[css-writing-modes-4] text-combine-upright should allow the author to specify that characters are not scaled to fit within 1 em

[palemieux]

text-combine-upright: all attempts to typeset horizontally all consecutive typographic character units within the box such that they take up the space of a single typographic character unit within the vertical line box.

As indicated at w3c/tt-module-cjk-ext-1#1, there are use cases, notably in subtitle applications, where it is desirable for an author to specify that the consecutive upright characters are not scaled to fit within the space of a single typographic character unit within the vertical line box.

See also https://www.w3.org/2019/09/15-css-irc#T00-57-05

[palemieux]

Questions raised during the 20190917 CSS plenary:

• Is text-emphasis allowed on upright characters? If so, what is the expected behavior?
• Is underline allowed on upright characters? If so, what is the expected behavior?
• What is the expected behavior when ruby text is used in combination with upright characters?
• What is the expected behavior when background is applied to upright characters?

[kojiishi]

Is text-emphasis allowed on upright characters?
Is underline allowed on upright characters?

Yes.

If so, what is the expected behavior?
What is the expected behavior when ruby text is used in combination with upright characters?
What is the expected behavior when background is applied to upright characters?

The same as they are applied to upright ideographic characters.

[akiseino]

As we have been servicing subtitling for a long time of Digital Cinema and Internet Distribution, here are comments from our post production experience.
First, those four are not used a lot in normal subtitling (vertical writing tate-chu-yoko) but a few cases will happen from our client special requests.

Is text-emphasis allowed on upright characters? If so, what is the expected behavior?

Yes for Digital Cinema. No for Internet Distribution.
And behavior is applied to upright ideographic characters as kojiishii mentioned.

Is underline allowed on upright characters? If so, what is the expected behavior?

No for both. We may have possibility in horizontal writing, though.

What is the expected behavior when ruby text is used in combination with upright characters?

Yes for both. Same behavior as text-emphasis.

What is the expected behavior when background is applied to upright characters?

Yes for Internet Distribution. No for Digital Cinema.
Same behavior as text-emphasis, but it should behavior as boundary box (one rectangle) not individual character to prevent zigzag shape by rectangles of each characters.

Thank you.

[cconcolato]

Is text-emphasis allowed on upright characters? If so, what is the expected behavior?

According to my Japanese linguists, if allowed, the emphasis should apply to the block of upright characters as if it was a single vertical character.

Is underline allowed on upright characters? If so, what is the expected behavior?

It should behave as the same as any other single character.

What is the expected behavior when ruby text is used in combination with upright characters?

It should behave as the same as any other single character.