Make OffscreenCanvas Transferable

third_party/WebKit/Source/modules/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 "modules/offscreencanvas/OffscreenCanvas.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "modules/offscreencanvas/OffscreenCanvasRenderingContext.h"
 #include "modules/offscreencanvas/OffscreenCanvasRenderingContextFactory.h"
@@ skipping 17 matching lines @@
 void OffscreenCanvas::setWidth(unsigned width)
 {
     m_size.setWidth(clampTo<int>(width));
 }
 
 void OffscreenCanvas::setHeight(unsigned height)
 {
     m_size.setHeight(clampTo<int>(height));
 }
 
-OffscreenCanvasRenderingContext2D* OffscreenCanvas::getContext(const String& id, const CanvasContextCreationAttributes& attributes)
+void OffscreenCanvas::setNeutered()
 {
+    ASSERT(!m_context);
+    m_isNeutered = true;
+    m_size.setWidth(0);
+    m_size.setHeight(0);
+}
+
+OffscreenCanvasRenderingContext2D* OffscreenCanvas::getContext(const String& id, const CanvasContextCreationAttributes& attributes, ExceptionState& exceptionState)
+{
+    if (m_isNeutered) {
+        exceptionState.throwDOMException(InvalidStateError, "Cannot get context of a neutered OffscreenCanvas");
+        return nullptr;
+    }
+
     OffscreenCanvasRenderingContext::ContextType contextType = OffscreenCanvasRenderingContext::contextTypeFromId(id);
 
     // Unknown type.
     if (contextType == OffscreenCanvasRenderingContext::ContextTypeCount)
         return nullptr;
 
     OffscreenCanvasRenderingContextFactory* factory = getRenderingContextFactory(contextType);
     if (!factory)
         return nullptr;
 
     if (m_context) {
         if (m_context->getContextType() != contextType) {
             factory->onError(this, "OffscreenCanvas has an existing context of a different type");
             return nullptr;
         }
     } else {
         m_context = factory->create(this, attributes);
     }
 
     // TODO: When there're more than one context type implemented in the future,
     // the return type here should be changed to base class of all Offscreen
     // context types.
     return static_cast<OffscreenCanvasRenderingContext2D*>(m_context.get());
 }
 
 ImageBitmap* OffscreenCanvas::transferToImageBitmap(ExceptionState& exceptionState)
 {
+    if (m_isNeutered) {
+        exceptionState.throwDOMException(InvalidStateError, "Cannot transfer an ImageBitmap from a neutered OffscreenCanvas");
+        return nullptr;
+    }
     if (!m_context) {
         exceptionState.throwDOMException(InvalidStateError, "Cannot transfer an ImageBitmap from an OffscreenCanvas with no context");
         return nullptr;
     }
     ImageBitmap* image = m_context->transferToImageBitmap(exceptionState);
     if (!image) {
         // Undocumented exception (not in spec)
         exceptionState.throwDOMException(V8GeneralError, "Out of memory");
     }
     return image;
 }
 
 OffscreenCanvasRenderingContext2D* OffscreenCanvas::renderingContext() const
 {
+    ASSERT(!m_isNeutered);
     // TODO: When there're more than one context type implemented in the future,
     // the return type here should be changed to base class of all Offscreen
     // context types.
     return static_cast<OffscreenCanvasRenderingContext2D*>(m_context.get());
 }
 
 OffscreenCanvas::ContextFactoryVector& OffscreenCanvas::renderingContextFactories()
 {
     DEFINE_STATIC_LOCAL(ContextFactoryVector, s_contextFactories, (OffscreenCanvasRenderingContext::ContextTypeCount));
     return s_contextFactories;
 }
 
 OffscreenCanvasRenderingContextFactory* OffscreenCanvas::getRenderingContextFactory(int type)
 {
     ASSERT(type < OffscreenCanvasRenderingContext::ContextTypeCount);
     return renderingContextFactories()[type].get();
 }
 
 void OffscreenCanvas::registerRenderingContextFactory(PassOwnPtr<OffscreenCanvasRenderingContextFactory> renderingContextFactory)
 {
     OffscreenCanvasRenderingContext::ContextType type = renderingContextFactory->getContextType();
     ASSERT(type < OffscreenCanvasRenderingContext::ContextTypeCount);
     ASSERT(!renderingContextFactories()[type]);
     renderingContextFactories()[type] = renderingContextFactory;
 }
 
 DEFINE_TRACE(OffscreenCanvas)
 {
     visitor->trace(m_context);
-    visitor->trace(m_canvas);
 }
 
 } // namespace blink