Fix recording of saveLayout with unusual Xfermodes.

src/core/SkRecordDraw.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRecordDraw.h"
 #include "SkPatchUtils.h"
 
@@ skipping 211 matching lines @@
     }
 
     void pushSaveBlock(const SkPaint* paint) {
         // Starting a new Save block.  Push a new entry to represent that.
         SaveBounds sb = { 0, Bounds::MakeEmpty(), paint };
         fSaveStack.push(sb);
         this->pushControl();
     }
 
     static bool PaintMayAffectTransparentBlack(const SkPaint* paint) {
-        // FIXME: this is very conservative
-        return paint && (paint->getImageFilter() || paint->getColorFilter());
+        if (paint) {
+            // FIXME: this is very conservative
+            if (paint->getImageFilter() || paint->getColorFilter()) {
+                return true;
+            }
+
+            // Unusual Xfermodes require us to process a saved layer
+            // even with operations outisde the clip.
+            // For example, DstIn is used by masking layers.
+            // https://code.google.com/p/skia/issues/detail?id=1291
+            // https://crbug.com/401593
+            SkXfermode* xfermode = paint->getXfermode();
+            SkXfermode::Mode mode;
+            // SrcOver is ok, and is also the common case with a NULL xfermode.
+            // So we should make that the fast path and bypass the mode extraction
+            // and test.
+            if (xfermode && xfermode->asMode(&mode)) {
+                switch (mode) {
+                    case SkXfermode::kClear_Mode:

[mtklein, 2014/09/12 20:57:16]

Might note something like,

// For each of these transfer modes, if the source alpha is zero (our
transparent black), the resulting blended alpha is not necessarily equal to the
original destination alpha.

[dneto, 2014/09/15 15:48:48]

Done.

+                    case SkXfermode::kSrc_Mode:
+                    case SkXfermode::kSrcIn_Mode:
+                    case SkXfermode::kDstIn_Mode:
+                    case SkXfermode::kSrcOut_Mode:
+                    case SkXfermode::kDstATop_Mode:
+                    case SkXfermode::kModulate_Mode:
+                        return true;
+                        break;
+                    default:
+                        break;
+                }
+            }
+        }
+        return false;
     }
 
     Bounds popSaveBlock() {
         // We're done the Save block.  Apply the block's bounds to all control ops inside it.
         SaveBounds sb;
         fSaveStack.pop(&sb);
 
         // If the paint affects transparent black, we can't trust any of our calculated bounds.
         const Bounds& bounds =
             PaintMayAffectTransparentBlack(sb.paint) ? fCurrentClipBounds : sb.bounds;
@@ skipping 228 matching lines @@
     // Used to track the bounds of Save/Restore blocks and the control ops inside them.
     SkTDArray<SaveBounds> fSaveStack;
     SkTDArray<unsigned>   fControlIndices;
 };
 
 }  // namespace SkRecords
 
 void SkRecordFillBounds(const SkRecord& record, SkBBoxHierarchy* bbh) {
     SkRecords::FillBounds(record, bbh);
 }