Submit Compositor Frame from OffscreenCanvas on main

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/offscreencanvas/OffscreenCanvas.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
 #include "platform/graphics/ImageBuffer.h"
+#include "platform/graphics/OffscreenCanvasFrameDispatcherImpl.h"
 #include "wtf/MathExtras.h"
 #include <memory>
 
 namespace blink {
 
 OffscreenCanvas::OffscreenCanvas(const IntSize& size)
     : m_size(size)
     , m_originClean(true)
 {
 }
 
 OffscreenCanvas* OffscreenCanvas::create(unsigned width, unsigned height)
 {
     return new OffscreenCanvas(IntSize(clampTo<int>(width), clampTo<int>(height)));
 }
 
 void OffscreenCanvas::setWidth(unsigned width)
 {
     m_size.setWidth(clampTo<int>(width));

[danakj, 2016/09/02 21:53:50]

While I'm reading this code, can you explain why there is setWidth/setHeight if
they dont change?

[xlai (Olivia), 2016/09/02 23:41:28]

You're right. I also feel that it's illogical to have setWidth when
OffscreenCanvas is transferred control
from html canvas; in fact, its size is purely determined by the size of HTML
canvas. 
I add an if statement here to make calling this function have no effect in this
particular case.
Now this function is reserved only for the use case when OffscreenCanvas is
constructed on its own without transfering control. 

On 2016/09/02 21:53:50, danakj wrote:

 }
 
 void OffscreenCanvas::setHeight(unsigned height)
 {
     m_size.setHeight(clampTo<int>(height));
 }
 
 void OffscreenCanvas::setNeutered()
 {
     ASSERT(!m_context);
@@ skipping 86 matching lines @@
     return m_originClean && !m_disableReadingFromCanvas;
 }
 
 bool OffscreenCanvas::isPaintable() const
 {
     if (!m_context)
         return ImageBuffer::canCreateImageBuffer(m_size);
     return m_context->isPaintable();
 }
 
+OffscreenCanvasFrameDispatcher* OffscreenCanvas::getOrCreateFrameDispatcher()
+{
+    if (!m_frameDispatcher)
+        m_frameDispatcher = wrapUnique(new OffscreenCanvasFrameDispatcherImpl(m_clientId, m_localId, m_nonce, width(), height()));
+    return m_frameDispatcher.get();
+}
+
 DEFINE_TRACE(OffscreenCanvas)
 {
     visitor->trace(m_context);
 }
 
 } // namespace blink