WebGL: optimize to draw WebGL on external destination. e.g. 2D Canvas.

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 279 matching lines @@
     m_context->produceTextureDirectCHROMIUM(frontColorBufferMailbox->textureInfo.textureId, GL_TEXTURE_2D, frontColorBufferMailbox->mailbox.name);
     m_context->flush();
     frontColorBufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
     frontColorBufferMailbox->mailbox.allowOverlay = frontColorBufferMailbox->textureInfo.imageId != 0;
     markLayerComposited();
 
     // set m_parentDrawingBuffer to make sure 'this' stays alive as long as it has live mailboxes
     ASSERT(!frontColorBufferMailbox->m_parentDrawingBuffer);
     frontColorBufferMailbox->m_parentDrawingBuffer = this;
     *outMailbox = frontColorBufferMailbox->mailbox;
-    m_frontColorBuffer = frontColorBufferMailbox->textureInfo;
+    m_frontColorBuffer = { frontColorBufferMailbox->textureInfo, frontColorBufferMailbox->mailbox };
     return true;
 }
 
 void DrawingBuffer::mailboxReleased(const WebExternalTextureMailbox& mailbox, bool lostResource)
 {
     if (m_destructionInProgress || m_context->isContextLost() || lostResource || m_isHidden) {
         mailboxReleasedWithoutRecycling(mailbox);
         return;
     }
 
@@ skipping 138 matching lines @@
         WGC3Dint stencilBits = 0;
         m_context->getIntegerv(GL_STENCIL_BITS, &stencilBits);
         m_actualAttributes.stencil = stencilBits > 0;
     }
     m_actualAttributes.antialias = multisample();
     return true;
 }
 
 bool DrawingBuffer::copyToPlatformTexture(WebGraphicsContext3D* context, Platform3DObject texture, GLenum internalFormat, GLenum destType, GLint level, bool premultiplyAlpha, bool flipY, bool fromFrontBuffer)
 {
-    GLint textureId = m_colorBuffer.textureId;
-    if (fromFrontBuffer && m_frontColorBuffer.textureId)
-        textureId = m_frontColorBuffer.textureId;
-
     if (m_contentsChanged) {
         if (m_multisampleMode != None) {
             commit();
             if (!m_framebufferBinding)
                 bind();
             else
                 restoreFramebufferBinding();
         }
         m_context->flush();
     }
 
     if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(internalFormat, destType, level))
         return false;
 
     // 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->produceTextureDirectCHROMIUM(textureId, GL_TEXTURE_2D, bufferMailbox->mailbox.name);
-    m_context->flush();
+    WebExternalTextureMailbox mailbox;
+    GLint textureId = 0;
+    if (fromFrontBuffer && m_frontColorBuffer.texInfo.textureId) {
+        textureId = m_frontColorBuffer.texInfo.textureId;
+        mailbox = m_frontColorBuffer.mailbox;
+    } else {
+        textureId = m_colorBuffer.textureId;
+        m_context->genMailboxCHROMIUM(mailbox.name);
+        m_context->produceTextureDirectCHROMIUM(textureId, GL_TEXTURE_2D, mailbox.name);
+        m_context->flush();
+        mailbox.syncPoint = m_context->insertSyncPoint();
+    }
 
-    bufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
-
-    context->waitSyncPoint(bufferMailbox->mailbox.syncPoint);
-    Platform3DObject sourceTexture = context->createAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+    context->waitSyncPoint(mailbox.syncPoint);

[Ken Russell (switch to Gerrit), 2014/10/31 00:54:21]

Forgive my ignorance, but is it legal to wait multiple times on the same sync
point? I assume it is, but this'll be the first time we do this in this class.

[dshwang, 2014/10/31 06:46:07]

Yes, it's legal. For example, video frame is used by both compositor and WebGL,
which wait for the sync point of the video frame. +danakj

[Ken Russell (switch to Gerrit), 2014/10/31 21:32:54]

Right, confirmed by reading CHROMIUM_sync_point.txt.

+    Platform3DObject sourceTexture = context->createAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, mailbox.name);
 
     bool unpackPremultiplyAlphaNeeded = false;
     bool unpackUnpremultiplyAlphaNeeded = false;
     if (m_actualAttributes.alpha && m_actualAttributes.premultipliedAlpha && !premultiplyAlpha)
         unpackUnpremultiplyAlphaNeeded = true;
     else if (m_actualAttributes.alpha && !m_actualAttributes.premultipliedAlpha && premultiplyAlpha)
         unpackPremultiplyAlphaNeeded = true;
 
     context->pixelStorei(GC3D_UNPACK_UNPREMULTIPLY_ALPHA_CHROMIUM, unpackUnpremultiplyAlphaNeeded);
     context->pixelStorei(GC3D_UNPACK_PREMULTIPLY_ALPHA_CHROMIUM, unpackPremultiplyAlphaNeeded);
@@ skipping 28 matching lines @@
     }
 
     return m_layer->layer();
 }
 
 void DrawingBuffer::paintCompositedResultsToCanvas(ImageBuffer* imageBuffer)
 {
     if (m_context->getGraphicsResetStatusARB() != GL_NO_ERROR)
         return;
 
-    if (!imageBuffer)
+    if (!imageBuffer || !m_frontColorBuffer.texInfo.textureId)
         return;
     Platform3DObject tex = imageBuffer->getBackingTexture();
     if (tex) {
-        RefPtr<MailboxInfo> bufferMailbox = adoptRef(new MailboxInfo());
-        m_context->genMailboxCHROMIUM(bufferMailbox->mailbox.name);
-        m_context->produceTextureDirectCHROMIUM(m_frontColorBuffer.textureId, GL_TEXTURE_2D, bufferMailbox->mailbox.name);
-        m_context->flush();
-
-        bufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
         OwnPtr<WebGraphicsContext3DProvider> provider =
             adoptPtr(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
         if (!provider)
             return;
         WebGraphicsContext3D* context = provider->context3d();
         if (!context)
             return;
 
-        context->waitSyncPoint(bufferMailbox->mailbox.syncPoint);
-        Platform3DObject sourceTexture = context->createAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, bufferMailbox->mailbox.name);
+        context->waitSyncPoint(m_frontColorBuffer.mailbox.syncPoint);
+        Platform3DObject sourceTexture = context->createAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, m_frontColorBuffer.mailbox.name);
         context->copyTextureCHROMIUM(GL_TEXTURE_2D, sourceTexture,
             tex, 0, GL_RGBA, GL_UNSIGNED_BYTE);
         context->deleteTexture(sourceTexture);
         context->flush();
         m_context->waitSyncPoint(context->insertSyncPoint());
         imageBuffer->didModifyBackingTexture();
-
         return;
     }
 
     Platform3DObject framebuffer = m_context->createFramebuffer();
     m_context->bindFramebuffer(GL_FRAMEBUFFER, framebuffer);
     // We don't need to bind a copy of m_frontColorBuffer since the texture parameters are untouched.
-    m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_frontColorBuffer.textureId, 0);
+    m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_frontColorBuffer.texInfo.textureId, 0);
 
     paintFramebufferToCanvas(framebuffer, size().width(), size().height(), !m_actualAttributes.premultipliedAlpha, imageBuffer);
     m_context->deleteFramebuffer(framebuffer);
     // Since we're using the same context as WebGL, we have to restore any state we change (in this case, just the framebuffer binding).
     restoreFramebufferBinding();
 }
 
 void DrawingBuffer::clearPlatformLayer()
 {
     if (m_layer)
@@ skipping 31 matching lines @@
         m_context->deleteRenderbuffer(m_stencilBuffer);
 
     if (m_colorBuffer.textureId) {
         deleteChromiumImageForTexture(&m_colorBuffer);
         m_context->deleteTexture(m_colorBuffer.textureId);
     }
 
     setSize(IntSize());
 
     m_colorBuffer = TextureInfo();
-    m_frontColorBuffer = TextureInfo();
+    m_frontColorBuffer = FrontBufferInfo();
     m_multisampleColorBuffer = 0;
     m_depthStencilBuffer = 0;
     m_depthBuffer = 0;
     m_stencilBuffer = 0;
     m_multisampleFBO = 0;
     m_fbo = 0;
     m_contextEvictionManager.clear();
 
     if (m_layer)
         GraphicsLayer::unregisterContentsLayer(m_layer->layer());
@@ skipping 429 matching lines @@
 void DrawingBuffer::deleteChromiumImageForTexture(TextureInfo* info)
 {
     if (info->imageId) {
         m_context->releaseTexImage2DCHROMIUM(GL_TEXTURE_2D, info->imageId);
         m_context->destroyImageCHROMIUM(info->imageId);
         info->imageId = 0;
     }
 }
 
 } // namespace blink