[css-overflow-4] display: -webkit-box and line-clamp without -webkit-box-orient: vertical

[frivoal]

In #10324, @andreubotella asked:

What should happen when you have display: -webkit-box and some value of line-clamp, but not -webkit-box-orient: vertical? If it was -webkit-line-clamp, it would create a flexbox and the line clamping would not apply, but it's not as clear with line-clamp.

One possible behavior is that it creates a flexbox, which causes line-clamp to not apply because it is not a block container. But if the flexbox has text content, that gets blockified, so would it get clamped?

[frivoal]

My expectation would be that nothing happens, because

• the -webkit-line-clamp compat hack needs -webkit-box-orient: vertical
• line-clamp without the compat hack only applies to block-containers, but display: -webkit-box yields a flexbox, not a block container.

This strange behavior that requires all 3 properties only exists for compat reasons, so we should stick to that behavior

[css-meeting-bot]

The CSS Working Group just discussed [css-overflow-4] display: -webkit-box and line-clamp without -webkit-box-orient: vertical, and agreed to the following:

• RESOLVED: no change to spec, add a note

The full IRC log of that discussion

<fantasai> andreubotella: We had agreed to a compat workaround for line-clamp
<fantasai> andreubotella: if you have -webkit-box and -webkit-box-orient: vertical
<fantasai> andreubotella: then either line-clamp or -webkit-line-clamp would make it not a flex, and make it a block
<fantasai> andreubotella: and -webkit-line-clamp would apply
<fantasai> andreubotella: issue is if you have line-clamp on block containers
<fantasai> andreubotella: should display: -webkit-box + line-clamp without box-orient, should it also trigger the behavior of making it a block container?
<fantasai> andreubotella: I agree with Florian that -webkit-line-clamp only applies with -webkit-box and -webkit-box-orient:vertical
<fantasai> andreubotella: but if you have [missed]
<florian> q+
<astearns> ack florian
<fantasai> andreubotella: if you have -webkit-box and line-clamp, is -box-orient also required?
<fantasai> florian: This problem is more difficult to dscribe than to solve
<fantasai> florian: we have a weird compat hack that is required when you have -webkit-line-clamp
<fantasai> florian: and is allowed for line-clamp
<fantasai> florian: I don't think we need to generlaize
<fantasai> florian: we need to support the set for -webkit-line-clamp to work
<fantasai> florian: it needs to not work when the whole set is not there, because the Web depends o nit not triggering if any piece is missing
<fantasai> florian: if you don't have the full thing, then don't blockify the flexbox
<fantasai> florian: the non-hacky version doesn't apply to flexboxes
<fantasai> florian: not helpful, and not needed for compat, so keep it simple
<fantasai> florian: already resolved that the new line-clamp works if you have the full set of weird stuff
<fantasai> florian: but if you only have one of them, then we don't trigger the magic condition, and shouldn't
<fantasai> florian: so proposal is no change, just clarify with a note
<fantasai> astearns: proposed no change to spec, add a note mentioning the new version doesn't interact with only part of the old hack
<fantasai> RESOLVED: no change to spec, add a note

[frivoal]

Actually, the note was already there. 3e2b38d

[frivoal]

Test coverage exists in http://wpt.live/css/css-overflow/line-clamp/line-clamp-029.html