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Re: [Public WebGL] Ambiguity and Non-deterministicness in the WebGL Spec

On Dec 15, 2010, at 8:06 PM, Mark Callow wrote:

> On 16/12/2010 10:40, Chris Marrin wrote:
>> In the iOS implementation compositing is a system operation. When you give up control of a buffer you are giving it to a separate system process and so you lose control of that buffer. Because compositing is asynchronous, attempting to read its pixels would lead to inconsistent results. Sometimes you might see the correct values, other times that buffer might have been given to another process and its contents changed.
> So the browser implementation is not composing the page itself? Then
> doesn't the same problem arise for toDataURL on 2D canvases?

Not today. The Webkit implementation keeps the buffer in system memory and does software rendering. If, in the future, we move the rendering to hardware, we'd have to make a copy for compatibility. In the WebGL case we can design it to avoid this performance killer.


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