From 2498da27456fe6558ac7224e9acaf9eab3e9fdf7 Mon Sep 17 00:00:00 2001
From: Seth Hillbrand <hillbrand@ucdavis.edu>
Date: Tue, 18 Dec 2018 06:17:01 -0700
Subject: [PATCH] Tesselation: Only set valid when successful

Tesselation can fail for a number of reasons.  When this happens, we set
the triangulationValid flag to false to prevent using the broken
triangulation.  This will fall back to the slow OpenGL triangulation
when DrawPolygon is called.
---
 common/geometry/shape_poly_set.cpp       | 15 +++++++++------
 include/geometry/polygon_triangulation.h |  3 ---
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/common/geometry/shape_poly_set.cpp b/common/geometry/shape_poly_set.cpp
index 99302e2f5e..a00a903d1a 100644
--- a/common/geometry/shape_poly_set.cpp
+++ b/common/geometry/shape_poly_set.cpp
@@ -1869,12 +1869,10 @@ void SHAPE_POLY_SET::CacheTriangulation()
         tmpSet.Fracture( PM_FAST );
 
     m_triangulatedPolys.clear();
+    m_triangulationValid = true;
 
     for( int i = 0; i < tmpSet.OutlineCount(); i++ )
     {
-        if( tmpSet.Outline( i ).PointCount() < 3 )  // malformed polygon
-            continue;
-
         m_triangulatedPolys.push_back( std::make_unique<TRIANGULATED_POLYGON>() );
         PolygonTriangulation tess( *m_triangulatedPolys.back() );
 
@@ -1883,12 +1881,17 @@ void SHAPE_POLY_SET::CacheTriangulation()
         if( !tess.TesselatePolygon( tmpSet.Polygon( i ).front() ) )
         {
             tmpSet.Fracture( PM_FAST );
-            tess.TesselatePolygon( tmpSet.Polygon( i ).front() );
+
+            if( !tess.TesselatePolygon( tmpSet.Polygon( i ).front() ) )
+            {
+                m_triangulatedPolys.pop_back();
+                m_triangulationValid = false;
+            }
         }
     }
 
-    m_triangulationValid = true;
-    m_hash = checksum();
+    if( m_triangulationValid )
+        m_hash = checksum();
 }
 
 
diff --git a/include/geometry/polygon_triangulation.h b/include/geometry/polygon_triangulation.h
index 8d9ad102df..335eee49da 100644
--- a/include/geometry/polygon_triangulation.h
+++ b/include/geometry/polygon_triangulation.h
@@ -651,9 +651,6 @@ public:
     {
         ClipperLib::Clipper c;
 
-        if( aPoly.PointCount() < 3 )    // Malformed polygon
-            return false;
-
         m_bbox = aPoly.BBox();
         m_result.Clear();