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[csswg-drafts] [css-writing-modes][css-values] Font metrics calculation on elements which writing-mode doesn't apply to

From: Xidorn Quan via GitHub <sysbot+gh@w3.org>
Date: Thu, 07 Sep 2017 04:17:11 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-255810102-1504757821-sysbot+gh@w3.org>
upsuper has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-writing-modes][css-values] Font metrics calculation on elements which writing-mode doesn't apply to ==
I realized that this could be an issue when I was thinking about #1773.

There are some elements that [`writing-mode`](https://drafts.csswg.org/css-writing-modes-3/#block-flow) doesn't applied to, specifically, table row groups, table column groups, table rows, table columns, ruby base container, and ruby annotation container, per css-writing-modes spec. However, there are some [font-relative units](https://drafts.csswg.org/css-values-3/#font-relative-lengths) defined in css-values which depend on `writing-mode` property.

The question is, for an element which `writing-mode` doesn't apply to, should the font-relative units be computed based on the value of the computed (but not applied) `writing-mode`, or the used `writing-mode` (from some ancestor)? I guess the same question applies to [logical properties](https://drafts.csswg.org/css-logical/) as well.

The description of "Applies to" in CSS 2.1 says
> All elements are considered to have all properties, but some properties have no rendering effect on some types of elements.

I guess it indicates that the computed value should be probably be used? It also seems to me that it could be hard to have style computation based on used value, because that would create more complicated dependencies.

Probably the spec should mention that, although `writing-mode` doesn't apply to these elements, the style computation is still done based on the computed value of `writing-mode` of the same element.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/1782 using your GitHub account
Received on Thursday, 7 September 2017 04:17:06 UTC

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