Re: [fxtf-drafts] [filter-effects-2] User feedback: backdrop-filter is way less useful because it requires children to not escape the "backdrop rectangle" (#408)

> As I understand it, @ell1e refers to this sentence in the ["Filtering and Clipping" section](https://drafts.fxtf.org/filter-effects-2/#backdrop-filter-operation):
> 
> > A computed value of other than none results in the creation of both a stacking context [CSS21] and a Containing Block for absolute and fixed position descendants, unless the element it applies to is a document root element in the current browsing context.
> 
> So in https://jsfiddle.net/SebastianZ/jp5ts2mv/ the "Headline" text is positioned differently when `backdrop-filter` is applied. If it is defined, `<section>` becomes a containing block and the `<h1>` is positioned relatively to it, without it, the `<h1>` is positioned absolutely.
> 
> To authors this is an unexpected and undesired behavior. And it's unclear why this behavior is copied over from the `filter` property. For the `filter` property it might still be clear because it applies the filters to the element itself, though `backdrop-filter` filters what's behind the element, so this shouldn't have an effect on the layout of the element's children.

Ahh, I see, the question is about the forced containing block. That is there for the same reasons as for `filter`, and it is more fundamental than just implementation convenience. @chrishtr can probably explain more succinctly than I can.

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Received on Monday, 22 March 2021 16:13:27 UTC