[whatwg] [canvas] request for {create, get, put}ImageDataHD and ctx.backingStorePixelRatio

Boris Zbarsky bzbarsky at MIT.EDU
Tue Mar 20 18:08:21 PDT 2012

On 3/20/12 7:04 PM, Glenn Maynard wrote:
> If you have previous drawing commands buffered, and you want to avoid extra
> copies, then putImageData has to block until the buffered drawing commands
> complete.

Yes, but if you're drawing to a GPU directly you want to make the copy 
up front, imo; otherwise you have to wait for the full GPU latency 
before you can return even if there are no other drawing commands in the 
pipeline, which is painful....

> The question is whether you'd need to make a copy *synchronously*, before
> putImageData returns.

If you want to do the image data put async in any way (and that includes 
any sort of direct-to-GPU setup, I'm told) then you need either sync 
copy or copy-on-write as far as I can tell.


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