WebGL 2: add types into glReadPixels

Source/modules/webgl/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 3720 matching lines @@
         return;
 
     DOMArrayBufferView::ViewType expectedViewType;
     switch (type) {
     case GL_UNSIGNED_BYTE:
         expectedViewType = DOMArrayBufferView::TypeUint8;
         break;
     case GL_BYTE:
         expectedViewType = DOMArrayBufferView::TypeInt8;
         break;
+    case GL_UNSIGNED_SHORT:

[Zhenyao Mo, 2015/08/13 15:22:01]

This is incorrect.  For OpenGL ES 2 / WebGL 1, it is clearly defined in Table
3.2 (page 62) what types are allowed.

[yunchao, 2015/08/14 00:07:11]

Yeah. I know that WebGL 1.0 should not support UNSIGNED_SHORT / SHORT. But for
these two types (and UNSIGNED_INT, UNSIGNED_INT_*, INT), the validation function
(validateReadPixelsFormatAndType) will report INVLID_ENUM and return. So the
code snippet is not wrong. 

Well, we  can override this code snippet respectively for WebGL 1 and WebGL 2 to
get 'expectedViewType', which should be more clearer. WDYT? 

     case GL_UNSIGNED_SHORT_5_6_5:
     case GL_UNSIGNED_SHORT_4_4_4_4:
     case GL_UNSIGNED_SHORT_5_5_5_1:
         expectedViewType = DOMArrayBufferView::TypeUint16;
         break;
+    case GL_SHORT:
+        expectedViewType = DOMArrayBufferView::TypeInt16;
+        break;
     case GL_FLOAT:
         expectedViewType = DOMArrayBufferView::TypeFloat32;
         break;
     case GL_HALF_FLOAT:
     case GL_HALF_FLOAT_OES:
         expectedViewType = DOMArrayBufferView::TypeUint16;
         break;
     case GL_UNSIGNED_INT:
     case GL_UNSIGNED_INT_2_10_10_10_REV:
     case GL_UNSIGNED_INT_10F_11F_11F_REV:
@@ skipping 2885 matching lines @@
 
     return totalBytesPerPixel;
 }
 
 DrawingBuffer* WebGLRenderingContextBase::drawingBuffer() const
 {
     return m_drawingBuffer.get();
 }
 
 } // namespace blink