Bug 496534

Summary:	Color of Underline/Undercurl cannot be set within vim when using Konsole
Product:	[Applications] konsole	Reporter:	terrycchau <terrycchau>
Component:	general	Assignee:	Konsole Developer <konsole-devel>
Status:	RESOLVED DOWNSTREAM
Severity:	normal	CC:	john.kizer, matan
Priority:	NOR
Version First Reported In:	24.08.2
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Example of what the undercurl color looks like in Konsole Example of what the undercurl color looks like in xfce-terminal Output showing that Konsole is capable of undercurl colors

Description terrycchau@gmail.com 2024-11-21 10:19:56 UTC

Created attachment 176000 [details]
Example of what the undercurl color looks like in Konsole

SUMMARY
The color of underline/undercurl as set in vim does not display in Konsole

STEPS TO REPRODUCE
1. In a .vimrc file in home directory (cd ~), add the following settings:
```
setlocal spell
try | lang en_US | catch | endtry
set spelllang=en_us
let &t_Cs = "\e[4:3m"
let &t_Ce = "\e[4:0m"
hi SpellBad term=underline cterm=underline gui=underline
```
then save the file.
2. Open vim, and then type a misspelled word.

OBSERVED RESULT
We see a red undercurl in other terminals such as: iterm2 and xfce4-terminal:1.1.3, but not in Konsole. The color of the undercurl remains the same color as the text.

EXPECTED RESULT
The undercurl color should red. 

SOFTWARE/OS VERSIONS
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 6.2.0
KDE Plasma Version: 6.2.0
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0

ADDITIONAL INFORMATION
Konsole clearly could support color undercurls as `echo -e "\e[4:3m\e[58:2::215:58:103mThis text has an undercurl with color\e[4:0m"` works in Konsole.  I have no idea why setting color undercurl in vim does not work.  This may be a vim specific issue, but it seems that my vim settings above work in other terminals, just not in Konsole, and I cannot figure out why.  If it helps, highlighting in vim is defined in https://github.com/vim/vim/blob/master/src/highlight.c.

Comment 1 terrycchau@gmail.com 2024-11-21 10:21:22 UTC

Created attachment 176001 [details]
Example of what the undercurl color looks like in xfce-terminal

Comment 2 terrycchau@gmail.com 2024-11-21 10:21:52 UTC

Created attachment 176002 [details]
Output showing that Konsole is capable of undercurl colors

Comment 3 Matan Ziv-Av 2024-11-22 10:54:21 UTC

(In reply to terrycchau@gmail.com from comment #2)
> Created attachment 176002 [details]
> Output showing that Konsole is capable of undercurl colors

What if you add the color sequence to t_Cs?

Since colored underlines do work, my first guess would be that vim sends different escape sequences. Is $TERM the same in both cases?

Can you run vim using `script` to see what escape sequences are actually sent?

Comment 4 terrycchau@gmail.com 2024-11-22 11:36:25 UTC

I should clarify that the .vimrc used contains:

```
set termguicolors
setlocal spell
try | lang en_US | catch | endtry
set spelllang=en_us
let &t_Cs = "\e[4:3m"
let &t_Ce = "\e[4:0m"
hi SpellBad term=undercurl cterm=undercurl gui=undercurl guifg=NONE ctermfg=NONE guisp=#d73a49 ctermbg=None
```

Comment 5 terrycchau@gmail.com 2024-11-22 11:51:24 UTC

(In reply to Matan Ziv-Av from comment #3)
> (In reply to terrycchau@gmail.com from comment #2)
> > Created attachment 176002 [details]
> > Output showing that Konsole is capable of undercurl colors
> 
> What if you add the color sequence to t_Cs?
> 
Setting let &t_Cs = "\e[4:3m\e[58:2::215:58:103m" would change the underline color to red.

> Since colored underlines do work, my first guess would be that vim sends
> different escape sequences. Is $TERM the same in both cases?
> 
$TERM for both xfce-terminal and konsole is `xterm-256color`.

> Can you run vim using `script` to see what escape sequences are actually
> sent?

If by script you mean Ex mode, I could enter that by pressing `Q` in the normal mode in vim, but I am not sure how to actually find the actual escape sequence.  Let me know if you have suggestions for commands to run.

Comment 6 terrycchau@gmail.com 2024-11-22 13:56:19 UTC

Good news. I figured out the issue.  Somehow &t_8u is being automatically set for vim in other terminals but not in konsole.  This is something that needs to be set in vims end.

Adding the following resolves issues.

```
let &t_8u = "\e[58;2;%lu;%lu;%lum"
```

&t_8u is set in https://github.com/vim/vim/blob/master/src/term.c I think.  Don't have the time to figure it all out atm.

Comment 7 John Kizer 2024-11-26 19:16:18 UTC

Nice catch! Indeed, looks like according to the comments the belief is/was that Konsole doesn't support something that it apparently does:

https://github.com/vim/vim/blob/7e501f4d9986866382888e67d8f11faf5767c8f4/src/term.c#L5176