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[compositing] 'isolation' and <img>

From: L. David Baron <dbaron@dbaron.org>
Date: Fri, 8 Mar 2013 15:02:19 -0800
To: public-fx@w3.org
Message-ID: <20130308230219.GA19340@crum.dbaron.org>
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 referenced through elements such as
<img>, <object>, and <iframe>.

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

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Friday, 8 March 2013 23:02:46 GMT

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