Print lower fractional layer heights before full ones, pt 2.

Take care of the order optimizer w.r.t. partially fractional-height support-layers.

part of CURA-10407

src/FffGcodeWriter.cpp

@@ -21,6 +21,7 @@
 #include "utils/math.h"
 #include "utils/orderOptimizer.h"
 
+#include <range/v3/view/concat.hpp>
 #include <range/v3/view/sliding.hpp>
 #include <range/v3/view/transform.hpp>
 #include <range/v3/view/zip.hpp>
@@ -3148,11 +3149,13 @@ bool FffGcodeWriter::processSupportInfill(const SliceDataStorage& storage, Layer
     const auto zag_skip_count = infill_extruder.settings.get<size_t>("support_zag_skip_count");
 
     // create a list of outlines and use PathOrderOptimizer to optimize the travel move
+    PathOrderOptimizer<const SupportInfillPart*> island_order_optimizer_initial(gcode_layer.getLastPlannedPositionOrStartingPosition());
     PathOrderOptimizer<const SupportInfillPart*> island_order_optimizer(gcode_layer.getLastPlannedPositionOrStartingPosition());
     for (const SupportInfillPart& part : support_layer.support_infill_parts)
     {
-        island_order_optimizer.addPolygon(&part);
+        (part.use_fractional_config ? island_order_optimizer_initial : island_order_optimizer).addPolygon(&part);
     }
+    island_order_optimizer_initial.optimize();
     island_order_optimizer.optimize();
 
     const auto support_connect_zigzags = infill_extruder.settings.get<bool>("support_connect_zigzags");
@@ -3165,7 +3168,7 @@ bool FffGcodeWriter::processSupportInfill(const SliceDataStorage& storage, Layer
     bool need_travel_to_end_of_last_spiral = true;
 
     // Print the thicker infill lines first. (double or more layer thickness, infill combined with previous layers)
-    for (const PathOrdering<const SupportInfillPart*>& path : island_order_optimizer.paths)
+    for (const PathOrdering<const SupportInfillPart*>& path : ranges::views::concat(island_order_optimizer_initial.paths, island_order_optimizer.paths))
     {
         const SupportInfillPart& part = *path.vertices;
         const auto& configs = part.use_fractional_config ? gcode_layer.configs_storage.support_fractional_infill_config : gcode_layer.configs_storage.support_infill_config;