[csswg-drafts] [css-fonts] Clarify font-optical-sizing behaviour under size-adjust (#6190)

drott has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-fonts] Clarify font-optical-sizing behaviour under size-adjust ==
In 
https://github.com/web-platform-tests/wpt/pull/28399
I made a ref-test ensuring that `font-optical-sizing: auto` behaves according to the adjusted / resulting font-size under `size-adjust`, pending review. 

Since the wording for `size-adjust` says:

> However, the computed font-size (and thus any values that derive from it, such as em units, percentages in text-underline-offset, etc.) remains unaffected.

And `font-optical-sizing: auto` says: 

> The user agent may modify the shape of glyphs based on the font-size and the pixel density of the screen. For OpenType and TrueType fonts using font variations, this is often done by using the "opsz" font variation.

we may want to  clarify that the applied optical sizing value should be based on the resulting/adjusted/displayed font-size, not on the computed font size, in order to avoid confusion?

I believe the behaviour as tested in the new test makes sense as the glyph size is changed by size-adjust, and the scaled glyphs should then be rendered with the scaled/new optical size value. Or in other words, the glyph is displayed larger/smaller, and so should its optical sizing value be adjusted accordingly.




Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6190 using your GitHub account


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Received on Wednesday, 7 April 2021 14:43:22 UTC