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Re: [fxtf-drafts] Clip backdrop root (input) image to border box of element (#342)

From: Markus Stange via GitHub <sysbot+gh@w3.org>
Date: Tue, 11 Jun 2019 17:26:59 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issue_comment.created-500943785-1560274017-sysbot+gh@w3.org>
This seems reasonable, but I think it needs clarification for what to do if the element with the backdrop-filter is transformed. The filter is applied "outside" the transform; but "outside" the transform, the element's border box is not necessarily an axis-aligned rectangle, and it's unclear how to apply a filter to such a shape. Is the clip applied to the axis-aligned bounding box of the shape? Or is the clip applied to the accurate shape, and then the filter is applied to the bounding box of the shape which now contains transparent parts?

Should we also say something about the edge mode of the `blur()` filter? [filter-effects-1](https://drafts.fxtf.org/filter-effects-1/#blurEquivalent) says that the edgeMode used for `blur()` filter depends on where it's used: If used in the `filter` property, the `edgeMode` is `none`, which means it will blur in transparency from the outside. So we could add a sentence that says that, when used in the `backdrop-filter` property, the `blur()` filter uses `edgeMode="duplicate"`, because otherwise the edges would become transparent even with the extra clipping.

(Also, can you add the link for [1] to your comment on this issue?)

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Received on Tuesday, 11 June 2019 17:27:00 UTC

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