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[css-fonts-4] font kerning in vertical text #5295
Description
6.3. Kerning: the font-kerning property
https://drafts.csswg.org/css-fonts-4/#font-kerning-prop
When kerning is enabled, the OpenType kern feature is enabled (for vertical text runs the vkrn feature is enabled instead).
I'm guessing that the vkrn feature is only applied to upright characters in a line of vertically-set text, whereas Latin text (say) that runs down the line on its side is not affected. Is this taken care of by the font only having vkrn settings for upright characters in vertical lines, or do we have an issue here?
Activity
svgeesus commentedon Jul 8, 2020
On reflection this text (which was also in CSS Fonts 3) is too brief:
how about
followed by three examples - one of horizontally set text, one of vertically set text with all characters upright, and one of vertically set text with some characters rotated. I'm imagining color-coded backgrounds behind each glyph, for
kernandvkern. That would also show (which should be obvious, but still) that a change between upright and rotated breaks kerning.fantasai commentedon Jul 8, 2020
You probably want to hook into https://www.w3.org/TR/css-writing-modes-4/#vertical-font-features
So
And then I should be sure to export those terms from Writing Modes. :)
[css-writing-modes] Export orientation terms. #5295
fantasai commentedon Jul 8, 2020
OK, exported. @svgeesus You might want to edit-in-place the resulting markup into the /TR versions of these specs? Then the cross-refs will work when you publish css-fonts-4 to /TR as well.
clarify kern vkrn #5295
svgeesus commentedon Jul 9, 2020
@fantasai I was going to suggest republishing Writing Modes 4, as it has been a year, but apparently there is only one change since then?
svgeesus commentedon Jul 9, 2020
@r12a you can see the altered text now; could you confirm whether this solves the issue or whether more changes are needed.
svgeesus commentedon Jul 9, 2020
@fantasai I am now confused; upright typesetting and sideways typesetting and typographic mode all work in the 2019 CR. In terms of generated markup, what did 6c54cd3 add?
r12a commentedon Jul 9, 2020
Better, yes, thanks. However, it occurred to me while reading that tate-chu-yoko text is also upright in vertical lines, but should used kern rather than vkrn. Do you think we need to clarify that?
svgeesus commentedon Jul 9, 2020
Definitely, and that needs another example. What spec should we link to, to explain that one?
By the way this example is not rendering correctly for me in Firefox or Chrome on Windows 10. Have not tried Safari yet. The test results led me to expect this would work.
litherum commentedon Jul 9, 2020
I wish the spec could have affordances for TrueType in addition to OpenType. Specifically calling out
kernandvkrnis probably fine, but there are other font technologies which are relevant too.svgeesus commentedon Jul 9, 2020
It does mention TrueType
kerntables in addition to the OpenTypekernandvkrnfeaturessvgeesus commentedon Nov 17, 2020
Ah, its that the changes is not up to date. The History shows 25 commits
svgeesus commentedon Nov 17, 2020
@r12a I'd like to work with you to get good examples of kerning (and non-kerning) in both horizontal, vertical, and horizontal-in-vertical text. One problem is that ideographic text typically doesn't use kerning.
https://www.w3.org/International/articles/vertical-text/ doesn't have examples of kerning in vertical contexts. Do you have examples from other articles, or do new examples need to be created and verified?
r12a commentedon Nov 30, 2020
@svgeesus do you have Ken Lunde's book CJKV Information Processing. You may find pp. 360 – 365 useful?
svgeesus commentedon Nov 30, 2020
Yes, but in Boston :(
myakura commentedon Dec 1, 2020
#5295 (comment)
The
digitsvalue is only implemented in Trident (under the name-ms-text-combine-horizontal). The one works across browsers istext-combine-upright: all.