Implementation of 2D canvas context lost/restored events

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 340 matching lines @@
     m_presentedImage.clear();
     updateExternallyAllocatedMemory();
 }
 
 void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
 {
     m_size = size;
     m_didFailToCreateImageBuffer = false;
     discardImageBuffer();
     clearCopiedImage();
+    if (m_context->is2d()) {
+        CanvasRenderingContext2D* context2d = toCanvasRenderingContext2D(m_context.get());
+        if (context2d->isContextLost()) {
+            context2d->restoreContext();
+        }
+    }
 }
 
 String HTMLCanvasElement::toEncodingMimeType(const String& mimeType)
 {
     String lowercaseMimeType = mimeType.lower();
 
     // FIXME: Make isSupportedImageMIMETypeForEncoding threadsafe (to allow this method to be used on a worker thread).
     if (mimeType.isNull() || !MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(lowercaseMimeType))
         lowercaseMimeType = "image/png";
 
@@ skipping 72 matching lines @@
         OwnPtr<ImageBufferSurface> surface = adoptPtr(new Canvas2DImageBufferSurface(size(), opacityMode, *msaaSampleCount));
         if (surface->isValid())
             return surface.release();
     }
 
     return adoptPtr(new UnacceleratedImageBufferSurface(size(), opacityMode));
 }
 
 void HTMLCanvasElement::createImageBuffer()
 {
+    createImageBufferInternal();
+    if (m_didFailToCreateImageBuffer && m_context && m_context->is2d())
+        toCanvasRenderingContext2D(m_context.get())->loseContext();
+}
+
+void HTMLCanvasElement::createImageBufferInternal()
+{
     ASSERT(!m_imageBuffer);
     ASSERT(!m_contextStateSaver);
 
     m_didFailToCreateImageBuffer = true;
     m_didClearImageBuffer = true;
 
     IntSize deviceSize = size();
     if (deviceSize.width() * deviceSize.height() > MaxCanvasArea)
         return;
 
     if (deviceSize.width() > MaxSkiaDim || deviceSize.height() > MaxSkiaDim)
         return;
 
     if (!deviceSize.width() || !deviceSize.height())
         return;
 
     int msaaSampleCount;
     OwnPtr<ImageBufferSurface> surface = createImageBufferSurface(deviceSize, &msaaSampleCount);
     if (!surface->isValid())
         return;
+
     m_imageBuffer = ImageBuffer::create(surface.release());
+    m_imageBuffer->setClient(this);
 
     m_didFailToCreateImageBuffer = false;
 
     updateExternallyAllocatedMemory();
 
     if (is3D()) {
         // Early out for WebGL canvases
         return;
     }
 
+    m_imageBuffer->setClient(this);
     m_imageBuffer->context()->setShouldClampToSourceRect(false);
     m_imageBuffer->context()->setImageInterpolationQuality(CanvasDefaultInterpolationQuality);
     // 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.
     if (!msaaSampleCount && document().settings() && !document().settings()->antialiased2dCanvasEnabled())
         m_imageBuffer->context()->setShouldAntialias(false);
     // GraphicsContext's defaults don't always agree with the 2d canvas spec.
     // See CanvasRenderingContext2D::State::State() for more information.
     m_imageBuffer->context()->setMiterLimit(10);
     m_imageBuffer->context()->setStrokeThickness(1);
     m_contextStateSaver = adoptPtr(new GraphicsContextStateSaver(*m_imageBuffer->context()));
 
     // Recalculate compositing requirements if acceleration state changed.
     if (m_context)
         scheduleLayerUpdate();
+    return;
+}
+
+void HTMLCanvasElement::notifySurfaceInvalid()
+{
+    if (m_context && m_context->is2d()) {
+        CanvasRenderingContext2D* context2d = toCanvasRenderingContext2D(m_context.get());
+        context2d->loseContext();
+    }
 }
 
 void HTMLCanvasElement::updateExternallyAllocatedMemory() const
 {
     int bufferCount = 0;
     if (m_imageBuffer)
         bufferCount++;
     if (is3D())
         bufferCount += 2;
     if (m_copiedImage)
@@ skipping 71 matching lines @@
     }
 }
 
 void HTMLCanvasElement::discardImageBuffer()
 {
     m_contextStateSaver.clear(); // uses context owned by m_imageBuffer
     m_imageBuffer.clear();
     updateExternallyAllocatedMemory();
 }
 
+bool HTMLCanvasElement::hasValidImageBuffer() const
+{
+    return m_imageBuffer && m_imageBuffer->isSurfaceValid();
+}
+
 void HTMLCanvasElement::clearCopiedImage()
 {
     m_copiedImage.clear();
     m_didClearImageBuffer = false;
     updateExternallyAllocatedMemory();
 }
 
 AffineTransform HTMLCanvasElement::baseTransform() const
 {
     ASSERT(hasImageBuffer() && !m_didFailToCreateImageBuffer);
@@ skipping 52 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }