Share Group plumbing in Blink; Remove WebGL from default share group

Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBuffer.cpp b/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 8b3bd008303b195f7fdd492ce4be180db5346f18..d9740e23b487860adc3990b69f2d343f0c25d0c3 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -329,14 +329,34 @@ bool DrawingBuffer::copyToPlatformTexture(blink::WebGraphicsContext3D* context,
         }
         m_context->flush();
     }
-    Platform3DObject sourceTexture = m_colorBuffer;
 
-    if (!context->makeContextCurrent())
+    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
         return false;
 
-    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
+    GLint boundTexture = 0;
+    m_context->getIntegerv(GL_TEXTURE_BINDING_2D, &boundTexture);

[Ken Russell (switch to Gerrit), 2014/03/12 21:23:38]

One of the two callers of this method is
ImageBuffer::copyRenderingResultsFromDrawingBuffer, called by
WebGLRenderingContextBase::paintRenderingResultsToCanvas. The latter method has
enough information to restore the bound texture, which would avoid this
save/restore. The other caller is WebGLRenderingContextBase::texImage2D, which
again can do the save/restore. I think DrawingBuffer::copyToPlatformTexture
should be documented as destroying the TEXTURE_2D binding of the active texture
unit of its owned context.

+
+    // Contexts may be in a different share group. We must transfer the texture through a mailbox first
+    RefPtr<MailboxInfo> bufferMailbox = adoptRef(new MailboxInfo());
+    m_context->genMailboxCHROMIUM(bufferMailbox->mailbox.name);
+    m_context->bindTexture(GL_TEXTURE_2D, m_colorBuffer);
+    m_context->produceTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+    m_context->bindTexture(GL_TEXTURE_2D, boundTexture);
+    m_context->flush();
+
+    bufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
+
+    if (!context->makeContextCurrent())
         return false;
 
+    Platform3DObject sourceTexture = context->createTexture();
+
+    context->getIntegerv(GL_TEXTURE_BINDING_2D, &boundTexture);

[Ken Russell (switch to Gerrit), 2014/03/12 21:23:38]

There are only two callers of DrawingBuffer::copyToPlatformTexture:
ImageBuffer::copyRenderingResultsFromDrawingBuffer and
WebGLRenderingContextBase::texImage2D. In the former case the shared offscreen
graphics context is passed, and in the latter case the WebGLRenderingContext's
WebGraphicsContext3D is passed. In the latter case the WebGLRenderingContext can
always restore the TEXTURE_2D binding, and in the former I'm not sure it's
necessary to restore it. I think DrawingBuffer::copyToPlatformTexture should be
documented as destroying the TEXTURE_2D binding of the active texture unit of
the passed context, and leave it up to the caller to restore it.

+    context->bindTexture(GL_TEXTURE_2D, sourceTexture);
+
+    context->waitSyncPoint(bufferMailbox->mailbox.syncPoint);
+    context->consumeTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+
     bool unpackPremultiplyAlphaNeeded = false;
     bool unpackUnpremultiplyAlphaNeeded = false;
     if (m_attributes.alpha && m_attributes.premultipliedAlpha && !premultiplyAlpha)
@@ -351,7 +371,12 @@ bool DrawingBuffer::copyToPlatformTexture(blink::WebGraphicsContext3D* context,
     context->pixelStorei(GC3D_UNPACK_FLIP_Y_CHROMIUM, false);
     context->pixelStorei(GC3D_UNPACK_UNPREMULTIPLY_ALPHA_CHROMIUM, false);
     context->pixelStorei(GC3D_UNPACK_PREMULTIPLY_ALPHA_CHROMIUM, false);
+
+    context->bindTexture(GL_TEXTURE_2D, boundTexture);

[Ken Russell (switch to Gerrit), 2014/03/12 21:23:38]

Again, this can bind NULL in order to delete sourceTexture in a timely fashion.

+    context->deleteTexture(sourceTexture);
+
     context->flush();
+    m_context->waitSyncPoint(context->insertSyncPoint());
 
     return true;
 }