Re: [csswg-drafts] [css-fonts-4] `font-variant-emoji` lacks fallback algorithm or outcome definition (#9291)

> > "However, a variation selector must be included in a previous cluster as defined by the [cluster matching](https://www.w3.org/TR/css-fonts-4/#cluster-matching) section above"
> 
> I fail to understand what that means - any pointers?

Looking closer at UAX 29 I think what this means is that a variation selector extends a grapheme cluster and does not cause a cluster break, because `extended grapheme cluster =   [...] precore* core postcore*`... and `postcore` is a production for `[Extend ZWJ SpacingMark]` and `Extend` here are all codepoints which have the character property `Grapheme_Extend=yes`. So those sequences are covered.



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Received on Tuesday, 5 September 2023 09:06:10 UTC