[css-lists] Should collapsible space after inside ::marker be preserved? · Issue #4891 · w3c/csswg-drafts (original) (raw)

In #4448 (comment) we resolved that ::marker should have white-space: pre in UA origin. That is needed for outside markers, and we decided to keep it simple and also apply it to inside markers.

But consider this case:

  1. Text
  2. Text

For block container elements like <li>, leading and trailing space doesn't matter. So just looking at the HTML, some authors may think that both Text will be aligned equally.

However, the ::marker is inserted at the very beginning of the <li>, and since it's inside, it behaves as a normal inline. So the leading space is no longer at the beginning of the line, and is not trimmed in §4.1.2.1.

Since the ::marker has a trailing space, both list items could still look the same via §4.1.1:

Any collapsible space immediately following another collapsible space [...] is collapsed

But that doesn't apply if the ::marker has white-space: pre. So the 1st list item ends up with 1 space and the 2nd list item with 2 spaces.

What behavior do we want here? We don't have interoperability:

So I guess we can choose among:

  1. Keep white-space: pre. Firefox is correct, changing Chromium will be trivial.
  2. Keep white-space: pre but add some magic that if a text ::marker has a trailing space and is followed by collapsible spaces, then these collapsible spaces are removed, even if the ::marker space is not collapsible. This will keep Chromium's behavior but implementing this magic would be annoying.
  3. Say that inside markers don't get assigned white-space: pre in UA origin. This is close to what Chromium does right now. But I guess doing this properly would need pseudo-classes like :📑inside and :📑outside, even if just for internal use, but that would create a circularity if in the future we allow setting list-style-position in the ::marker itself.

I lean towards 1.