
+    void translate(Point translation)
+    {
+        for (Point& p : *this)
+        {
+            p += translation;
+        }
+    }
+
+    /*! 
+     * Removes consecutive line segments with same orientation and changes this polygon.
+     * 
+     * Removes verts which are connected to line segments which are both too small.
+     * Removes verts which detour from a direct line from the previous and next vert by a too small amount.
+     * 
+     * \param smallest_line_segment_squared maximal squared length of removed line segments
+     * \param allowed_error_distance_squared The square of the distance of the middle point to the line segment of the consecutive and previous point for which the middle point is removed
+     */
+    void simplify(int smallest_line_segment_squared = 100, int allowed_error_distance_squared = 25);
+
+    void pop_back()
+    { 
+        path->pop_back();
+    }
+};
+
 class Polygon : public PolygonRef
 {
     ClipperLib::Path poly;
@@ -384,7 +434,7 @@ public:
     {
     }
 
-    Polygon(const PolygonRef& other)
+    Polygon(PolygonRef& other)
     : PolygonRef(poly)
     {
         poly = *other.path;
@@ -397,6 +447,7 @@ class Polygons
 {
     friend class Polygon;
     friend class PolygonRef;
+    friend class ConstPolygonRef;
 protected:
     ClipperLib::Paths paths;
 public:
@@ -410,11 +461,12 @@ public:
     PolygonRef operator[] (unsigned int index)
     {
         POLY_ASSERT(index < size() && index <= std::numeric_limits<int>::max());
-        return PolygonRef(paths[index]);
+        return paths[index];
     }
-    const PolygonRef operator[] (unsigned int index) const
+    ConstPolygonRef operator[] (unsigned int index) const
     {
-        return const_cast<Polygons*>(this)->operator[](index);
+        POLY_ASSERT(index < size() && index <= std::numeric_limits<int>::max());
+        return paths[index];
     }
     ClipperLib::Paths::iterator begin()
     {
@@ -457,7 +509,11 @@ public:
     {
         paths.clear();
     }
-    void add(const PolygonRef& poly)
+    void add(ConstPolygonRef& poly)
+    {
+        paths.push_back(*poly.path);
+    }
+    void add(const ConstPolygonRef& poly)
     {
         paths.push_back(*poly.path);
     }
@@ -493,6 +549,10 @@ public:
     {
         return PolygonRef(paths.back());
     }
+    ConstPolygonRef back() const
+    {
+        return ConstPolygonRef(paths.back());
+    }
 
     Polygons() {}
 
@@ -647,7 +707,7 @@ public:
      * \param remove_length The length of the largest segment removed
      * \return The smoothed polygon
      */
-    Polygons smooth(int remove_length);
+    Polygons smooth(int remove_length) const;
 
     /*!
      * Smooth out sharp inner corners, by taking a shortcut which bypasses the corner
@@ -658,7 +718,7 @@ public:
      */
     Polygons smooth_outward(float angle, int shortcut_length);
 
-    Polygons smooth2(int remove_length, int min_area); //!< removes points connected to small lines
+    Polygons smooth2(int remove_length, int min_area) const; //!< removes points connected to small lines
     
     /*!
      * removes points connected to similarly oriented lines
@@ -798,16 +858,16 @@ public:
      * Removes the same polygons from this set (and also empty polygons).
      * Polygons are considered the same if all points lie within [same_distance] of their counterparts.
      */
-    Polygons remove(Polygons& to_be_removed, int same_distance = 0)
+    Polygons remove(const Polygons& to_be_removed, int same_distance = 0) const
     {
         Polygons result;
         for (unsigned int poly_keep_idx = 0; poly_keep_idx < size(); poly_keep_idx++)
         {
-            PolygonRef poly_keep = (*this)[poly_keep_idx];
+            ConstPolygonRef poly_keep = (*this)[poly_keep_idx];
             bool should_be_removed = false;
             if (poly_keep.size() > 0) 
 //             for (int hole_poly_idx = 0; hole_poly_idx < to_be_removed.size(); hole_poly_idx++)
-            for (PolygonRef poly_rem : to_be_removed)
+            for (ConstPolygonRef poly_rem : to_be_removed)
             {
 //                 PolygonRef poly_rem = to_be_removed[hole_poly_idx];
                 if (poly_rem.size() != poly_keep.size() || poly_rem.size() == 0) continue;
@@ -923,10 +983,13 @@ public:
 class PolygonsPart : public Polygons
 {   
 public:
-    PolygonRef outerPolygon() 
+    PolygonRef outerPolygon()
     {
-        Polygons& thiss = *this;
-        return thiss[0];
+        return this->paths[0];
+    }
+    ConstPolygonRef outerPolygon() const
+    {
+        return this->paths[0];
     }
     
     bool inside(Point p)
@@ -959,7 +1022,7 @@ public:
      * \param boundary_poly_idx Optional output parameter: The index of the boundary polygon of the part in \p polygons
      * \return The PolygonsPart containing the polygon with index \p poly_idx
      */
-    unsigned int getPartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx = nullptr);
+    unsigned int getPartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx = nullptr) const;
     /*!
      * Assemble the PolygonsPart of which the polygon with index \p poly_idx is part.
      * 
@@ -967,7 +1030,7 @@ public:
      * \param boundary_poly_idx Optional output parameter: The index of the boundary polygon of the part in \p polygons
      * \return The PolygonsPart containing the polygon with index \p poly_idx
      */
-    PolygonsPart assemblePartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx = nullptr);
+    PolygonsPart assemblePartContaining(unsigned int poly_idx, unsigned int* boundary_poly_idx = nullptr) const;
     /*!
      * Assemble the PolygonsPart of which the polygon with index \p poly_idx is part.
      * 

src/utils/polygonUtils.cpp

@@ -22,7 +22,7 @@ int64_t PolygonUtils::segmentLength(PolygonsPointIndex start, PolygonsPointIndex
     assert(start.poly_idx == end.poly_idx);
     int64_t segment_length = 0;
     Point prev_vert = start.p();
-    const PolygonRef poly = (*start.polygons)[start.poly_idx];
+    ConstPolygonRef poly = (*start.polygons)[start.poly_idx];
     for (unsigned int point_idx = 1; point_idx <= poly.size(); point_idx++)
     {
         unsigned int vert_idx = (start.point_idx + point_idx) % poly.size();
@@ -44,7 +44,7 @@ void PolygonUtils::spreadDots(PolygonsPointIndex start, PolygonsPointIndex end,
     assert(start.poly_idx == end.poly_idx);
     int64_t segment_length = segmentLength(start, end);
 
-    const PolygonRef poly = (*start.polygons)[start.poly_idx];
+    ConstPolygonRef poly = (*start.polygons)[start.poly_idx];
     unsigned int n_dots_in_between = n_dots;
     if (start == end)
     {
@@ -80,7 +80,7 @@ void PolygonUtils::spreadDots(PolygonsPointIndex start, PolygonsPointIndex end,
     assert(result.size() == n_dots && "we didn't generate as many wipe locations as we asked for.");
 }
 
-Point PolygonUtils::getVertexInwardNormal(PolygonRef poly, unsigned int point_idx)
+Point PolygonUtils::getVertexInwardNormal(ConstPolygonRef poly, unsigned int point_idx)
 {
     Point p1 = poly[point_idx];
 
@@ -110,7 +110,7 @@ Point PolygonUtils::getVertexInwardNormal(PolygonRef poly, unsigned int point_id
             break;
         }
     }
-    Point& p2 = poly[p2_idx];
+    const Point& p2 = poly[p2_idx];
 
     Point off0 = turn90CCW(normal(p1 - p0, MM2INT(10.0))); // 10.0 for some precision
     Point off1 = turn90CCW(normal(p2 - p1, MM2INT(10.0))); // 10.0 for some precision
@@ -119,7 +119,7 @@ Point PolygonUtils::getVertexInwardNormal(PolygonRef poly, unsigned int point_id
 }
 
 
-Point PolygonUtils::getBoundaryPointWithOffset(PolygonRef poly, unsigned int point_idx, int64_t offset)
+Point PolygonUtils::getBoundaryPointWithOffset(ConstPolygonRef poly, unsigned int point_idx, int64_t offset)
 {
     return poly[point_idx] + normal(getVertexInwardNormal(poly, point_idx), -offset);
 }
@@ -130,7 +130,7 @@ Point PolygonUtils::moveInsideDiagonally(ClosestPolygonPoint point_on_boundary,
     {
         return no_point;
     }
-    PolygonRef poly = *point_on_boundary.poly;
+    ConstPolygonRef poly = *point_on_boundary.poly;
     Point p0 = poly[point_on_boundary.point_idx];
     Point p1 = poly[(point_on_boundary.point_idx + 1) % poly.size()];
     if (vSize2(p0 - point_on_boundary.location) < vSize2(p1 - point_on_boundary.location))
@@ -163,7 +163,7 @@ ClosestPolygonPoint PolygonUtils::moveInside2(const Polygons& polygons, Point& f
     return _moveInside2(*closest_polygon_point, distance, from, max_dist2);
 }
 
-ClosestPolygonPoint PolygonUtils::moveInside2(const Polygons& loc_to_line_polygons, const PolygonRef polygon, Point& from, const int distance, const int64_t max_dist2, const LocToLineGrid* loc_to_line_grid, const std::function<int(Point)>& penalty_function)
+ClosestPolygonPoint PolygonUtils::moveInside2(const Polygons& loc_to_line_polygons, ConstPolygonRef polygon, Point& from, const int distance, const int64_t max_dist2, const LocToLineGrid* loc_to_line_grid, const std::function<int(Point)>& penalty_function)
 {
     std::optional<ClosestPolygonPoint> closest_polygon_point;
     if (loc_to_line_grid)
@@ -225,7 +225,7 @@ unsigned int PolygonUtils::moveInside(const Polygons& polygons, Point& from, int
     bool is_already_on_correct_side_of_boundary = false; // whether [from] is already on the right side of the boundary
     for (unsigned int poly_idx = 0; poly_idx < polygons.size(); poly_idx++)
     {
-        const PolygonRef poly = polygons[poly_idx];
+        ConstPolygonRef poly = polygons[poly_idx];
         if (poly.size() < 2)
             continue;
         Point p0 = poly[poly.size()-2];
@@ -344,11 +344,11 @@ Point PolygonUtils::moveInside(const ClosestPolygonPoint& cpp, const int distanc
     { // the point which is assumed to be on the boundary doesn't have to be moved
         return cpp.location;
     }
-    const PolygonRef poly = *cpp.poly;
+    ConstPolygonRef poly = *cpp.poly;
     unsigned int point_idx = cpp.point_idx;
     const Point& on_boundary = cpp.location;
 
-    Point& p1 = poly[point_idx];
+    const Point& p1 = poly[point_idx];
     unsigned int p2_idx;
     for (p2_idx = point_idx + 1; p2_idx != point_idx; p2_idx = p2_idx + 1)
     { // find the next point different from p1
@@ -361,7 +361,7 @@ Point PolygonUtils::moveInside(const ClosestPolygonPoint& cpp, const int distanc
             break;
         }
     }
-    Point& p2 = poly[p2_idx];
+    const Point& p2 = poly[p2_idx];
 
     if (on_boundary == p1)
     {
@@ -392,7 +392,7 @@ ClosestPolygonPoint PolygonUtils::ensureInsideOrOutside(const Polygons& polygons
     {
         return ClosestPolygonPoint(); // we couldn't move inside
     }
-    PolygonRef closest_poly = *closest_polygon_point.poly;
+    ConstPolygonRef closest_poly = *closest_polygon_point.poly;
     bool is_outside_boundary = closest_poly.orientation();
 
     {
@@ -481,8 +481,8 @@ void PolygonUtils::findSmallestConnection(ClosestPolygonPoint& poly1_result, Clo
     {
         return;
     }
-    PolygonRef poly1 = *poly1_result.poly;
-    PolygonRef poly2 = *poly2_result.poly;
+    ConstPolygonRef poly1 = *poly1_result.poly;
+    ConstPolygonRef poly2 = *poly2_result.poly;
     if (poly1.size() == 0 || poly2.size() == 0)
     {
         return;
@@ -515,8 +515,8 @@ void PolygonUtils::walkToNearestSmallestConnection(ClosestPolygonPoint& poly1_re
     {
         return;
     }
-    PolygonRef poly1 = *poly1_result.poly;
-    PolygonRef poly2 = *poly2_result.poly;
+    ConstPolygonRef poly1 = *poly1_result.poly;
+    ConstPolygonRef poly2 = *poly2_result.poly;
     if (poly1_result.point_idx < 0 || poly2_result.point_idx < 0)
     {
         return;
@@ -537,7 +537,7 @@ void PolygonUtils::walkToNearestSmallestConnection(ClosestPolygonPoint& poly1_re
     }
 }
 
-ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, PolygonRef polygon, int start_idx)
+ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, ConstPolygonRef polygon, int start_idx)
 {
     ClosestPolygonPoint forth = findNearestClosest(from, polygon, start_idx, 1);
     if (!forth.isValid())
@@ -556,7 +556,7 @@ ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, PolygonRef poly
     }
 }
 
-ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, PolygonRef polygon, int start_idx, int direction)
+ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, ConstPolygonRef polygon, int start_idx, int direction)
 {
     if (polygon.size() == 0)
     {
@@ -572,8 +572,8 @@ ClosestPolygonPoint PolygonUtils::findNearestClosest(Point from, PolygonRef poly
     {
         int p1_idx = (polygon.size() + direction*p + start_idx) % polygon.size();
         int p2_idx = (polygon.size() + direction*(p+1) + start_idx) % polygon.size();
-        Point& p1 = polygon[p1_idx];
-        Point& p2 = polygon[p2_idx];
+        const Point& p1 = polygon[p1_idx];
+        const Point& p2 = polygon[p2_idx];
 
         Point closest_here = LinearAlg2D::getClosestOnLineSegment(from, p1 ,p2);
         int64_t dist = vSize2(from - closest_here);
@@ -600,7 +600,7 @@ ClosestPolygonPoint PolygonUtils::findClosest(Point from, const Polygons& polygo
     {
         return none;
     }
-    PolygonRef any_polygon = polygons[0];
+    ConstPolygonRef any_polygon = polygons[0];
     unsigned int any_poly_idx;
     for (any_poly_idx = 0; any_poly_idx < polygons.size(); any_poly_idx++)
     { // find first point in all polygons
@@ -620,7 +620,7 @@ ClosestPolygonPoint PolygonUtils::findClosest(Point from, const Polygons& polygo
     
     for (unsigned int ply = 0; ply < polygons.size(); ply++)
     {
-        const PolygonRef poly = polygons[ply];
+        ConstPolygonRef poly = polygons[ply];
         if (poly.size() == 0) continue;
         ClosestPolygonPoint closest_here = findClosest(from, poly, penalty_function);
         if (!closest_here.isValid())
@@ -639,7 +639,7 @@ ClosestPolygonPoint PolygonUtils::findClosest(Point from, const Polygons& polygo
     return best;
 }
 
-ClosestPolygonPoint PolygonUtils::findClosest(Point from, const PolygonRef polygon, const std::function<int(Point)>& penalty_function)
+ClosestPolygonPoint PolygonUtils::findClosest(Point from, ConstPolygonRef polygon, const std::function<int(Point)>& penalty_function)
 {
     if (polygon.size() == 0)
     {
@@ -653,11 +653,11 @@ ClosestPolygonPoint PolygonUtils::findClosest(Point from, const PolygonRef polyg
 //
     for (unsigned int p = 0; p<polygon.size(); p++)
     {
-        Point& p1 = polygon[p];
+        const Point& p1 = polygon[p];
 
         unsigned int p2_idx = p+1;
         if (p2_idx >= polygon.size()) p2_idx = 0;
-        Point& p2 = polygon[p2_idx];
+        const Point& p2 = polygon[p2_idx];
 
         Point closest_here = LinearAlg2D::getClosestOnLineSegment(from, p1 ,p2);
         int64_t dist2_score = vSize2(from - closest_here) + penalty_function(closest_here);
@@ -678,7 +678,7 @@ PolygonsPointIndex PolygonUtils::findNearestVert(const Point from, const Polygon
     PolygonsPointIndex closest_vert;
     for (unsigned int poly_idx = 0; poly_idx < polys.size(); poly_idx++)
     {
-        const PolygonRef poly = polys[poly_idx];
+        ConstPolygonRef poly = polys[poly_idx];
         for (unsigned int point_idx = 0; point_idx < poly.size(); point_idx++)
         {
             int64_t dist2 = vSize2(poly[point_idx] - from);
@@ -692,7 +692,7 @@ PolygonsPointIndex PolygonUtils::findNearestVert(const Point from, const Polygon
     return closest_vert;
 }
 
-unsigned int PolygonUtils::findNearestVert(const Point from, const PolygonRef poly)
+unsigned int PolygonUtils::findNearestVert(const Point from, ConstPolygonRef poly)
 {
     int64_t best_dist2 = std::numeric_limits<int64_t>::max();
     unsigned int closest_vert_idx = -1;
@@ -721,7 +721,7 @@ LocToLineGrid* PolygonUtils::createLocToLineGrid(const Polygons& polygons, int s
 
     for (unsigned int poly_idx = 0; poly_idx < polygons.size(); poly_idx++)
     {
-        const PolygonRef poly = polygons[poly_idx];
+        ConstPolygonRef poly = polygons[poly_idx];
         for (unsigned int point_idx = 0; point_idx < poly.size(); point_idx++)
         {
             ret->insert(PolygonsPointIndex(&polygons, poly_idx, point_idx));
@@ -752,9 +752,9 @@ std::optional<ClosestPolygonPoint> PolygonUtils::findClose(
     PolygonsPointIndex best_point_poly_idx(nullptr, NO_INDEX, NO_INDEX);
     for (PolygonsPointIndex& point_poly_index : near_lines)
     {
-        const PolygonRef poly = polygons[point_poly_index.poly_idx];
-        Point& p1 = poly[point_poly_index.point_idx];
-        Point& p2 = poly[(point_poly_index.point_idx + 1) % poly.size()];
+        ConstPolygonRef poly = polygons[point_poly_index.poly_idx];
+        const Point& p1 = poly[point_poly_index.point_idx];
+        const Point& p2 = poly[(point_poly_index.point_idx + 1) % poly.size()];
 
         Point closest_here = LinearAlg2D::getClosestOnLineSegment(from, p1 ,p2);
         int64_t dist2_score = vSize2(from - closest_here) + penalty_function(closest_here);
@@ -778,7 +778,7 @@ std::optional<ClosestPolygonPoint> PolygonUtils::findClose(
 
 
 std::vector<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> PolygonUtils::findClose(
-    const PolygonRef from, const Polygons& destination,
+    ConstPolygonRef from, const Polygons& destination,
     const LocToLineGrid& destination_loc_to_line,
     const std::function<int(Point)>& penalty_function)
 {
@@ -817,7 +817,7 @@ std::vector<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> PolygonUtils::f
 
 
 
-bool PolygonUtils::getNextPointWithDistance(Point from, int64_t dist, const PolygonRef poly, int start_idx, int poly_start_idx, GivenDistPoint& result)
+bool PolygonUtils::getNextPointWithDistance(Point from, int64_t dist, ConstPolygonRef poly, int start_idx, int poly_start_idx, GivenDistPoint& result)
 {
     
     Point prev_poly_point = poly[(start_idx + poly_start_idx) % poly.size()];
@@ -825,7 +825,7 @@ bool PolygonUtils::getNextPointWithDistance(Point from, int64_t dist, const Poly
     for (unsigned int prev_idx = start_idx; prev_idx < poly.size(); prev_idx++) 
     {
         int next_idx = (prev_idx + 1 + poly_start_idx) % poly.size(); // last checked segment is between last point in poly and poly[0]...
-        Point& next_poly_point = poly[next_idx];
+        const Point& next_poly_point = poly[next_idx];
         if ( !shorterThen(next_poly_point - from, dist) )
         {
             /*
@@ -932,7 +932,7 @@ bool PolygonUtils::polygonCollidesWithLineSegment(const Point from, const Point
     return ret;
 }
 
-bool PolygonUtils::polygonCollidesWithLineSegment(const PolygonRef poly, Point& transformed_startPoint, Point& transformed_endPoint, PointMatrix transformation_matrix)
+bool PolygonUtils::polygonCollidesWithLineSegment(ConstPolygonRef poly, const Point& transformed_startPoint, const Point& transformed_endPoint, PointMatrix transformation_matrix)
 {
     Point p0 = transformation_matrix.apply(poly.back());
     for(Point p1_ : poly)
@@ -947,7 +947,7 @@ bool PolygonUtils::polygonCollidesWithLineSegment(const PolygonRef poly, Point&
     return false;
 }
 
-bool PolygonUtils::polygonCollidesWithLineSegment(const PolygonRef poly, Point& startPoint, Point& endPoint)
+bool PolygonUtils::polygonCollidesWithLineSegment(ConstPolygonRef poly, const Point& startPoint, const Point& endPoint)
 {
     Point diff = endPoint - startPoint;
 
@@ -958,9 +958,9 @@ bool PolygonUtils::polygonCollidesWithLineSegment(const PolygonRef poly, Point&
     return PolygonUtils::polygonCollidesWithLineSegment(poly, transformed_startPoint, transformed_endPoint, transformation_matrix);
 }
 
-bool PolygonUtils::polygonCollidesWithLineSegment(const Polygons& polys, Point& transformed_startPoint, Point& transformed_endPoint, PointMatrix transformation_matrix)
+bool PolygonUtils::polygonCollidesWithLineSegment(const Polygons& polys, const Point& transformed_startPoint, const Point& transformed_endPoint, PointMatrix transformation_matrix)
 {
-    for (const PolygonRef poly : const_cast<Polygons&>(polys))
+    for (ConstPolygonRef poly : polys)
     {
         if (poly.size() == 0) { continue; }
         if (PolygonUtils::polygonCollidesWithLineSegment(poly, transformed_startPoint, transformed_endPoint, transformation_matrix))
@@ -973,7 +973,7 @@ bool PolygonUtils::polygonCollidesWithLineSegment(const Polygons& polys, Point&
 }
 
 
-bool PolygonUtils::polygonCollidesWithLineSegment(const Polygons& polys, Point& startPoint, Point& endPoint)
+bool PolygonUtils::polygonCollidesWithLineSegment(const Polygons& polys, const Point& startPoint, const Point& endPoint)
 {
     Point diff = endPoint - startPoint;
 

src/utils/polygonUtils.h

@@ -20,12 +20,12 @@ namespace cura
 struct ClosestPolygonPoint
 {
     Point location; //!< Result location
-    std::optional<PolygonRef> poly; //!< Polygon in which the result was found (or none if no result was found)
+    std::optional<ConstPolygonRef> poly; //!< Polygon in which the result was found (or none if no result was found)
     unsigned int poly_idx; //!< The index of the polygon in some Polygons where ClosestPolygonPoint::poly can be found
     unsigned int point_idx; //!< Index to the first point in the polygon of the line segment on which the result was found
-    ClosestPolygonPoint(Point p, int pos, PolygonRef poly) :  location(p), poly(true, poly), poly_idx(NO_INDEX), point_idx(pos) {};
-    ClosestPolygonPoint(Point p, int pos, PolygonRef poly, int poly_idx) :  location(p), poly(true, poly), poly_idx(poly_idx), point_idx(pos) {};
-    ClosestPolygonPoint(PolygonRef poly) : poly(true, poly), poly_idx(NO_INDEX), point_idx(NO_INDEX) {};
+    ClosestPolygonPoint(Point p, int pos, ConstPolygonRef poly) :  location(p), poly(true, poly), poly_idx(NO_INDEX), point_idx(pos) {};
+    ClosestPolygonPoint(Point p, int pos, ConstPolygonRef poly, int poly_idx) :  location(p), poly(true, poly), poly_idx(poly_idx), point_idx(pos) {};
+    ClosestPolygonPoint(ConstPolygonRef poly) : poly(true, poly), poly_idx(NO_INDEX), point_idx(NO_INDEX) {};
     ClosestPolygonPoint() : poly_idx(NO_INDEX), point_idx(NO_INDEX) {};
     Point p() const
     { // conformity with other classes
@@ -53,7 +53,7 @@ struct PolygonsPointIndexSegmentLocator
 {
     std::pair<Point, Point> operator()(const PolygonsPointIndex& val) const
     {
-        PolygonRef poly = (*val.polygons)[val.poly_idx];
+        ConstPolygonRef poly = (*val.polygons)[val.poly_idx];
         Point start = poly[val.point_idx];
         unsigned int next_point_idx = (val.point_idx + 1) % poly.size();
         Point end = poly[next_point_idx];
@@ -104,7 +104,7 @@ public:
      * \param poly The polygon.
      * \param point_idx The index of the point in the polygon.
      */
-    static Point getVertexInwardNormal(PolygonRef poly, unsigned int point_idx);
+    static Point getVertexInwardNormal(ConstPolygonRef poly, unsigned int point_idx);
 
     /*!
     * Get a point from the \p poly with a given \p offset.
@@ -114,7 +114,7 @@ public:
     * \param offset The distance the point has to be moved outward from the polygon.
     * \return A point at the given distance inward from the point on the boundary polygon.
     */
-    static Point getBoundaryPointWithOffset(PolygonRef poly, unsigned int point_idx, int64_t offset);
+    static Point getBoundaryPointWithOffset(ConstPolygonRef poly, unsigned int point_idx, int64_t offset);
 
     /*!
      * Move a point away from the boundary by looking at the boundary normal of the nearest vert.
@@ -178,7 +178,7 @@ public:
      * \param penalty_function A function returning a penalty term on the squared distance score of a candidate point.
      * \return The point on the polygon closest to \p from
      */
-    static ClosestPolygonPoint moveInside2(const Polygons& loc_to_line_polygons, const PolygonRef polygon, Point& from, const int distance = 0, const int64_t max_dist2 = std::numeric_limits<int64_t>::max(), const LocToLineGrid* loc_to_line_grid = nullptr, const std::function<int(Point)>& penalty_function = no_penalty_function);
+    static ClosestPolygonPoint moveInside2(const Polygons& loc_to_line_polygons, ConstPolygonRef polygon, Point& from, const int distance = 0, const int64_t max_dist2 = std::numeric_limits<int64_t>::max(), const LocToLineGrid* loc_to_line_grid = nullptr, const std::function<int(Point)>& penalty_function = no_penalty_function);
 
     /*!
      * The opposite of moveInside.
@@ -298,7 +298,7 @@ public:
     * \param start_idx The index of the point in the polygon from which to start looking.
     * \return The nearest point from \p start_idx going along the \p polygon (in both directions) with a locally minimal distance to \p from.
     */
-    static ClosestPolygonPoint findNearestClosest(Point from, const PolygonRef polygon, int start_idx);
+    static ClosestPolygonPoint findNearestClosest(Point from, ConstPolygonRef polygon, int start_idx);
 
     /*!
     * Find the nearest closest point on a polygon from a given index walking in one direction along the polygon.
@@ -309,7 +309,7 @@ public:
     * \param direction The direction to walk: 1 for walking along the \p polygon, -1 for walking in opposite direction
     * \return The nearest point from \p start_idx going along the \p polygon with a locally minimal distance to \p from.
     */
-    static ClosestPolygonPoint findNearestClosest(const Point from, const PolygonRef polygon, int start_idx, int direction);
+    static ClosestPolygonPoint findNearestClosest(const Point from, ConstPolygonRef polygon, int start_idx, int direction);
 
     /*!
      * Find the point closest to \p from in all polygons in \p polygons.
@@ -327,7 +327,7 @@ public:
      * 
      * \param penalty_function A function returning a penalty term on the squared distance score of a candidate point.
      */
-    static ClosestPolygonPoint findClosest(Point from, const PolygonRef polygon, const std::function<int(Point)>& penalty_function = no_penalty_function);
+    static ClosestPolygonPoint findClosest(Point from, ConstPolygonRef polygon, const std::function<int(Point)>& penalty_function = no_penalty_function);
 
     /*!
      * Find the nearest vertex to \p from in \p polys
@@ -343,7 +343,7 @@ public:
      * \param poly The polygon in which to search
      * \return The index to the nearest vertex on the polygon
      */
-    static unsigned int findNearestVert(const Point from, const PolygonRef poly);
+    static unsigned int findNearestVert(const Point from, ConstPolygonRef poly);
 
     /*!
      * Create a SparsePointGridInclusive mapping from locations to line segments occurring in the \p polygons
@@ -382,7 +382,7 @@ public:
      * \param penalty_function A function returning a penalty term on the squared distance score of a candidate point.
      * \return A collection of near crossing from the \p from polygon to the \p destination polygon. Each element in the sollection is a pair with as first a cpp in the \p from polygon and as second a cpp in the \p destination polygon.
      */
-    static std::vector<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> findClose(const PolygonRef from, const Polygons& destination, const LocToLineGrid& destination_loc_to_line, const std::function<int(Point)>& penalty_function = no_penalty_function);
+    static std::vector<std::pair<ClosestPolygonPoint, ClosestPolygonPoint>> findClose(ConstPolygonRef from, const Polygons& destination, const LocToLineGrid& destination_loc_to_line, const std::function<int(Point)>& penalty_function = no_penalty_function);
 
     /*!
      * Checks whether a given line segment collides with polygons as given in a loc_to_line grid.
@@ -409,7 +409,7 @@ public:
     * \param start_idx the index of the prev poly point on the poly.
     * \param poly_start_idx The index of the point in the polygon which is to be handled as the start of the polygon. No point further than this point will be the result.
     */
-    static bool getNextPointWithDistance(Point from, int64_t dist, const PolygonRef poly, int start_idx, int poly_start_idx, GivenDistPoint& result);
+    static bool getNextPointWithDistance(Point from, int64_t dist, ConstPolygonRef poly, int start_idx, int poly_start_idx, GivenDistPoint& result);
 
 
 
@@ -433,7 +433,7 @@ public:
      * \return whether the line segment collides with the boundary of the
      * polygon(s)
      */
-    static bool polygonCollidesWithLineSegment(const PolygonRef poly, Point& transformed_startPoint, Point& transformed_endPoint, PointMatrix transformation_matrix);
+    static bool polygonCollidesWithLineSegment(ConstPolygonRef poly, const Point& transformed_startPoint, const Point& transformed_endPoint, PointMatrix transformation_matrix);
 
     /*!
      * Checks whether a given line segment collides with a given polygon(s).
@@ -449,7 +449,7 @@ public:
      * \return whether the line segment collides with the boundary of the
      * polygon(s)
      */
-    static bool polygonCollidesWithLineSegment(const PolygonRef poly, Point& startPoint, Point& endPoint);
+    static bool polygonCollidesWithLineSegment(ConstPolygonRef poly, const Point& startPoint, const Point& endPoint);
 
     /*!
      * Checks whether a given line segment collides with a given polygon(s).
@@ -471,7 +471,7 @@ public:
      * \return whether the line segment collides with the boundary of the
      * polygon(s)
      */
-    static bool polygonCollidesWithLineSegment(const Polygons& polys, Point& transformed_startPoint, Point& transformed_endPoint, PointMatrix transformation_matrix);
+    static bool polygonCollidesWithLineSegment(const Polygons& polys, const Point& transformed_startPoint, const Point& transformed_endPoint, PointMatrix transformation_matrix);
 
     /*!
      * Checks whether a given line segment collides with a given polygon(s).
@@ -487,7 +487,7 @@ public:
      * \return whether the line segment collides with the boundary of the
      * polygon(s)
      */
-    static bool polygonCollidesWithLineSegment(const Polygons& polys, Point& startPoint, Point& endPoint);
+    static bool polygonCollidesWithLineSegment(const Polygons& polys, const Point& startPoint, const Point& endPoint);
 
 private:
     /*!

src/utils/string.h

@@ -1,3 +1,6 @@
+//Copyright (c) 2017 Ultimaker B.V.
+//CuraEngine is released under the terms of the AGPLv3 or higher.
+
 #ifndef UTILS_STRING_H
 #define UTILS_STRING_H
 
@@ -35,7 +38,7 @@ static inline void writeInt2mm(const int64_t coord, std::ostream& ss)
 {
     constexpr size_t buffer_size = 24;
     char buffer[buffer_size];
-    int char_count = sprintf(buffer, "%" PRId64, coord); // convert int to string
+    int char_count = sprintf(buffer, "%d", int(coord)); // convert int to string
 #ifdef DEBUG
     if (char_count + 1 >= int(buffer_size)) // + 1 for the null character
     {

src/wallOverlap.cpp

@@ -18,7 +18,7 @@ WallOverlapComputation::WallOverlapComputation(Polygons& polygons, int line_widt
 }
 
 
-float WallOverlapComputation::getFlow(Point& from, Point& to)
+float WallOverlapComputation::getFlow(const Point& from, const Point& to)
 {
     using Point2LinkIt = PolygonProximityLinker::Point2Link::iterator;
 

src/wallOverlap.h

@@ -60,7 +60,7 @@ public:
      * \param to The ending of the line segment
      * \return a value between zero and one representing the reduced flow of the line segment
      */
-    float getFlow(Point& from, Point& to);
+    float getFlow(const Point& from, const Point& to);
 
     /*!
      * Computes the neccesary priliminaries in order to efficiently compute the flow when generatign gcode paths.

tests/runtest.py

@@ -235,11 +235,14 @@ class Setting:
             tree = ast.parse(code, "eval")
             compiled = compile(code, self._key, "eval")
         except (SyntaxError, TypeError) as e:
-            print("Parse error in function (" + code + ") for setting", self._key + ":", str(e))
+            print("Parse error in function (" + str(code) + ") for setting", self._key + ":", str(e))
+            return None
         except IllegalMethodError as e:
             print("Use of illegal method", str(e), "in function (" + code + ") for setting", self._key)
+            return None
         except Exception as e:
             print("Exception in function (" + code + ") for setting", self._key + ":", str(e))
+            return None
 
         return eval(compiled, globals(), locals)