Refactoring ImageBuffer to decouple it from Canvas2DLayerBridge

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 90b660c4213213862e7b1f0f2ae23e311cf9de09..1bf3459b2655240fa12bddf02f432141a28a5c3c 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -43,10 +43,13 @@
 #include "core/html/canvas/WebGLRenderingContext.h"
 #include "core/frame/Frame.h"
 #include "core/page/Settings.h"
+#include "core/platform/graphics/Canvas2DImageBufferSurface.h"
 #include "core/platform/graphics/GraphicsContextStateSaver.h"
 #include "core/platform/graphics/ImageBuffer.h"
+#include "core/platform/graphics/gpu/NonDrawableAcceleratedImageBufferSurface.h"
 #include "core/rendering/RenderHTMLCanvas.h"
 #include "platform/MIMETypeRegistry.h"
+#include "platform/graphics/UnacceleratedImageBufferSurface.h"
 #include "public/platform/Platform.h"
 
 namespace WebCore {
@@ -432,6 +435,30 @@ bool HTMLCanvasElement::shouldAccelerate(const IntSize& size) const
     return true;
 }
 
+PassOwnPtr<ImageBufferSurface> HTMLCanvasElement::createImageBufferSurface(const IntSize& deviceSize, int* msaaSampleCount)
+{
+    OwnPtr<ImageBufferSurface> surface;
+    OpacityMode opacityMode = !m_context || m_context->hasAlpha() ? NonOpaque : Opaque;
+    *msaaSampleCount = 0;
+    if (is3D()) {
+        // Note: No MSAA for 3D canvases because the image buffer is only used for capturing contents.
+        // The actual rendering happens in DrawingBuffer.
+        surface = adoptPtr(new NonDrawableAcceleratedImageBufferSurface(size(), opacityMode, m_deviceScaleFactor));
+    } else {
+        if (shouldAccelerate(deviceSize)) {
+            if (document().settings())
+                *msaaSampleCount = document().settings()->accelerated2dCanvasMSAASampleCount();
+            surface = adoptPtr(new Canvas2DImageBufferSurface(size(), opacityMode, m_deviceScaleFactor, *msaaSampleCount));
+        }
+
+        if (!surface || !surface->isValid()) {
+            surface = adoptPtr(new UnacceleratedImageBufferSurface(size(), opacityMode, m_deviceScaleFactor));

[Stephen White, 2013/12/04 21:18:40]

I'd prefer a Create() method on the surface subclasses that returns a
PassOwnPtr. Then we don't need to call isValid() or adoptPtr() at the call
sites, making them more robust.

+        }
+    }
+
+    return surface.release();
+}
+
 void HTMLCanvasElement::createImageBuffer()
 {
     ASSERT(!m_imageBuffer);
@@ -449,15 +476,15 @@ void HTMLCanvasElement::createImageBuffer()
     if (!deviceSize.width() || !deviceSize.height())
         return;
 
-    RenderingMode renderingMode = is3D() ? TextureBacked : (shouldAccelerate(deviceSize) ? Accelerated : UnacceleratedNonPlatformBuffer);
-    int msaaSampleCount = 0;
-    if (document().settings())
-        msaaSampleCount = document().settings()->accelerated2dCanvasMSAASampleCount();
-    OpacityMode opacityMode = !m_context || m_context->hasAlpha() ? NonOpaque : Opaque;
-    m_imageBuffer = ImageBuffer::create(size(), m_deviceScaleFactor, renderingMode, opacityMode, msaaSampleCount);
-    if (!m_imageBuffer)
+    int msaaSampleCount;
+    OwnPtr<ImageBufferSurface> surface = createImageBufferSurface(deviceSize, &msaaSampleCount);
+    if (!surface || !surface->isValid())
         return;
+
     m_didFailToCreateImageBuffer = false;
+
+    m_imageBuffer = adoptPtr(new ImageBuffer(surface.release()));
+
     setExternallyAllocatedMemory(4 * width() * height());
     m_imageBuffer->context()->setShouldClampToSourceRect(false);
     m_imageBuffer->context()->setImageInterpolationQuality(DefaultInterpolationQuality);