[css-ruby] Size and position of empty ruby level containers

[upsuper]

The spec currently says:

Each ruby base container is sized and positioned to contain exactly all of its ruby bases’ margin boxes.

and

Each ruby annotation container is sized and positioned to contain exactly all of its ruby annotations’ margin boxes.

However, it is unclear what should happen when a ruby level container doesn't have any child.

I suggest that for empty ruby base container, it should probably behave as if there is an empty ruby base inside, so that it would laid out like a normal empty inline element.

I'm not sure what would be a useful behavior for ruby annotation container. I kinda tend to think that it should keep being zero size in that case, but we may need to define its position somehow as well?

This issue is raised because of a bug report to Gecko after I changed the behavior to match the spec.

[fantasai]

I suggest that for empty ruby base container, it should probably behave as if there is an empty ruby base inside, so that it would laid out like a normal empty inline element.

I agree with this 100%. Ruby shouldn't lay out differently on an empty base vs. a zero-width glyph.

I'm not sure what would be a useful behavior for ruby annotation container. I kinda tend to think that it should keep being zero size in that case, but we may need to define its position somehow as well?

I think we might want to go with the same principle, lay out as if it contained a zero-width glyph. Otherwise stacking levels could get confused.

[css-meeting-bot]

The CSS Working Group just discussed [css-ruby] Size and position of empty ruby level containers, and agreed to the following:

• RESOLVED: Empty ruby containers are sized as if they have empty things in them

The full IRC log of that discussion

<dael> Topic: [css-ruby] Size and position of empty ruby level containers
<dael> github: https://github.com//issues/4631
<dael> florian: Spec doesn't say how to size if the containers are empty. Size to 0 is bad.
<dael> florian: If they're empty want to be sizes as if contain empty ruby base or ruby annotation
<dael> florian: Makes sense
<dael> astearns: Opinions?
<dael> astearns: Can you summarize?
<dael> florian: If a ruby-base container or ruby-annotation container is emty should be sized as if contain an empty ruby base or ruby annotation
<dael> florian: Empty thing container should be sized as if has empty of that thing.
<dael> AmeliaBR: If both base and annotation are empty we still want overall container to have vertical space?
<dael> florian: If you have ruby on an empty base you don't want ruby on base of whole thing just in the ruby thing. You want ruby to take the vertical space. If base container lakes a base you pretend it's emty and there
<dael> AmeliaBR: Like a strut that preserves line height for inline base and annotation?
<dael> florian: Yes
<dael> florian: To remind people there's a ruby box that contains a ruby base container that contains a ruby base and a ruby annotation container that contains a ruby annotation. When containers are empty they should not collapse to 0
<dael> astearns: Both empty containers and don't collapse so it's an empty space?
<dael> florian: Yes but width of 0
<dael> astearns: Prop: empty ruby containers are sizes as if they have empty things in them
<dael> nigel: Point on not observable.
<dael> fantasai: It is obervable if it's only constant of line. Will determine height of line
<fantasai> s/constant/content/
<dael> nigel: In inline direction...if you have ruby text that takes more inline space than ruby base if can spill out. Does an empty ruby base container effect flow of adjacent ruby text?
<dael> fantasai: You want to make sure thigns are paired correctly. Height of annotation and base are contained so stack at correct level. Don't want annotation to collapse to base
<dael> astearns: Purpose was to see if we should scope to if one of a pair is empty it's sized as if empty but if both are empty they collapse
<dael> fantasai: I don't think there's any prescedence to do that. Inline elements don't collapse to 0 when empty, they have height. Shoudl be consistent
<dael> astearns: nigel you okay with the side effects?
<dael> nigel: I was more concerned about width.
<dael> florian: I think this is about overhang?
<dael> nigel: Yeah
<dael> florian: 2 modes. One where you don't and one where UA does whatever it wants. Given it's not spec this doesn't interfere.
<dael> nigel: I could imagine that and empty thing with size 0 has position inline and that could overhang and effect adjacent things
<dael> fantasai: I think that's fine. THe empty thing holds its place. SHould be expected. If you don't want it to hold it's place it shouldn't be there
<dael> nigel: Feature. fair enough :)
<dael> fantasai: I think it's an edge case. I don't think there's anything to worry about in terms of edge cases
<dael> astearns: Good enough nigel?
<dael> nigel: yeah
<fantasai> s/edge/use/
<dael> astearns: Prop: Empty ruby containers are sized as if they have empty thigns in them
<dael> RESOLVED: Empty ruby containers are sized as if they have empty things in them