From 64f1fb9e792ceadb29cb19692ad583d8c432b19c Mon Sep 17 00:00:00 2001
From: Seth Hillbrand <hillbrand@ucdavis.edu>
Date: Tue, 18 Dec 2018 17:22:32 -0700
Subject: [PATCH] tesselation: Re-check polygon count after fracturing

The fracture() call may result in zero polygons remaining, which will
cause failure in our tesselation routine, so we need to check whether
this is a valid POLYGON before re-tesselating.
---
 common/geometry/shape_poly_set.cpp       | 6 +++++-
 include/geometry/polygon_triangulation.h | 2 --
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/common/geometry/shape_poly_set.cpp b/common/geometry/shape_poly_set.cpp
index a00a903d1a..3dd21d32aa 100644
--- a/common/geometry/shape_poly_set.cpp
+++ b/common/geometry/shape_poly_set.cpp
@@ -1882,11 +1882,15 @@ void SHAPE_POLY_SET::CacheTriangulation()
         {
             tmpSet.Fracture( PM_FAST );
 
-            if( !tess.TesselatePolygon( tmpSet.Polygon( i ).front() ) )
+            // After fracturing, we may have zero or one polygon
+            // Check for zero polygons before tesselating and break regardless
+            if( !tmpSet.OutlineCount() ||  !tess.TesselatePolygon( tmpSet.Polygon( i ).front() ) )
             {
                 m_triangulatedPolys.pop_back();
                 m_triangulationValid = false;
             }
+
+            break;
         }
     }
 
diff --git a/include/geometry/polygon_triangulation.h b/include/geometry/polygon_triangulation.h
index 335eee49da..b419b45c6f 100644
--- a/include/geometry/polygon_triangulation.h
+++ b/include/geometry/polygon_triangulation.h
@@ -649,8 +649,6 @@ public:
 
     bool TesselatePolygon( const SHAPE_LINE_CHAIN& aPoly )
     {
-        ClipperLib::Clipper c;
-
         m_bbox = aPoly.BBox();
         m_result.Clear();