Implement image-rendering:pixelated for accelerated 2D canvases.

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 101 matching lines @@
 }
 
 RenderObject* HTMLCanvasElement::createRenderer(RenderStyle* style)
 {
     LocalFrame* frame = document().frame();
     if (frame && frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return new RenderHTMLCanvas(this);
     return HTMLElement::createRenderer(style);
 }
 
+void HTMLCanvasElement::didRecalcStyle(StyleRecalcChange)
+{
+    m_imageBuffer->setNearestNeighbor(computedStyle()->imageRendering() == ImageRenderingPixelated);
+}
+
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
 {
     setIsInCanvasSubtree(true);
     return HTMLElement::insertedInto(node);
 }
 
 void HTMLCanvasElement::addObserver(CanvasObserver* observer)
 {
     m_observers.add(observer);
 }
@@ skipping 190 matching lines @@
     if (!m_context->isAccelerated())
         return true;
 
     if (renderBox() && renderBox()->hasAcceleratedCompositing())
         return false;
 
     return true;
 }
 
 
 void HTMLCanvasElement::paint(GraphicsContext* context, const LayoutRect& r)

[Justin Novosad, 2014/09/10 14:28:31]

You have to make changes to this function to make nearest neighbor work when the
canvas is  not GPU-accelerated.

[jackhou1, 2014/09/11 08:26:31]

This should already work, the logic is in RenderHTMLCanvas.cpp:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

But maybe it should be moved here so that we handle the different types of
canvases in the same place?

 {
     if (m_context) {
         if (!paintsIntoCanvasBuffer() && !document().printing())
             return;
         m_context->paintRenderingResultsToCanvas();
     }
 
     if (hasImageBuffer()) {
         ImageBuffer* imageBuffer = buffer();
         if (imageBuffer) {
@@ skipping 397 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }