Add curled and dotted underline for diagnostics

[epbuennig]

I'm wondering if support for underline styles (helix#3015, superseded by helix#4064) is planned. This would bring the themes in this repo on par with the default themes in terms of diagnostic support.

There are currently 4 underline styles:

• curl
• dashed
• dotted (docs mention dot but that is not correct on master)
• double_underline

These should ideally feel familiar, so the color should match the gutter icon's color, the style should match what other popular editors do.

Other Editors

Diagnostic differences:

helix/lsp	intelij-based	vscode
error	error	error
warning	warning	warning
info	hint	info
hint	suggestion	info (different styling)

IntelliJ-based IDEs

severity	underline type	color	styling
error	undercurled	vibrant red	-
warning	undercurled	soft red	-
info	underdotted	vibrant cyan	short span, nothing we have control over
hint	undercurled	soft yellow	-

Visual Studio Code

severity	underline type	color	styling
error	undercurled	vibrant red	-
warning	undercurled	vibrant yellow	-
info	underdashed	vibrant cyan	short span, nothing we have control over
hint	underdashed	soft yellow	-

Most themes for these editors don't interfere with the default styling of the diagnostics. The changes are simple

+ "diagnostic.hint" = { underline = { color = <hint>, style = "dotted" } }
+ "diagnostic.info" = { underline = { color = <info>, style = "dotted" } }
+ "diagnostic.warning" = { underline = { color = <warning>, style = "curl" } }
+ "diagnostic.error" = { underline = { color = <error>, style = "curl" } }

As well as removing the deprecated option for the fallback style and changing it to curl (same as the default theme):

- "diagnostic" = { modifiers = ["underlined"] }
+ "diagnostic" = { underline = { style = "line" } }

I've tried this with gruvbox_original_dark_hard only, but I figure this Is simple enough that it should work for all of them.
It's up to you if prefer curl for all of them or dashed over dotted, I thought the distinction from color only is a bit hard to see, and the dashed underline looked kind of weird to me.

[CptPotato]

Thanks for the heads up, I'm definitely in favor of this.

I'll have to check which versions I prefer, but I think info/hint as dotted and warn/error as curled sounds good.

The terminal I'm using (wezterm) doesn't seem to support these underline styles, so it's difficult for me to test this. Would you mind providing a screenshot?

[epbuennig]

Using gruvbox original dark hard in alacritty:

Using gruvbox original dark hard in kitty:

The same with dashed as reference:

[epbuennig]

I see this on wezterm (20221119-145034-49b9839f), are you up to date?

[CptPotato]

Looks great! Interestingly, I'm using the same wezterm version but the styled underlines don't show up for me:

I'll have to check why that happens. Regardless, the changes and visuals look good to me, so unless there's other things you want to address I'd go ahead and merge this.

[epbuennig]

Perhaps you're still on helix 22.08, I'm running master because the arch package is always a bit late. So while it is released, it may not be available on your system either.

[epbuennig]

If you're ok with dotted over dashed then it's good to merge.

[CptPotato]

Thanks!