Implement transferToImageBitmap() in WebGLRenderingContext

third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/graphics/StaticBitmapImage.h"
 
+#include "gpu/command_buffer/client/gles2_interface.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/ImageObserver.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebGraphicsContext3DProvider.h"
+#include "skia/ext/texture_handle.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkImage.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkShader.h"
 
 namespace blink {
 
 PassRefPtr<StaticBitmapImage> StaticBitmapImage::create(PassRefPtr<SkImage> image)
 {
     if (!image)
         return nullptr;
     return adoptRef(new StaticBitmapImage(image));
 }
 
+PassRefPtr<StaticBitmapImage> StaticBitmapImage::create(WebExternalTextureMailbox& mailbox)
+{
+    return adoptRef(new StaticBitmapImage(mailbox));
+}
+
 StaticBitmapImage::StaticBitmapImage(PassRefPtr<SkImage> image) : m_image(image)
 {
     ASSERT(m_image);
 }
 
+StaticBitmapImage::StaticBitmapImage(WebExternalTextureMailbox& mailbox) : m_mailbox(mailbox)
+{
+}
+
 StaticBitmapImage::~StaticBitmapImage() { }
 
 IntSize StaticBitmapImage::size() const
 {
     return IntSize(m_image->width(), m_image->height());
 }
 
 bool StaticBitmapImage::currentFrameKnownToBeOpaque(MetadataMode)
 {
     return m_image->isOpaque();
@@ skipping 10 matching lines @@
 
     canvas->drawImageRect(m_image.get(), adjustedSrcRect, dstRect, &paint,
         WebCoreClampingModeToSkiaRectConstraint(clampMode));
 
     if (ImageObserver* observer = getImageObserver())
         observer->didDraw(this);
 }
 
 PassRefPtr<SkImage> StaticBitmapImage::imageForCurrentFrame()
 {
-    return m_image;
+    if (m_image)
+        return m_image;
+    DCHECK(isMainThread());
+    // In the place when we consume an ImageBitmap that is gpu texture backed,
+    // create a new SkImage from that texture.
+    // TODO(xidachen): make this work on a worker thread.
+    OwnPtr<WebGraphicsContext3DProvider> provider = adoptPtr(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());

[Ken Russell (switch to Gerrit), 2016/05/19 00:15:12]

Someone who understands this code better needs to confirm that this is the
correct context into which to consume the texture mailbox.

[xidachen, 2016/05/19 13:48:29]

I believe this can be verified. Please take a look at the updated layout test
case in worker. Basically I created 2 webgl contexts in worker, one clear the
canvas with red and the other one with green. Then I call transferToImageBitmap
on both contexts. If the code here doesn't get the correct context, the
ImageBitmap that we got back will have the wrong color. Locally I run the test
under debug mode with repeat=20, and it always passes.

+    if (!provider)
+        return nullptr;
+    GrContext* grContext = provider->grContext();
+    if (!grContext)
+        return nullptr;
+    gpu::gles2::GLES2Interface* gl = provider->contextGL();
+    if (!gl)
+        return nullptr;
+    gl->WaitSyncTokenCHROMIUM(m_mailbox.syncToken);
+    GLuint textureId = gl->CreateAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, m_mailbox.name);
+    GrGLTextureInfo textureInfo;
+    textureInfo.fTarget = GL_TEXTURE_2D;
+    textureInfo.fID = textureId;
+    GrBackendTextureDesc backendTexture;
+    backendTexture.fOrigin = kBottomLeft_GrSurfaceOrigin;
+    backendTexture.fWidth = m_mailbox.textureSize.width;
+    backendTexture.fHeight = m_mailbox.textureSize.height;
+    backendTexture.fConfig = kSkia8888_GrPixelConfig;
+    backendTexture.fTextureHandle = skia::GrGLTextureInfoToGrBackendObject(textureInfo);
+    sk_sp<SkImage> skImage = SkImage::MakeFromTexture(grContext, backendTexture);

[Ken Russell (switch to Gerrit), 2016/05/19 00:15:11]

junov@ or bsalomon@ should review this code for correctness.

[bsalomon, 2016/05/19 12:57:20]

It seems OK to me but want to raise two potential issues:

1) Does gl->CreateAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, ...) return a texture
ID of target type GL_TEXTURE_2D or of m_mailbox.textureTarget?

2) This wraps a SkImage around the texture ID but doesn't turn responsibility
for deleting the texture over to Skia. If that is not the intention here then
you use SkImage::MakeFromAdoptedTexture() so that the Skia will free the texture
when it is done with it.

[xidachen, 2016/05/19 13:48:29]

Thanks for the comments.
1). In my opinion, it returns the ID of target type GL_TEXTURE_2D. kbr@: could
you verify that?

2). Good point. I believe that now the texture is consumed, SkImage should be
responsible for freeing the texture. junov@: WDYT?

[Ken Russell (switch to Gerrit), 2016/05/19 18:04:47]

It returns a texture of the type passed to CreateAndConsumeTextureCHROMIUM, in
this case GL_TEXTURE_2D. The texture mailbox does not have an associated target.
See DoCreateAndConsumeTextureCHROMIUM in
src/gpu/command_buffer/service/gles2_cmd_decoder.cc.

+    return fromSkSp(skImage);
 }
 
 } // namespace blink