Add plot-based purging to GrLayerCache

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "effects/GrBicubicEffect.h"
@@ skipping 20 matching lines @@
 #include "SkPicture.h"
 #include "SkPictureData.h"
 #include "SkPictureRangePlayback.h"
 #include "SkPictureReplacementPlayback.h"
 #include "SkRRect.h"
 #include "SkStroke.h"
 #include "SkSurface.h"
 #include "SkTLazy.h"
 #include "SkUtils.h"
 #include "SkVertState.h"
+#include "SkXfermode.h"
 #include "SkErrorInternals.h"
 
 #define CACHE_COMPATIBLE_DEVICE_TEXTURES 1
 
 #if 0
     extern bool (*gShouldDrawProc)();
     #define CHECK_SHOULD_DRAW(draw, forceI)                     \
         do {                                                    \
             if (gShouldDrawProc && !gShouldDrawProc()) return;  \
             this->prepareDraw(draw, forceI);                    \
@@ skipping 1965 matching lines @@
                 // Add a rect clip to make sure the rendering doesn't
                 // extend beyond the boundaries of the atlased sub-rect
                 SkRect bound = SkRect::Make(layerInfo->fSrcRect);
                 canvas->clipRect(bound);
 
                 if (layer->isAtlased()) {
                     // Since 'clear' doesn't respect the clip we need to draw a rect
                     // TODO: ensure none of the atlased layers contain a clear call!
                     SkPaint paint;
                     paint.setColor(SK_ColorTRANSPARENT);
+                    paint.setXfermode(SkXfermode::Create(SkXfermode::kSrc_Mode))->unref();
                     canvas->drawRect(bound, paint);
                 } else {
                     canvas->clear(SK_ColorTRANSPARENT);
                 }
 
                 // info.fCTM maps the layer's top/left to the origin.
                 // If this layer is atlased the top/left corner needs
                 // to be offset to some arbitrary location in the backing 
                 // texture.
                 canvas->translate(bound.fLeft, bound.fTop);
@@ skipping 15 matching lines @@
     playback.draw(canvas, NULL);
 
     // unlock the layers
     for (int i = 0; i < gpuData->numSaveLayers(); ++i) {
         GrCachedLayer* layer = fContext->getLayerCache()->findLayer(picture, i);
         fContext->getLayerCache()->unlock(layer);
     }
 
     return true;
 }