Implement transferToImageBitmap() in WebGLRenderingContext

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index ceb485bdbf6c7e4ddd84cb242e0e556ae3c88ebf..47e96325c52731497901e656d540dff5ef0ba307 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -633,6 +633,22 @@ void WebGLRenderingContextBase::forceNextWebGLContextCreationToFail()
     shouldFailContextCreationForTesting = true;
 }
 
+ImageBitmap* WebGLRenderingContextBase::transferToImageBitmapBase()
+{
+    if (!drawingBuffer())
+        return nullptr;
+    GrContext* grContext = drawingBuffer()->contextProvider()->grContext();
+    if (!grContext)
+        return nullptr;
+    SkAlphaType alphaType = (m_requestedAttributes.premultipliedAlpha()) ? kPremul_SkAlphaType : kOpaque_SkAlphaType;
+    SkImageInfo info = SkImageInfo::MakeN32(drawingBufferWidth(), drawingBufferHeight(), alphaType);
+    SkSurfaceProps disableLCDProps(0, kUnknown_SkPixelGeometry);
+    sk_sp<SkSurface> surface = SkSurface::MakeRenderTarget(grContext, SkBudgeted::kNo, info, 0, (m_requestedAttributes.premultipliedAlpha()) ? &disableLCDProps : nullptr);

[xidachen, 2016/05/13 18:56:08]

junov@: could you take a look? I am not sure what am I missing here, I looked at
the pixels in this surface, and it is all 0s.

[Ken Russell (switch to Gerrit), 2016/05/13 20:08:30]

The code above is referencing the Ganesh context for the DrawingBuffer which
surely won't do what you want. Skia and Ganesh know nothing about the textures
the DrawingBuffer allocates internally. Look at DrawingBuffer::prepareMailbox
for the code structure which sends the back buffer's texture over to the
compositor's context. Something like that will be needed. I don't know what the
"receiving" context will be for the texture. Maybe it doesn't need to be known
at the time the ImageBitmap is constructed, only when it's consumed. So the
process of creating an ImageBitmap from a WebGLRenderingContext base may be: put
the back buffer texture into a texture mailbox, and construct the ImageBitmap
from that mailbox. When the ImageBitmap is later transferred into an
ImageBitmapRenderingContext, that's when the mailbox is consumed into the target
canvas's context.

[Justin Novosad, 2016/05/13 20:36:27]

I agree with what Ken wrote.  Sorry for the bad path I put you on earlier.  The
various code paths that consume ImageBitmaps are going to need to provide a
GrContext in order to access the mailbox.  This might be tricky.

+    RefPtr<StaticBitmapImage> image = StaticBitmapImage::create(surface->makeImageSnapshot(SkBudgeted::kNo).release());
+    ImageBitmap* imageBitmap = ImageBitmap::create(image.release());
+    return imageBitmap;
+}
+
 namespace {
 
 // ES2 enums
@@ -1164,6 +1180,9 @@ void WebGLRenderingContextBase::markContextChanged(ContentChangeType changeType)
 
     drawingBuffer()->markContentsChanged();
 
+    if (!canvas())
+        return;
+
     LayoutBox* layoutBox = canvas()->layoutBox();
     if (layoutBox && layoutBox->hasAcceleratedCompositing()) {
         m_markedCanvasDirty = true;