Re: [compositing] 'isolation' and <img>

On Fri, Mar 8, 2013 at 3:02 PM, L. David Baron <dbaron@dbaron.org> wrote:

> https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#isolation
> currently says:
>
>   # In CSS, the ‘isolation’ property of an <img> or a background image
>   # must always be ‘isolate’. For instance, if you link to an SVG file
>   # through the ‘img’ tag, the content of that SVG will not blend with
>   # its backdrop.
>
> This is an incorrect description of what you're trying to describe,
> and implementing it would break existing content.
>
> For example:
>
>   <img style="background: rgba(0, 255, 0, 0.5)"
>        src="image-with-transparent-regions.png" />
>
> has the background-color of the img element (to which the
> 'isolation' property applies) blend with the backdrop of the image.
>
> Instead, you should say something about the isolation of the
> rendering of sub-documents


Correct. That's what I was trying to say.
Maybe the text should be:
 # In CSS, the content of an <img> or a background image
  # must always in an isolated group. For instance, if you link to an SVG
file
  # through the ‘img’ tag, the content of that SVG will not blend with
  # the backdrop of the img element.


> referenced through elements such as
> <img>, <object>, and <iframe>.
>

I haven't thought about <object> or <iframe>...


>
> However, I'm not even sure that they should always be isolated.


That's a good question.
When we incorporate PDF documents into applications like InDesign, that pdf
will always render in an isolated group.
The reason is that people consider placed artwork a separate piece of
content and they don't want it to interact with content outside of that
document. I was just applying the same logic.

I think it will be very confusing if that wouldn't be the case.