Fix for empty saveLayer() with a filter which affects transparent black.

src/core/SkBBoxHierarchyRecord.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBBoxHierarchyRecord.h"
 #include "SkPictureStateTree.h"
@@ skipping 17 matching lines @@
 }
 
 void SkBBoxHierarchyRecord::willSave(SaveFlags flags) {
     fStateTree->appendSave();
     this->INHERITED::willSave(flags);
 }
 
 SkCanvas::SaveLayerStrategy SkBBoxHierarchyRecord::willSaveLayer(const SkRect* bounds,
                                                                  const SkPaint* paint,
                                                                  SaveFlags flags) {
+    // For now, assume all filters affect transparent black.
+    // FIXME: This could be made less conservative as an optimization.
+    bool paintAffectsTransparentBlack = NULL != paint &&
+        ((NULL != paint->getImageFilter()) ||
+         (NULL != paint->getColorFilter()));
+    SkRect drawBounds;
+    if (paintAffectsTransparentBlack) {
+        if (bounds) {
+            drawBounds = *bounds;
+            this->getTotalMatrix().mapRect(&drawBounds);
+        } else {
+            SkIRect deviceBounds;
+            this->getClipDeviceBounds(&deviceBounds);
+            drawBounds.set(deviceBounds);
+        }
+    }
     fStateTree->appendSaveLayer(this->writeStream().bytesWritten());
-    return this->INHERITED::willSaveLayer(bounds, paint, flags);
+    SkCanvas::SaveLayerStrategy strategy = this->INHERITED::willSaveLayer(bounds, paint, flags);
+    if (paintAffectsTransparentBlack) {
+        this->handleBBox(drawBounds);
+        this->addNoOp();
+    }
+    return strategy;
 }
 
 void SkBBoxHierarchyRecord::willRestore() {
     fStateTree->appendRestore();
     this->INHERITED::willRestore();
 }
 
 void SkBBoxHierarchyRecord::didConcat(const SkMatrix& matrix) {
     fStateTree->appendTransform(getTotalMatrix());
     INHERITED::didConcat(matrix);
@@ skipping 33 matching lines @@
 
 bool SkBBoxHierarchyRecord::shouldRewind(void* data) {
     // SkBBoxHierarchy::rewindInserts is called by SkPicture after the
     // SkPicture has rewound its command stream.  To match that rewind in the
     // BBH, we rewind all draws that reference commands that were recorded
     // past the point to which the SkPicture has rewound, which is given by
     // writeStream().bytesWritten().
     SkPictureStateTree::Draw* draw = static_cast<SkPictureStateTree::Draw*>(data);
     return draw->fOffset >= writeStream().bytesWritten();
 }