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

[Oliver Hunt]

On Apr 16, 2012, at 11:07 AM, Darin Fisher <darin at chromium.org> wrote:
> 
> See synchronous XMLHttpRequest.  I'm sure every browser vendor wishes that
> didn't exist.  Note how we recently withdrew support for synchronous
> ArrayBuffer access on XHR?  We did this precisely to discourage use of
> synchronous mode XHR. Doing so actually broke some existing web pages.  The
> pain was deemed worth it.

Yes, but the reason for this is very simple: synchronous IO can take a literally interminable amount of time, in which nothing else can happen.  We're talking about something entirely client side, that is theoretically going to be done sufficiently quickly to update a frame.

The IO case has a best case of hundreds of milliseconds, whereas that is likely to be close to the worst case on the graphics side.

--Oliver