Fix transform feedback bugs

third_party/WebKit/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 "modules/webgl/WebGL2RenderingContextBase.h"
 
 #include "bindings/modules/v8/WebGLAny.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLImageElement.h"
@@ skipping 1988 matching lines @@
 {
     if (isContextLost())
         return nullptr;
     WebGLTransformFeedback* o = WebGLTransformFeedback::create(this);
     addSharedObject(o);
     return o;
 }
 
 void WebGL2RenderingContextBase::deleteTransformFeedback(WebGLTransformFeedback* feedback)
 {
+    if (transformFeedbackActive()) {
+        synthesizeGLError(GL_INVALID_OPERATION, "deleteTransformFeedback", "transform feedback is active");
+        return;
+    }
     if (feedback == m_transformFeedbackBinding)
         m_transformFeedbackBinding = nullptr;
 
     deleteObject(feedback);
 }
 
 GLboolean WebGL2RenderingContextBase::isTransformFeedback(WebGLTransformFeedback* feedback)
 {
     if (isContextLost() || !feedback)
         return 0;
@@ skipping 200 matching lines @@
     if (!validateAndUpdateBufferBindBaseTarget("bindBufferBase", target, index, buffer))
         return;
 
     // ES 3.0.4 spec section 2.15.2 "Transform Feedback Primitive Capture"
     if (target == GL_TRANSFORM_FEEDBACK_BUFFER && transformFeedbackActive()) {
         synthesizeGLError(GL_INVALID_OPERATION, "bindBufferBase", "target is TRANSFORM_FEEDBACK_BUFFER and transform feedback is active");
         return;
     }
 
     webContext()->bindBufferBase(target, index, objectOrZero(buffer));
+    webContext()->bindBuffer(target, objectOrZero(buffer));

[Zhenyao Mo, 2016/03/01 22:33:01]

I am not sure this is the right fix.

I don't think we need to explicitly call bindBuffer(), because bindBufferBase()
should take care of that.  So it's either a driver bug (I doubt it), or there
are some place in Chrome we fail to change the cached bound buffer. That is the
bug we need to fix.

[qiankun, 2016/03/01 23:52:06]

The driver really call bindBuffer() when do bindBuferBase(). But Chrome didn't
change the cached bound buffer, so bindBuffer() may be not called to driver. See
commit log in https://github.com/KhronosGroup/WebGL/pull/1513. 

bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer); // buffer_in_driver = buffer
buffer_chaced_by_chrome = buffer
bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, null);// buffer_in_driver = null
buffer_chaced_by_chrome = buffer
bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer); // buffer_in_driver = null
buffer_chaced_by_chrome = buffer;  Between two calls of
"bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, buffer);"
bound_transform_feedback_buffer_ doesn't change, so
GLES2Implementation::BindBufferHelper doesn't issue bindBuffer to
command buffer server side. 

 }
 
 void WebGL2RenderingContextBase::bindBufferRange(GLenum target, GLuint index, WebGLBuffer* buffer, long long offset, long long size)
 {
     if (isContextLost())
         return;
     bool deleted;
     if (!checkObjectToBeBound("bindBufferRange", buffer, deleted))
         return;
     if (deleted)
@@ skipping 1194 matching lines @@
     params.alignment = m_unpackAlignment;
     params.rowLength = m_unpackRowLength;
     params.imageHeight = m_unpackImageHeight;
     params.skipPixels = m_unpackSkipPixels;
     params.skipRows = m_unpackSkipRows;
     params.skipImages = m_unpackSkipImages;
     return params;
 }
 
 } // namespace blink