Merge remote-tracking branch 'origin/master' into ys_color_print_extension

39 files changed, 1068 insertions, 141 deletions

diff --git a/src/libslic3r/Arrange.cpp b/src/libslic3r/Arrange.cpp
index aed6e41f7..3fa7e1841 100644
--- a/src/libslic3r/Arrange.cpp
+++ b/src/libslic3r/Arrange.cpp
@@ -375,7 +375,7 @@ public:
         
         for(unsigned idx = 0; idx < fixeditems.size(); ++idx) {
             Item& itm = fixeditems[idx];
-            itm.markAsFixedInBin(0);
+            itm.markAsFixedInBin(itm.binId());
         }
 
         m_pck.configure(m_pconf);
diff --git a/src/libslic3r/CMakeLists.txt b/src/libslic3r/CMakeLists.txt
index cbaa24e9c..0388b1ac0 100644
--- a/src/libslic3r/CMakeLists.txt
+++ b/src/libslic3r/CMakeLists.txt
@@ -22,6 +22,8 @@ add_library(libslic3r STATIC
     Config.hpp
     EdgeGrid.cpp
     EdgeGrid.hpp
+    ElephantFootCompensation.cpp
+    ElephantFootCompensation.hpp
     ExPolygon.cpp
     ExPolygon.hpp
     ExPolygonCollection.cpp
@@ -222,6 +224,7 @@ target_link_libraries(libslic3r
     qhull
     semver
     TBB::tbb
+    # OpenVDB::openvdb
     ${CMAKE_DL_LIBS}
     )
 
diff --git a/src/libslic3r/ClipperUtils.cpp b/src/libslic3r/ClipperUtils.cpp
index b863b4712..3db2f1f00 100644
--- a/src/libslic3r/ClipperUtils.cpp
+++ b/src/libslic3r/ClipperUtils.cpp
@@ -107,8 +107,7 @@ void AddOuterPolyNodeToExPolygons(ClipperLib::PolyNode& polynode, ExPolygons* ex
   }
 }
  
-ExPolygons
-PolyTreeToExPolygons(ClipperLib::PolyTree& polytree)
+ExPolygons PolyTreeToExPolygons(ClipperLib::PolyTree& polytree)
 {
     ExPolygons retval;
     for (int i = 0; i < polytree.ChildCount(); ++i)
@@ -151,8 +150,7 @@ Slic3r::Polylines ClipperPaths_to_Slic3rPolylines(const ClipperLib::Paths &input
     return retval;
 }
 
-ExPolygons
-ClipperPaths_to_Slic3rExPolygons(const ClipperLib::Paths &input)
+ExPolygons ClipperPaths_to_Slic3rExPolygons(const ClipperLib::Paths &input)
 {
     // init Clipper
     ClipperLib::Clipper clipper;
@@ -167,8 +165,7 @@ ClipperPaths_to_Slic3rExPolygons(const ClipperLib::Paths &input)
     return PolyTreeToExPolygons(polytree);
 }
 
-ClipperLib::Path
-Slic3rMultiPoint_to_ClipperPath(const MultiPoint &input)
+ClipperLib::Path Slic3rMultiPoint_to_ClipperPath(const MultiPoint &input)
 {
     ClipperLib::Path retval;
     for (Points::const_iterator pit = input.points.begin(); pit != input.points.end(); ++pit)
@@ -176,8 +173,7 @@ Slic3rMultiPoint_to_ClipperPath(const MultiPoint &input)
     return retval;
 }
 
-ClipperLib::Path
-Slic3rMultiPoint_to_ClipperPath_reversed(const Slic3r::MultiPoint &input)
+ClipperLib::Path Slic3rMultiPoint_to_ClipperPath_reversed(const Slic3r::MultiPoint &input)
 {
     ClipperLib::Path output;
     output.reserve(input.points.size());
@@ -521,7 +517,7 @@ T _clipper_do(const ClipperLib::ClipType     clipType,
 
 // Fix of #117: A large fractal pyramid takes ages to slice
 // The Clipper library has difficulties processing overlapping polygons.
-// Namely, the function Clipper::JoinCommonEdges() has potentially a terrible time complexity if the output
+// Namely, the function ClipperLib::JoinCommonEdges() has potentially a terrible time complexity if the output
 // of the operation is of the PolyTree type.
 // This function implmenets a following workaround:
 // 1) Peform the Clipper operation with the output to Paths. This method handles overlaps in a reasonable time.
@@ -918,4 +914,320 @@ Polygons top_level_islands(const Slic3r::Polygons &polygons)
     return out;
 }
 
+// Outer offset shall not split the input contour into multiples. It is expected, that the solution will be non empty and it will contain just a single polygon.
+ClipperLib::Paths fix_after_outer_offset(const ClipperLib::Path &input, ClipperLib::PolyFillType filltype, bool reverse_result)
+{
+  	ClipperLib::Paths solution;
+  	if (! input.empty()) {
+		ClipperLib::Clipper clipper;
+	  	clipper.AddPath(input, ClipperLib::ptSubject, true);
+		clipper.ReverseSolution(reverse_result);
+		clipper.Execute(ClipperLib::ctUnion, solution, filltype, filltype);
+	}
+    return solution;
+}
+
+// Inner offset may split the source contour into multiple contours, but one shall not be inside the other.
+ClipperLib::Paths fix_after_inner_offset(const ClipperLib::Path &input, ClipperLib::PolyFillType filltype, bool reverse_result)
+{
+  	ClipperLib::Paths solution;
+  	if (! input.empty()) {
+		ClipperLib::Clipper clipper;
+		clipper.AddPath(input, ClipperLib::ptSubject, true);
+		ClipperLib::IntRect r = clipper.GetBounds();
+		r.left -= 10; r.top -= 10; r.right += 10; r.bottom += 10;
+		if (filltype == ClipperLib::pftPositive)
+			clipper.AddPath({ ClipperLib::IntPoint(r.left, r.bottom), ClipperLib::IntPoint(r.left, r.top), ClipperLib::IntPoint(r.right, r.top), ClipperLib::IntPoint(r.right, r.bottom) }, ClipperLib::ptSubject, true);
+		else
+			clipper.AddPath({ ClipperLib::IntPoint(r.left, r.bottom), ClipperLib::IntPoint(r.right, r.bottom), ClipperLib::IntPoint(r.right, r.top), ClipperLib::IntPoint(r.left, r.top) }, ClipperLib::ptSubject, true);
+		clipper.ReverseSolution(reverse_result);
+		clipper.Execute(ClipperLib::ctUnion, solution, filltype, filltype);
+		if (! solution.empty())
+			solution.erase(solution.begin());
+	}
+	return solution;
+}
+
+ClipperLib::Path mittered_offset_path_scaled(const Points &contour, const std::vector<float> &deltas, double miter_limit)
+{
+	assert(contour.size() == deltas.size());
+#ifndef NDEBUG
+	// Verify that the deltas are either all positive, or all negative.
+	bool positive = false;
+	bool negative = false;
+	for (float delta : deltas)
+		if (delta < 0.f)
+			negative = true;
+		else if (delta > 0.f)
+			positive = true;
+	assert(! (negative && positive));
+#endif /* NDEBUG */
+
+	ClipperLib::Path out;
+
+	if (deltas.size() > 2)
+	{
+		out.reserve(contour.size() * 2);
+
+		// Clamp miter limit to 2.
+		miter_limit = (miter_limit > 2.) ? 2. / (miter_limit * miter_limit) : 0.5;
+		
+		// perpenduclar vector
+		auto   perp = [](const Vec2d &v) -> Vec2d { return Vec2d(v.y(), - v.x()); };
+
+		// Add a new point to the output, scale by CLIPPER_OFFSET_SCALE and round to ClipperLib::cInt.
+		auto   add_offset_point = [&out](Vec2d pt) {
+			pt *= double(CLIPPER_OFFSET_SCALE);
+			pt += Vec2d(0.5 - (pt.x() < 0), 0.5 - (pt.y() < 0));
+			out.emplace_back(ClipperLib::cInt(pt.x()), ClipperLib::cInt(pt.y()));
+		};
+
+		// Minimum edge length, squared.
+		double lmin  = *std::max_element(deltas.begin(), deltas.end()) * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR;
+		double l2min = lmin * lmin;
+		// Minimum angle to consider two edges to be parallel.
+		double sin_min_parallel = EPSILON + 1. / double(CLIPPER_OFFSET_SCALE);
+
+		// Find the last point further from pt by l2min.
+		Vec2d  pt     = contour.front().cast<double>();
+		size_t iprev  = contour.size() - 1;
+		Vec2d  ptprev;
+		for (; iprev > 0; -- iprev) {
+			ptprev = contour[iprev].cast<double>();
+			if ((ptprev - pt).squaredNorm() > l2min)
+				break;
+		}
+
+		if (iprev != 0) {
+			size_t ilast = iprev;
+			// Normal to the (pt - ptprev) segment.
+			Vec2d nprev = perp(pt - ptprev).normalized();
+			for (size_t i = 0; ; ) {
+				// Find the next point further from pt by l2min.
+				size_t j = i + 1;
+				Vec2d ptnext;
+				for (; j <= ilast; ++ j) {
+					ptnext = contour[j].cast<double>();
+					double l2 = (ptnext - pt).squaredNorm();
+					if (l2 > l2min)
+						break;
+				}
+				if (j > ilast)
+					ptnext = contour.front().cast<double>();
+
+				// Normal to the (ptnext - pt) segment.
+				Vec2d nnext  = perp(ptnext - pt).normalized();
+
+				double delta  = deltas[i];
+				double sin_a  = clamp(-1., 1., cross2(nprev, nnext));
+				double convex = sin_a * delta;
+				if (convex <= - sin_min_parallel) {
+					// Concave corner.
+					add_offset_point(pt + nprev * delta);
+					add_offset_point(pt);
+					add_offset_point(pt + nnext * delta);
+				} else if (convex < sin_min_parallel) {
+					// Nearly parallel.
+					add_offset_point((nprev.dot(nnext) > 0.) ? (pt + nprev * delta) : pt);
+				} else {
+					// Convex corner
+					double dot = nprev.dot(nnext);
+					double r = 1. + dot;
+				  	if (r >= miter_limit)
+						add_offset_point(pt + (nprev + nnext) * (delta / r));
+				  	else {
+						double dx = std::tan(std::atan2(sin_a, dot) / 4.);
+						Vec2d  newpt1 = pt + (nprev - perp(nprev) * dx) * delta;
+						Vec2d  newpt2 = pt + (nnext + perp(nnext) * dx) * delta;
+#ifndef NDEBUG
+						Vec2d vedge = 0.5 * (newpt1 + newpt2) - pt;
+						double dist_norm = vedge.norm();
+						assert(std::abs(dist_norm - delta) < EPSILON);
+#endif /* NDEBUG */
+						add_offset_point(newpt1);
+						add_offset_point(newpt2);
+				  	}
+				}
+
+				if (i == ilast)
+					break;
+
+				ptprev = pt;
+				nprev  = nnext;
+				pt     = ptnext;
+				i = j;
+			}
+		}
+	}
+
+#if 0
+	{
+		ClipperLib::Path polytmp(out);
+		unscaleClipperPolygon(polytmp);
+		Slic3r::Polygon offsetted = ClipperPath_to_Slic3rPolygon(polytmp);
+		BoundingBox bbox = get_extents(contour);
+		bbox.merge(get_extents(offsetted));
+		static int iRun = 0;
+		SVG svg(debug_out_path("mittered_offset_path_scaled-%d.svg", iRun ++).c_str(), bbox);
+		svg.draw_outline(Polygon(contour), "blue", scale_(0.01));
+		svg.draw_outline(offsetted, "red", scale_(0.01));
+		svg.draw(contour, "blue", scale_(0.03));
+		svg.draw((Points)offsetted, "blue", scale_(0.03));
+	}
+#endif
+
+	return out;
+}
+
+Polygons variable_offset_inner(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
+{
+#ifndef NDEBUG
+	// Verify that the deltas are all non positive.
+	for (const std::vector<float> &ds : deltas)
+		for (float delta : ds)
+			assert(delta <= 0.);
+	assert(expoly.holes.size() + 1 == deltas.size());
+#endif /* NDEBUG */
+
+	// 1) Offset the outer contour.
+	ClipperLib::Paths contours = fix_after_inner_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftNegative, true);
+
+	// 2) Offset the holes one by one, collect the results.
+	ClipperLib::Paths holes;
+	holes.reserve(expoly.holes.size());
+	for (const Polygon& hole : expoly.holes)
+		append(holes, fix_after_outer_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftPositive, false));
+
+	// 3) Subtract holes from the contours.
+	ClipperLib::Paths output;
+	if (holes.empty())
+		output = std::move(contours);
+	else {
+		ClipperLib::Clipper clipper;
+		clipper.Clear();
+		clipper.AddPaths(contours, ClipperLib::ptSubject, true);
+		clipper.AddPaths(holes, ClipperLib::ptClip, true);
+		clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
+	}
+
+	// 4) Unscale the output.
+	unscaleClipperPolygons(output);
+	return ClipperPaths_to_Slic3rPolygons(output);
+}
+
+Polygons variable_offset_outer(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
+{
+#ifndef NDEBUG
+	// Verify that the deltas are all non positive.
+for (const std::vector<float>& ds : deltas)
+		for (float delta : ds)
+			assert(delta >= 0.);
+	assert(expoly.holes.size() + 1 == deltas.size());
+#endif /* NDEBUG */
+
+	// 1) Offset the outer contour.
+	ClipperLib::Paths contours = fix_after_outer_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftPositive, false);
+
+	// 2) Offset the holes one by one, collect the results.
+	ClipperLib::Paths holes;
+	holes.reserve(expoly.holes.size());
+	for (const Polygon& hole : expoly.holes)
+		append(holes, fix_after_inner_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftPositive, true));
+
+	// 3) Subtract holes from the contours.
+	ClipperLib::Paths output;
+	if (holes.empty())
+		output = std::move(contours);
+	else {
+		ClipperLib::Clipper clipper;
+		clipper.Clear();
+		clipper.AddPaths(contours, ClipperLib::ptSubject, true);
+		clipper.AddPaths(holes, ClipperLib::ptClip, true);
+		clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
+	}
+
+	// 4) Unscale the output.
+	unscaleClipperPolygons(output);
+	return ClipperPaths_to_Slic3rPolygons(output);
+}
+
+ExPolygons variable_offset_outer_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
+{
+#ifndef NDEBUG
+	// Verify that the deltas are all non positive.
+for (const std::vector<float>& ds : deltas)
+		for (float delta : ds)
+			assert(delta >= 0.);
+	assert(expoly.holes.size() + 1 == deltas.size());
+#endif /* NDEBUG */
+
+	// 1) Offset the outer contour.
+	ClipperLib::Paths contours = fix_after_outer_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftPositive, false);
+
+	// 2) Offset the holes one by one, collect the results.
+	ClipperLib::Paths holes;
+	holes.reserve(expoly.holes.size());
+	for (const Polygon& hole : expoly.holes)
+		append(holes, fix_after_inner_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftPositive, true));
+
+	// 3) Subtract holes from the contours.
+	unscaleClipperPolygons(contours);
+	ExPolygons output;
+	if (holes.empty()) {
+		output.reserve(contours.size());
+		for (ClipperLib::Path &path : contours) 
+			output.emplace_back(ClipperPath_to_Slic3rPolygon(path));
+	} else {
+		ClipperLib::Clipper clipper;
+		unscaleClipperPolygons(holes);
+		clipper.AddPaths(contours, ClipperLib::ptSubject, true);
+		clipper.AddPaths(holes, ClipperLib::ptClip, true);
+	    ClipperLib::PolyTree polytree;
+		clipper.Execute(ClipperLib::ctDifference, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
+	    output = PolyTreeToExPolygons(polytree);
+	}
+
+	return output;
+}
+
+
+ExPolygons variable_offset_inner_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
+{
+#ifndef NDEBUG
+	// Verify that the deltas are all non positive.
+for (const std::vector<float>& ds : deltas)
+		for (float delta : ds)
+			assert(delta <= 0.);
+	assert(expoly.holes.size() + 1 == deltas.size());
+#endif /* NDEBUG */
+
+	// 1) Offset the outer contour.
+	ClipperLib::Paths contours = fix_after_inner_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftNegative, false);
+
+	// 2) Offset the holes one by one, collect the results.
+	ClipperLib::Paths holes;
+	holes.reserve(expoly.holes.size());
+	for (const Polygon& hole : expoly.holes)
+		append(holes, fix_after_outer_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftNegative, true));
+
+	// 3) Subtract holes from the contours.
+	unscaleClipperPolygons(contours);
+	ExPolygons output;
+	if (holes.empty()) {
+		output.reserve(contours.size());
+		for (ClipperLib::Path &path : contours) 
+			output.emplace_back(ClipperPath_to_Slic3rPolygon(path));
+	} else {
+		ClipperLib::Clipper clipper;
+		unscaleClipperPolygons(holes);
+		clipper.AddPaths(contours, ClipperLib::ptSubject, true);
+		clipper.AddPaths(holes, ClipperLib::ptClip, true);
+	    ClipperLib::PolyTree polytree;
+		clipper.Execute(ClipperLib::ctDifference, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
+	    output = PolyTreeToExPolygons(polytree);
+	}
+
+	return output;
+}
+
 }
diff --git a/src/libslic3r/ClipperUtils.hpp b/src/libslic3r/ClipperUtils.hpp
index d8f8a8f94..5a41a6a90 100644
--- a/src/libslic3r/ClipperUtils.hpp
+++ b/src/libslic3r/ClipperUtils.hpp
@@ -238,6 +238,11 @@ void safety_offset(ClipperLib::Paths* paths);
 
 Polygons top_level_islands(const Slic3r::Polygons &polygons);
 
+Polygons  variable_offset_inner(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit = 2.);
+Polygons  variable_offset_outer(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit = 2.);
+ExPolygons variable_offset_outer_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit = 2.);
+ExPolygons variable_offset_inner_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit = 2.);
+
 }
 
 #endif
diff --git a/src/libslic3r/EdgeGrid.cpp b/src/libslic3r/EdgeGrid.cpp
index a97210da6..52ac4a0aa 100644
--- a/src/libslic3r/EdgeGrid.cpp
+++ b/src/libslic3r/EdgeGrid.cpp
@@ -113,6 +113,7 @@ void EdgeGrid::Grid::create(const ExPolygonCollection &expolygons, coord_t resol
 // m_contours has been initialized. Now fill in the edge grid.
 void EdgeGrid::Grid::create_from_m_contours(coord_t resolution)
 {
+	assert(resolution > 0);
 	// 1) Measure the bounding box.
 	for (size_t i = 0; i < m_contours.size(); ++ i) {
 		const Slic3r::Points &pts = *m_contours[i];
@@ -281,7 +282,11 @@ void EdgeGrid::Grid::create_from_m_contours(coord_t resolution)
 		Visitor(std::vector<std::pair<size_t, size_t>> &cell_data, std::vector<Cell> &cells, size_t cols) :
 			cell_data(cell_data), cells(cells), cols(cols), i(0), j(0) {}
 
-		void operator()(coord_t iy, coord_t ix) { cell_data[cells[iy*cols + ix].end++] = std::pair<size_t, size_t>(i, j); }
+		inline bool operator()(coord_t iy, coord_t ix) {
+			cell_data[cells[iy*cols + ix].end++] = std::pair<size_t, size_t>(i, j);
+			// Continue traversing the grid along the edge.
+			return true;
+		}
 
 		std::vector<std::pair<size_t, size_t>> &cell_data;
 		std::vector<Cell> 					   &cells;
@@ -1017,8 +1022,139 @@ float EdgeGrid::Grid::signed_distance_bilinear(const Point &pt) const
 
 	return f;
 }
- 
-bool EdgeGrid::Grid::signed_distance_edges(const Point &pt, coord_t search_radius, coordf_t &result_min_dist, bool *pon_segment) const {
+
+EdgeGrid::Grid::ClosestPointResult EdgeGrid::Grid::closest_point(const Point &pt, coord_t search_radius) const 
+{
+	BoundingBox bbox;
+	bbox.min = bbox.max = Point(pt(0) - m_bbox.min(0), pt(1) - m_bbox.min(1));
+	bbox.defined = true;
+	// Upper boundary, round to grid and test validity.
+	bbox.max(0) += search_radius;
+	bbox.max(1) += search_radius;
+	ClosestPointResult result;
+	if (bbox.max(0) < 0 || bbox.max(1) < 0)
+		return result;
+	bbox.max(0) /= m_resolution;
+	bbox.max(1) /= m_resolution;
+	if ((size_t)bbox.max(0) >= m_cols)
+		bbox.max(0) = m_cols - 1;
+	if ((size_t)bbox.max(1) >= m_rows)
+		bbox.max(1) = m_rows - 1;
+	// Lower boundary, round to grid and test validity.
+	bbox.min(0) -= search_radius;
+	bbox.min(1) -= search_radius;
+	if (bbox.min(0) < 0)
+		bbox.min(0) = 0;
+	if (bbox.min(1) < 0)
+		bbox.min(1) = 0;
+	bbox.min(0) /= m_resolution;
+	bbox.min(1) /= m_resolution;
+	// Is the interval empty?
+	if (bbox.min(0) > bbox.max(0) ||
+		bbox.min(1) > bbox.max(1))
+		return result;
+	// Traverse all cells in the bounding box.
+	double d_min = double(search_radius);
+	// Signum of the distance field at pt.
+	int sign_min = 0;
+	double l2_seg_min = 1.;
+	for (int r = bbox.min(1); r <= bbox.max(1); ++ r) {
+		for (int c = bbox.min(0); c <= bbox.max(0); ++ c) {
+			const Cell &cell = m_cells[r * m_cols + c];
+			for (size_t i = cell.begin; i < cell.end; ++ i) {
+				const size_t          contour_idx = m_cell_data[i].first;
+				const Slic3r::Points &pts         = *m_contours[contour_idx];
+				size_t ipt = m_cell_data[i].second;
+				// End points of the line segment.
+				const Slic3r::Point &p1 = pts[ipt];
+				const Slic3r::Point &p2 = pts[(ipt + 1 == pts.size()) ? 0 : ipt + 1];
+				const Slic3r::Point v_seg = p2 - p1;
+				const Slic3r::Point v_pt  = pt - p1;
+				// dot(p2-p1, pt-p1)
+				int64_t t_pt = int64_t(v_seg(0)) * int64_t(v_pt(0)) + int64_t(v_seg(1)) * int64_t(v_pt(1));
+				// l2 of seg
+				int64_t l2_seg = int64_t(v_seg(0)) * int64_t(v_seg(0)) + int64_t(v_seg(1)) * int64_t(v_seg(1));
+				if (t_pt < 0) {
+					// Closest to p1.
+					double dabs = sqrt(int64_t(v_pt(0)) * int64_t(v_pt(0)) + int64_t(v_pt(1)) * int64_t(v_pt(1)));
+					if (dabs < d_min) {
+						// Previous point.
+						const Slic3r::Point &p0 = pts[(ipt == 0) ? (pts.size() - 1) : ipt - 1];
+						Slic3r::Point v_seg_prev = p1 - p0;
+						int64_t t2_pt = int64_t(v_seg_prev(0)) * int64_t(v_pt(0)) + int64_t(v_seg_prev(1)) * int64_t(v_pt(1));
+						if (t2_pt > 0) {
+							// Inside the wedge between the previous and the next segment.
+							d_min = dabs;
+							// Set the signum depending on whether the vertex is convex or reflex.
+							int64_t det = int64_t(v_seg_prev(0)) * int64_t(v_seg(1)) - int64_t(v_seg_prev(1)) * int64_t(v_seg(0));
+							assert(det != 0);
+							sign_min = (det > 0) ? 1 : -1;
+							result.contour_idx = contour_idx;
+							result.start_point_idx = ipt;
+							result.t = 0.;
+#ifndef NDEBUG
+							Vec2d vfoot = (p1 - pt).cast<double>();
+							double dist_foot = vfoot.norm();
+							double dist_foot_err = dist_foot - d_min;
+							assert(std::abs(dist_foot_err) < 1e-7 * d_min);
+#endif /* NDEBUG */
+						}
+					}
+				}
+				else if (t_pt > l2_seg) {
+					// Closest to p2. Then p2 is the starting point of another segment, which shall be discovered in the same cell.
+					continue;
+				} else {
+					// Closest to the segment.
+					assert(t_pt >= 0 && t_pt <= l2_seg);
+					int64_t d_seg = int64_t(v_seg(1)) * int64_t(v_pt(0)) - int64_t(v_seg(0)) * int64_t(v_pt(1));
+					double d = double(d_seg) / sqrt(double(l2_seg));
+					double dabs = std::abs(d);
+					if (dabs < d_min) {
+						d_min = dabs;
+						sign_min = (d_seg < 0) ? -1 : ((d_seg == 0) ? 0 : 1);
+						l2_seg_min = l2_seg;
+						result.contour_idx = contour_idx;
+						result.start_point_idx = ipt;
+						result.t = t_pt;
+#ifndef NDEBUG
+						Vec2d foot = p1.cast<double>() * (1. - result.t / l2_seg_min) + p2.cast<double>() * (result.t / l2_seg_min);
+						Vec2d vfoot = foot - pt.cast<double>();
+						double dist_foot = vfoot.norm();
+						double dist_foot_err = dist_foot - d_min;
+						assert(std::abs(dist_foot_err) < 1e-7 * d_min);
+#endif /* NDEBUG */
+					}
+				}
+			}
+		}
+	}
+	if (result.contour_idx != -1 && d_min <= double(search_radius)) {
+		result.distance = d_min * sign_min;
+		result.t /= l2_seg_min;
+		assert(result.t >= 0. && result.t < 1.);
+#ifndef NDEBUG
+		{
+			const Slic3r::Points &pts = *m_contours[result.contour_idx];
+			const Slic3r::Point  &p1  = pts[result.start_point_idx];
+			const Slic3r::Point  &p2  = pts[(result.start_point_idx + 1 == pts.size()) ? 0 : result.start_point_idx + 1];
+			Vec2d vfoot;
+			if (result.t == 0)
+				vfoot = p1.cast<double>() - pt.cast<double>();
+			else
+				vfoot = p1.cast<double>() * (1. - result.t) + p2.cast<double>() * result.t - pt.cast<double>();
+			double dist_foot = vfoot.norm();
+			double dist_foot_err = dist_foot - std::abs(result.distance);
+			assert(std::abs(dist_foot_err) < 1e-7 * std::abs(result.distance));
+		}
+#endif /* NDEBUG */
+	} else
+		result = ClosestPointResult();
+	return result;
+}
+
+bool EdgeGrid::Grid::signed_distance_edges(const Point &pt, coord_t search_radius, coordf_t &result_min_dist, bool *pon_segment) const 
+{
 	BoundingBox bbox;
 	bbox.min = bbox.max = Point(pt(0) - m_bbox.min(0), pt(1) - m_bbox.min(1));
 	bbox.defined = true;
@@ -1047,7 +1183,7 @@ bool EdgeGrid::Grid::signed_distance_edges(const Point &pt, coord_t search_radiu
 		bbox.min(1) > bbox.max(1))
 		return false;
 	// Traverse all cells in the bounding box.
-	float d_min = search_radius;
+	double d_min = double(search_radius);
 	// Signum of the distance field at pt.
 	int sign_min = 0;
 	bool on_segment = false;
diff --git a/src/libslic3r/EdgeGrid.hpp b/src/libslic3r/EdgeGrid.hpp
index cad20e07b..92cee8362 100644
--- a/src/libslic3r/EdgeGrid.hpp
+++ b/src/libslic3r/EdgeGrid.hpp
@@ -25,6 +25,8 @@ public:
 	void create(const ExPolygons &expolygons, coord_t resolution);
 	void create(const ExPolygonCollection &expolygons, coord_t resolution);
 
+	const std::vector<const Slic3r::Points*>& contours() const { return m_contours; }
+
 #if 0
 	// Test, whether the edges inside the grid intersect with the polygons provided.
 	bool intersect(const MultiPoint &polyline, bool closed);
@@ -46,7 +48,19 @@ public:
 	float signed_distance_bilinear(const Point &pt) const;
 
 	// Calculate a signed distance to the contours in search_radius from the point.
-	bool signed_distance_edges(const Point &pt, coord_t search_radius, coordf_t &result_min_dist, bool *pon_segment = NULL) const;
+	struct ClosestPointResult {
+		size_t contour_idx  	= size_t(-1);
+		size_t start_point_idx  = size_t(-1);
+		// Signed distance to the closest point.
+		double distance 		= std::numeric_limits<double>::max();
+		// Parameter of the closest point on edge starting with start_point_idx <0, 1)
+		double t 				= 0.;
+
+		bool valid() const { return contour_idx != size_t(-1); }
+	};
+	ClosestPointResult closest_point(const Point &pt, coord_t search_radius) const;
+
+	bool signed_distance_edges(const Point &pt, coord_t search_radius, coordf_t &result_min_dist, bool *pon_segment = nullptr) const;
 
 	// Calculate a signed distance to the contours in search_radius from the point. If no edge is found in search_radius,
 	// return an interpolated value from m_signed_distance_field, if it exists.
@@ -65,7 +79,7 @@ public:
 	std::vector<std::pair<ContourEdge, ContourEdge>> intersecting_edges() const;
 	bool 											 has_intersecting_edges() const;
 
-	template<typename FUNCTION> void visit_cells_intersecting_line(Slic3r::Point p1, Slic3r::Point p2, FUNCTION func) const
+	template<typename VISITOR> void visit_cells_intersecting_line(Slic3r::Point p1, Slic3r::Point p2, VISITOR &visitor) const
 	{
 		// End points of the line segment.
 		p1(0) -= m_bbox.min(0);
@@ -82,8 +96,7 @@ public:
 		assert(ixb >= 0 && size_t(ixb) < m_cols);
 		assert(iyb >= 0 && size_t(iyb) < m_rows);
 		// Account for the end points.
-		func(iy, ix);
-		if (ix == ixb && iy == iyb)
+		if (! visitor(iy, ix) || (ix == ixb && iy == iyb))
 			// Both ends fall into the same cell.
 			return;
 		// Raster the centeral part of the line.
@@ -113,7 +126,8 @@ public:
 						ey = int64_t(dx) * m_resolution;
 						iy += 1;
 					}
-					func(iy, ix);
+					if (! visitor(iy, ix))
+						return;
 				} while (ix != ixb || iy != iyb);
 			}
 			else {
@@ -131,7 +145,8 @@ public:
 						ey = int64_t(dx) * m_resolution;
 						iy -= 1;
 					}
-					func(iy, ix);
+					if (! visitor(iy, ix))
+						return;
 				} while (ix != ixb || iy != iyb);
 			}
 		}
@@ -153,7 +168,8 @@ public:
 						ey = int64_t(dx) * m_resolution;
 						iy += 1;
 					}
-					func(iy, ix);
+					if (! visitor(iy, ix))
+						return;
 				} while (ix != ixb || iy != iyb);
 			}
 			else {
@@ -185,7 +201,8 @@ public:
 						ey = int64_t(dx) * m_resolution;
 						iy -= 1;
 					}
-					func(iy, ix);
+					if (! visitor(iy, ix))
+						return;
 				} while (ix != ixb || iy != iyb);
 			}
 		}
diff --git a/src/libslic3r/ElephantFootCompensation.cpp b/src/libslic3r/ElephantFootCompensation.cpp
new file mode 100644
index 000000000..5bdeaa954
--- /dev/null
+++ b/src/libslic3r/ElephantFootCompensation.cpp
@@ -0,0 +1,321 @@
+#include "clipper/clipper_z.hpp"
+
+#include "libslic3r.h"
+#include "ClipperUtils.hpp"
+#include "EdgeGrid.hpp"
+#include "ExPolygon.hpp"
+#include "ElephantFootCompensation.hpp"
+#include "Flow.hpp"
+#include "Geometry.hpp"
+#include "SVG.hpp"
+
+#include <cmath>
+#include <cassert>
+
+// #define CONTOUR_DISTANCE_DEBUG_SVG
+
+namespace Slic3r {
+
+struct ResampledPoint {
+	ResampledPoint(size_t idx_src, bool interpolated, double curve_parameter) : idx_src(idx_src), interpolated(interpolated), curve_parameter(curve_parameter) {}
+
+	size_t		idx_src;
+	// Is this point interpolated or initial?
+	bool 		interpolated;
+	// Euclidean distance along the curve from the 0th point.
+	double		curve_parameter;
+};
+
+std::vector<float> contour_distance(const EdgeGrid::Grid &grid, const size_t idx_contour, const Slic3r::Points &contour, const std::vector<ResampledPoint> &resampled_point_parameters, double search_radius)
+{
+	assert(! contour.empty());
+	assert(contour.size() >= 2);
+
+	std::vector<float> out;
+
+	if (contour.size() > 2) 
+	{
+#ifdef CONTOUR_DISTANCE_DEBUG_SVG
+		static int iRun = 0;
+		++ iRun;
+		BoundingBox bbox = get_extents(contour);
+		bbox.merge(grid.bbox());
+		ExPolygon expoly_grid;
+		expoly_grid.contour = Polygon(*grid.contours().front());
+		for (size_t i = 1; i < grid.contours().size(); ++ i)
+			expoly_grid.holes.emplace_back(Polygon(*grid.contours()[i]));
+#endif
+		struct Visitor {
+			Visitor(const EdgeGrid::Grid &grid, const size_t idx_contour, const std::vector<ResampledPoint> &resampled_point_parameters, double dist_same_contour_reject) :
+				grid(grid), idx_contour(idx_contour), resampled_point_parameters(resampled_point_parameters), dist_same_contour_reject(dist_same_contour_reject) {}
+
+			void init(const size_t aidx_point_start, const Point &apt_start, Vec2d dir, const double radius) {
+				this->idx_point_start = aidx_point_start;
+				this->pt       = apt_start.cast<double>() + SCALED_EPSILON * dir;
+				dir *= radius;
+				this->pt_start = this->pt.cast<coord_t>();
+				// Trim the vector by the grid's bounding box.
+				const BoundingBox &bbox = this->grid.bbox();
+				double t = 1.;
+				for (size_t axis = 0; axis < 2; ++ axis) {
+					double dx = std::abs(dir(axis));
+					if (dx >= EPSILON) {
+						double tedge = (dir(axis) > 0) ? (double(bbox.max(axis)) - EPSILON - this->pt(axis)) : (this->pt(axis) - double(bbox.min(axis)) - EPSILON);
+						if (tedge < dx)
+							t = tedge / dx;
+					}
+				}
+				this->dir      = dir;
+				if (t < 1.)
+					dir *= t;
+				this->pt_end   = (this->pt + dir).cast<coord_t>();
+				this->t_min    = 1.;
+			}
+
+			bool operator()(coord_t iy, coord_t ix) {
+				// Called with a row and colum of the grid cell, which is intersected by a line.
+				auto cell_data_range = this->grid.cell_data_range(iy, ix);
+				bool valid = true;
+				for (auto it_contour_and_segment = cell_data_range.first; it_contour_and_segment != cell_data_range.second; ++ it_contour_and_segment) {
+					// End points of the line segment and their vector.
+					auto segment = this->grid.segment(*it_contour_and_segment);
+					if (Geometry::segments_intersect(segment.first, segment.second, this->pt_start, this->pt_end)) {
+						// The two segments intersect. Calculate the intersection.
+						Vec2d pt2 = segment.first.cast<double>();
+						Vec2d dir2 = segment.second.cast<double>() - pt2;
+						Vec2d vptpt2 = pt - pt2;
+						double denom = dir(0) * dir2(1) - dir2(0) * dir(1);
+
+						if (std::abs(denom) >= EPSILON) {
+							double t = cross2(dir2, vptpt2) / denom;
+							assert(t > 0. && t <= 1.);
+							bool this_valid = true;
+							if (it_contour_and_segment->first == idx_contour) {
+								// The intersected segment originates from the same contour as the starting point.
+								// Reject the intersection if it is close to the starting point.
+								// Find the start and end points of this segment
+								double param_lo = resampled_point_parameters[idx_point_start].curve_parameter;
+								double param_hi;
+								double param_end = resampled_point_parameters.back().curve_parameter;
+								{
+									const Slic3r::Points &ipts = *grid.contours()[it_contour_and_segment->first];
+									size_t ipt = it_contour_and_segment->second;
+									ResampledPoint key(ipt, false, 0.);
+									auto lower = [](const ResampledPoint& l, const ResampledPoint r) { return l.idx_src < r.idx_src || (l.idx_src == r.idx_src && int(l.interpolated) > int(r.interpolated)); };
+									auto it = std::lower_bound(resampled_point_parameters.begin(), resampled_point_parameters.end(), key, lower);
+									assert(it != resampled_point_parameters.end() && it->idx_src == ipt && ! it->interpolated);
+									double t2 = cross2(dir, vptpt2) / denom;
+									assert(t2 >= 0. && t2 <= 1.);
+									if (++ ipt == ipts.size())
+										param_hi = t2 * dir2.norm();
+									else
+										param_hi = it->curve_parameter + t2 * dir2.norm();
+								}
+								if (param_lo > param_hi)
+									std::swap(param_lo, param_hi);
+								assert(param_lo >= 0. && param_lo <= param_end);
+								assert(param_hi >= 0. && param_hi <= param_end);
+								this_valid = param_hi > param_lo + dist_same_contour_reject && param_hi - param_end < param_lo - dist_same_contour_reject;
+							}
+							if (t < this->t_min) {
+								this->t_min = t;
+								valid = this_valid;
+							}
+						}
+					}
+					if (! valid)
+						this->t_min = 1.;
+				}
+				// Continue traversing the grid along the edge.
+				return true;
+			}
+
+			const EdgeGrid::Grid 			   &grid;
+			const size_t 		  				idx_contour;
+			const std::vector<ResampledPoint>  &resampled_point_parameters;
+			const double 						dist_same_contour_reject;
+
+			size_t 								idx_point_start;
+			Point			      				pt_start;
+			Point				  				pt_end;
+			Vec2d				  				pt;
+			Vec2d                 				dir;
+			// Minium parameter along the vector (pt_end - pt_start).
+			double				  				t_min;
+		} visitor(grid, idx_contour, resampled_point_parameters, search_radius);
+
+		const Point *pt_this = &contour.back();
+		size_t       idx_pt_this = contour.size() - 1;
+		const Point *pt_prev = pt_this - 1;
+		// perpenduclar vector
+		auto		 perp    = [](const Vec2d& v) -> Vec2d { return Vec2d(v.y(), -v.x()); };
+		Vec2d        vprev   = (*pt_this - *pt_prev).cast<double>().normalized();
+		out.reserve(contour.size() + 1);
+		for (const Point &pt_next : contour) {
+			Vec2d    vnext   = (pt_next - *pt_this).cast<double>().normalized();
+			Vec2d    dir     = - (perp(vprev) + perp(vnext)).normalized();
+			Vec2d    dir_perp = perp(dir);
+			double   cross   = cross2(vprev, vnext);
+			double   dot     = vprev.dot(vnext);
+			double   a       = (cross < 0 || dot > 0.5) ? (M_PI / 3.) : (0.48 * acos(std::min(1., - dot)));
+			// Throw rays, collect distances.
+			std::vector<double> distances;
+			int num_rays = 15;
+
+#ifdef CONTOUR_DISTANCE_DEBUG_SVG
+			SVG svg(debug_out_path("contour_distance_raycasted-%d-%d.svg", iRun, &pt_next - contour.data()).c_str(), bbox);
+			svg.draw(expoly_grid);
+			svg.draw_outline(Polygon(contour), "blue", scale_(0.01));
+			svg.draw(*pt_this, "red", scale_(0.1));
+#endif /* CONTOUR_DISTANCE_DEBUG_SVG */
+
+			for (int i = - num_rays + 1; i < num_rays; ++ i) {
+				double angle = a * i / (int)num_rays;
+				double c = cos(angle);
+				double s = sin(angle);
+				Vec2d  v = c * dir + s * dir_perp;
+				visitor.init(idx_pt_this, *pt_this, v, search_radius);
+				grid.visit_cells_intersecting_line(visitor.pt_start, visitor.pt_end, visitor);
+				distances.emplace_back(visitor.t_min);
+#ifdef CONTOUR_DISTANCE_DEBUG_SVG
+				svg.draw(Line(visitor.pt_start, visitor.pt_end), "yellow", scale_(0.01));
+				if (visitor.t_min < 1.) {
+					Vec2d pt = visitor.pt + visitor.dir * visitor.t_min;
+					svg.draw(Point(pt), "red", scale_(0.1));
+				}
+#endif /* CONTOUR_DISTANCE_DEBUG_SVG */
+			}
+#ifdef CONTOUR_DISTANCE_DEBUG_SVG
+			svg.Close();
+#endif /* CONTOUR_DISTANCE_DEBUG_SVG */
+			std::sort(distances.begin(), distances.end());
+#if 0
+			double median = distances[distances.size() / 2];
+			double standard_deviation = 0;
+			for (double d : distances)
+				standard_deviation += (d - median) * (d - median);
+			standard_deviation = sqrt(standard_deviation / (distances.size() - 1));
+			double avg = 0;
+			size_t cnt = 0;
+			for (double d : distances)
+				if (d > median - standard_deviation - EPSILON && d < median + standard_deviation + EPSILON) {
+					avg += d;
+					++ cnt;
+				}
+			avg /= double(cnt);
+			out.emplace_back(float(avg * search_radius));
+#else
+			out.emplace_back(float(distances.front() * search_radius));
+#endif
+#ifdef CONTOUR_DISTANCE_DEBUG_SVG
+			printf("contour_distance_raycasted-%d-%d.svg - distance %lf\n", iRun, &pt_next - contour.data(), unscale<double>(out.back()));
+#endif /* CONTOUR_DISTANCE_DEBUG_SVG */
+			pt_this = &pt_next;
+			idx_pt_this = &pt_next - contour.data();
+			vprev   = vnext;
+		}
+		// Rotate the vector by one item.
+		out.emplace_back(out.front());
+		out.erase(out.begin());
+	}
+
+	return out;
+}
+
+Points resample_polygon(const Points &contour, double dist, std::vector<ResampledPoint> &resampled_point_parameters)
+{
+	Points out;
+	out.reserve(contour.size());
+	resampled_point_parameters.reserve(contour.size());
+    if (contour.size() > 2) {
+    	Vec2d  pt_prev  = contour.back().cast<double>();
+    	for (const Point &pt : contour) {
+			size_t idx_this = &pt - contour.data();
+    		const Vec2d  pt_this = pt.cast<double>();
+    		const Vec2d  v		 = pt_this - pt_prev;
+			const double l		 = v.norm();
+    		const size_t n		 = size_t(ceil(l / dist));
+			const double l_step  = l / n;
+    		for (size_t i = 1; i < n; ++ i) {
+				double interpolation_parameter = double(i) / n;
+    			Vec2d new_pt = pt_prev + v * interpolation_parameter;
+    			out.emplace_back(new_pt.cast<coord_t>());
+				resampled_point_parameters.emplace_back(idx_this, true, l_step);
+			}
+    		out.emplace_back(pt);
+			resampled_point_parameters.emplace_back(idx_this, false, l_step);
+    		pt_prev = pt_this;
+    	}
+		for (size_t i = 1; i < resampled_point_parameters.size(); ++i)
+			resampled_point_parameters[i].curve_parameter += resampled_point_parameters[i - 1].curve_parameter;
+    }
+    return out;
+}
+
+static inline void smooth_compensation(std::vector<float> &compensation, float strength, size_t num_iterations)
+{
+	std::vector<float> out(compensation);
+	for (size_t iter = 0; iter < num_iterations; ++ iter) {
+		for (size_t i = 0; i < compensation.size(); ++ i) {
+			float prev = (i == 0) ? compensation.back() : compensation[i - 1];
+			float next = (i + 1 == compensation.size()) ? compensation.front() : compensation[i + 1];
+			float laplacian = compensation[i] * (1.f - strength) + 0.5f * strength * (prev + next);
+			// Compensations are negative. Only apply the laplacian if it leads to lower compensation.
+			out[i] = std::max(laplacian, compensation[i]);
+		}
+		out.swap(compensation);
+	}
+}
+
+ExPolygon elephant_foot_compensation(const ExPolygon &input_expoly, const Flow &external_perimeter_flow, const double compensation)
+{
+	// The contour shall be wide enough to apply the external perimeter plus compensation on both sides.
+	double min_contour_width = double(external_perimeter_flow.scaled_width() + external_perimeter_flow.scaled_spacing());
+	double scaled_compensation = scale_(compensation);
+	double min_contour_width_compensated = min_contour_width + 2. * scaled_compensation;
+	// Make the search radius a bit larger for the averaging in contour_distance over a fan of rays to work.
+	double search_radius = min_contour_width_compensated + min_contour_width * 0.5;
+
+	EdgeGrid::Grid grid;
+	ExPolygon simplified = input_expoly.simplify(SCALED_EPSILON).front();
+	BoundingBox bbox = get_extents(simplified.contour);
+	bbox.offset(SCALED_EPSILON);
+	grid.set_bbox(bbox);
+	grid.create(simplified, coord_t(0.7 * search_radius));
+	std::vector<std::vector<float>> deltas;
+	deltas.reserve(simplified.holes.size() + 1);
+	ExPolygon resampled(simplified);
+	for (size_t idx_contour = 0; idx_contour <= simplified.holes.size(); ++ idx_contour) {
+		Polygon &poly = (idx_contour == 0) ? resampled.contour : resampled.holes[idx_contour - 1];
+		std::vector<ResampledPoint> resampled_point_parameters;
+		poly.points = resample_polygon(poly.points, scale_(0.5), resampled_point_parameters);
+		std::vector<float> dists = contour_distance(grid, idx_contour, poly.points, resampled_point_parameters, search_radius);
+		for (float &d : dists) {
+//			printf("Point %d, Distance: %lf\n", int(&d - dists.data()), unscale<double>(d));
+			// Convert contour width to available compensation distance.
+			if (d < min_contour_width)
+				d = 0.f;
+			else if (d > min_contour_width_compensated)
+				d = - float(scaled_compensation);
+			else
+				d = - (d - float(min_contour_width)) / 2.f;
+			assert(d >= - float(scaled_compensation) && d <= 0.f);
+		}
+		smooth_compensation(dists, 0.4f, 10);
+		deltas.emplace_back(dists);
+	}
+
+	ExPolygons out = variable_offset_inner_ex(resampled, deltas, 2.);
+	return out.front();
+}
+
+ExPolygons elephant_foot_compensation(const ExPolygons &input, const Flow &external_perimeter_flow, const double compensation)
+{
+	ExPolygons out;
+	out.reserve(input.size());
+	for (const ExPolygon &expoly : input)
+		out.emplace_back(elephant_foot_compensation(expoly, external_perimeter_flow, compensation));
+	return out;
+}
+
+} // namespace Slic3r
diff --git a/src/libslic3r/ElephantFootCompensation.hpp b/src/libslic3r/ElephantFootCompensation.hpp
new file mode 100644
index 000000000..0119df1af
--- /dev/null
+++ b/src/libslic3r/ElephantFootCompensation.hpp
@@ -0,0 +1,16 @@
+#ifndef slic3r_ElephantFootCompensation_hpp_
+#define slic3r_ElephantFootCompensation_hpp_
+
+#include "libslic3r.h"
+#include <vector>
+
+namespace Slic3r {
+
+class Flow;
+
+ExPolygon  elephant_foot_compensation(const ExPolygon  &input, const Flow &external_perimeter_flow, const double compensation);
+ExPolygons elephant_foot_compensation(const ExPolygons &input, const Flow &external_perimeter_flow, const double compensation);
+
+} // Slic3r
+
+#endif /* slic3r_ElephantFootCompensation_hpp_ */
diff --git a/src/libslic3r/ExPolygon.hpp b/src/libslic3r/ExPolygon.hpp
index c510b848f..7833c9c91 100644
--- a/src/libslic3r/ExPolygon.hpp
+++ b/src/libslic3r/ExPolygon.hpp
@@ -28,6 +28,8 @@ public:
 	explicit ExPolygon(Polygon &&contour, Polygon &&hole) : contour(std::move(contour)) { holes.emplace_back(std::move(hole)); }
 	explicit ExPolygon(const Points &contour, const Points &hole) : contour(contour) { holes.emplace_back(hole); }
 	explicit ExPolygon(Points &&contour, Polygon &&hole) : contour(std::move(contour)) { holes.emplace_back(std::move(hole)); }
+	ExPolygon(std::initializer_list<Point> contour) : contour(contour) {}
+	ExPolygon(std::initializer_list<Point> contour, std::initializer_list<Point> hole) : contour(contour), holes({ hole }) {}
 
     ExPolygon& operator=(const ExPolygon &other) { contour = other.contour; holes = other.holes; return *this; }
     ExPolygon& operator=(ExPolygon &&other) { contour = std::move(other.contour); holes = std::move(other.holes); return *this; }
@@ -77,6 +79,9 @@ public:
     Lines lines() const;
 };
 
+inline bool operator==(const ExPolygon &lhs, const ExPolygon &rhs) { return lhs.contour == rhs.contour && lhs.holes == rhs.holes; }
+inline bool operator!=(const ExPolygon &lhs, const ExPolygon &rhs) { return lhs.contour != rhs.contour || lhs.holes != rhs.holes; }
+
 // Count a nuber of polygons stored inside the vector of expolygons.
 // Useful for allocating space for polygons when converting expolygons to polygons.
 inline size_t number_polygons(const ExPolygons &expolys)
@@ -301,6 +306,15 @@ inline bool expolygons_contain(ExPolygons &expolys, const Point &pt)
     return false;
 }
 
+inline ExPolygons expolygons_simplify(const ExPolygons &expolys, double tolerance)
+{
+	ExPolygons out;
+	out.reserve(expolys.size());
+	for (const ExPolygon &exp : expolys)
+		exp.simplify(tolerance, &out);
+	return out;
+}
+
 extern BoundingBox get_extents(const ExPolygon &expolygon);
 extern BoundingBox get_extents(const ExPolygons &expolygons);
 extern BoundingBox get_extents_rotated(const ExPolygon &poly, double angle);
diff --git a/src/libslic3r/Format/AMF.cpp b/src/libslic3r/Format/AMF.cpp
index 2d77d3daa..181d6cb99 100644
--- a/src/libslic3r/Format/AMF.cpp
+++ b/src/libslic3r/Format/AMF.cpp
@@ -584,8 +584,16 @@ void AMFParserContext::endElement(const char * /* name */)
         stl_get_size(&stl);
         mesh.repair();
 		m_volume->set_mesh(std::move(mesh));
-        // pass false if the mesh offset has been already taken from the data 
-        m_volume->center_geometry_after_creation(m_volume->source.input_file.empty());
+        if (m_volume->source.input_file.empty() && (m_volume->type() == ModelVolumeType::MODEL_PART))
+        {
+            m_volume->source.object_idx = (int)m_model.objects.size() - 1;
+            m_volume->source.volume_idx = (int)m_model.objects.back()->volumes.size() - 1;
+            m_volume->center_geometry_after_creation();
+        }
+        else
+            // pass false if the mesh offset has been already taken from the data 
+            m_volume->center_geometry_after_creation(m_volume->source.input_file.empty());
+
         m_volume->calculate_convex_hull();
         m_volume_facets.clear();
         m_volume = nullptr;
@@ -799,6 +807,15 @@ bool load_amf_file(const char *path, DynamicPrintConfig *config, Model *model)
     if (result)
         ctx.endDocument();
 
+    for (ModelObject* o : model->objects)
+    {
+        for (ModelVolume* v : o->volumes)
+        {
+            if (v->source.input_file.empty() && (v->type() == ModelVolumeType::MODEL_PART))
+                v->source.input_file = path;
+        }
+    }
+
     return result;
 }
 
diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index f3fe802cc..2a74de41d 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -543,7 +543,7 @@ std::vector<GCode::LayerToPrint> GCode::collect_layers_to_print(const PrintObjec
 	//FIXME should we use the printing extruders instead?
 	double gap_over_supports = object.config().support_material_contact_distance;
 	// FIXME should we test object.config().support_material_synchronize_layers ? Currently the support layers are synchronized with object layers iff soluble supports.
-    assert(gap_over_supports != 0. || object.config().support_material_synchronize_layers);
+    assert(! object.config().support_material || gap_over_supports != 0. || object.config().support_material_synchronize_layers);
     if (gap_over_supports != 0.) {
         gap_over_supports = std::max(0., gap_over_supports);
 		// Not a soluble support,
@@ -778,22 +778,26 @@ void GCode::_do_export(Print &print, FILE *file)
         {
             m_silent_time_estimator.reset();
             m_silent_time_estimator.set_dialect(print.config().gcode_flavor);
-			m_silent_time_estimator.set_max_acceleration((float)print.config().machine_max_acceleration_extruding.values[1]);
-			m_silent_time_estimator.set_retract_acceleration((float)print.config().machine_max_acceleration_retracting.values[1]);
-			m_silent_time_estimator.set_minimum_feedrate((float)print.config().machine_min_extruding_rate.values[1]);
-			m_silent_time_estimator.set_minimum_travel_feedrate((float)print.config().machine_min_travel_rate.values[1]);
-			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::X, (float)print.config().machine_max_acceleration_x.values[1]);
-			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::Y, (float)print.config().machine_max_acceleration_y.values[1]);
-			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::Z, (float)print.config().machine_max_acceleration_z.values[1]);
-			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::E, (float)print.config().machine_max_acceleration_e.values[1]);
-			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::X, (float)print.config().machine_max_feedrate_x.values[1]);
-			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::Y, (float)print.config().machine_max_feedrate_y.values[1]);
-			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::Z, (float)print.config().machine_max_feedrate_z.values[1]);
-			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::E, (float)print.config().machine_max_feedrate_e.values[1]);
-			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::X, (float)print.config().machine_max_jerk_x.values[1]);
-			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Y, (float)print.config().machine_max_jerk_y.values[1]);
-			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Z, (float)print.config().machine_max_jerk_z.values[1]);
-			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::E, (float)print.config().machine_max_jerk_e.values[1]);
+            /* "Stealth mode" values can be just a copy of "normal mode" values 
+            * (when they aren't input for a printer preset).
+            * Thus, use back value from values, instead of second one, which could be absent
+            */
+			m_silent_time_estimator.set_max_acceleration((float)print.config().machine_max_acceleration_extruding.values.back());
+			m_silent_time_estimator.set_retract_acceleration((float)print.config().machine_max_acceleration_retracting.values.back());
+			m_silent_time_estimator.set_minimum_feedrate((float)print.config().machine_min_extruding_rate.values.back());
+			m_silent_time_estimator.set_minimum_travel_feedrate((float)print.config().machine_min_travel_rate.values.back());
+			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::X, (float)print.config().machine_max_acceleration_x.values.back());
+			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::Y, (float)print.config().machine_max_acceleration_y.values.back());
+			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::Z, (float)print.config().machine_max_acceleration_z.values.back());
+			m_silent_time_estimator.set_axis_max_acceleration(GCodeTimeEstimator::E, (float)print.config().machine_max_acceleration_e.values.back());
+			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::X, (float)print.config().machine_max_feedrate_x.values.back());
+			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::Y, (float)print.config().machine_max_feedrate_y.values.back());
+			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::Z, (float)print.config().machine_max_feedrate_z.values.back());
+			m_silent_time_estimator.set_axis_max_feedrate(GCodeTimeEstimator::E, (float)print.config().machine_max_feedrate_e.values.back());
+			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::X, (float)print.config().machine_max_jerk_x.values.back());
+			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Y, (float)print.config().machine_max_jerk_y.values.back());
+			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Z, (float)print.config().machine_max_jerk_z.values.back());
+			m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::E, (float)print.config().machine_max_jerk_e.values.back());
             if (print.config().single_extruder_multi_material) {
                 // As of now the fields are shown at the UI dialog in the same combo box as the ramming values, so they
                 // are considered to be active for the single extruder multi-material printers only.
diff --git a/src/libslic3r/GCode/Analyzer.cpp b/src/libslic3r/GCode/Analyzer.cpp
index 78f6c6806..3f0b8735f 100644
--- a/src/libslic3r/GCode/Analyzer.cpp
+++ b/src/libslic3r/GCode/Analyzer.cpp
@@ -285,6 +285,11 @@ void GCodeAnalyzer::_process_gcode_line(GCodeReader&, const GCodeReader::GCodeLi
                         _processM108orM135(line);
                         break;
                     }
+                case 132: // Recall stored home offsets
+                    {
+                        _processM132(line);
+                        break;
+                    }
                 case 401: // Repetier: Store x, y and z position
                     {
                         _processM401(line);
@@ -504,6 +509,25 @@ void GCodeAnalyzer::_processM108orM135(const GCodeReader::GCodeLine& line)
     }
 }
 
+void GCodeAnalyzer::_processM132(const GCodeReader::GCodeLine& line)
+{
+    // This command is used by Makerbot to load the current home position from EEPROM
+    // see: https://github.com/makerbot/s3g/blob/master/doc/GCodeProtocol.md
+    // Using this command to reset the axis origin to zero helps in fixing: https://github.com/prusa3d/PrusaSlicer/issues/3082
+
+    if (line.has_x())
+        _set_axis_origin(X, 0.0f);
+
+    if (line.has_y())
+        _set_axis_origin(Y, 0.0f);
+
+    if (line.has_z())
+        _set_axis_origin(Z, 0.0f);
+
+    if (line.has_e())
+        _set_axis_origin(E, 0.0f);
+}
+
 void GCodeAnalyzer::_processM401(const GCodeReader::GCodeLine& line)
 {
     if (m_gcode_flavor != gcfRepetier)
diff --git a/src/libslic3r/GCode/Analyzer.hpp b/src/libslic3r/GCode/Analyzer.hpp
index e90175c49..df4f6f652 100644
--- a/src/libslic3r/GCode/Analyzer.hpp
+++ b/src/libslic3r/GCode/Analyzer.hpp
@@ -182,6 +182,9 @@ private:
     // Set tool (MakerWare and Sailfish flavor)
     void _processM108orM135(const GCodeReader::GCodeLine& line);
 
+    // Recall stored home offsets
+    void _processM132(const GCodeReader::GCodeLine& line);
+
     // Repetier: Store x, y and z position
     void _processM401(const GCodeReader::GCodeLine& line);
 
diff --git a/src/libslic3r/GCode/SpiralVase.hpp b/src/libslic3r/GCode/SpiralVase.hpp
index 7872b1d3c..e35ca640c 100644
--- a/src/libslic3r/GCode/SpiralVase.hpp
+++ b/src/libslic3r/GCode/SpiralVase.hpp
@@ -1,8 +1,8 @@
 #ifndef slic3r_SpiralVase_hpp_
 #define slic3r_SpiralVase_hpp_
 
-#include "libslic3r.h"
-#include "GCodeReader.hpp"
+#include "../libslic3r.h"
+#include "../GCodeReader.hpp"
 
 namespace Slic3r {
 
diff --git a/src/libslic3r/GCode/WipeTower.cpp b/src/libslic3r/GCode/WipeTower.cpp
index b464a39b8..73dc91c40 100644
--- a/src/libslic3r/GCode/WipeTower.cpp
+++ b/src/libslic3r/GCode/WipeTower.cpp
@@ -331,15 +331,18 @@ public:
 
 	// Let the firmware back up the active speed override value.
 	WipeTowerWriter& speed_override_backup()
-	{
-		m_gcode += "M220 B\n";
+    {
+        // This is only supported by Prusa at this point (https://github.com/prusa3d/PrusaSlicer/issues/3114)
+        if (m_gcode_flavor == gcfMarlin)
+            m_gcode += "M220 B\n";
 		return *this;
     }
 
 	// Let the firmware restore the active speed override value.
 	WipeTowerWriter& speed_override_restore()
 	{
-		m_gcode += "M220 R\n";
+        if (m_gcode_flavor == gcfMarlin)
+            m_gcode += "M220 R\n";
 		return *this;
     }
 
diff --git a/src/libslic3r/Geometry.cpp b/src/libslic3r/Geometry.cpp
index e926b9997..46d7ef154 100644
--- a/src/libslic3r/Geometry.cpp
+++ b/src/libslic3r/Geometry.cpp
@@ -663,7 +663,6 @@ namespace Voronoi { namespace Internal {
     typedef boost::polygon::point_data<coordinate_type> point_type;
     typedef boost::polygon::segment_data<coordinate_type> segment_type;
     typedef boost::polygon::rectangle_data<coordinate_type> rect_type;
-//    typedef voronoi_builder<int> VB;
     typedef boost::polygon::voronoi_diagram<coordinate_type> VD;
     typedef VD::cell_type cell_type;
     typedef VD::cell_type::source_index_type source_index_type;
@@ -710,15 +709,15 @@ namespace Voronoi { namespace Internal {
         if (cell1.contains_point() && cell2.contains_point()) {
             point_type p1 = retrieve_point(segments, cell1);
             point_type p2 = retrieve_point(segments, cell2);
-            origin.x((p1(0) + p2(0)) * 0.5);
-            origin.y((p1(1) + p2(1)) * 0.5);
-            direction.x(p1(1) - p2(1));
-            direction.y(p2(0) - p1(0));
+            origin.x((p1.x() + p2.x()) * 0.5);
+            origin.y((p1.y() + p2.y()) * 0.5);
+            direction.x(p1.y() - p2.y());
+            direction.y(p2.x() - p1.x());
         } else {
             origin = cell1.contains_segment() ? retrieve_point(segments, cell2) : retrieve_point(segments, cell1);
             segment_type segment = cell1.contains_segment() ? segments[cell1.source_index()] : segments[cell2.source_index()];
-            coordinate_type dx = high(segment)(0) - low(segment)(0);
-            coordinate_type dy = high(segment)(1) - low(segment)(1);
+            coordinate_type dx = high(segment).x() - low(segment).x();
+            coordinate_type dy = high(segment).y() - low(segment).y();
             if ((low(segment) == origin) ^ cell1.contains_point()) {
                 direction.x(dy);
                 direction.y(-dx);
@@ -727,19 +726,19 @@ namespace Voronoi { namespace Internal {
                 direction.y(dx);
             }
         }
-        coordinate_type koef = bbox_max_size / (std::max)(fabs(direction(0)), fabs(direction(1)));
+        coordinate_type koef = bbox_max_size / (std::max)(fabs(direction.x()), fabs(direction.y()));
         if (edge.vertex0() == NULL) {
             clipped_edge->push_back(point_type(
-                origin(0) - direction(0) * koef,
-                origin(1) - direction(1) * koef));
+                origin.x() - direction.x() * koef,
+                origin.y() - direction.y() * koef));
         } else {
             clipped_edge->push_back(
                 point_type(edge.vertex0()->x(), edge.vertex0()->y()));
         }
         if (edge.vertex1() == NULL) {
             clipped_edge->push_back(point_type(
-                origin(0) + direction(0) * koef,
-                origin(1) + direction(1) * koef));
+                origin.x() + direction.x() * koef,
+                origin.y() + direction.y() * koef));
         } else {
             clipped_edge->push_back(
                 point_type(edge.vertex1()->x(), edge.vertex1()->y()));
@@ -759,7 +758,7 @@ namespace Voronoi { namespace Internal {
 
 } /* namespace Internal */ } // namespace Voronoi
 
-static inline void dump_voronoi_to_svg(const Lines &lines, /* const */ voronoi_diagram<double> &vd, const ThickPolylines *polylines, const char *path)
+static inline void dump_voronoi_to_svg(const Lines &lines, /* const */ boost::polygon::voronoi_diagram<double> &vd, const ThickPolylines *polylines, const char *path)
 {
     const double        scale                       = 0.2;
     const std::string   inputSegmentPointColor      = "lightseagreen";
@@ -803,7 +802,7 @@ static inline void dump_voronoi_to_svg(const Lines &lines, /* const */ voronoi_d
             Voronoi::Internal::point_type(double(it->b(0)), double(it->b(1)))));
     
     // Color exterior edges.
-    for (voronoi_diagram<double>::const_edge_iterator it = vd.edges().begin(); it != vd.edges().end(); ++it)
+    for (boost::polygon::voronoi_diagram<double>::const_edge_iterator it = vd.edges().begin(); it != vd.edges().end(); ++it)
         if (!it->is_finite())
             Voronoi::Internal::color_exterior(&(*it));
 
@@ -818,11 +817,11 @@ static inline void dump_voronoi_to_svg(const Lines &lines, /* const */ voronoi_d
 
 #if 1
     // Draw voronoi vertices.
-    for (voronoi_diagram<double>::const_vertex_iterator it = vd.vertices().begin(); it != vd.vertices().end(); ++it)
+    for (boost::polygon::voronoi_diagram<double>::const_vertex_iterator it = vd.vertices().begin(); it != vd.vertices().end(); ++it)
         if (! internalEdgesOnly || it->color() != Voronoi::Internal::EXTERNAL_COLOR)
-            svg.draw(Point(coord_t((*it)(0)), coord_t((*it)(1))), voronoiPointColor, voronoiPointRadius);
+            svg.draw(Point(coord_t(it->x()), coord_t(it->y())), voronoiPointColor, voronoiPointRadius);
 
-    for (voronoi_diagram<double>::const_edge_iterator it = vd.edges().begin(); it != vd.edges().end(); ++it) {
+    for (boost::polygon::voronoi_diagram<double>::const_edge_iterator it = vd.edges().begin(); it != vd.edges().end(); ++it) {
         if (primaryEdgesOnly && !it->is_primary())
             continue;
         if (internalEdgesOnly && (it->color() == Voronoi::Internal::EXTERNAL_COLOR))
@@ -845,7 +844,7 @@ static inline void dump_voronoi_to_svg(const Lines &lines, /* const */ voronoi_d
                 color = voronoiLineColorSecondary;
         }
         for (std::size_t i = 0; i + 1 < samples.size(); ++i)
-            svg.draw(Line(Point(coord_t(samples[i](0)), coord_t(samples[i](1))), Point(coord_t(samples[i+1](0)), coord_t(samples[i+1](1)))), color, voronoiLineWidth);
+            svg.draw(Line(Point(coord_t(samples[i].x()), coord_t(samples[i].y())), Point(coord_t(samples[i+1].x()), coord_t(samples[i+1].y()))), color, voronoiLineWidth);
     }
 #endif
 
diff --git a/src/libslic3r/Geometry.hpp b/src/libslic3r/Geometry.hpp
index 44303711b..d996658f2 100644
--- a/src/libslic3r/Geometry.hpp
+++ b/src/libslic3r/Geometry.hpp
@@ -11,8 +11,6 @@
 #include <cereal/access.hpp>
 
 #include "boost/polygon/voronoi.hpp"
-using boost::polygon::voronoi_builder;
-using boost::polygon::voronoi_diagram;
 
 namespace ClipperLib {
 class PolyNode;
@@ -192,7 +190,7 @@ class MedialAxis {
     void build(Polylines* polylines);
     
     private:
-    class VD : public voronoi_diagram<double> {
+    class VD : public boost::polygon::voronoi_diagram<double> {
     public:
         typedef double                                          coord_type;
         typedef boost::polygon::point_data<coordinate_type>     point_type;
diff --git a/src/libslic3r/Layer.cpp b/src/libslic3r/Layer.cpp
index 74deabf3e..53a7f2fc4 100644
--- a/src/libslic3r/Layer.cpp
+++ b/src/libslic3r/Layer.cpp
@@ -88,8 +88,12 @@ ExPolygons Layer::merged(float offset_scaled) const
 		offset_scaled2 = float(- EPSILON);
     }
     Polygons polygons;
-    for (LayerRegion *layerm : m_regions)
-		append(polygons, offset(to_expolygons(layerm->slices.surfaces), offset_scaled));
+	for (LayerRegion *layerm : m_regions) {
+		const PrintRegionConfig &config = layerm->region()->config();
+		// Our users learned to bend Slic3r to produce empty volumes to act as subtracters. Only add the region if it is non-empty.
+		if (config.bottom_solid_layers > 0 || config.top_solid_layers > 0 || config.fill_density > 0. || config.perimeters > 0)
+			append(polygons, offset(to_expolygons(layerm->slices.surfaces), offset_scaled));
+	}
     ExPolygons out = union_ex(polygons);
 	if (offset_scaled2 != 0.f)
 		out = offset_ex(out, offset_scaled2);
diff --git a/src/libslic3r/LayerRegion.cpp b/src/libslic3r/LayerRegion.cpp
index 658bcf709..35acaf998 100644
--- a/src/libslic3r/LayerRegion.cpp
+++ b/src/libslic3r/LayerRegion.cpp
@@ -88,7 +88,6 @@ void LayerRegion::make_perimeters(const SurfaceCollection &slices, SurfaceCollec
 
 void LayerRegion::process_external_surfaces(const Layer *lower_layer, const Polygons *lower_layer_covered)
 {
-    const Surfaces &surfaces   = this->fill_surfaces.surfaces;
     const bool      has_infill = this->region()->config().fill_density.value > 0.;
     const float		margin 	   = float(scale_(EXTERNAL_INFILL_MARGIN));
 
diff --git a/src/libslic3r/Polygon.cpp b/src/libslic3r/Polygon.cpp
index bd5ec3de5..e1e299144 100644
--- a/src/libslic3r/Polygon.cpp
+++ b/src/libslic3r/Polygon.cpp
@@ -254,6 +254,11 @@ Point Polygon::point_projection(const Point &point) const
     return proj;
 }
 
+BoundingBox get_extents(const Points &points)
+{ 
+	return BoundingBox(points);
+}
+
 BoundingBox get_extents(const Polygon &poly) 
 { 
     return poly.bounding_box();
diff --git a/src/libslic3r/Polygon.hpp b/src/libslic3r/Polygon.hpp
index 19be3068b..8230b49f8 100644
--- a/src/libslic3r/Polygon.hpp
+++ b/src/libslic3r/Polygon.hpp
@@ -22,7 +22,8 @@ public:
     const Point& operator[](Points::size_type idx) const { return this->points[idx]; }
 
     Polygon() {}
-    explicit Polygon(const Points &points): MultiPoint(points) {}
+    explicit Polygon(const Points &points) : MultiPoint(points) {}
+	Polygon(std::initializer_list<Point> points) : MultiPoint(points) {}
     Polygon(const Polygon &other) : MultiPoint(other.points) {}
     Polygon(Polygon &&other) : MultiPoint(std::move(other.points)) {}
 	static Polygon new_scale(const std::vector<Vec2d> &points) { 
@@ -66,6 +67,10 @@ public:
     Point point_projection(const Point &point) const;
 };
 
+inline bool operator==(const Polygon &lhs, const Polygon &rhs) { return lhs.points == rhs.points; }
+inline bool operator!=(const Polygon &lhs, const Polygon &rhs) { return lhs.points != rhs.points; }
+
+extern BoundingBox get_extents(const Points &points);
 extern BoundingBox get_extents(const Polygon &poly);
 extern BoundingBox get_extents(const Polygons &polygons);
 extern BoundingBox get_extents_rotated(const Polygon &poly, double angle);
@@ -102,6 +107,15 @@ inline void        polygons_append(Polygons &dst, Polygons &&src)
     }
 }
 
+inline Polygons polygons_simplify(const Polygons &polys, double tolerance)
+{
+	Polygons out;
+	out.reserve(polys.size());
+	for (const Polygon &p : polys)
+		polygons_append(out, p.simplify(tolerance));
+	return out;
+}
+
 inline void polygons_rotate(Polygons &polys, double angle)
 {
     const double cos_angle = cos(angle);
diff --git a/src/libslic3r/PolygonTrimmer.cpp b/src/libslic3r/PolygonTrimmer.cpp
index 3e3c9b498..2c4e06fc5 100644
--- a/src/libslic3r/PolygonTrimmer.cpp
+++ b/src/libslic3r/PolygonTrimmer.cpp
@@ -12,12 +12,11 @@ TrimmedLoop trim_loop(const Polygon &loop, const EdgeGrid::Grid &grid)
 	TrimmedLoop out;
 
 	if (loop.size() >= 2) {
-		size_t cnt = loop.points.size();
 
 		struct Visitor {
 			Visitor(const EdgeGrid::Grid &grid, const Slic3r::Point *pt_prev, const Slic3r::Point *pt_this) : grid(grid), pt_prev(pt_prev), pt_this(pt_this) {}
 
-			void operator()(coord_t iy, coord_t ix) {
+			bool operator()(coord_t iy, coord_t ix) {
 				// Called with a row and colum of the grid cell, which is intersected by a line.
 				auto cell_data_range = grid.cell_data_range(iy, ix);
 				for (auto it_contour_and_segment = cell_data_range.first; it_contour_and_segment != cell_data_range.second; ++ it_contour_and_segment) {
@@ -27,6 +26,8 @@ TrimmedLoop trim_loop(const Polygon &loop, const EdgeGrid::Grid &grid)
 						// The two segments intersect. Add them to the output.
 					}
 				}
+				// Continue traversing the grid along the edge.
+				return true;
 			}
 
 			const EdgeGrid::Grid &grid;
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index d87e63c27..b334b70fc 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -1,6 +1,7 @@
 #include "Print.hpp"
 #include "BoundingBox.hpp"
 #include "ClipperUtils.hpp"
+#include "ElephantFootCompensation.hpp"
 #include "Geometry.hpp"
 #include "I18N.hpp"
 #include "SupportMaterial.hpp"
@@ -1769,6 +1770,7 @@ end:
                 Layer *layer = m_layers[layer_id];
                 // Apply size compensation and perform clipping of multi-part objects.
                 float delta = float(scale_(m_config.xy_size_compensation.value));
+                //FIXME only apply the compensation if no raft is enabled.
                 float elephant_foot_compensation = 0.f;
                 if (layer_id == 0)
                     elephant_foot_compensation = float(scale_(m_config.elefant_foot_compensation.value));
@@ -1789,19 +1791,8 @@ end:
                             to_expolygons(std::move(layerm->slices.surfaces)) :
                             offset_ex(to_expolygons(std::move(layerm->slices.surfaces)), delta);
                         // Apply the elephant foot compensation.
-                        if (elephant_foot_compensation > 0) {
-                            float elephant_foot_spacing     = float(layerm->flow(frExternalPerimeter).scaled_elephant_foot_spacing());
-                            float external_perimeter_nozzle = float(scale_(this->print()->config().nozzle_diameter.get_at(layerm->region()->config().perimeter_extruder.value - 1)));
-                            // Apply the elephant foot compensation by steps of 1/10 nozzle diameter.
-                            float  steps  = std::ceil(elephant_foot_compensation / (0.1f * external_perimeter_nozzle));
-                            size_t nsteps = size_t(steps);
-                            float  step   = elephant_foot_compensation / steps;
-                            for (size_t i = 0; i < nsteps; ++ i) {
-    							Polygons tmp = offset(expolygons, - step);
-    							append(tmp, diff(to_polygons(expolygons), offset(offset_ex(expolygons, -elephant_foot_spacing - step), elephant_foot_spacing + step)));
-    							expolygons = union_ex(tmp);
-                            }
-                        }
+                        if (elephant_foot_compensation > 0)
+							expolygons = union_ex(Slic3r::elephant_foot_compensation(expolygons, layerm->flow(frExternalPerimeter), unscale<double>(elephant_foot_compensation)));
                         layerm->slices.set(std::move(expolygons), stInternal);
                     }
                 } else {
@@ -1825,33 +1816,17 @@ end:
                             layerm->slices.set(std::move(slices), stInternal);
                         }
                     }
-                    if (delta < 0.f) {
+                    if (delta < 0.f || elephant_foot_compensation > 0.f) {
                         // Apply the negative XY compensation.
-                        Polygons trimming = offset(layer->merged(float(EPSILON)), delta - float(EPSILON));
+                        Polygons trimming;
+                        if (elephant_foot_compensation > 0.f) {
+							trimming = to_polygons(Slic3r::elephant_foot_compensation(offset_ex(layer->merged(float(EPSILON)), std::min(delta, 0.f) - float(EPSILON)), 
+								layer->m_regions.front()->flow(frExternalPerimeter), unscale<double>(elephant_foot_compensation)));
+                        } else
+	                        trimming = offset(layer->merged(float(EPSILON)), delta - float(EPSILON));
                         for (size_t region_id = 0; region_id < layer->m_regions.size(); ++ region_id)
                             layer->m_regions[region_id]->trim_surfaces(trimming);
                     }
-                    if (elephant_foot_compensation > 0.f) {
-                        // Apply the elephant foot compensation.
-                        std::vector<float> elephant_foot_spacing;
-                        elephant_foot_spacing.reserve(layer->m_regions.size());
-                        float external_perimeter_nozzle = 0.f;
-                        for (size_t region_id = 0; region_id < layer->m_regions.size(); ++ region_id) {
-                            LayerRegion *layerm = layer->m_regions[region_id];
-                            elephant_foot_spacing.emplace_back(float(layerm->flow(frExternalPerimeter).scaled_elephant_foot_spacing()));
-                            external_perimeter_nozzle += float(scale_(this->print()->config().nozzle_diameter.get_at(layerm->region()->config().perimeter_extruder.value - 1)));
-                        }
-                        external_perimeter_nozzle /= (float)layer->m_regions.size();
-                        // Apply the elephant foot compensation by steps of 1/10 nozzle diameter.
-                        float  steps  = std::ceil(elephant_foot_compensation / (0.1f * external_perimeter_nozzle));
-                        size_t nsteps = size_t(steps);
-                        float  step   = elephant_foot_compensation / steps;
-                        for (size_t i = 0; i < nsteps; ++ i) {
-                            Polygons trimming_polygons = offset(layer->merged(float(EPSILON)), - step - float(EPSILON));
-                            for (size_t region_id = 0; region_id < layer->m_regions.size(); ++ region_id)
-                                layer->m_regions[region_id]->elephant_foot_compensation_step(elephant_foot_spacing[region_id] + step, trimming_polygons);
-                        }
-                    }
                 }
                 // Merge all regions' slices to get islands, chain them by a shortest path.
                 layer->make_slices();
diff --git a/src/libslic3r/SVG.cpp b/src/libslic3r/SVG.cpp
index 03f55802e..6e4b973ea 100644
--- a/src/libslic3r/SVG.cpp
+++ b/src/libslic3r/SVG.cpp
@@ -368,6 +368,10 @@ void SVG::export_expolygons(const char *path, const std::vector<std::pair<Slic3r
             color_holes = color_contour;
         svg.draw_outline(exp_with_attr.first, color_contour, color_holes, exp_with_attr.second.outline_width);
     }
+    for (const auto &exp_with_attr : expolygons_with_attributes)
+    	if (exp_with_attr.second.radius_points > 0)
+			for (const ExPolygon &expoly : exp_with_attr.first)
+    			svg.draw((Points)expoly, exp_with_attr.second.color_points, exp_with_attr.second.radius_points);
     svg.Close();
 }
 
diff --git a/src/libslic3r/SVG.hpp b/src/libslic3r/SVG.hpp
index 3a5602196..c1b387554 100644
--- a/src/libslic3r/SVG.hpp
+++ b/src/libslic3r/SVG.hpp
@@ -105,19 +105,25 @@ public:
             const std::string &color_contour,
             const std::string &color_holes,
             const coord_t      outline_width = scale_(0.05),
-            const float        fill_opacity  = 0.5f) :
+            const float        fill_opacity  = 0.5f,
+            const std::string &color_points = "black",
+            const coord_t      radius_points = 0) :
             color_fill      (color_fill),
             color_contour   (color_contour),
             color_holes     (color_holes),
             outline_width   (outline_width),
-            fill_opacity    (fill_opacity) 
+            fill_opacity    (fill_opacity),
+            color_points 	(color_points),
+            radius_points	(radius_points)
             {}
 
         std::string     color_fill;
         std::string     color_contour;
         std::string     color_holes;
+        std::string   	color_points;
         coord_t         outline_width;
         float           fill_opacity;
+        coord_t			radius_points;
     };
 
     static void export_expolygons(const char *path, const std::vector<std::pair<Slic3r::ExPolygons, ExPolygonAttributes>> &expolygons_with_attributes);
diff --git a/src/libslic3r/utils.cpp b/src/libslic3r/utils.cpp
index 8d2a6a866..678ad9ed2 100644
--- a/src/libslic3r/utils.cpp
+++ b/src/libslic3r/utils.cpp
@@ -424,14 +424,19 @@ int copy_file(const std::string &from, const std::string &to)
     static const auto perms = boost::filesystem::owner_read | boost::filesystem::owner_write | boost::filesystem::group_read | boost::filesystem::others_read;   // aka 644
 
     // Make sure the file has correct permission both before and after we copy over it.
-    try {
-        if (boost::filesystem::exists(target))
-            boost::filesystem::permissions(target, perms);
-        boost::filesystem::copy_file(source, target, boost::filesystem::copy_option::overwrite_if_exists);
-        boost::filesystem::permissions(target, perms);
-    } catch (std::exception & /* ex */) {
+    // NOTE: error_code variants are used here to supress expception throwing.
+    // Error code of permission() calls is ignored on purpose - if they fail,
+    // the copy_file() function will fail appropriately and we don't want the permission()
+    // calls to cause needless failures on permissionless filesystems (ie. FATs on SD cards etc.)
+    // or when the target file doesn't exist.
+    boost::system::error_code ec;
+    boost::filesystem::permissions(target, perms, ec);
+    boost::filesystem::copy_file(source, target, boost::filesystem::copy_option::overwrite_if_exists, ec);
+    if (ec) {
         return -1;
     }
+    boost::filesystem::permissions(target, perms, ec);
+
     return 0;
 }
 
diff --git a/src/qhull/CMakeLists.txt b/src/qhull/CMakeLists.txt
index 9ca0bdff2..ab9aba9af 100644
--- a/src/qhull/CMakeLists.txt
+++ b/src/qhull/CMakeLists.txt
@@ -18,11 +18,13 @@ if(Qhull_FOUND)
 
 message(STATUS "Using qhull from system.")
 if(SLIC3R_STATIC)
+    slic3r_remap_configs("Qhull::qhullcpp;Qhull::qhullstatic_r" RelWithDebInfo Release)
     target_link_libraries(qhull INTERFACE Qhull::qhullcpp Qhull::qhullstatic_r)
 else()
+    slic3r_remap_configs("Qhull::qhullcpp;Qhull::qhull_r" RelWithDebInfo Release)
     target_link_libraries(qhull INTERFACE Qhull::qhullcpp Qhull::qhull_r)
 endif()
-    
+
 else(Qhull_FOUND)
 
 project(qhull)
diff --git a/src/slic3r/Config/Version.cpp b/src/slic3r/Config/Version.cpp
index 3f8f960f1..da522dd5e 100644
--- a/src/slic3r/Config/Version.cpp
+++ b/src/slic3r/Config/Version.cpp
@@ -235,9 +235,9 @@ size_t Index::load(const boost::filesystem::path &path)
 			value = left_trim(value + 1);
 		*key_end = 0;
     	boost::optional<Semver> semver;
-    	if (maybe_semver)
+        if (maybe_semver)
     		semver = Semver::parse(key);
-		if (key_value_pair) {
+        if (key_value_pair) {
     		if (semver)
     			throw file_parser_error("Key cannot be a semantic version", path, idx_line);\
     		// Verify validity of the key / value pair.
@@ -288,7 +288,6 @@ Index::const_iterator Index::find(const Semver &ver) const
 
 Index::const_iterator Index::recommended() const
 {
-	int idx = -1;
 	const_iterator highest = this->end();
 	for (const_iterator it = this->begin(); it != this->end(); ++ it)
 		if (it->is_current_slic3r_supported() &&
diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.cpp b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
index a1db6884e..6c138d4d0 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.cpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
@@ -55,6 +55,7 @@ bool BackgroundSlicingProcess::select_technology(PrinterTechnology tech)
 		switch (tech) {
 		case ptFFF: m_print = m_fff_print; break;
 		case ptSLA: m_print = m_sla_print; break;
+        default: assert(false); break;
 		}
 		changed = true;
 	}
diff --git a/src/slic3r/GUI/Field.cpp b/src/slic3r/GUI/Field.cpp
index 07d75c947..42e3448fc 100644
--- a/src/slic3r/GUI/Field.cpp
+++ b/src/slic3r/GUI/Field.cpp
@@ -150,7 +150,13 @@ void Field::get_value_by_opt_type(wxString& str, const bool check_value/* = true
 	case coFloat:{
 		if (m_opt.type == coPercent && !str.IsEmpty() &&  str.Last() == '%') 
 			str.RemoveLast();
-		else if (check_value && !str.IsEmpty() && str.Last() == '%')	{
+		else if (!str.IsEmpty() && str.Last() == '%')
+        {
+            if (!check_value) {
+                m_value.clear();
+                break;
+            }
+
 			wxString label = m_Label->GetLabel();
 			if		(label.Last() == '\n')	label.RemoveLast();
 			while	(label.Last() == ' ')	label.RemoveLast();
@@ -169,13 +175,21 @@ void Field::get_value_by_opt_type(wxString& str, const bool check_value/* = true
         {
             if (m_opt.nullable && str == na_value())
                 val = ConfigOptionFloatsNullable::nil_value();
-            else if (check_value && !str.ToCDouble(&val))
+            else if (!str.ToCDouble(&val))
             {
+                if (!check_value) {
+                    m_value.clear();
+                    break;
+                }
                 show_error(m_parent, _(L("Invalid numeric input.")));
                 set_value(double_to_string(val), true);
             }
-            if (check_value && (m_opt.min > val || val > m_opt.max))
+            if (m_opt.min > val || val > m_opt.max)
             {
+                if (!check_value) {
+                    m_value.clear();
+                    break;
+                }
                 show_error(m_parent, _(L("Input value is out of range")));
                 if (m_opt.min > val) val = m_opt.min;
                 if (val > m_opt.max) val = m_opt.max;
@@ -192,15 +206,24 @@ void Field::get_value_by_opt_type(wxString& str, const bool check_value/* = true
             double val = 0.;
 			// Replace the first occurence of comma in decimal number.
 			str.Replace(",", ".", false);
-            if (check_value && !str.ToCDouble(&val))
+            if (!str.ToCDouble(&val))
             {
+                if (!check_value) {
+                    m_value.clear();
+                    break;
+                }
                 show_error(m_parent, _(L("Invalid numeric input.")));
                 set_value(double_to_string(val), true);
             }
-            else if (check_value && ((m_opt.sidetext.rfind("mm/s") != std::string::npos && val > m_opt.max) ||
+            else if (((m_opt.sidetext.rfind("mm/s") != std::string::npos && val > m_opt.max) ||
                      (m_opt.sidetext.rfind("mm ") != std::string::npos && val > 1)) &&
                      (m_value.empty() || std::string(str.ToUTF8().data()) != boost::any_cast<std::string>(m_value)))
             {
+                if (!check_value) {
+                    m_value.clear();
+                    break;
+                }
+
                 const std::string sidetext = m_opt.sidetext.rfind("mm/s") != std::string::npos ? "mm/s" : "mm";
                 const wxString stVal = double_to_string(val, 2);
                 const wxString msg_text = wxString::Format(_(L("Do you mean %s%% instead of %s %s?\n"
@@ -351,6 +374,7 @@ bool TextCtrl::value_was_changed()
     boost::any val = m_value;
     wxString ret_str = static_cast<wxTextCtrl*>(window)->GetValue();
     // update m_value!
+    // ret_str might be changed inside get_value_by_opt_type
     get_value_by_opt_type(ret_str);
 
     switch (m_opt.type) {
@@ -396,8 +420,10 @@ void TextCtrl::set_value(const boost::any& value, bool change_event/* = false*/)
 
     if (!change_event) {
         wxString ret_str = static_cast<wxTextCtrl*>(window)->GetValue();
-        // update m_value to correct work of next value_was_changed(), 
-        // but don't check/change inputed value and don't show a warning message
+        /* Update m_value to correct work of next value_was_changed(). 
+         * But after checking of entered value, don't fix the "incorrect" value and don't show a warning message, 
+         * just clear m_value in this case. 
+         */
         get_value_by_opt_type(ret_str, false);
     }
 }
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 6b9232e1d..7e782dee3 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1949,7 +1949,7 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                 if (it->new_geometry()) {
                     // New volume.
                     unsigned int old_id = find_old_volume_id(it->composite_id);
-                    if (old_id != -1)
+                    if (old_id != (unsigned int)-1)
                         map_glvolume_old_to_new[old_id] = m_volumes.volumes.size();
                     m_volumes.load_object_volume(&model_object, obj_idx, volume_idx, instance_idx, m_color_by, m_initialized);
                     m_volumes.volumes.back()->geometry_id = key.geometry_id;
diff --git a/src/slic3r/GUI/GUI_App.hpp b/src/slic3r/GUI/GUI_App.hpp
index c5ddc0152..9bfc34543 100644
--- a/src/slic3r/GUI/GUI_App.hpp
+++ b/src/slic3r/GUI/GUI_App.hpp
@@ -87,7 +87,7 @@ class GUI_App : public wxApp
     wxFont		    m_bold_font;
 	wxFont			m_normal_font;
 
-    size_t          m_em_unit; // width of a "m"-symbol in pixels for current system font 
+    int          m_em_unit; // width of a "m"-symbol in pixels for current system font
                                // Note: for 100% Scale m_em_unit = 10 -> it's a good enough coefficient for a size setting of controls
 
     std::unique_ptr<wxLocale> 	  m_wxLocale;
@@ -105,7 +105,7 @@ public:
     bool            initialized() const { return m_initialized; }
 
     GUI_App();
-    ~GUI_App();
+    ~GUI_App() override;
 
     static unsigned get_colour_approx_luma(const wxColour &colour);
     static bool     dark_mode();
@@ -124,8 +124,7 @@ public:
     const wxFont&   small_font()            { return m_small_font; }
     const wxFont&   bold_font()             { return m_bold_font; }
     const wxFont&   normal_font()           { return m_normal_font; }
-    size_t          em_unit() const         { return m_em_unit; }
-    void            set_em_unit(const size_t em_unit)    { m_em_unit = em_unit; }
+    int             em_unit() const         { return m_em_unit; }
     float           toolbar_icon_scale(const bool is_limited = false) const;
 
     void            recreate_GUI();
@@ -155,7 +154,7 @@ public:
 	// Translate the language code to a code, for which Prusa Research maintains translations. Defaults to "en_US".
     wxString 		current_language_code_safe() const;
 
-    virtual bool OnExceptionInMainLoop();
+    virtual bool OnExceptionInMainLoop() override;
 
 #ifdef __APPLE__
     // wxWidgets override to get an event on open files.
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index 377c26e79..1cbfc2bdf 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -445,7 +445,7 @@ void ObjectList::update_extruder_values_for_items(const size_t max_extruder)
         auto object = (*m_objects)[i];
         wxString extruder;
         if (!object->config.has("extruder") ||
-            object->config.option<ConfigOptionInt>("extruder")->value > max_extruder)
+            size_t(object->config.option<ConfigOptionInt>("extruder")->value) > max_extruder)
             extruder = _(L("default"));
         else
             extruder = wxString::Format("%d", object->config.option<ConfigOptionInt>("extruder")->value);
@@ -457,7 +457,7 @@ void ObjectList::update_extruder_values_for_items(const size_t max_extruder)
                 item = m_objects_model->GetItemByVolumeId(i, id);
                 if (!item) continue;
                 if (!object->volumes[id]->config.has("extruder") ||
-                    object->volumes[id]->config.option<ConfigOptionInt>("extruder")->value > max_extruder)
+                    size_t(object->volumes[id]->config.option<ConfigOptionInt>("extruder")->value) > max_extruder)
                     extruder = _(L("default"));
                 else
                     extruder = wxString::Format("%d", object->volumes[id]->config.option<ConfigOptionInt>("extruder")->value); 
diff --git a/src/slic3r/GUI/GUI_ObjectManipulation.cpp b/src/slic3r/GUI/GUI_ObjectManipulation.cpp
index d1cb1348c..5e939cb71 100644
--- a/src/slic3r/GUI/GUI_ObjectManipulation.cpp
+++ b/src/slic3r/GUI/GUI_ObjectManipulation.cpp
@@ -634,7 +634,11 @@ void ObjectManipulation::update_reset_buttons_visibility()
         show_drop_to_bed = (std::abs(min_z) > EPSILON);
     }
 
-    wxGetApp().CallAfter([this, show_rotation, show_scale, show_drop_to_bed]{
+    wxGetApp().CallAfter([this, show_rotation, show_scale, show_drop_to_bed] {
+        // There is a case (under OSX), when this function is called after the Manipulation panel is hidden
+        // So, let check if Manipulation panel is still shown for this moment
+        if (!this->IsShown())
+            return;
         m_reset_rotation_button->Show(show_rotation);
         m_reset_scale_button->Show(show_scale);
         m_drop_to_bed_button->Show(show_drop_to_bed);
diff --git a/src/slic3r/GUI/GUI_Preview.cpp b/src/slic3r/GUI/GUI_Preview.cpp
index 064fcb5c5..81367081f 100644
--- a/src/slic3r/GUI/GUI_Preview.cpp
+++ b/src/slic3r/GUI/GUI_Preview.cpp
@@ -375,6 +375,8 @@ void Preview::load_print(bool keep_z_range)
         load_print_as_fff(keep_z_range);
     else if (tech == ptSLA)
         load_print_as_sla();
+
+    Layout();
 }
 
 void Preview::reload_print(bool keep_volumes)
diff --git a/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp b/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
index f649c98b2..0defb1348 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmosManager.hpp
@@ -114,8 +114,17 @@ public:
 
         m_serializing = true;
 
+        // Following is needed to know which to be turn on, but not actually modify
+        // m_current prematurely, so activate_gizmo is not confused.
+        EType old_current = m_current;
         ar(m_current);
+        EType new_current = m_current;
+        m_current = old_current;
 
+        // activate_gizmo call sets m_current and calls set_state for the gizmo
+        // it does nothing in case the gizmo is already activated
+        // it can safely be called for Undefined gizmo
+        activate_gizmo(new_current);
         if (m_current != Undefined)
             m_gizmos[m_current]->load(ar);
     }
diff --git a/src/slic3r/GUI/OptionsGroup.cpp b/src/slic3r/GUI/OptionsGroup.cpp
index 698c1e034..8b6f5bc30 100644
--- a/src/slic3r/GUI/OptionsGroup.cpp
+++ b/src/slic3r/GUI/OptionsGroup.cpp
@@ -233,7 +233,7 @@ void OptionsGroup::append_line(const Line& line, wxStaticText**	full_Label/* = n
 
 		add_undo_buttuns_to_sizer(sizer, field);
 		if (is_window_field(field)) 
-			sizer->Add(field->getWindow(), option.opt.full_width ? 1 : 0, //(option.opt.full_width ? wxEXPAND : 0) |
+            sizer->Add(field->getWindow(), option.opt.full_width ? 1 : 0, //(option.opt.full_width ? wxEXPAND : 0) |
             wxBOTTOM | wxTOP | (option.opt.full_width ? wxEXPAND : wxALIGN_CENTER_VERTICAL), (wxOSX || !staticbox) ? 0 : 2);
 		if (is_sizer_field(field)) 
 			sizer->Add(field->getSizer(), 1, /*(*/option.opt.full_width ? wxEXPAND : /*0) |*/ wxALIGN_CENTER_VERTICAL, 0);
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 5b1fdc91c..14fbdf72c 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -4794,7 +4794,7 @@ bool Plater::undo_redo_string_getter(const bool is_undo, int idx, const char** o
     const std::vector<UndoRedo::Snapshot>& ss_stack = p->undo_redo_stack().snapshots();
     const int idx_in_ss_stack = p->get_active_snapshot_index() + (is_undo ? -(++idx) : idx);
 
-    if (0 < idx_in_ss_stack && idx_in_ss_stack < ss_stack.size() - 1) {
+    if (0 < idx_in_ss_stack && (size_t)idx_in_ss_stack < ss_stack.size() - 1) {
         *out_text = ss_stack[idx_in_ss_stack].name.c_str();
         return true;
     }
@@ -4807,7 +4807,7 @@ void Plater::undo_redo_topmost_string_getter(const bool is_undo, std::string& ou
     const std::vector<UndoRedo::Snapshot>& ss_stack = p->undo_redo_stack().snapshots();
     const int idx_in_ss_stack = p->get_active_snapshot_index() + (is_undo ? -1 : 0);
 
-    if (0 < idx_in_ss_stack && idx_in_ss_stack < ss_stack.size() - 1) {
+    if (0 < idx_in_ss_stack && (size_t)idx_in_ss_stack < ss_stack.size() - 1) {
         out_text = ss_stack[idx_in_ss_stack].name;
         return;
     }
diff --git a/src/slic3r/GUI/wxExtensions.cpp b/src/slic3r/GUI/wxExtensions.cpp
index 238860ce7..40f509ad7 100644
--- a/src/slic3r/GUI/wxExtensions.cpp
+++ b/src/slic3r/GUI/wxExtensions.cpp
@@ -1061,7 +1061,7 @@ wxDataViewItem ObjectDataViewModel::Delete(const wxDataViewItem &item)
 		node_parent->GetChildren().Remove(node);
 
 		if (id > 0) { 
-			if(id == node_parent->GetChildCount()) id--;
+            if (size_t(id) == node_parent->GetChildCount()) id--;
 			ret_item = wxDataViewItem(node_parent->GetChildren().Item(id));
 		}