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

Source/platform/graphics/Canvas2DLayerBridge.cpp

Index: Source/platform/graphics/Canvas2DLayerBridge.cpp
diff --git a/Source/platform/graphics/Canvas2DLayerBridge.cpp b/Source/platform/graphics/Canvas2DLayerBridge.cpp
index e74a1c7a0a0bcbbe47e46c8605a3faa68c7880c9..577e93ecd0b0cd17761db7c281a82845b61f3b34 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.cpp
+++ b/Source/platform/graphics/Canvas2DLayerBridge.cpp
@@ -88,6 +88,7 @@ Canvas2DLayerBridge::Canvas2DLayerBridge(PassOwnPtr<WebGraphicsContext3DProvider
     , m_framesSinceMailboxRelease(0)
     , m_destructionInProgress(false)
     , m_rateLimitingEnabled(false)
+    , m_filterLevel(SkPaint::kLow_FilterLevel)
     , m_isHidden(false)
     , m_next(0)
     , m_prev(0)
@@ -104,6 +105,7 @@ Canvas2DLayerBridge::Canvas2DLayerBridge(PassOwnPtr<WebGraphicsContext3DProvider
     m_layer->setBlendBackgroundColor(opacityMode != Opaque);
     GraphicsLayer::registerContentsLayer(m_layer->layer());
     m_layer->setRateLimitContext(m_rateLimitingEnabled);
+    m_layer->setFilterLevel(m_filterLevel);
     m_canvas->setNotificationClient(this);
 #ifndef NDEBUG
     canvas2DLayerBridgeInstanceCounter.increment();
@@ -152,6 +154,17 @@ void Canvas2DLayerBridge::beginDestruction()
     ASSERT(!m_bytesAllocated);
 }
 
+void Canvas2DLayerBridge::setFilterLevel(SkPaint::FilterLevel filterLevel)
+{
+    printf("Canvas2dLayerBridge::setFilterLevel %d\n", filterLevel);

[Justin Novosad, 2014/10/28 20:27:44]

Don't commit this line.

[jackhou1, 2014/10/29 00:56:39]

Sorry. I'll remove all these before asking for a final review. Leaving them in
for now until I get it all working.

+    ASSERT(!m_destructionInProgress);
+    if (m_filterLevel != filterLevel) {
+        m_filterLevel = filterLevel;
+        m_layer->setFilterLevel(m_filterLevel);
+        m_imageBuffer->notifySurfaceInvalid();
+    }
+}
+
 void Canvas2DLayerBridge::setIsHidden(bool hidden)
 {
     ASSERT(!m_destructionInProgress);
@@ -414,7 +427,8 @@ bool Canvas2DLayerBridge::prepareMailbox(WebExternalTextureMailbox* outMailbox,
     RefPtr<SkImage> image = adoptRef(m_canvas->newImageSnapshot());
 
     // Early exit if canvas was not drawn to since last prepareMailbox
-    if (image->uniqueID() == m_lastImageId)
+    GLenum filter = m_filterLevel == SkPaint::kNone_FilterLevel ? GL_NEAREST : GL_LINEAR;
+    if (image->uniqueID() == m_lastImageId && filter == m_lastFilter)
         return false;
     m_lastImageId = image->uniqueID();
 
@@ -443,8 +457,8 @@ bool Canvas2DLayerBridge::prepareMailbox(WebExternalTextureMailbox* outMailbox,
     mailboxInfo->m_image->getTexture()->textureParamsModified();
 
     webContext->bindTexture(GL_TEXTURE_2D, mailboxInfo->m_image->getTexture()->getTextureHandle());
-    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, filter);
+    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);

[Justin Novosad, 2014/10/28 20:27:44]

Does this even matter?

[jackhou1, 2014/10/29 00:56:39]

Without this change, a pixelated canvas is intially drawn properly, but when I
switch to another tab and back, it's blurry again. I'm not sure exactly why that
happens, maybe it should be fixed somewhere else in the code?

     webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     webContext->produceTextureCHROMIUM(GL_TEXTURE_2D, mailboxInfo->m_mailbox.name);