[whatwg] drawImage with non-existent images

Ian Hickson ian at hixie.ch
Thu Jun 12 15:24:09 PDT 2008

On Sun, 17 Feb 2008, Jeff Walden wrote:
> <http://www.whatwg.org/specs/web-apps/current-work/multipage/section-the-canvas.html#drawimage>:
> > If the image argument is an HTMLImageElement object whose complete 
> > attribute is false, then the implementation must raise an 
> > INVALID_STATE_ERR exception.
> This is all well and good in the case where the image being drawn has 
> the same origin as the document where the canvas resides, but if the two 
> have different origins, this makes it possible to determine the 
> existence of an image on a foreign server.  This exception must only be 
> thrown if the image element's origin is the same as that of the document 
> containing the canvas being modified.
> (You can already determine image existence by seeing how an image 
> affects page layout, but this still seems like a reasonable behavior 
> anyway.)

There's all kinds of ways to determine if a remote resource is present or 
not -- onload/onerror on <img> or <iframe>, importing a script from that 
host, layout effects of an image, layout effects of a style sheet...

I think that ship has sailed.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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