WebGL: clarify which Front or Back buffer is used by each API.

Source/core/html/canvas/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 73 matching lines @@
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/UnacceleratedImageBufferSurface.h"
 #include "platform/graphics/gpu/AcceleratedImageBufferSurface.h"
 #include "platform/graphics/gpu/DrawingBuffer.h"
 #include "public/platform/Platform.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
 
+namespace {
+
 const double secondsBetweenRestoreAttempts = 1.0;
 const int maxGLErrorsAllowedToConsole = 256;
 const unsigned maxGLActiveContexts = 16;
 
+} // namesapce
+
 // FIXME: Oilpan: static vectors to heap allocated WebGLRenderingContextBase objects
 // are kept here. This relies on the WebGLRenderingContextBase finalization to
 // explicitly retire themselves from these vectors, but it'd be preferable if
 // the references were traced as per usual.
 Vector<WebGLRenderingContextBase*>& WebGLRenderingContextBase::activeContexts()
 {
     DEFINE_STATIC_LOCAL(Vector<WebGLRenderingContextBase*>, activeContexts, ());
     return activeContexts;
 }
 
@@ skipping 772 matching lines @@
     if (!isContextLost())
         drawingBuffer()->markLayerComposited();
 }
 
 void WebGLRenderingContextBase::setIsHidden(bool hidden)
 {
     if (drawingBuffer())
         drawingBuffer()->setIsHidden(hidden);
 }
 
-void WebGLRenderingContextBase::paintRenderingResultsToCanvas(SourceBuffer source)
+void WebGLRenderingContextBase::paintRenderingResultsToCanvas(SourceDrawingBuffer sourceBuffer)
 {
     if (isContextLost())
         return;
 
     clearIfComposited();
 
     if (!m_markedCanvasDirty && !m_layerCleared)
         return;
 
     canvas()->clearCopiedImage();
     m_markedCanvasDirty = false;
 
     ScopedTexture2DRestorer restorer(this);
 
     drawingBuffer()->commit();
-    if (!canvas()->buffer()->copyRenderingResultsFromDrawingBuffer(drawingBuffer(), source == Front)) {
+    if (!canvas()->buffer()->copyRenderingResultsFromDrawingBuffer(drawingBuffer(), sourceBuffer)) {
         canvas()->ensureUnacceleratedImageBuffer();
         if (canvas()->hasImageBuffer())
             drawingBuffer()->paintRenderingResultsToCanvas(canvas()->buffer());
     }
 
     if (m_framebufferBinding)
         webContext()->bindFramebuffer(GL_FRAMEBUFFER, objectOrZero(m_framebufferBinding.get()));
     else
         drawingBuffer()->bind();
 }
 
-PassRefPtrWillBeRawPtr<ImageData> WebGLRenderingContextBase::paintRenderingResultsToImageData()
+PassRefPtrWillBeRawPtr<ImageData> WebGLRenderingContextBase::paintRenderingResultsToImageData(SourceDrawingBuffer sourceBuffer)
 {
     if (isContextLost())
         return nullptr;
 
     clearIfComposited();
     drawingBuffer()->commit();
     int width, height;
-    RefPtr<Uint8ClampedArray> imageDataPixels = drawingBuffer()->paintRenderingResultsToImageData(width, height);
+    RefPtr<Uint8ClampedArray> imageDataPixels =
+        drawingBuffer()->paintRenderingResultsToImageData(width, height, sourceBuffer);
     if (!imageDataPixels)
         return nullptr;
 
-    if (m_framebufferBinding)
-        webContext()->bindFramebuffer(GL_FRAMEBUFFER, objectOrZero(m_framebufferBinding.get()));
-    else
-        drawingBuffer()->bind();
-
     return ImageData::create(IntSize(width, height), imageDataPixels);
 }
 
 void WebGLRenderingContextBase::reshape(int width, int height)
 {
     if (isContextLost())
         return;
 
     // This is an approximation because at WebGLRenderingContextBase level we don't
     // know if the underlying FBO uses textures or renderbuffers.
@@ skipping 2598 matching lines @@
             ImageBuffer* buffer = canvas->buffer();
             if (buffer && buffer->copyToPlatformTexture(webContext(), texture->object(), internalformat, type,
                 level, m_unpackPremultiplyAlpha, m_unpackFlipY)) {
                 texture->setLevelInfo(target, level, internalformat, canvas->width(), canvas->height(), type);
                 return;
             }
         } else {
             WebGLRenderingContextBase* gl = toWebGLRenderingContextBase(canvas->renderingContext());
             ScopedTexture2DRestorer restorer(gl);
             if (gl && gl->drawingBuffer()->copyToPlatformTexture(webContext(), texture->object(), internalformat, type,
-                level, m_unpackPremultiplyAlpha, !m_unpackFlipY, DrawingBuffer::Back)) {
+                level, m_unpackPremultiplyAlpha, !m_unpackFlipY, BackBuffer)) {
                 texture->setLevelInfo(target, level, internalformat, canvas->width(), canvas->height(), type);
                 return;
             }
         }
     }
 
-    RefPtrWillBeRawPtr<ImageData> imageData = canvas->getImageData();
-    if (imageData)
-        texImage2D(target, level, internalformat, format, type, imageData.get(), exceptionState);
-    else
-        texImage2DImpl(target, level, internalformat, format, type, canvas->copiedImage(), WebGLImageConversion::HtmlDomCanvas, m_unpackFlipY, m_unpackPremultiplyAlpha, exceptionState);
+    texImage2DImpl(target, level, internalformat, format, type, canvas->copiedImage(BackBuffer), WebGLImageConversion::HtmlDomCanvas, m_unpackFlipY, m_unpackPremultiplyAlpha, exceptionState);
 }
 
 PassRefPtr<Image> WebGLRenderingContextBase::videoFrameToImage(HTMLVideoElement* video, BackingStoreCopy backingStoreCopy)
 {
     IntSize size(video->videoWidth(), video->videoHeight());
     ImageBuffer* buf = m_generatedImageCache.imageBuffer(size);
     if (!buf) {
         synthesizeGLError(GL_OUT_OF_MEMORY, "texImage2D", "out of memory");
         return nullptr;
     }
@@ skipping 213 matching lines @@
     texSubImage2DImpl(target, level, xoffset, yoffset, format, type, imageForRender.get(), WebGLImageConversion::HtmlDomImage, m_unpackFlipY, m_unpackPremultiplyAlpha, exceptionState);
 }
 
 void WebGLRenderingContextBase::texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
     GLenum format, GLenum type, HTMLCanvasElement* canvas, ExceptionState& exceptionState)
 {
     if (isContextLost() || !validateHTMLCanvasElement("texSubImage2D", canvas, exceptionState)
         || !validateTexFunc("texSubImage2D", TexSubImage2D, SourceHTMLCanvasElement, target, level, format, canvas->width(), canvas->height(), 0, format, type, xoffset, yoffset))
         return;
 
-    RefPtrWillBeRawPtr<ImageData> imageData = canvas->getImageData();
-    if (imageData)
-        texSubImage2D(target, level, xoffset, yoffset, format, type, imageData.get(), exceptionState);
-    else
-        texSubImage2DImpl(target, level, xoffset, yoffset, format, type, canvas->copiedImage(), WebGLImageConversion::HtmlDomCanvas, m_unpackFlipY, m_unpackPremultiplyAlpha, exceptionState);
+    texSubImage2DImpl(target, level, xoffset, yoffset, format, type, canvas->copiedImage(BackBuffer), WebGLImageConversion::HtmlDomCanvas, m_unpackFlipY, m_unpackPremultiplyAlpha, exceptionState);
 }
 
 void WebGLRenderingContextBase::texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
     GLenum format, GLenum type, HTMLVideoElement* video, ExceptionState& exceptionState)
 {
     if (isContextLost() || !validateHTMLVideoElement("texSubImage2D", video, exceptionState)
         || !validateTexFunc("texSubImage2D", TexSubImage2D, SourceHTMLVideoElement, target, level, format, video->videoWidth(), video->videoHeight(), 0, format, type, xoffset, yoffset))
         return;
 
     RefPtr<Image> image = videoFrameToImage(video, ImageBuffer::fastCopyImageMode());
@@ skipping 1993 matching lines @@
     return m_sharedWebGraphicsContext3D ? m_sharedWebGraphicsContext3D->drawingBuffer() : 0;
 }
 #else
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 #endif
 
 } // namespace blink