WebGL GL_RGB emulation to support IOSurfaces on Mac.

third_party/WebKit/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 224 matching lines @@
 
 void DrawingBuffer::setFilterQuality(SkFilterQuality filterQuality)
 {
     if (m_filterQuality != filterQuality) {
         m_filterQuality = filterQuality;
         if (m_layer)
             m_layer->setNearestNeighbor(filterQuality == kNone_SkFilterQuality);
     }
 }
 
+bool DrawingBuffer::requiresRGBEmulation()
+{
+#if OS(MACOSX)
+    return !m_drawFramebufferBinding && !m_wantAlphaChannel && m_colorBuffer.imageId;
+#else
+    return false;
+#endif
+}
+
 void DrawingBuffer::freeRecycledMailboxes()
 {
     if (m_recycledMailboxQueue.isEmpty())
         return;
     while (!m_recycledMailboxQueue.isEmpty())
         deleteMailbox(m_recycledMailboxQueue.takeLast());
 }
 
 bool DrawingBuffer::prepareMailbox(WebExternalTextureMailbox* outMailbox, WebExternalBitmap* bitmap)
 {
@@ skipping 98 matching lines @@
     ASSERT_NOT_REACHED();
 }
 
 DrawingBuffer::TextureParameters DrawingBuffer::chromiumImageTextureParameters()
 {
 #if OS(MACOSX)
     // A CHROMIUM_image backed texture requires a specialized set of parameters
     // on OSX.
     TextureParameters parameters;
     parameters.target = GC3D_TEXTURE_RECTANGLE_ARB;
-    parameters.internalColorFormat = GL_BGRA_EXT;
+    parameters.internalColorFormat = GL_RGBA;
     parameters.internalRenderbufferFormat = GL_RGBA8_OES;
-    parameters.colorFormat = GL_RGBA;
+
+    // Unused.
+    parameters.colorFormat = 0;
     return parameters;
 #else
     return defaultTextureParameters();
 #endif
 }
 
 DrawingBuffer::TextureParameters DrawingBuffer::defaultTextureParameters()
 {
     TextureParameters parameters;
     parameters.target = GL_TEXTURE_2D;
@@ skipping 381 matching lines @@
         } while (!adjustedSize.isEmpty());
 
         setSize(adjustedSize);
 
         if (adjustedSize.isEmpty())
             return false;
     }
 
     m_gl->Disable(GL_SCISSOR_TEST);
     m_gl->ClearColor(0, 0, 0, 0);
-    m_gl->ColorMask(true, true, true, true);
+    m_gl->ColorMask(true, true, true, !requiresRGBEmulation());
 
     GLbitfield clearMask = GL_COLOR_BUFFER_BIT;
     if (!!m_depthStencilBuffer) {
         m_gl->ClearDepthf(1.0f);
         clearMask |= GL_DEPTH_BUFFER_BIT;
         m_gl->DepthMask(true);
     }
     if (!!m_depthStencilBuffer) {
         m_gl->ClearStencil(0);
         clearMask |= GL_STENCIL_BUFFER_BIT;
         m_gl->StencilMaskSeparate(GL_FRONT, 0xFFFFFFFF);
     }
 
     clearFramebuffers(clearMask);
+    m_gl->ColorMask(true, true, true, true);
     return true;
 }
 
 void DrawingBuffer::commit()
 {
     if (m_multisampleFBO && !m_contentsChangeCommitted) {
         m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER_ANGLE, m_multisampleFBO);
         m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER_ANGLE, m_fbo);
 
         if (m_scissorEnabled)
@@ skipping 149 matching lines @@
 void DrawingBuffer::deleteChromiumImageForTexture(TextureInfo* info)
 {
     if (info->imageId) {
         m_gl->BindTexture(info->parameters.target, info->textureId);
         m_gl->ReleaseTexImage2DCHROMIUM(info->parameters.target, info->imageId);
         m_gl->DestroyImageCHROMIUM(info->imageId);
         info->imageId = 0;
     }
 }
 
+void DrawingBuffer::clearChromiumImageIfNecessary(const TextureInfo& info)
+{
+    if (m_wantAlphaChannel)
+        return;
+
+    GLuint fbo = 0;
+    m_gl->GenFramebuffers(1, &fbo);
+    m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
+    m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, info.parameters.target, info.textureId, 0);
+    m_gl->ClearColor(0, 0, 0, 1);
+    m_gl->ColorMask(false, false, false, true);
+    m_gl->Clear(GL_COLOR_BUFFER_BIT);
+    m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, info.parameters.target, 0, 0);
+    m_gl->DeleteFramebuffers(1, &fbo);
+    restoreFramebufferBindings();
+}
+
 DrawingBuffer::TextureInfo DrawingBuffer::createTextureAndAllocateMemory(const IntSize& size)
 {
-    // TODO(erikchen): Add support for a CHROMIUM_image back buffer whose
-    // behavior mimics a texture with internal format GL_RGB.
-    // https://crbug.com/581777.
-    if (!m_wantAlphaChannel)
-        return createDefaultTextureAndAllocateMemory(size);
-
     if (!RuntimeEnabledFeatures::webGLImageChromiumEnabled())
         return createDefaultTextureAndAllocateMemory(size);
 
     // First, try to allocate a CHROMIUM_image. This always has the potential to
     // fail.
     TextureParameters parameters = chromiumImageTextureParameters();
     GLuint imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(size.width(), size.height(), parameters.internalColorFormat, GC3D_SCANOUT_CHROMIUM);
     if (!imageId)
         return createDefaultTextureAndAllocateMemory(size);
 
     GLuint textureId = createColorTexture(parameters);
     m_gl->BindTexImage2DCHROMIUM(parameters.target, imageId);
 
     TextureInfo info;
     info.textureId = textureId;
     info.imageId = imageId;
     info.parameters = parameters;
+    clearChromiumImageIfNecessary(info);
     return info;
 }
 
 DrawingBuffer::TextureInfo DrawingBuffer::createDefaultTextureAndAllocateMemory(const IntSize& size)
 {
     TextureParameters parameters = defaultTextureParameters();
     GLuint textureId = createColorTexture(parameters);
     texImage2DResourceSafe(parameters.target, 0, parameters.internalColorFormat, size.width(), size.height(), 0, parameters.colorFormat, GL_UNSIGNED_BYTE);
 
     DrawingBuffer::TextureInfo info;
     info.textureId = textureId;
     info.parameters = parameters;
     return info;
 }
 
 void DrawingBuffer::resizeTextureMemory(TextureInfo* info, const IntSize& size)
 {
     ASSERT(info->textureId);
     if (info->imageId) {
         deleteChromiumImageForTexture(info);
         info->imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(size.width(), size.height(), info->parameters.internalColorFormat, GC3D_SCANOUT_CHROMIUM);
         if (info->imageId) {
             m_gl->BindTexture(info->parameters.target, info->textureId);
             m_gl->BindTexImage2DCHROMIUM(info->parameters.target, info->imageId);
+            clearChromiumImageIfNecessary(*info);
             return;
         }
 
         // If the desired texture target is different, there's no way to fall back
         // to a non CHROMIUM_image texture.
         if (chromiumImageTextureParameters().target != defaultTextureParameters().target)
             return;
     }
 
     m_gl->BindTexture(info->parameters.target, info->textureId);
     texImage2DResourceSafe(info->parameters.target, 0, info->parameters.internalColorFormat, size.width(), size.height(), 0, info->parameters.colorFormat, GL_UNSIGNED_BYTE);
 }
 
 void DrawingBuffer::attachColorBufferToCurrentFBO()
 {
     GLenum target = m_colorBuffer.parameters.target;
 
     m_gl->BindTexture(target, m_colorBuffer.textureId);
 
     if (m_antiAliasingMode == MSAAImplicitResolve)
         m_gl->FramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, target, m_colorBuffer.textureId, 0, m_sampleCount);
     else
         m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, target, m_colorBuffer.textureId, 0);
 
     m_gl->BindTexture(GL_TEXTURE_2D, m_texture2DBinding);
 }
 
 } // namespace blink