Fixing Canvas2DLayerBridge to handle lost graphics contexts

Source/core/platform/graphics/skia/ImageBufferSkia.cpp

Index: Source/core/platform/graphics/skia/ImageBufferSkia.cpp
diff --git a/Source/core/platform/graphics/skia/ImageBufferSkia.cpp b/Source/core/platform/graphics/skia/ImageBufferSkia.cpp
index 69464c730bc365519ba91d864583d131be64a74c..135512e03ac68674f25ec68b998a0c5093c2c2a1 100644
--- a/Source/core/platform/graphics/skia/ImageBufferSkia.cpp
+++ b/Source/core/platform/graphics/skia/ImageBufferSkia.cpp
@@ -73,25 +73,12 @@ static SkCanvas* createAcceleratedCanvas(const IntSize& size, ImageBufferData* d
     RefPtr<GraphicsContext3D> context3D = SharedGraphicsContext3D::get();
     if (!context3D)
         return 0;
-    GrContext* gr = context3D->grContext();
-    if (!gr)
-        return 0;
-    gr->resetContext();
     Canvas2DLayerBridge::OpacityMode bridgeOpacityMode = opacityMode == Opaque ? Canvas2DLayerBridge::Opaque : Canvas2DLayerBridge::NonOpaque;
     Canvas2DLayerBridge::ThreadMode threadMode = WebKit::Platform::current()->isThreadedCompositingEnabled() ? Canvas2DLayerBridge::Threaded : Canvas2DLayerBridge::SingleThread;
-    SkImage::Info info;
-    info.fWidth = size.width();
-    info.fHeight = size.height();
-    info.fColorType = SkImage::kPMColor_ColorType;
-    info.fAlphaType = SkImage::kPremul_AlphaType;
-    SkAutoTUnref<SkSurface> surface(SkSurface::NewRenderTarget(context3D->grContext(), info));
-    if (!surface.get())
-        return 0;
-    SkDeferredCanvas* canvas = new SkDeferredCanvas(surface.get());
-    data->m_layerBridge = Canvas2DLayerBridge::create(context3D.release(), canvas, bridgeOpacityMode, threadMode);
+    data->m_layerBridge = Canvas2DLayerBridge::create(context3D.release(), size, bridgeOpacityMode, threadMode);
     // If canvas buffer allocation failed, debug build will have asserted
     // For release builds, we must verify whether the device has a render target
-    return canvas;
+    return data->m_layerBridge ? data->m_layerBridge->getCanvas() : 0;
 }
 
 static SkCanvas* createNonPlatformCanvas(const IntSize& size)
@@ -193,6 +180,13 @@ GraphicsContext* ImageBuffer::context() const
     return m_context.get();
 }
 
+bool ImageBuffer::isValid() const
+{
+    if (m_data.m_layerBridge)
+        return const_cast<Canvas2DLayerBridge*>(m_data.m_layerBridge.get())->isValid();
+    return true;
+}
+
 static SkBitmap deepSkBitmapCopy(const SkBitmap& bitmap)
 {
     SkBitmap tmp;
@@ -204,6 +198,9 @@ static SkBitmap deepSkBitmapCopy(const SkBitmap& bitmap)
 
 PassRefPtr<Image> ImageBuffer::copyImage(BackingStoreCopy copyBehavior, ScaleBehavior) const
 {
+    if (!isValid())
+        return BitmapImage::create(NativeImageSkia::create());
+
     const SkBitmap& bitmap = *context()->bitmap();
     // FIXME: Start honoring ScaleBehavior to scale 2x buffers down to 1x.
     return BitmapImage::create(NativeImageSkia::create(copyBehavior == CopyBackingStore ? deepSkBitmapCopy(bitmap) : bitmap, m_resolutionScale));
@@ -221,7 +218,7 @@ PlatformLayer* ImageBuffer::platformLayer() const
 
 bool ImageBuffer::copyToPlatformTexture(GraphicsContext3D& context, Platform3DObject texture, GC3Denum internalFormat, GC3Denum destType, GC3Dint level, bool premultiplyAlpha, bool flipY)
 {
-    if (!m_data.m_layerBridge || !platformLayer())
+    if (!m_data.m_layerBridge || !platformLayer() || !isValid())
         return false;
 
     Platform3DObject sourceTexture = m_data.m_layerBridge->backBufferTexture();
@@ -261,6 +258,9 @@ static bool drawNeedsCopy(GraphicsContext* src, GraphicsContext* dst)
 void ImageBuffer::draw(GraphicsContext* context, ColorSpace styleColorSpace, const FloatRect& destRect, const FloatRect& srcRect,
     CompositeOperator op, BlendMode blendMode, bool useLowQualityScale)
 {
+    if (!isValid())
+        return;
+
     const SkBitmap& bitmap = *m_context->bitmap();
     RefPtr<Image> image = BitmapImage::create(NativeImageSkia::create(drawNeedsCopy(m_context.get(), context) ? deepSkBitmapCopy(bitmap) : bitmap));
     context->drawImage(image.get(), styleColorSpace, destRect, srcRect, op, blendMode, DoNotRespectImageOrientation, useLowQualityScale);
@@ -269,6 +269,9 @@ void ImageBuffer::draw(GraphicsContext* context, ColorSpace styleColorSpace, con
 void ImageBuffer::drawPattern(GraphicsContext* context, const FloatRect& srcRect, const AffineTransform& patternTransform,
                               const FloatPoint& phase, ColorSpace styleColorSpace, CompositeOperator op, const FloatRect& destRect)
 {
+    if (!isValid())
+        return;
+
     const SkBitmap& bitmap = *m_context->bitmap();
     RefPtr<Image> image = BitmapImage::create(NativeImageSkia::create(drawNeedsCopy(m_context.get(), context) ? deepSkBitmapCopy(bitmap) : bitmap));
     image->drawPattern(context, srcRect, patternTransform, phase, styleColorSpace, op, destRect);
@@ -277,7 +280,7 @@ void ImageBuffer::drawPattern(GraphicsContext* context, const FloatRect& srcRect
 void ImageBuffer::platformTransformColorSpace(const Vector<int>& lookUpTable)
 {
     // FIXME: Disable color space conversions on accelerated canvases (for now).
-    if (context()->isAccelerated())
+    if (context()->isAccelerated() || !isValid())
         return;
 
     const SkBitmap& bitmap = *context()->bitmap();
@@ -332,16 +335,27 @@ PassRefPtr<Uint8ClampedArray> getImageData(const IntRect& rect, GraphicsContext*
 
 PassRefPtr<Uint8ClampedArray> ImageBuffer::getUnmultipliedImageData(const IntRect& rect, CoordinateSystem) const
 {
+    if (!isValid()) {
+        RefPtr<Uint8ClampedArray> result = Uint8ClampedArray::create(rect.width() * rect.height() * 4);
+        return result.release();

[Stephen White, 2013/05/28 14:23:10]

Nit: I think you could just return the result of Uint8ClampedArray::create()
without storing it in a temporary.

+    }
     return getImageData<Unmultiplied>(rect, context(), m_size);
 }
 
 PassRefPtr<Uint8ClampedArray> ImageBuffer::getPremultipliedImageData(const IntRect& rect, CoordinateSystem) const
 {
+    if (!isValid()) {
+        RefPtr<Uint8ClampedArray> result = Uint8ClampedArray::create(rect.width() * rect.height() * 4);

[Stephen White, 2013/05/28 14:23:10]

Same here.

+        return result.release();
+    }
     return getImageData<Premultiplied>(rect, context(), m_size);
 }
 
 void ImageBuffer::putByteArray(Multiply multiplied, Uint8ClampedArray* source, const IntSize& sourceSize, const IntRect& sourceRect, const IntPoint& destPoint, CoordinateSystem)
 {
+    if (!isValid())
+        return;
+
     ASSERT(sourceRect.width() > 0);
     ASSERT(sourceRect.height() > 0);
 
@@ -412,12 +426,13 @@ String ImageBuffer::toDataURL(const String& mimeType, const double* quality, Coo
 {
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
 
-    Vector<char> encodedImage;
-    if (!encodeImage(*context()->bitmap(), mimeType, quality, &encodedImage))
-        return "data:,";
-
     Vector<char> base64Data;
-    base64Encode(encodedImage, base64Data);
+    if (isValid()) {
+        Vector<char> encodedImage;
+        if (!encodeImage(*context()->bitmap(), mimeType, quality, &encodedImage))
+            return "data:,";
+        base64Encode(encodedImage, base64Data);
+    }
 
     return "data:" + mimeType + ";base64," + base64Data;
 }