W3C home > Mailing lists > Public > public-i18n-archive@w3.org > January to March 2017

Re: [clreq] Position of ruby, text-emphasis, under/overline, etc in vertical-LR writing mode

From: r12a via GitHub <sysbot+gh@w3.org>
Date: Mon, 20 Mar 2017 19:04:33 +0000
To: public-i18n-archive@w3.org
Message-ID: <issue_comment.created-287864868-1490036672-sysbot+gh@w3.org>
Here's some additional background information about how these things are handled by default in the current CSS drafts.

The CSS spec makes a distinction in the Writing Modes spec between `before` and `over`, and between `after` and `under` (i prefer to use the synonyms `line-over`/`line-under` rather than `over`/`under` in this case, since it's less ambiguous) at https://drafts.csswg.org/css-writing-modes-3/#over.  Basically, `before` means to the left of the vertical line when using `vertical-lr`, and to the right when using `vertical-rl`; `line-over` means to the right in either case.

In other words, `line-over` and `line-under` are the opposite of `before` and `after` locations when text is in writing-mode `vertical-lr`, but the same when text is in writing-mode `vertical-rl`.

For CSS `text-emphasis-position` the default is `over right`. The term `over` is used slightly differently here, but the word `right` is the important one for vertical text. The table in that section sets the expectation that in vertical writing modes text-emphasis will appear to the right by default, even where Chinese favours text emphais appearing below the line for horizontal text. See https://drafts.csswg.org/css-text-decor-3/#text-emphasis-position-property

For CSS `text-underline-position` the word `under` has a slightly different meaning again (signifying a position that is unlikely to cut through descenders), and the default value (`auto`) doesn't seem to clearly address the expectation for vertical text defaults.  The example in that section for CJK text implies, however, that CSS expects that, by default, user agents will position underlines to the right for Japanese and Korean, but to the left for Chinese text.  There is no mention of Mongolian.  Overlines appear on the opposite side of the text from the underline. See https://drafts.csswg.org/css-text-decor-3/#text-underline-position-property

For CSS ruby-position in the current draft the default is `line-over` (in the sense defined for writing modes), ie. ruby appears to the right, whether the text is vertical-lr or vertical-rl. See https://drafts.csswg.org/css-ruby-1/#rubypos

(@fantasai @kojiishii please say if i got any of that wrong.)

GitHub Notification of comment by r12a
Please view or discuss this issue at https://github.com/w3c/clreq/issues/136#issuecomment-287864868 using your GitHub account
Received on Monday, 20 March 2017 19:04:40 UTC

This archive was generated by hypermail 2.4.0 : Monday, 4 July 2022 18:09:36 UTC