From a0fbec142e91ccac03c25d62dcbd5ea2dc703e01 Mon Sep 17 00:00:00 2001
From: Vojtech Bubnik <bubnikv@gmail.com>
Date: Thu, 2 Dec 2021 18:18:26 +0100
Subject: [PATCH] Fixed ironing over areas with modifier meshes: 1) Areas
 inside modifier meshes were ironed multiple times. 2) Ironing areas were not
 properly merged.

Layer::lslices were not always properly merged with modifier meshes
applied, which lead to the ironed surface being split and not fully
ironed, as there were artificial gaps created between regions as if
they were covered by perimeters (we don't iron over perimeters).
---
 src/libslic3r/Fill/Fill.cpp | 20 +++++++++++++-------
 src/libslic3r/Layer.cpp     |  2 +-
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/libslic3r/Fill/Fill.cpp b/src/libslic3r/Fill/Fill.cpp
index 726ba17a448..a3e4aee3115 100644
--- a/src/libslic3r/Fill/Fill.cpp
+++ b/src/libslic3r/Fill/Fill.cpp
@@ -539,7 +539,7 @@ void Layer::make_ironing()
     fill_params.density 	 = 1.;
     fill_params.monotonic    = true;
 
-	for (size_t i = 0; i < by_extruder.size(); ++ i) {
+	for (size_t i = 0; i < by_extruder.size();) {
 		// Find span of regions equivalent to the ironing operation.
 		IroningParams &ironing_params = by_extruder[i];
 		size_t j = i;
@@ -589,14 +589,17 @@ void Layer::make_ironing()
 							polygons_append(infills, surface.expolygon);
 				}
 			}
+
+			if (! infills.empty() || j > i + 1) {
+				// Ironing over more than a single region or over solid internal infill.
+				if (! infills.empty())
+					// For IroningType::AllSolid only:
+					// Add solid infill areas for layers, that contain some non-ironable infil (sparse infill, bridge infill).
+					append(polys, std::move(infills));
+				polys = union_safety_offset(polys);
+			}
 			// Trim the top surfaces with half the nozzle diameter.
 			ironing_areas = intersection_ex(polys, offset(this->lslices, - float(scale_(0.5 * nozzle_dmr))));
-			if (! infills.empty()) {
-				// For IroningType::AllSolid only:
-				// Add solid infill areas for layers, that contain some non-ironable infil (sparse infill, bridge infill).
-				append(infills, to_polygons(std::move(ironing_areas)));
-				ironing_areas = union_safety_offset_ex(infills);
-			}
 		}
 
         // Create the filler object.
@@ -626,6 +629,9 @@ void Layer::make_ironing()
 		            flow_mm3_per_mm, extrusion_width, float(extrusion_height));
 		    }
 		}
+
+		// Regions up to j were processed.
+		i = j;
 	}
 }
 
diff --git a/src/libslic3r/Layer.cpp b/src/libslic3r/Layer.cpp
index 39228516c00..5c661ed68b0 100644
--- a/src/libslic3r/Layer.cpp
+++ b/src/libslic3r/Layer.cpp
@@ -45,7 +45,7 @@ void Layer::make_slices()
         Polygons slices_p;
         for (LayerRegion *layerm : m_regions)
             polygons_append(slices_p, to_polygons(layerm->slices.surfaces));
-        slices = union_ex(slices_p);
+        slices = union_safety_offset_ex(slices_p);
     }
     
     this->lslices.clear();