[whatwg] A question about the drawimage() canvas function

[Rik Cabanier]

On Fri, Mar 1, 2013 at 7:01 PM, Kang-Hao (Kenny) Lu <kanghaol at oupeng.com>wrote:

> (13/03/02 5:59), Glenn Maynard wrote:
> > I recommend leaving Firefox alone and changing WebKit (and the spec) to
> > match Firefox, because we already have interop (at least in the cases I
> > tested) between Firefox and IE, and we already have interop during loads
> in
> > all three.  Changing WebKit to throw after loading will get everyone
> doing
> > the same thing--changing Firefox will still leave IE out.
> >
> > (I haven't tested with IE10, FWIW, only IE9.)
>
> IE10 behaves the same in your test case.
>
> (13/03/02 6:45), Rik Cabanier wrote:
> > Sorry about being unclear. Yes, I meant in addition of.
> > So:
> > - add your suggested step 1
> > - change HTMLImageElement from original step 2 to CanvasImageSource
>
> Did you mean to say "change *HTMLCanvasElement* from original step 2 to
> CanvasImageSource" here?


Yes


> The original step 2 has
>
>   # If the image argument is an HTMLCanvasElement object with either a
>   # horizontal dimension or a vertical dimension equal to zero, then
>   # the implementation throw an InvalidStateError exception and return
>   # aborted.
>
> (13/03/02 9:41), Glenn Maynard wrote:
> > But why does it throw this exception in the first place?  It's a weird
> > special case.  Blitting a zero-size image should do nothing, just like
> > drawImage(src, 0, 0, 0, 0).
>
> Just curious. Does it have to be SVG for an image to be zero-sized?


I think a canvas element can have 0x0 size too