Removing the dependency on GraphicsContext for drawing images in 2D canvas

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 271 matching lines @@
 {
     if (rect.isEmpty())
         return;
     m_imageBufferIsClear = false;
     clearCopiedImage();
     if (layoutObject())
         layoutObject()->setMayNeedPaintInvalidation();
     m_dirtyRect.unite(rect);
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
-    notifyObserversCanvasChanged(m_dirtyRect);
+    notifyObserversCanvasChanged(rect);

[Stephen White, 2015/05/27 15:46:02]

Out of curiosity, is this a bugfix / optimization?

[Justin Novosad, 2015/05/27 20:08:16]

Drive-by optimization. We use to do these notification per frame instead of per
draw, but that led to sync issues. Before, when it was per frame, m_dirtyRect
was the right thing. This change probably won't make any significant difference
except in degenerate  cases of -webkit-canvas

 }
 
 void HTMLCanvasElement::didFinalizeFrame()
 {
     if (m_dirtyRect.isEmpty())
         return;
 
     // Propagate the m_dirtyRect accumulated so far to the compositor
     // before restarting with a blank dirty rect.
     FloatRect srcRect(0, 0, size().width(), size().height());
@@ skipping 372 matching lines @@
     m_didFailToCreateImageBuffer = false;
 
     updateExternallyAllocatedMemory();
 
     if (is3D()) {
         // Early out for WebGL canvases
         return;
     }
 
     m_imageBuffer->setClient(this);
-    m_imageBuffer->context()->setShouldClampToSourceRect(false);
-    m_imageBuffer->context()->disableAntialiasingOptimizationForHairlineImages();
     m_imageBuffer->context()->setImageInterpolationQuality(CanvasDefaultInterpolationQuality);

[Stephen White, 2015/05/27 15:46:02]

Is this still used / necessary? If we're no longer using the GC, we should be
setting this on the new SkCanvas instead, no?

[Justin Novosad, 2015/05/27 20:08:16]

Acknowledged.

     // Enabling MSAA overrides a request to disable antialiasing. This is true regardless of whether the
     // rendering mode is accelerated or not. For consistency, we don't want to apply AA in accelerated
     // canvases but not in unaccelerated canvases.
     if (!msaaSampleCount && document().settings() && !document().settings()->antialiased2dCanvasEnabled())
         m_imageBuffer->context()->setShouldAntialias(false);
 #if ENABLE(ASSERT)
     m_imageBuffer->context()->disableDestructionChecks(); // 2D canvas is allowed to leave context in an unfinalized state.
 #endif
     m_contextStateSaver = adoptPtr(new GraphicsContextStateSaver(*m_imageBuffer->context()));
 
@@ skipping 200 matching lines @@
 {
     return FloatSize(width(), height());
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // blink