Improving canvas 2D performance by switching graphics rendering pipeline.

third_party/WebKit/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 129 matching lines @@
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     : HTMLElement(canvasTag, document)
     , ContextLifecycleObserver(&document)
     , PageVisibilityObserver(document.page())
     , m_size(DefaultWidth, DefaultHeight)
     , m_ignoreReset(false)
     , m_externallyAllocatedMemory(0)
     , m_originClean(true)
     , m_didFailToCreateImageBuffer(false)
     , m_imageBufferIsClear(false)
+    , m_numFramesSinceLastRenderingModeSwitch(0)
 {
     CanvasMetrics::countCanvasContextUsage(CanvasMetrics::CanvasCreated);
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
 
 HTMLCanvasElement::~HTMLCanvasElement()
 {
     v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(-m_externallyAllocatedMemory);
 }
@@ skipping 125 matching lines @@
         FloatRect inflatedRect = rect;
         inflatedRect.inflate(1);
         m_dirtyRect.unite(inflatedRect);
     } else {
         m_dirtyRect.unite(rect);
     }
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
 }
 
+static void disableAccelerationWrapper(WeakPtr<ImageBuffer> buffer)
+{
+    if (buffer) {
+        buffer->disableAcceleration();
+    }
+}
+
 void HTMLCanvasElement::didFinalizeFrame()
 {
     notifyListenersCanvasChanged();
 
     if (m_dirtyRect.isEmpty())
         return;
 
     // Propagate the m_dirtyRect accumulated so far to the compositor
     // before restarting with a blank dirty rect.
     FloatRect srcRect(0, 0, size().width(), size().height());
     m_dirtyRect.intersect(srcRect);
     LayoutBox* ro = layoutBox();
     // Canvas content updates do not need to be propagated as
     // paint invalidations if the canvas is accelerated, since
     // the canvas contents are sent separately through a texture layer.
     if (ro && (!m_context || !m_context->isAccelerated())) {
         LayoutRect mappedDirtyRect(enclosingIntRect(mapRect(m_dirtyRect, srcRect, FloatRect(ro->contentBoxRect()))));
         // For querying PaintLayer::compositingState()
         // FIXME: is this invalidation using the correct compositing state?
         DisableCompositingQueryAsserts disabler;
         ro->invalidatePaintRectangle(mappedDirtyRect);
     }
     m_dirtyRect = FloatRect();
+
+    m_numFramesSinceLastRenderingModeSwitch++;
+    if (m_context->is2d() && buffer()->isAccelerated()
+        && m_numFramesSinceLastRenderingModeSwitch >= ExpensiveCanvasHeuristicParameters::MinFramesBeforeSwitch) {
+        if (RuntimeEnabledFeatures::enableCanvas2dDynamicRenderingModeEnabled()) {
+            if (!m_context->isAccelerationOptimalForCanvasContent()) {
+                Platform::current()->currentThread()->getWebTaskRunner()->postTask(

[Justin Novosad, 2016/07/14 18:07:10]

Add a comment to explain why the switch is asynchronous (can't switch during
paint invalidation step)

[sebastienlc, 2016/07/14 22:26:53]

Done.

+                    BLINK_FROM_HERE, WTF::bind(&disableAccelerationWrapper, m_imageBuffer->m_weakPtrFactory.createWeakPtr()));

[Stephen White, 2016/07/14 18:53:04]

Out of curiosity, would it be possible to use a lambda here?
disableAccelerationWrapper() seems simple enough that it would be nice to put
its contents inline.

[sebastienlc, 2016/07/14 22:26:53]

Done.

+                m_numFramesSinceLastRenderingModeSwitch = 0;
+            }
+        }
+    }
 }
 
 void HTMLCanvasElement::didDisableAcceleration()
 {
     // We must force a paint invalidation on the canvas even if it's
     // content did not change because it layer was destroyed.
     didDraw(FloatRect(0, 0, size().width(), size().height()));
 }
 
 void HTMLCanvasElement::restoreCanvasMatrixClipStack(SkCanvas* canvas) const
@@ skipping 866 matching lines @@
 
 bool HTMLCanvasElement::createSurfaceLayer()
 {
     DCHECK(!m_surfaceLayerBridge);
     std::unique_ptr<CanvasSurfaceLayerBridgeClient> bridgeClient = wrapUnique(new CanvasSurfaceLayerBridgeClientImpl());
     m_surfaceLayerBridge = wrapUnique(new CanvasSurfaceLayerBridge(std::move(bridgeClient)));
     return m_surfaceLayerBridge->createSurfaceLayer(this->width(), this->height());
 }
 
 } // namespace blink