Fix: Windows and Linux has different order of polygons after Clipper simplify

To unify behavior between platforms: Polygons are sorted on the end of function.

+ Remove Slic3r::ExPolygons simplify_polygons_ex(const Slic3r::Polygons &subject);  // different definition and declaration, unused function

src/libslic3r/ClipperUtils.cpp

@@ -1041,8 +1041,7 @@ Polygons union_parallel_reduce(const Polygons &subject)
         });
 }
 
-Polygons simplify_polygons(const Polygons &subject)
-{
+Polygons simplify_polygons(const Polygons &subject) {    
     CLIPPER_UTILS_TIME_LIMIT_MILLIS(CLIPPER_UTILS_TIME_LIMIT_DEFAULT);
 
     ClipperLib::Paths output;
@@ -1052,27 +1051,9 @@ Polygons simplify_polygons(const Polygons &subject)
     c.StrictlySimple(true);
     c.AddPaths(ClipperUtils::PolygonsProvider(subject), ClipperLib::ptSubject, true);
     c.Execute(ClipperLib::ctUnion, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
-
-    // convert into Slic3r polygons
     return to_polygons(std::move(output));
 }
 
-ExPolygons simplify_polygons_ex(const Polygons &subject, bool preserve_collinear)
-{
-    CLIPPER_UTILS_TIME_LIMIT_MILLIS(CLIPPER_UTILS_TIME_LIMIT_DEFAULT);
-
-    ClipperLib::PolyTree polytree;
-    ClipperLib::Clipper c;
-//    c.PreserveCollinear(true);
-    //FIXME StrictlySimple is very expensive! Is it needed?
-    c.StrictlySimple(true);
-    c.AddPaths(ClipperUtils::PolygonsProvider(subject), ClipperLib::ptSubject, true);
-    c.Execute(ClipperLib::ctUnion, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
-    
-    // convert into ExPolygons
-    return PolyTreeToExPolygons(std::move(polytree));
-}
-
 Polygons top_level_islands(const Slic3r::Polygons &polygons)
 {
     CLIPPER_UTILS_TIME_LIMIT_MILLIS(CLIPPER_UTILS_TIME_LIMIT_DEFAULT);

src/libslic3r/ClipperUtils.hpp

@@ -641,7 +641,6 @@ void traverse_pt(const ClipperLib::PolyNodes &nodes, ExOrJustPolygons *retval)
 
 /* OTHER */
 Slic3r::Polygons simplify_polygons(const Slic3r::Polygons &subject);
-Slic3r::ExPolygons simplify_polygons_ex(const Slic3r::Polygons &subject);
 
 Polygons top_level_islands(const Slic3r::Polygons &polygons);
 

src/libslic3r/SLA/SupportIslands/UniformSupportIsland.cpp

@@ -135,8 +135,39 @@ ExPolygon get_simplified(const ExPolygon &island, const SampleConfig &config) {
     //// "Close" operation still create neighbor pixel for sharp triangle tip - cause VD issues
 
     ExPolygons simplified_expolygons = island.simplify(config.simplification_tolerance);
-    return simplified_expolygons.empty() ?
-        island : get_expolygon_with_biggest_contour(simplified_expolygons);
+    if (simplified_expolygons.empty())
+        return island;
+        
+    ExPolygon biggest = get_expolygon_with_biggest_contour(simplified_expolygons);
+
+    // NOTE: Order of polygon is different for Windows and Linux 
+    // to unify behavior one have to sort holes
+    std::sort(biggest.holes.begin(), biggest.holes.end(), 
+        // first sort by size of polygons than by coordinates of points
+        [](const Polygon &polygon1, const Polygon &polygon2) {
+            if (polygon1.size() > polygon2.size())
+                return true;
+            if (polygon1.size() < polygon2.size())
+                return false;
+            // NOTE: polygon1.size() == polygon2.size()
+            for (size_t point_index = 0; point_index < polygon1.size(); ++point_index) {
+                const Point &p1 = polygon1[point_index];
+                const Point &p2 = polygon2[point_index];
+                if (p1.x() > p2.x())
+                    return true;
+                if (p1.x() < p2.x())
+                    return false;
+                // NOTE: p1.x() == p2.x()
+                if (p1.y() > p2.y())
+                    return true;
+                if (p1.y() < p2.y())
+                    return false;
+                // NOTE: p1 == p2 check next point
+            }
+            return true;
+        });
+        
+    return biggest;
 }
 
 /// <summary>