WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index 999af825100a4abb54ef8ccb4109e5fc320d7936..acc0478cc3868e08a5beb9ac814bd13d19921bf3 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -100,6 +100,8 @@
 #include "wtf/text/StringUTF8Adaptor.h"
 #include "wtf/typed_arrays/ArrayBufferContents.h"
 
+#include <memory>
+
 namespace blink {
 
 namespace {
@@ -122,6 +124,24 @@ WebGLRenderingContextBaseMap& forciblyEvictedContexts()
     return forciblyEvictedContexts;
 }
 
+class ScopedRGBEmulationColorMask {

[Zhenyao Mo, 2016/04/29 22:54:15]

Does this bug also exist in core profile?  If yes, then you need to expose it to
.h file, and use it in WebGL2RenderingContextBase also (a few draw calls there).

[erikchen, 2016/05/03 22:58:07]

It does. I've done as you suggested.

+public:
+    ScopedRGBEmulationColorMask(gpu::gles2::GLES2Interface* contextGL, GLboolean* colorMask)
+        : m_contextGL(contextGL)
+    {
+        memcpy(m_colorMask, colorMask, 4 * sizeof(GLboolean));
+        m_contextGL->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2], false);
+    }
+    ~ScopedRGBEmulationColorMask()
+    {
+        m_contextGL->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2], m_colorMask[3]);
+    }
+
+private:
+    gpu::gles2::GLES2Interface* m_contextGL;
+    GLboolean m_colorMask[4];
+};
+
 } // namespace
 
 void WebGLRenderingContextBase::forciblyLoseOldestContext(const String& reason)
@@ -1117,7 +1137,7 @@ WebGLRenderingContextBase::HowToClear WebGLRenderingContextBase::clearIfComposit
     } else {
         contextGL()->ClearColor(0, 0, 0, 0);
     }
-    contextGL()->ColorMask(true, true, true, true);
+    contextGL()->ColorMask(true, true, true, !drawingBuffer()->requiresRGBEmulation());
     GLbitfield clearMask = GL_COLOR_BUFFER_BIT;
     if (contextAttributes.get().depth()) {
         if (!combinedClear || !m_depthMask || !(mask & GL_DEPTH_BUFFER_BIT))
@@ -1409,6 +1429,9 @@ void WebGLRenderingContextBase::bindRenderbuffer(ScriptState* scriptState, GLenu
     m_renderbufferBinding = renderBuffer;
     contextGL()->BindRenderbuffer(target, objectOrZero(renderBuffer));
     preserveObjectWrapper(scriptState, this, "renderbuffer", 0, renderBuffer);
+
+    drawingBuffer()->setRenderbufferBinding(objectOrZero(renderBuffer));
+
     if (renderBuffer)
         renderBuffer->setHasEverBeenBound();
 }
@@ -1647,6 +1670,11 @@ void WebGLRenderingContextBase::clear(GLbitfield mask)
         synthesizeGLError(GL_INVALID_FRAMEBUFFER_OPERATION, "clear", reason);
         return;
     }
+
+    std::unique_ptr<ScopedRGBEmulationColorMask> scopedColorMask;

[Ken Russell (switch to Gerrit), 2016/04/29 09:33:09]

I'd suggest changing ScopedRGBEmulationColorMask's constructor to take
contextGL, the color mask, and the drawing buffer, and internalize whether it
does its work. That way this block can just be

ScopedRGBEmulationColorMask scopedColorMask(contextGL(), m_colorMask,
m_drawingBuffer);

throughout the CL.

[erikchen, 2016/05/03 22:58:07]

Done.

+    if (m_drawingBuffer->requiresRGBEmulation())
+        scopedColorMask.reset(new ScopedRGBEmulationColorMask(contextGL(), m_colorMask));
+
     if (clearIfComposited(mask) != CombinedClear) {
         // If clearing the default back buffer's depth buffer, also clear the stencil buffer, if one
         // was allocated implicitly. This avoids performance problems on some GPUs.
@@ -1918,8 +1946,10 @@ void WebGLRenderingContextBase::deleteRenderbuffer(WebGLRenderbuffer* renderbuff
 {
     if (!deleteObject(renderbuffer))
         return;
-    if (renderbuffer == m_renderbufferBinding)
+    if (renderbuffer == m_renderbufferBinding) {
         m_renderbufferBinding = nullptr;
+        drawingBuffer()->setRenderbufferBinding(0);
+    }
     if (m_framebufferBinding)
         m_framebufferBinding->removeAttachmentFromBoundFramebuffer(GL_FRAMEBUFFER, renderbuffer);
     if (getFramebufferBinding(GL_READ_FRAMEBUFFER))
@@ -2067,6 +2097,9 @@ void WebGLRenderingContextBase::drawArrays(GLenum mode, GLint first, GLsizei cou
     if (!validateDrawArrays("drawArrays"))
         return;
 
+    std::unique_ptr<ScopedRGBEmulationColorMask> scopedColorMask;
+    if (m_drawingBuffer->requiresRGBEmulation())
+        scopedColorMask.reset(new ScopedRGBEmulationColorMask(contextGL(), m_colorMask));
     clearIfComposited();
     contextGL()->DrawArrays(mode, first, count);
     markContextChanged(CanvasChanged);
@@ -2082,6 +2115,9 @@ void WebGLRenderingContextBase::drawElements(GLenum mode, GLsizei count, GLenum
         return;
     }
 
+    std::unique_ptr<ScopedRGBEmulationColorMask> scopedColorMask;
+    if (m_drawingBuffer->requiresRGBEmulation())
+        scopedColorMask.reset(new ScopedRGBEmulationColorMask(contextGL(), m_colorMask));
     clearIfComposited();
     contextGL()->DrawElements(mode, count, type, reinterpret_cast<void*>(static_cast<intptr_t>(offset)));
     markContextChanged(CanvasChanged);
@@ -2092,6 +2128,9 @@ void WebGLRenderingContextBase::drawArraysInstancedANGLE(GLenum mode, GLint firs
     if (!validateDrawArrays("drawArraysInstancedANGLE"))
         return;
 
+    std::unique_ptr<ScopedRGBEmulationColorMask> scopedColorMask;
+    if (m_drawingBuffer->requiresRGBEmulation())
+        scopedColorMask.reset(new ScopedRGBEmulationColorMask(contextGL(), m_colorMask));
     clearIfComposited();
     contextGL()->DrawArraysInstancedANGLE(mode, first, count, primcount);
     markContextChanged(CanvasChanged);
@@ -2102,6 +2141,9 @@ void WebGLRenderingContextBase::drawElementsInstancedANGLE(GLenum mode, GLsizei
     if (!validateDrawElements("drawElementsInstancedANGLE", type, offset))
         return;
 
+    std::unique_ptr<ScopedRGBEmulationColorMask> scopedColorMask;
+    if (m_drawingBuffer->requiresRGBEmulation())
+        scopedColorMask.reset(new ScopedRGBEmulationColorMask(contextGL(), m_colorMask));
     clearIfComposited();
     contextGL()->DrawElementsInstancedANGLE(mode, count, type, reinterpret_cast<void*>(static_cast<intptr_t>(offset)), primcount);
     markContextChanged(CanvasChanged);
@@ -2533,6 +2575,8 @@ ScriptValue WebGLRenderingContextBase::getParameter(ScriptState* scriptState, GL
     case GL_ALIASED_POINT_SIZE_RANGE:
         return getWebGLFloatArrayParameter(scriptState, pname);
     case GL_ALPHA_BITS:
+        if (m_drawingBuffer->requiresRGBEmulation())
+            return WebGLAny(scriptState, 0);
         return getIntParameter(scriptState, pname);
     case GL_ARRAY_BUFFER_BINDING:
         return WebGLAny(scriptState, m_boundArrayBuffer.get());
@@ -4954,6 +4998,7 @@ void WebGLRenderingContextBase::loseContextImpl(WebGLRenderingContextBase::LostC
     // Make absolutely sure we do not refer to an already-deleted texture or framebuffer.
     drawingBuffer()->setTexture2DBinding(0);
     drawingBuffer()->setFramebufferBinding(GL_FRAMEBUFFER, 0);
+    drawingBuffer()->setRenderbufferBinding(0);
 
     detachAndRemoveAllObjects();