This CL implements the first draft of Canvas 2D Context Attributes, aka getContext('2d', { alpha: f…

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 959faf574c04aa50414a64561283402cde7d18a5..8e9d1e27d6c20aa10e812816d06a3d7b5380d779 100644
--- a/Source/core/platform/graphics/skia/ImageBufferSkia.cpp
+++ b/Source/core/platform/graphics/skia/ImageBufferSkia.cpp
@@ -69,7 +69,7 @@ ImageBufferData::ImageBufferData(const IntSize& size)
 {
 }
 
-static SkCanvas* createAcceleratedCanvas(const IntSize& size, ImageBufferData* data)
+static SkCanvas* createAcceleratedCanvas(const IntSize& size, ImageBufferData* data, OpacityMode opacityMode)
 {
     RefPtr<GraphicsContext3D> context3D = SharedGraphicsContext3D::get();
     if (!context3D)
@@ -89,8 +89,9 @@ static SkCanvas* createAcceleratedCanvas(const IntSize& size, ImageBufferData* d
         return 0;
     SkCanvas* canvas;
     SkAutoTUnref<SkDevice> device(new SkGpuDevice(gr, texture.get()));
+    Canvas2DLayerBridge::OpacityMode bridgeOpacityMode = opacityMode == Opaque ? Canvas2DLayerBridge::Opaque : Canvas2DLayerBridge::NonOpaque;
     Canvas2DLayerBridge::ThreadMode threadMode = WebKit::Platform::current()->isThreadedCompositingEnabled() ? Canvas2DLayerBridge::Threaded : Canvas2DLayerBridge::SingleThread;
-    data->m_layerBridge = Canvas2DLayerBridge::create(context3D.release(), size, threadMode, texture.get()->getTextureHandle());
+    data->m_layerBridge = Canvas2DLayerBridge::create(context3D.release(), size, bridgeOpacityMode, threadMode, texture.get()->getTextureHandle());
     canvas = data->m_layerBridge->skCanvas(device.get());
     data->m_platformContext.setAccelerated(true);
     return canvas;
@@ -144,7 +145,7 @@ ImageBuffer::ImageBuffer(const IntSize& size, float resolutionScale, ColorSpace,
     success = true;
 }
 
-ImageBuffer::ImageBuffer(const IntSize& size, float resolutionScale, ColorSpace, RenderingMode renderingMode, bool& success)
+ImageBuffer::ImageBuffer(const IntSize& size, float resolutionScale, ColorSpace, RenderingMode renderingMode, OpacityMode opacityMode, bool& success)
     : m_data(size)
     , m_size(size)
     , m_logicalSize(size)
@@ -153,7 +154,7 @@ ImageBuffer::ImageBuffer(const IntSize& size, float resolutionScale, ColorSpace,
     OwnPtr<SkCanvas> canvas;
 
     if (renderingMode == Accelerated)
-        canvas = adoptPtr(createAcceleratedCanvas(size, &m_data));
+        canvas = adoptPtr(createAcceleratedCanvas(size, &m_data, opacityMode));
     else if (renderingMode == UnacceleratedNonPlatformBuffer)
         canvas = adoptPtr(createNonPlatformCanvas(size));
 
@@ -168,13 +169,16 @@ ImageBuffer::ImageBuffer(const IntSize& size, float resolutionScale, ColorSpace,
     m_data.m_canvas = canvas.release();
     m_data.m_platformContext.setCanvas(m_data.m_canvas.get());
     m_context = adoptPtr(new GraphicsContext(&m_data.m_platformContext));
-    m_context->setShouldSmoothFonts(false);
+    m_context->setShouldSmoothFonts(opacityMode == Opaque);

[jamesr, 2013/04/26 18:30:09]

is this a sufficient check? what about transforms, etc etc?

     m_context->scale(FloatSize(m_resolutionScale, m_resolutionScale));
 
-    // Make the background transparent. It would be nice if this wasn't
+    // Clear the background transparent or opaque, as required. It would be nice if this wasn't
     // required, but the canvas is currently filled with the magic transparency
     // color. Can we have another way to manage this?
-    m_data.m_canvas->drawARGB(0, 0, 0, 0, SkXfermode::kClear_Mode);
+    if (opacityMode == Opaque)
+        m_data.m_canvas->drawARGB(255, 0, 0, 0, SkXfermode::kSrc_Mode);
+    else
+        m_data.m_canvas->drawARGB(0, 0, 0, 0, SkXfermode::kClear_Mode);
 
     success = true;
 }