FORM element adjacent to a named field messes up overlays

[lua-vr]

It seems that having a FORM element right next to a field element can leave the overlays in a bad state. Consider the following three tempel expansions:

(tempel-insert '((if (length> str 1) "{" "") " " (s str) " " (if (length> str 1) "}" "")))
(tempel-insert '((if (length> str 1) "{" "")     (s str)     (if (length> str 1) "}" "")))
(tempel-insert '((if (length> str 1) "y" "n")    (s str)     (if (length> str 1) "y" "n")))

In the first one, the FORM elements work as expected. In the second one, both FORM overlays appear behind the field, and in the third one both FORM overlays appear after the named field. They also stop updating correctly on further input.

[minad]

Yes, adjacent overlays (fields or forms) are not supported well. There have been reports about these problems before. Patches improving this are welcome, if possible. The problem is that we have no underlying text to pin the different overlays to, if they appear at the same position. So this issue may not be fixable.

[lua-vr]

@minad I realized it's possible to do something relatively simple to make it work. It uses the fact the overlays are added to the state in order to make sure they stay in order whenever a field is modified. It's in lua-vr@f6f3ec0. Do you think this would make a good PR? I still need to test it a bit more.

[lua-vr]

I think there was a small "issue" in tempel that was not manifesting before my modification, tempel--synchronize-fields attempts to modify the range overlay but it is also being called during tempel--field, where the range overlay does not exist yet (so it was modifying the field overlay itself, which was not a problem anyway). But now I will need to change this to make the modification work in more cases.

[lua-vr]

I think I've solved most of the previous issues: main...lucasvreis:tempel:main. This means I can go to sleep happy because my LaTeX templates will not insert unnecessary braces { } when the subscript is one character long :)

If you think it makes sense I can open a PR.

[lua-vr]

The template in #99 also works after this

[minad]

Great! I looked at your code. Can you please create separate commits with a clear description, such that I can see which problem is solved by which commit. Also, do you have copyright assigment, see https://github.com/minad/tempel?tab=readme-ov-file#contributions?