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 c973b76cc16dc14a910240b61cf98b8e403e03e8..733e17d863e9a3d7d7a12b85e26bc514013a5ff3 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -153,6 +153,8 @@ void HTMLCanvasElement::didRecalcStyle(StyleRecalcChange)
         toWebGLRenderingContext(m_context.get())->setFilterLevel(filterLevel);
         setNeedsCompositingUpdate();
     }
+    if (hasImageBuffer())
+        m_imageBuffer->setFilterLevel(filterLevel);
 }
 
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
@@ -624,8 +626,13 @@ 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, 2014/12/16 19:22:32]

You don't need this line or the bool pixelated or the computedStyle() call. Just
invoke updateRenderTreeIfNeeded on this line after seting m_imageBuffer and the
willRecalcStyle callback will do this work.

[jackhou1, 2014/12/17 01:28:09]

This is what I tried earlier but it didn't work. I may have done something
wrong. I've uploaded it as Patch Set 25 if you want to take a look. My
understanding is that the style may already be calculated before
createImageBufferInternal is called, but setFilterLevel is not called because
there was no image buffer at the time; when the image buffer is created,
updateRenderTreeIfNeeded doesn't recalc the style because it thinks it's already
done. 

 
     m_didFailToCreateImageBuffer = false;
 
@@ -639,7 +646,7 @@ 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);

[esprehn, 2014/12/16 19:22:32]

Doesn't this need to be dynamically updated in willRecalcStyle?

[jackhou1, 2014/12/17 01:28:09]

Done.

     // 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.
@@ -810,6 +817,8 @@ PassRefPtr<Image> HTMLCanvasElement::getSourceImageForCanvas(SourceImageMode mod
         return createTransparentImage(size());
     }
 
+    m_imageBuffer->willAccessPixels();
+
     if (m_context->is3d()) {
         m_context->paintRenderingResultsToCanvas(BackBuffer);
         *status = ExternalSourceImageStatus;