From e41ddda34dc8b1ef598d38f97116a9b19241f0c9 Mon Sep 17 00:00:00 2001
From: Remco Burema <r.burema@ultimaker.com>
Date: Wed, 31 Jul 2024 11:10:46 +0200
Subject: [PATCH 1/2] Remove early-out: Restore 'side-effects' of unioning with
 empty.

This is actually actively wanted and used in the code (see the unionPolygons() signature, note the missing argument), to solve self-overlap and the like. The added early outs where blocking that use here, leading to hard to trace problems, like tree support stopping midway.

CURA-12061
---
 src/geometry/Shape.cpp | 26 ++------------------------
 1 file changed, 2 insertions(+), 24 deletions(-)

diff --git a/src/geometry/Shape.cpp b/src/geometry/Shape.cpp
index ed5dffbbf0..7c52d249ca 100644
--- a/src/geometry/Shape.cpp
+++ b/src/geometry/Shape.cpp
@@ -177,18 +177,7 @@ Shape Shape::difference(const Polygon& other) const
 
 Shape Shape::unionPolygons(const Shape& other, ClipperLib::PolyFillType fill_type) const
 {
-    if (empty() && other.empty())
-    {
-        return {};
-    }
-    if (empty() && other.size() <= 1)
-    {
-        return other;
-    }
-    if (other.empty() && size() <= 1)
-    {
-        return *this;
-    }
+    // No early out, as shapes should be able to be 'unioned' with themselves, which will resolve certain issues like self-overlapping polygons.
     ClipperLib::Paths ret;
     ClipperLib::Clipper clipper(clipper_init);
     addPaths(clipper, ClipperLib::ptSubject);
@@ -199,18 +188,7 @@ Shape Shape::unionPolygons(const Shape& other, ClipperLib::PolyFillType fill_typ
 
 Shape Shape::unionPolygons(const Polygon& polygon, ClipperLib::PolyFillType fill_type) const
 {
-    if (empty() && polygon.empty())
-    {
-        return {};
-    }
-    if (empty())
-    {
-        return Shape(polygon);
-    }
-    if (polygon.empty() && size() <= 1)
-    {
-        return *this;
-    }
+    // No early out, as unioning even with another empty polygon has some beneficial side-effects, such as removing self-overlapping polygons.
     ClipperLib::Paths ret;
     ClipperLib::Clipper clipper(clipper_init);
     addPaths(clipper, ClipperLib::ptSubject);

From 078c20a04b71d220fb9dc22f54c6a70230e43263 Mon Sep 17 00:00:00 2001
From: Remco Burema <r.burema@ultimaker.com>
Date: Wed, 31 Jul 2024 11:22:08 +0200
Subject: [PATCH 2/2] Reintroduce _one_ of the early outs (_both_ empty should
 still be ok).

CURA-12061
---
 src/geometry/Shape.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/geometry/Shape.cpp b/src/geometry/Shape.cpp
index 7c52d249ca..61d029c4e2 100644
--- a/src/geometry/Shape.cpp
+++ b/src/geometry/Shape.cpp
@@ -177,7 +177,11 @@ Shape Shape::difference(const Polygon& other) const
 
 Shape Shape::unionPolygons(const Shape& other, ClipperLib::PolyFillType fill_type) const
 {
-    // No early out, as shapes should be able to be 'unioned' with themselves, which will resolve certain issues like self-overlapping polygons.
+    if (empty() && other.empty())
+    {
+        return {};
+    }
+    // No further early outs, as shapes should be able to be 'unioned' with themselves, which will resolve certain issues like self-overlapping polygons.
     ClipperLib::Paths ret;
     ClipperLib::Clipper clipper(clipper_init);
     addPaths(clipper, ClipperLib::ptSubject);
@@ -188,7 +192,11 @@ Shape Shape::unionPolygons(const Shape& other, ClipperLib::PolyFillType fill_typ
 
 Shape Shape::unionPolygons(const Polygon& polygon, ClipperLib::PolyFillType fill_type) const
 {
-    // No early out, as unioning even with another empty polygon has some beneficial side-effects, such as removing self-overlapping polygons.
+    if (empty() && polygon.empty())
+    {
+        return {};
+    }
+    // No further early outs, as unioning even with another empty polygon has some beneficial side-effects, such as removing self-overlapping polygons.
     ClipperLib::Paths ret;
     ClipperLib::Clipper clipper(clipper_init);
     addPaths(clipper, ClipperLib::ptSubject);