Re: [csswg-drafts] [css-fonts-5] font-size-adjust: ic-height (#8792)

> What do Blink and WebKit use as the vertical advance of "水" if they're rendering `writing-mode: vertical-rl` content but the font being used has no vertical-layout metrics? I think I'd expect `ic-height` to match whatever fallback is used there.

Blink and WebKit use the font height (i.e., Ascent + Descent) as the fallback.

I do not object to having the font height as the fallback for `ic-height` as long as the spec document clarifies it. But I want to note two concerns here.

1. As we can see from the numbers above, a non-negligible difference exists between the actual advance height of “水” and the `ascent + descent` values.
2. In `writing-mode: vertical-rl`, the `ascent + descent` may not represent the CJK font height. While `ic-height` is absolute regardless of the text orientation, the font height (i.e., ascent + descent) is not. Please refer to case [B] at https://github.com/w3c/csswg-drafts/issues/9599. In [B], the `ascent + descent` represents a horizontal measure rather than a vertical one, so it could make users confused in deciding the scaling level by `font-size-adjust`.

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Received on Thursday, 4 January 2024 20:11:54 UTC