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 2c11a5249288e29ee1344187a6629797c782939f..7d34a08e60459653497c660af1f1848f7cc0a05a 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -34,6 +34,7 @@
 #include "core/HTMLNames.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/dom/NodeRenderStyle.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/ImageData.h"
@@ -112,6 +113,7 @@ inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     , m_didFailToCreateImageBuffer(false)
     , m_imageBufferIsClear(false)
 {
+    setHasCustomStyleCallbacks();
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
@@ -138,12 +140,21 @@ 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);
     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(renderStyle()->imageRendering() == ImageRenderingPixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);

[Justin Novosad, 2014/12/04 15:27:07]

This seems wrong to me. We should always use the computedStyle. Is the bug
caused by the fact that the style is not recomputed when an offscreen canvas is
attached to the DOM? If that is the issue, then the solution should be to make
sure style recalculation are properly triggered at that time.

[jackhou1, 2014/12/05 02:00:58]

Done.

+}
+
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
 {
     setIsInCanvasSubtree(true);
@@ -593,8 +604,12 @@ void HTMLCanvasElement::createImageBufferInternal()
     if (!surface->isValid())
         return;
 
+    RenderStyle* style = renderStyle();

[Justin Novosad, 2014/12/04 15:27:07]

Same thing here

[jackhou1, 2014/12/05 02:00:58]

Done.

+    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);
 
     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;