Make non-rectangular clip region apply in the correct location....

skia/ext/platform_device_win.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "skia/ext/platform_device_win.h"
 
 #include "skia/ext/skia_utils_win.h"
 #include "SkMatrix.h"
 #include "SkPath.h"
 #include "SkRegion.h"
@@ skipping 182 matching lines @@
 
 // static
 void PlatformDeviceWin::LoadClippingRegionToDC(HDC context,
                                                const SkRegion& region,
                                                const SkMatrix& transformation) {
   HRGN hrgn;
   if (region.isEmpty()) {
     // region can be empty, in which case everything will be clipped.
     hrgn = CreateRectRgn(0, 0, 0, 0);
   } else if (region.isRect()) {
-    // Do the transformation.
-    SkRect rect;
-    rect.set(region.getBounds());
-    transformation.mapRect(&rect);
-    SkIRect irect;
-    rect.round(&irect);
-    hrgn = CreateRectRgnIndirect(&SkIRectToRECT(irect));
+    // We don't apply transformation, because the translation is already applied
+    // to the region.
+    hrgn = CreateRectRgnIndirect(&SkIRectToRECT(region.getBounds()));
   } else {
     // It is complex.
     SkPath path;
     region.getBoundaryPath(&path);
     // Clip. Note that windows clipping regions are not affected by the
     // transform so apply it manually.
-    path.transform(transformation);
+    // Since the transform is given as the original translation of canvas, we
+    // should apply it in reverse.
+    SkMatrix t(transformation);
+    t.setTranslateX(-t.getTranslateX());
+    t.setTranslateY(-t.getTranslateY());
+    path.transform(t);
     LoadPathToDC(context, path);
     hrgn = PathToRegion(context);
   }
   int result = SelectClipRgn(context, hrgn);
   SkASSERT(result != ERROR);
   result = DeleteObject(hrgn);
   SkASSERT(result != 0);
 }
 
 }  // namespace skia