SkGrPixelRef can only reference the subset of the Surface specified by its SkImageInfo

src/gpu/SkGrPixelRef.cpp

 
 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 
@@ skipping 109 matching lines @@
     // target)
     fSurface = surface->asTexture();
 #else
     fSurface = NULL;
 #endif
     if (NULL == fSurface) {
         fSurface = surface;
     }
     fUnlock = transferCacheLock;
     SkSafeRef(surface);
+
+    if (fSurface) {
+        SkASSERT(info.fWidth <= fSurface->width());
+        SkASSERT(info.fHeight <= fSurface->height());
+    }
 }
 
 SkGrPixelRef::~SkGrPixelRef() {
     if (fUnlock) {
         GrContext* context = fSurface->getContext();
         GrTexture* texture = fSurface->asTexture();
         if (NULL != context && NULL != texture) {
             context->unlockScratchTexture(texture);
         }
     }
@@ skipping 27 matching lines @@
     }
 
     int left, top, width, height;
     if (NULL != subset) {
         left = subset->fLeft;
         width = subset->width();
         top = subset->fTop;
         height = subset->height();
     } else {
         left = 0;
-        width = fSurface->width();
+        width = this->info().fWidth;
         top = 0;
-        height = fSurface->height();
+        height = this->info().fHeight;
     }
     if (!dst->allocPixels(SkImageInfo::MakeN32Premul(width, height))) {
         SkDebugf("SkGrPixelRef::onReadPixels failed to alloc bitmap for result!\n");
         return false;
     }
     SkAutoLockPixels al(*dst);
     void* buffer = dst->getPixels();
     return fSurface->readPixels(left, top, width, height,
                                 kSkia8888_GrPixelConfig,
                                 buffer, dst->rowBytes());
 }