WebGL 2: validate read buffer attachment when reading from FBO

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 1525 matching lines @@
 
 bool WebGLRenderingContextBase::validateSettableTexFormat(const char* functionName, GLenum format)
 {
     if (WebGLImageConversion::getChannelBitsByFormat(format) & WebGLImageConversion::ChannelDepthStencil) {
         synthesizeGLError(GL_INVALID_OPERATION, functionName, "format can not be set, only rendered to");
         return false;
     }
     return true;
 }
 
+bool WebGLRenderingContextBase::validateReadBufferAttachment(const char* functionName, const WebGLFramebuffer* readFramebufferBinding)
+{
+    if (readFramebufferBinding) {
+        GLenum readBuffer = readFramebufferBinding->getReadBuffer();
+        WebGLSharedObject* attachmentObject = readFramebufferBinding->getAttachmentObject(readBuffer);
+        if (!attachmentObject) {
+            synthesizeGLError(GL_INVALID_OPERATION, functionName, "no image attached to read buffer");
+            return false;
+        }
+    }
+    return true;

[Zhenyao Mo, 2015/07/06 17:52:25]

Shouldn't you also check here that the back buffer's readbuffer is not NONE? in
which case, you should define m_readbuffer in this base class, and its value
will just stay GL_BACK in WebGL 1.

[Ken Russell (switch to Gerrit), 2015/07/06 21:19:13]

Agree with Mo's observation, though if the underlying GL implementation will
catch this (since the call to glReadBuffer(GL_NONE) will go through to the
driver), it's OK to not explicitly check it here.

I generally agree with Mo's observation to move m_readBuffer to the base class
and initialize it to GL_BACK. Also, I think should be renamed to something like
m_defaultFramebufferReadBuffer.

[yunchao, 2015/07/07 08:10:39]

Done.

+}
+
 void WebGLRenderingContextBase::copyTexImage2D(GLenum target, GLint level, GLenum internalformat, GLint x, GLint y, GLsizei width, GLsizei height, GLint border)
 {
     if (isContextLost())
         return;
     if (!validateTexFuncParameters("copyTexImage2D", NotTexSubImage2D, target, level, internalformat, width, height, border, internalformat, GL_UNSIGNED_BYTE))
         return;
     if (!validateSettableTexFormat("copyTexImage2D", internalformat))
         return;
     WebGLTexture* tex = validateTextureBinding("copyTexImage2D", target, true);
     if (!tex)
@@ skipping 10 matching lines @@
         synthesizeGLError(GL_INVALID_VALUE, "copyTexImage2D", "level > 0 not power of 2");
         return;
     }
     const char* reason = "framebuffer incomplete";
     GLenum framebufferTarget = isWebGL2OrHigher() ? GL_READ_FRAMEBUFFER : GL_FRAMEBUFFER;
     WebGLFramebuffer* readFramebufferBinding = getFramebufferBinding(framebufferTarget);
     if (readFramebufferBinding && !readFramebufferBinding->onAccess(webContext(), &reason)) {
         synthesizeGLError(GL_INVALID_FRAMEBUFFER_OPERATION, "copyTexImage2D", reason);
         return;
     }
+    if (!validateReadBufferAttachment("copyTexImage2D", readFramebufferBinding))
+        return;
     clearIfComposited();
     ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
     webContext()->copyTexImage2D(target, level, internalformat, x, y, width, height, border);
     // FIXME: if the framebuffer is not complete, none of the below should be executed.
     tex->setLevelInfo(target, level, internalformat, width, height, 1, GL_UNSIGNED_BYTE);
 }
 
 void WebGLRenderingContextBase::copyTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height)
 {
     if (isContextLost())
@@ skipping 25 matching lines @@
         synthesizeGLError(GL_INVALID_OPERATION, "copyTexSubImage2D", "framebuffer is incompatible format");
         return;
     }
     const char* reason = "framebuffer incomplete";
     GLenum framebufferTarget = isWebGL2OrHigher() ? GL_READ_FRAMEBUFFER : GL_FRAMEBUFFER;
     WebGLFramebuffer* readFramebufferBinding = getFramebufferBinding(framebufferTarget);
     if (readFramebufferBinding && !readFramebufferBinding->onAccess(webContext(), &reason)) {
         synthesizeGLError(GL_INVALID_FRAMEBUFFER_OPERATION, "copyTexSubImage2D", reason);
         return;
     }
+    if (!validateReadBufferAttachment("copyTexSubImage2D", readFramebufferBinding))
+        return;
     clearIfComposited();
     ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
     webContext()->copyTexSubImage2D(target, level, xoffset, yoffset, x, y, width, height);
 }
 
 PassRefPtrWillBeRawPtr<WebGLBuffer> WebGLRenderingContextBase::createBuffer()
 {
     if (isContextLost())
         return nullptr;
     RefPtrWillBeRawPtr<WebGLBuffer> o = WebGLBuffer::create(this);
@@ skipping 1721 matching lines @@
     GLenum error = WebGLImageConversion::computeImageSizeInBytes(format, type, width, height, m_packAlignment, &totalBytesRequired, &padding);
     if (error != GL_NO_ERROR) {
         synthesizeGLError(error, "readPixels", "invalid dimensions");
         return;
     }
     if (pixels->byteLength() < totalBytesRequired) {
         synthesizeGLError(GL_INVALID_OPERATION, "readPixels", "ArrayBufferView not large enough for dimensions");
         return;
     }
 
+    if (!validateReadBufferAttachment("readPixels", readFramebufferBinding))
+        return;
+
     clearIfComposited();
     void* data = pixels->baseAddress();
 
     {
         ScopedDrawingBufferBinder binder(drawingBuffer(), readFramebufferBinding);
         webContext()->readPixels(x, y, width, height, format, type, data);
     }
 
 #if OS(MACOSX)
     // FIXME: remove this section when GL driver bug on Mac is fixed, i.e.,
@@ skipping 2860 matching lines @@
 
     return totalBytesPerPixel;
 }
 
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 
 } // namespace blink