From c71bb246e62fd71f431861b3bc38e390bd6dbdf5 Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sat, 22 Aug 2020 23:45:39 +0100
Subject: [PATCH] Don't allow preview to try and draw empty polygons.

Fixes https://gitlab.com/kicad/code/kicad/issues/5314
---
 common/preview_items/polygon_item.cpp | 22 +++++++++++++++++-----
 pcbnew/tools/drawing_tool.cpp         | 20 +++++++++++---------
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/common/preview_items/polygon_item.cpp b/common/preview_items/polygon_item.cpp
index 9698793f33..6f0f57bd9f 100644
--- a/common/preview_items/polygon_item.cpp
+++ b/common/preview_items/polygon_item.cpp
@@ -57,14 +57,26 @@ void POLYGON_ITEM::drawPreviewShape( KIGFX::VIEW* aView ) const
     auto& gal = *aView->GetGAL();
     auto rs = aView->GetPainter()->GetSettings();
 
-    gal.SetLineWidth( (float) aView->ToWorld( POLY_LINE_WIDTH ) );
-    gal.DrawPolyline( m_lockedChain );
+    if( m_lockedChain.PointCount() >= 2 )
+    {
+        gal.SetLineWidth( (float) aView->ToWorld( POLY_LINE_WIDTH ) );
+        gal.DrawPolyline( m_lockedChain );
+    }
 
     // draw the leader line in a different color
-    gal.SetStrokeColor( rs->GetLayerColor( LAYER_AUX_ITEMS ) );
-    gal.DrawPolyline( m_leaderChain );
+    if( m_leaderChain.PointCount() >= 2 )
+    {
+        gal.SetStrokeColor( rs->GetLayerColor( LAYER_AUX_ITEMS ) );
+        gal.DrawPolyline( m_leaderChain );
+    }
 
-    gal.DrawPolygon( m_polyfill );
+    for( int j = 0; j < m_polyfill.OutlineCount(); ++j )
+    {
+        const SHAPE_LINE_CHAIN& outline = m_polyfill.COutline( j );
+
+        if( outline.PointCount() >= 2 )
+            gal.DrawPolygon( outline );
+    }
 }
 
 
diff --git a/pcbnew/tools/drawing_tool.cpp b/pcbnew/tools/drawing_tool.cpp
index f121481d8d..eda8782449 100644
--- a/pcbnew/tools/drawing_tool.cpp
+++ b/pcbnew/tools/drawing_tool.cpp
@@ -1548,8 +1548,9 @@ int DRAWING_TOOL::DrawZone( const TOOL_EVENT& aEvent )
         grid.SetSnap( !evt->Modifier( MD_SHIFT ) );
         grid.SetUseGrid( !evt->Modifier( MD_ALT ) );
         m_controls->SetSnapping( !evt->Modifier( MD_ALT ) );
-        VECTOR2I cursorPos = grid.BestSnapAnchor(
-                evt->IsPrime() ? evt->Position() : m_controls->GetMousePosition(), layers );
+        VECTOR2I cursorPos = grid.BestSnapAnchor( evt->IsPrime() ? evt->Position()
+                                                                 : m_controls->GetMousePosition(),
+                                                  layers );
         m_controls->ForceCursorPosition( true, cursorPos );
 
         if( ( sourceZone && sourceZone->GetHV45() ) || constrainAngle || evt->Modifier( MD_CTRL ) )
@@ -1557,13 +1558,14 @@ int DRAWING_TOOL::DrawZone( const TOOL_EVENT& aEvent )
         else
             polyGeomMgr.SetLeaderMode( POLYGON_GEOM_MANAGER::LEADER_MODE::DIRECT );
 
-        auto cleanup = [&] () {
-            polyGeomMgr.Reset();
-            started = false;
-            grid.ClearSkipPoint();
-            m_controls->SetAutoPan( false );
-            m_controls->CaptureCursor( false );
-        };
+        auto cleanup = [&] ()
+                       {
+                           polyGeomMgr.Reset();
+                           started = false;
+                           grid.ClearSkipPoint();
+                           m_controls->SetAutoPan( false );
+                           m_controls->CaptureCursor( false );
+                       };
 
         if( evt->IsCancelInteractive())
         {