[whatwg] More random comments on the putImageData definition

Robert O'Callahan robert at ocallahan.org
Mon Feb 11 00:37:00 PST 2008

On Feb 11, 2008 2:57 PM, Oliver Hunt <oliver at apple.com> wrote:

> On Feb 10, 2008, at 5:44 PM, Robert O'Callahan wrote:
> On Feb 11, 2008 1:05 PM, Oliver Hunt <oliver at apple.com> wrote:
> >
> > i was thinking having a style property, say, canvas-dpi: auto|device or
> > something, where the default auto value automagically does the evil
> > downsampling the moment a data routine is used, and device would result in
> > the right thing.  That said neither of these are particularly nice. OTOH it
> > would allow those who use get/putImageData to implement a basic video buffer
> > (eg. the msx demo, etc) to continue to do so.
> >
> Wouldn't it be equivalent, yet simpler, to just define get/putImageData to
> do the evil 'auto' thing, and have additional methods to do the right
> 'device' thing?
> Not really -- a developer would need to do work to handle browsers that
> did not support the newer hidpi apis. The alternative (a css property or
> whatever) would allow a developer to use a single API, but tell the browser
> that they were aware that there may not be a 1:1 ratio between the requested
> region and the amount of data returned -- effectively it would be a flag to
> say "hey i actually do know the spec, and am not blindly expecting this to
> work on everyone else's computer just because it works on mine"

OK, but I wouldn't use a property, I'd use a content attribute, because you
want to be able to work with <canvas> elements that aren't in a document and
thus don't really have style.

"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
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