[css-text-decor] Should text-decoration-skip apply to overline and line-through?

[upsuper]

It seems currently all the usecase of text-decoration-skip: ink is about underline. It is not clear whether this should also be applied to overline and line-through. My guess is overline may want that as well, but not line-through.

cc @kojiishi @litherum

[kojiishi]

cc @drott

[drott]

I think it makes sense for all line types and styles and giving the author the flexibility to decide. The implementation I have almost ready for Chrome does it for all line positions and styles.

[upsuper]

That gives author flexibility, yes, but is that what author wants? I don't know. Especially if you are going to make ink the default value of text-decoration-skip like what Safari does, you would likely break every delete line badly.

[drott]

Good point, yes, I believe we can split this into two problems: What should auto do for line-through, etc. and - should skip: ink be available for all line types. For the latter, I still think it should be, while I agree with you that applying it by default to line-through for skip: auto; as a change of the default might not be desirable.

[upsuper]

Oh, do we have auto? That could be a game changer, though, if that can provide a decent default behavior everywhere.

However, the problem may still be valid. If author decides to use a different value for underline, they would effectively need to specify the value everywhere when there is a text-decoration-line presents, otherwise they may get undesired broken line-through, or undesired non-broken underline (considering <u>some thing important <del>deleted</del></u> and <del>deleted <u>something was important</u></del>).

If that is something we want, then text-decoration-skip should probably not be inherited by default, and should be part of text-decoration shorthand.

I have no idea why text-decoration-skip is inherited currently, though. @kojiishi thoughts?

[frivoal]

There's no auto in the spec, either in level 3 or 4, but having one sounds like it may be a good idea. While we're thinking about how auto would work, we should probably keep in mind issue 2 or level 4, as that may also be something we can solve with auto. Or maybe not. I guess it depends how we define it.

[kojiishi]

I have no idea why text-decoration-skip is inherited currently, though.

From what you wrote, it looks to me that it is more problematic for text-decoration-skip to apply to all decoration lines rather than it inherits?

I agree your use case of mixing underline and strikethrough is valid, and from a test, WebKit skips underlines but not strikethrough, so intentionally or not, WebKit doesn't break your use case.

[kojiishi]

On second thought, I didn't answer to your question; do you think inherited is an orthogonal issue to this issue, or is it questionable if text-decoration-skip applies to all line types?

I think there are valid cases where inherited is useful. In some styles, underlines skipping space characters are preferred. It's probably more useful to inherit than to propagate. For object value, authors may want to underline to all images but not to other objects.

On the other hand, your use case is valid, so I'm wondering whether we should solve this by line type, or by inherited-or-not, or both.

[upsuper]

From what you wrote, it looks to me that it is more problematic for text-decoration-skip to apply to all decoration lines rather than it inherits?

That really depends on how we spec it.

For example, if

• text-decoration-skip is not inherited by default, and
• it is part of text-decoration shorthand, and
• we have auto value which is computed to
  • objects ink if text-decoration-line is underline, or
  • objects otherwise,

then author would just need to specify text-decoration, and this is not an issue anymore. But whether that settings would lead to other issues, I don't know.

[kojiishi]

Sorry, I can't understand how inherited or not affects your example -- I mean, in your example, the result looks the same to me even when it inherits. Could you point out what I missed?

[upsuper]

Hmmm, if text-decoration-skip is part of text-decoration, then whether it is inherited probably doesn't matter a lot. But if that way, why should we keep it inherited?

I don't think we usually mix inherited and non-inherited properties in one shorthand property. And if it is expected to be overridden whenever text-decoration is set, it seems making it not inherited makes more sense.