WebGL 2: add readPixels API to read pixels into pixel pack buffer

Source/modules/webgl/WebGL2RenderingContextBase.cpp

 // Copyright 2015 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 "config.h"
 #include "modules/webgl/WebGL2RenderingContextBase.h"
 
 #include "bindings/modules/v8/WebGLAny.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLImageElement.h"
@@ skipping 226 matching lines @@
     } else {
         if (mode == GL_BACK) {
             synthesizeGLError(GL_INVALID_OPERATION, "readBuffer", "invalid read buffer");
             return;
         }
         readFramebufferBinding->readBuffer(mode);
     }
     webContext()->readBuffer(mode);
 }
 
+void WebGL2RenderingContextBase::readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, DOMArrayBufferView* pixels)
+{
+    if (isContextLost())
+        return;
+    if (m_boundPixelPackBuffer.get()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "PIXEL_PACK buffer should not be bound");
+        return;
+    }
+
+    WebGLRenderingContextBase::readPixels(x, y, width, height, format, type, pixels);
+}
+
+void WebGL2RenderingContextBase::readPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, long long offset)
+{
+    if (isContextLost())
+        return;
+
+    // Due to WebGL's same-origin restrictions, it is not possible to
+    // taint the origin using the WebGL API.
+    ASSERT(canvas()->originClean());
+
+    if (!validateValueFitNonNegInt32("readPixels", "offset", offset))
+        return;
+
+    WebGLBuffer* buffer = m_boundPixelPackBuffer.get();
+    if (!buffer) {
+        synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "no PIXEL_PACK buffer bound");
+        return;
+    }
+
+    // Need to validate whether the pixel pack buffer is mapped,
+    // if we decide to expose mapBufferRange() to web developers.
+
+    long long size = buffer->getSize() - offset;
+
+    // If size is negative, or size is not large enough to store pixels, those cases
+    // are handled by validateReadPixelsFuncParameters to generate INVALID_OPERATION.
+    if (!validateReadPixelsFuncParameters(width, height, format, type, size))
+        return;
+
+    clearIfComposited();
+
+    WebGLFramebuffer* readFramebufferBinding = getFramebufferBinding(GL_READ_FRAMEBUFFER);
+    {
+        ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
+        webContext()->readPixels(x, y, width, height, format, type, reinterpret_cast<void*>(offset));
+    }
+}
+
 void WebGL2RenderingContextBase::renderbufferStorageImpl(
     GLenum target, GLsizei samples, GLenum internalformat, GLsizei width, GLsizei height,
     const char* functionName)
 {
     switch (internalformat) {
     case GL_R8UI:
     case GL_R8I:
     case GL_R16UI:
     case GL_R16I:
     case GL_R32UI:
@@ skipping 2220 matching lines @@
 GLenum WebGL2RenderingContextBase::boundFramebufferColorFormat()
 {
     if (m_readFramebufferBinding && m_readFramebufferBinding->object())
         return m_readFramebufferBinding->colorBufferFormat();
     if (m_requestedAttributes.alpha())
         return GL_RGBA;
     return GL_RGB;
 }
 
 } // namespace blink