\overline and MathML Core horizontal stretching (in Chrome)

[physikerwelt]

While \overline{abcd} renders fine with Firefox the line is too short in chrome

However, if one replaces the second part of the mover with <mo id="p1.1.m1.1.1.1" xref="p1.1.m1.1.1.1.cmml">&oline;</mo> it renders fine

I am unsure how to fix that (for my own project). Should one use ‾ (which works in both browsers) or ¯ (and ask for a fix in Chrome) or even use another alternative such as ı. Does LaTeXML has a clear statement why one solution is better than the other?

related https://phabricator.wikimedia.org/T352698

[dginev]

Thank you for opening the issue!

Here is a codepen reproducing the lack of horizontal stretching (in Chrome): https://codepen.io/dginev/pen/mdozrBr

I am pretty sure this is something I had left a comment for in the Chrome MathML issue tracker, see the still open issue: https://issues.chromium.org/issues/40889045#comment5

Changing to ‾ as a short-term patch would be fine, as long as we are sure we won't be changing back to the macron at a later date.

In the long term I think we need some kind of a browser fix since it is less clear to me why only ‾ works. Or is it even font related?

Overline seems to be the exception more than the rule. For example, its Unicode block also has Dashed Overline (﹉), Centreline Overline (﹊), Wavy Overline (﹋), Double Wavy Overline (﹌) and none of them stretches horizontally in today's Chrome. Actually those don't stretch horizontally in Firefox either. So this may be tricky to navigate...

Edit: there are also a few open issues related to horizontal stretching in MathML Core, but I am unsure if one of them exactly applies to these characters: https://github.com/w3c/mathml-core/issues?q=is%3Aissue+is%3Aopen+horizontal+stretching