ensure dirtyRects are added if dirtyState not cleared between updates

diff --git a/src/OpenTKGameWindow.cs b/src/OpenTKGameWindow.cs
index 48080912019141ee53192e51a27a7a1bb2835625..bc5c5cc4da0dd1cef350d6649fbf5afcc52ee3cf 100644 (file)
--- a/src/OpenTKGameWindow.cs
+++ b/src/OpenTKGameWindow.cs
@@ -351,8 +351,12 @@ namespace Crow
                                                clipping.stroke (ctx, Color.Red.AdjustAlpha(0.5));
                                                #endif
 
+                                               if (isDirty)
+                                                       DirtyRect += clipping.Bounds;
+                                               else
+                                                       DirtyRect = clipping.Bounds;
                                                isDirty = true;
-                                               DirtyRect = clipping.Bounds;
+
                                                DirtyRect.Left = Math.Max (0, DirtyRect.Left);
                                                DirtyRect.Top = Math.Max (0, DirtyRect.Top);
                                                DirtyRect.Width = Math.Min (ClientRectangle.Width - DirtyRect.Left, DirtyRect.Width);