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

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 05e2a22819dca4e956262e159244bbb40eaf5844..9c73f48291ccf1cdffe27efe085e9f419c722872 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -112,6 +112,7 @@ inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     , m_didFailToCreateImageBuffer(false)
     , m_imageBufferIsClear(false)
 {
+    setHasCustomStyleCallbacks();
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
@@ -138,12 +139,21 @@ void HTMLCanvasElement::parseAttribute(const QualifiedName& name, const AtomicSt
 
 RenderObject* HTMLCanvasElement::createRenderer(RenderStyle* style)
 {
+    if (hasImageBuffer())
+        m_imageBuffer->setFilterLevel(style->imageRendering() == ImageRenderingPixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);

[esprehn, 2014/12/15 20:24:51]

If you have code in ::didRecalcStyle, you shouldn't need this too.

[jackhou1, 2014/12/15 23:17:24]

Done.

This was added for the case where a canvas is created off screen and then
appended to the DOM. But that seems to work without this now, so maybe there was
a bug in whatever commit I was based off.

     LocalFrame* frame = document().frame();
     if (frame && frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return new RenderHTMLCanvas(this);
     return HTMLElement::createRenderer(style);
 }
 
+void HTMLCanvasElement::didRecalcStyle(StyleRecalcChange)
+{
+    if (!hasImageBuffer())
+        return;
+    m_imageBuffer->setFilterLevel(computedStyle()->imageRendering() == ImageRenderingPixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);
+}
+
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
 {
     setIsInCanvasSubtree(true);
@@ -593,8 +603,13 @@ void HTMLCanvasElement::createImageBufferInternal()
     if (!surface->isValid())
         return;
 
+    document().updateRenderTreeIfNeeded();
+    RenderStyle* style = computedStyle();
+    bool pixelated = style && (style->imageRendering() == ImageRenderingPixelated || style->imageRendering() == ImageRenderingOptimizeContrast);
+
     m_imageBuffer = ImageBuffer::create(surface.release());
     m_imageBuffer->setClient(this);
+    m_imageBuffer->setFilterLevel(pixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);

[esprehn, 2014/12/15 20:24:51]

Why can't this just wait until didRecalcStyle to run?

[jackhou1, 2014/12/15 23:17:24]

It doesn't seem like didRecalcStyle will always run after this, even if I move
the updateRenderTreeIfNeeded after ImageBuffer::create.

 
     m_didFailToCreateImageBuffer = false;
 
@@ -608,7 +623,7 @@ void HTMLCanvasElement::createImageBufferInternal()
     m_imageBuffer->setClient(this);
     m_imageBuffer->context()->setShouldClampToSourceRect(false);
     m_imageBuffer->context()->disableAntialiasingOptimizationForHairlineImages();
-    m_imageBuffer->context()->setImageInterpolationQuality(CanvasDefaultInterpolationQuality);
+    m_imageBuffer->context()->setImageInterpolationQuality(pixelated ? InterpolationLow : CanvasDefaultInterpolationQuality);
     // 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.
@@ -779,6 +794,8 @@ PassRefPtr<Image> HTMLCanvasElement::getSourceImageForCanvas(SourceImageMode mod
         return createTransparentImage(size());
     }
 
+    m_imageBuffer->willAccessPixels();
+
     if (m_context->is3d()) {
         m_context->paintRenderingResultsToCanvas(BackBuffer);
         *status = ExternalSourceImageStatus;