Implement "hole" video frame.

cc/gl_renderer.cc

 // Copyright 2010 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 "cc/gl_renderer.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 971 matching lines @@
 
 void GLRenderer::drawStreamVideoQuad(const DrawingFrame& frame, const StreamVideoDrawQuad* quad)
 {
     static float glMatrix[16];
 
     DCHECK(m_capabilities.usingEglImage);
 
     const VideoStreamTextureProgram* program = videoStreamTextureProgram();
     setUseProgram(program->program());
 
+    if (quad->texture_id == 0) {

[Vangelis Kokkevis, 2013/02/21 18:52:54]

I'm not too fond of the idea of using texture_id == 0 as a signal to punch a
hole, as it's also a possible valid failure condition. I'm thinking that we
should create a new quad type for holes that also uses a much simpler shader (no
need to do any sort of blending, just blast zeros to the backbuffer). 

[danakj, 2013/02/21 19:01:51]

That sounds like a solid color quad with needs blending forced off?

[wonsik2, 2013/02/26 04:52:24]

Created a new quad type; PTAL

[wonsik2, 2013/02/26 04:52:24]

I tried SolidColorDrawQuad with needs_blending == false, but it didn't work as
expected.

I ended up implementing a new quad. PTAL.

[wonsik2, 2013/02/26 06:47:03]

With further investigation, it turned out that an approach with
SolidColorDrawQuad worked.

+        // When texture_id == 0, punch a hole instead of rendering. The video
+        // will be composited outside of Chrome rendering pipeline, and where
+        // video should be composited should remain transparent in this case.
+        GLC(m_context, m_context->blendFunc(GL_ZERO, GL_ONE_MINUS_SRC_ALPHA));
+        drawQuadGeometry(frame, quad->quadTransform(), quad->rect, program->vertexShader().matrixLocation());
+        GLC(m_context, m_context->blendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA));
+        return;
+    }
+
     toGLMatrix(&glMatrix[0], quad->matrix);
     GLC(context(), context()->uniformMatrix4fv(program->vertexShader().texMatrixLocation(), 1, false, glMatrix));
 
     GLC(context(), context()->bindTexture(GL_TEXTURE_EXTERNAL_OES, quad->texture_id));
 
     GLC(context(), context()->uniform1i(program->fragmentShader().samplerLocation(), 0));
 
     setShaderOpacity(quad->opacity(), program->fragmentShader().alphaLocation());
     drawQuadGeometry(frame, quad->quadTransform(), quad->rect, program->vertexShader().matrixLocation());
 }
@@ skipping 829 matching lines @@
 
     releaseRenderPassTextures();
 }
 
 bool GLRenderer::isContextLost()
 {
     return (m_context->getGraphicsResetStatusARB() != GL_NO_ERROR);
 }
 
 }  // namespace cc