Fixing 2D canvas invalidation region tracking.

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 177 matching lines @@
     }
 
     return 0;
 }
 
 void HTMLCanvasElement::didDraw(const FloatRect& rect)
 {
     clearCopiedImage();
 
     if (RenderBox* ro = renderBox()) {
-        FloatRect destRect = ro->contentBoxRect();
-        FloatRect r = mapRect(rect, FloatRect(0, 0, size().width(), size().height()), destRect);
-        r.intersect(destRect);
+        FloatRect srcRect(0, 0, size().width(), size().height());
+        FloatRect r = rect;
+        r.intersect(srcRect);
         if (r.isEmpty() || m_dirtyRect.contains(r))
             return;
+        m_dirtyRect.unite(r);
+        FloatRect mappedDirtyRect = mapRect(r, srcRect, ro->contentBoxRect());

[Justin Novosad, 2014/07/17 15:13:24]

The change to this function does not actually fix anything, it is just a
drive-by optimization. I changed it so that we accumulate the dirty rect in
local space. This way, the early exit happens before the mapRect call.

 
-        m_dirtyRect.unite(r);
-        ro->invalidatePaintRectangle(enclosingIntRect(m_dirtyRect));
+        ro->invalidatePaintRectangle(enclosingIntRect(mappedDirtyRect));
     }
 
     notifyObserversCanvasChanged(rect);
 }
 
+void HTMLCanvasElement::didPresent()
+{
+    // Canvas was presented externally (without going through paint())
+    m_dirtyRect = FloatRect();
+}
+
 void HTMLCanvasElement::notifyObserversCanvasChanged(const FloatRect& rect)
 {
     WillBeHeapHashSet<RawPtrWillBeWeakMember<CanvasObserver> >::iterator end = m_observers.end();
     for (WillBeHeapHashSet<RawPtrWillBeWeakMember<CanvasObserver> >::iterator it = m_observers.begin(); it != end; ++it)
         (*it)->canvasChanged(this, rect);
 }
 
 void HTMLCanvasElement::reset()
 {
     if (m_ignoreReset)
         return;
 
+    m_dirtyRect = FloatRect();
+
     bool ok;
     bool hadImageBuffer = hasImageBuffer();
 
     int w = getAttribute(widthAttr).toInt(&ok);
     if (!ok || w < 0)
         w = DefaultWidth;
 
     int h = getAttribute(heightAttr).toInt(&ok);
     if (!ok || h < 0)
         h = DefaultHeight;
@@ skipping 459 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }