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Re: [fxtf-drafts] [filters] Backdrop filters should not use BackgroundImage

From: Dirk Schulze via GitHub <sysbot+gh@w3.org>
Date: Tue, 24 Apr 2018 05:00:29 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issue_comment.created-383803699-1524546028-sysbot+gh@w3.org>
@AmeliaBR @mstange From looking at the example, nothing escapes isolation as far as I can see.

1. Backdrop filter takes the entire content of the backdrop. 
2. Everything drawn up to the backdrop filter respects the `isolation` property.
3. The white circle is drawn on top of the element that is drawn with the backdrop filter (and the actual backdrop)
4. Difference filter is still isolated to the common group of the element with the backdrop filter and the white circle with difference.

I understand that it sounds strange but isolation rules are still met for blending. The one is independent of the other.

As @grorg says, we need a new term to describe this behavior.
* `BackgroundImage` and `BackgroundAlpha` stop at isolation. Nothing before the isolation gets used.
* `Backdrop` wouldn't stop at isolation but the rest of the drawing (`filter`, `mix-blend-mode`) would still respect isolation.

It would be interesting to see if Safari runs into issues where it normally would create a compositing layer. So if the group would have an animation of the `transform` property for instance. Or a 3D transform gets applied. This usually complicates things for implementations. I would be impressed if both still work. If not, we probably need separate definitions of `isolation`.

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Received on Tuesday, 24 April 2018 05:01:17 UTC

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