Enable customization of the undercurl

[Shatur]

Describe the bug

Undercurl looks like a dotted line:

To Reproduce
Steps to reproduce the behavior:

1. hi SpellBad gui=undercurl guisp=Red
2. hi SpellBad

Expected behavior

Current behavior

Desktop (please complete the following information):

• OS: Linux
• Neovide Version: 82b745c (latest commit at the time of writing)
• Neovim Version: bdf3df4027a5389a46b4c9a75b50aff5c0ecb351 (latest commit at the time of writing)

Please run neovide --log and paste the contents of the .log file here:

neovide_rCURRENT.log

[Kethku]

I would argue this is a nitpick rather than a bug. Is there a big benefit to doing undercurls as a wavy line? The dashed line was done just because its the simplest to implement, but in using it I've actually grown to like it.

Maybe a better request here is to give a way to customize the underline graphic. Maybe underline, dashed, wave, other??

[Shatur]

Maybe a better request here is to give a way to customize the underline graphic. Maybe underline, dashed, wave, other??

I would render this as undercurl. This is how it implemented in all editors (not even just all Neovim clients). I even thought that this is a bug :)

[Kethku]

Note: this isn't strictly true. There are some neovim guis which render it as an underline.

I think I'm gonna swap this to an enhancement and label it "add customization of undercurl rendering". But honestly there are some bigger fish to fry atm. I will get back to this, but it may be a bit

[Shatur]

Note: this isn't strictly true. There are some neovim guis which render it as an underline.

Did not know.
I used Neovim Qt, Gonvim, firenvim and oni2 - all of them renders undercurl as undercurl (expected). Also GVim behaves the same.

I think I'm gonna swap this to an enhancement and label it "add customization of undercurl rendering". But honestly there are some bigger fish to fry atm. I will get back to this, but it may be a bit

You may find this PR useful for the algorithm of the implementation: equalsraf/neovim-qt#803

[clason]

Are you sure that this is not in fact an undercurl that is just clipped to much (so it cuts off the lower part of the curl, leaving a dotted line)?

I've noticed a similar off-center cut-off where the top of lines is cropped too much (most visible in floats):

(Note how the top of the parentheses touches the float boundary, while there is ample space at the bottom.)

[calops]

I would argue this is a nitpick rather than a bug. Is there a big benefit to doing undercurls as a wavy line?

I don't know if it was like that at the time of this question, but there's a very simple reason now: neovim supports multiple "underlining" styles, including undercurl, underdotted and underdashed. It seems pretty straightforward to me that these should all be supported (and look different by default) by neovide.

[calops]

I'll add another point: currently in neovide, undercurl is "supported" (as a weird, uneven dashed line), while underdotted and underdashed aren't (nothing is displayed).