Emphasis Dots (text-emphasis) and Fonts

[bobbytung]

Hello JLREQ folks!

There is a quite old issue confusing me for years.

傍点 (emphasis dots) in Japanese is also 着重号 in Simplified Chinese. It's not used in Taiwan, but more and more translated novels from Japanese used this way for emphasis.

This requirement is fulfilled by CSS properties "text-emphasis" and supported by browser with vertical writing many years ago.

But the implement depends on font design. Only a few Japanese fonts can display as intended. With other fonts, line-height will be expanded to break layout.

Here's a sample: Oe Kenzaburo's novel in TC. line-height set to 1.7, and obviously expanded by emphasis dots.

I've found that Apple's system font, such as Hiragino Mincho, Yu Mincho...the glyphs used by text-emphasis are designed with narrow width as this:

But most all the other TC / SC / JP fonts are using width 1000 as default. That will cause line-height broadened.

I've filed an issue on Webkit rader several years ago. But nothing changed.

I'd like to hear your opinion and figure out how to solve this old problem.

[xfq]

There are at least two potential solutions:

The first is to create a comprehensive font guideline and collaborate with font vendors to ensure adherence. While this could standardize practices, challenges may persist with legacy fonts and niche fonts.

The second solution is to introduce a new CSS mechanism to force the browser to choose a font that display emphasis mark correctly (and do not widen the line spacing). We already have this text in CSS Text Decoration:

the UA may opt to use a font known to be good for emphasis marks, or the marks may instead be synthesized by the UA.

But it may not be enough, because it is only a MAY and there is no way for authors to force it.

[xfq]

cc @frivoal

[r12a]

I have been in discussions about this one more than one occasion before with the JLReq folks, and though i was unable to find a mention of it in JLReq when i looked just now, my recollection is that their answer was: if a text will contain emphasis marks or ruby, it is the author's responsibility when designing the kihon hanmen to set the line spacing for the whole page so that it supports a large enough inter-line gap to fit in the emphasis marks and/or ruby without increasing the line height. This avoids situations where one line has more line height that the others. Perhaps this approach solves the problem described, whether the emphasis marks are provided by the font or synthesized by the browser.

[xfq]

I think the problem now is that the line spacing is sufficient, but the distance between the emphasis mark and the Han characters is too far, so just ensuring the inter-line gap is not enough.

[r12a]

I think, as mentioned in today's telecon, that a good first step would be to fix the test page so that we have a reliable base to work from.

Also note that the quotation from the CSS Text Decoration spec only shows 2 out of 3 possibilities — the first of those has a SHOULD, and the two following MAYs are possible fallbacks.