From 4ea2fc14822037460901f5887dcb0450e373ecf4 Mon Sep 17 00:00:00 2001
From: remi durand <remi-j.durand@thalesgroup.com>
Date: Mon, 14 Jun 2021 00:36:37 +0200
Subject: [PATCH] fix negative area from elephant foot reduction assert was
 screaming, with reason.

---
 src/libslic3r/ClipperUtils.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/libslic3r/ClipperUtils.cpp b/src/libslic3r/ClipperUtils.cpp
index 1502834c3..5b47e7a98 100644
--- a/src/libslic3r/ClipperUtils.cpp
+++ b/src/libslic3r/ClipperUtils.cpp
@@ -1228,6 +1228,11 @@ ExPolygons variable_offset_inner_ex(const ExPolygon &expoly, const std::vector<s
 	holes.reserve(expoly.holes.size());
 	for (const Polygon& hole : expoly.holes)
 		append(holes, fix_after_outer_offset(mittered_offset_path_scaled(hole.points, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftNegative, false));
+    for (auto it = holes.begin(); it != holes.end();)
+        if (ClipperLib::Area(*it) < 0.) {
+            it = holes.erase(it);
+        }
+        else ++it;
 #ifndef NDEBUG
 	for (auto &c : holes)
 		assert(ClipperLib::Area(c) > 0.);