Integrating SkSurface with SkDeferredCanvas

src/image/SkSurface_Raster.cpp

Index: src/image/SkSurface_Raster.cpp
===================================================================
--- src/image/SkSurface_Raster.cpp	(revision 8402)
+++ src/image/SkSurface_Raster.cpp	(working copy)
@@ -25,7 +25,7 @@
     virtual SkImage* onNewImageShapshot() SK_OVERRIDE;
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y,
                         const SkPaint*) SK_OVERRIDE;
-    virtual void onCopyOnWrite(SkImage*, SkCanvas*) SK_OVERRIDE;
+    virtual void onCopyOnWrite(SkImage*, SkCanvas*, bool overwrite) SK_OVERRIDE;
 
 private:
     SkBitmap    fBitmap;
@@ -124,12 +124,20 @@
     return SkNewImageFromBitmap(fBitmap, fWeOwnThePixels);
 }
 
-void SkSurface_Raster::onCopyOnWrite(SkImage* image, SkCanvas* canvas) {
+void SkSurface_Raster::onCopyOnWrite(SkImage* image, SkCanvas* canvas, bool overwrite) {
     // are we sharing pixelrefs with the image?
     if (SkBitmapImageGetPixelRef(image) == fBitmap.pixelRef()) {
         SkASSERT(fWeOwnThePixels);
-        SkBitmap prev(fBitmap);
-        prev.deepCopyTo(&fBitmap, prev.config());
+        if (!overwrite) {
+            SkBitmap prev(fBitmap);
+            prev.deepCopyTo(&fBitmap, prev.config());
+        } else {
+            SkBitmap newBitmap;
+            newBitmap.setConfig(fBitmap.getConfig(), fBitmap.width(), fBitmap.height(),
+                                fBitmap.rowBytes());
+            newBitmap.allocPixels();
+            fBitmap.swap(newBitmap);
+        }
         // Now fBitmap is a deep copy of itself (and therefore different from

[Stephen White, 2013/03/26 20:51:44]

Nit:  this comment is not strictly true anymore, since it may not be a deep
copy.

         // what is being used by the image. Next we update the canvas to use
         // this as its backend, so we can't modify the image's pixels anymore.