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

Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 311 matching lines @@
     if (m_contentsChanged) {
         if (m_multisampleMode != None) {
             commit();
             if (!m_framebufferBinding)
                 bind();
             else
                 restoreFramebufferBinding();
         }
         m_context->flush();
     }
-    Platform3DObject sourceTexture = m_colorBuffer;
+
+    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
+        return false;
+
+    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;
 
-    if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
-        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)
         unpackUnpremultiplyAlphaNeeded = true;
     else if (m_attributes.alpha && !m_attributes.premultipliedAlpha && premultiplyAlpha)
         unpackPremultiplyAlphaNeeded = true;
 
     context->pixelStorei(GC3D_UNPACK_UNPREMULTIPLY_ALPHA_CHROMIUM, unpackUnpremultiplyAlphaNeeded);
     context->pixelStorei(GC3D_UNPACK_PREMULTIPLY_ALPHA_CHROMIUM, unpackPremultiplyAlphaNeeded);
     context->pixelStorei(GC3D_UNPACK_FLIP_Y_CHROMIUM, flipY);
     context->copyTextureCHROMIUM(GL_TEXTURE_2D, sourceTexture, texture, level, internalFormat, destType);
     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;
 }
 
 Platform3DObject DrawingBuffer::framebuffer() const
 {
     return m_fbo;
 }
 
 blink::WebLayer* DrawingBuffer::platformLayer()
@@ skipping 531 matching lines @@
     }
 }
 
 void DrawingBuffer::texImage2DResourceSafe(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, GLint unpackAlignment)
 {
     ASSERT(unpackAlignment == 1 || unpackAlignment == 2 || unpackAlignment == 4 || unpackAlignment == 8);
     m_context->texImage2D(target, level, internalformat, width, height, border, format, type, 0);
 }
 
 } // namespace WebCore