[whatwg] Origin of a data: URL for an img

Gavin Kistner gkistner at nvidia.com
Wed Nov 16 14:42:32 PST 2011

From: Ian Hickson [mailto:ian at hixie.ch] 
> On Wed, 16 Nov 2011, Gavin Kistner wrote:
> > Section 6.3 "Origin" of the HTML Living Standard has this text (excerpted):
> > 
> > > For images:
> > >
> > > If an image was generated from a data: URL found in another Document 
> > > or in a script The origin is the origin of the Document or script that loaded that image.
> > >
> > > If an image was obtained in some other manner (e.g. a data: URL 
> > > typed in by the user) The origin is a globally unique identifier assigned when the image is created.
> > 
> > I'm going to refer to the first case above as the "found specs" and 
> > the second case as the "other specs". (Aside: it would be convenient 
> > for discussion if items in this section would have unique identifying 
> > numbers.)
> > 
> > What does "found" mean?
> > What is the difference between these two cases?
> > When do we switch from one case to the other?
> > Does a JavaScript String object carry an origin along with it, but any 
> > mutation (and all new strings) switch to "other specs"?
> In all three cases here, the image was generated from a URL found in the src="" content attribute of the <img> element created by the script. The image data is CORS-same-origin, and so the entry that applies in the origin section is:
>  If an image is the image of an img element and its image data is  CORS-same-origin
>  The origin is the origin of the img element's Document.

OK, that does help, though mostly to illustrate that all of my guesses were all wrong. :) 

Can you provide an example in script of when the "found specs" would apply, and when the "other specs" would apply?
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