Long standing annoying issue in ghci

MarLinn monkleyon at gmail.com
Fri Dec 8 17:24:23 UTC 2017

I opened an issue on the Haskeline github 

But it seems to be completely Haskeline-side, so I'm not sure if it's 
worth re-opening the one for ghci? As missing documentation maybe?
(BTW, I found this on the wiki: https://wiki.haskell.org/GHCi_in_colour. 
Might be a good place to put it, if linked.)

If you want to, here are my test cases rewritten as ghci prompts:

     -- single line, positioning error
     :set prompt " \ESC[36m%\ESC[0m "
     -- single line, works
     :set prompt " \ESC[36m\STX%\ESC[0m\STX "
     -- multiline, bad output
     :set prompt "\ESC[32m\STX–––\ESC[0m\STX\n \ESC[36m\STX%\ESC[0m\STX "
     -- multiline, works but is inconsistent
     :set prompt "\ESC[32m–––\ESC[0m\n \ESC[36m\STX%\ESC[0m\STX "

In my tests, the positioning errors consistently happen if there are any 
"unclosed" escape-sequences on the last line of the prompt, regardless 
of its length. Escape sequences on previous lines consistently create 
"weird characters", but don't influence the positioning. Also regardless 
of their lengths. That makes sense, as both sets of lines seem to be 
handled quite differently.

Are multiline prompts even used by a lot of people? I like mine because 
it gives me a both a list of modules and a consistent cursor position. 
But maybe I'm the exception?


On 2017-12-07 23:15, cheater00 cheater00 wrote:
> Interesting. Would you mind reopening the issue and providing a buggy 
> example? Amd alerting haskeline maintainers? How does it work on a 1 
> line prompt that is so long it wraps?
> On Thu, 7 Dec 2017 23:11 MarLinn, <monkleyon at gmail.com 
> <mailto:monkleyon at gmail.com>> wrote:
>     > Here's what I use:
>     >
>     > :set prompt "\ESC[46m\STX%s>\ESC[39;49m\STX "
>     >
>     > I believe \STX is a signal to haskeline for control sequences.
>     > Documentation is here:
>     > https://github.com/judah/haskeline/wiki/ControlSequencesInPrompt
>     Note: If you're using a multi-line prompt, things may be different
>     again. I don't know what the rules are, but I found that if I put \STX
>     on any but the last line of prompts I get weird characters. The same
>     goes for any \SOH you might want to add for some reason.
>     Cheers,
>     MarLinn

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-devs/attachments/20171208/3e95137f/attachment.html>

More information about the ghc-devs mailing list