Readline behavior with colored custom prompt

Readline behavior with colored custom prompt

[Matthew Keeter]

Hi all,

I’m seeing strange behavior with readline's interaction with ANSI codes.

Here’s a minimal sample script that reproduces the behavior:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(use-modules (system repl repl) (system repl common))
(use-modules (ice-9 readline))

(define (custom-prompt repl)  "\x1b[34m :D > \x1b[0m")

(activate-readline)
(repl-default-option-set! 'prompt custom-prompt)

(start-repl)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Run this and you’ll get a Guile shell.  Into that shell, type

    '(1 2 3 4 5 6 7 8 9 10)

The final parenthesis will highlight a character midway through the string
(instead of the first parenthesis).

The same issues happen if you try to scroll through history: lines end up
overlapping in strange ways.

Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
like to have a colored prompt and correct readline behavior.

Does anyone have any ideas?

Thanks,
Matt

Re: Readline behavior with colored custom prompt

[Mike Gran]

On Thursday, February 25, 2016 9:21 AM, Matthew Keeter <matt.j.keeter@gmail.com> wrote:

>
>Run this and you’ll get a Guile shell.  Into that shell, type
>
>    '(1 2 3 4 5 6 7 8 9 10)
>
>The final parenthesis will highlight a character midway through the string
>(instead of the first parenthesis).
>
>The same issues happen if you try to scroll through history: lines end up
>overlapping in strange ways.
>
>Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
>like to have a colored prompt and correct readline behavior.
>
>Does anyone have any ideas?

The conflict is likely between your codes and the bounce-parens functionality
of the readline prompt.
 
(readline-set! bounce-parens 0)  should disable that functionality and make the
colored prompt work.
 
To get your escape sequences and bounce-parens working would probably require
more thinking...
 
-Mike

Re: Readline behavior with colored custom prompt

[Matthew Keeter]

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I think the fundamental issue is incorrect prompt length calculation, since it’s not just bounce-parens:
even with that turned off, scrolling through history ends up printing weird mismatched lines.

Here’s a similar issue discussed in nodejs:
https://github.com/nodejs/node-v0.x-archive/issues/3860

Any suggestions where to look for prompt length calculations?
I flipped through guile-readline/readline.c but didn’t see any obvious places to apply a fix.

Thanks,
Matt

On Feb 25, 2016, at 1:05 PM, Mike Gran <spk121@yahoo.com> wrote:

> 
> 
> 
> On Thursday, February 25, 2016 9:21 AM, Matthew Keeter <matt.j.keeter@gmail.com> wrote:
> 
>> 
>> Run this and you’ll get a Guile shell.  Into that shell, type
>> 
>>   '(1 2 3 4 5 6 7 8 9 10)
>> 
>> The final parenthesis will highlight a character midway through the string
>> (instead of the first parenthesis).
>> 
>> The same issues happen if you try to scroll through history: lines end up
>> overlapping in strange ways.
>> 
>> Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
>> like to have a colored prompt and correct readline behavior.
>> 
>> Does anyone have any ideas?
> 
> The conflict is likely between your codes and the bounce-parens functionality
> of the readline prompt.
> 
> (readline-set! bounce-parens 0)  should disable that functionality and make the
> colored prompt work.
> 
> To get your escape sequences and bounce-parens working would probably require
> more thinking...
> 
> -Mike


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Re: Readline behavior with colored custom prompt

[Matthew Keeter]

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Figured it out, after a bit more searching – it’s purely due to readline's behavior.

readline obeys the magic characters \x01 and \x02, ignoring anything in between then
when calculating prompt length.  Wrapping the escape sequences makes everything
behave correctly.

(similar bug: https://bugs.python.org/issue17337)

-Matt

On Feb 25, 2016, at 1:53 PM, Matthew Keeter <matt.j.keeter@gmail.com> wrote:

> I think the fundamental issue is incorrect prompt length calculation, since it’s not just bounce-parens:
> even with that turned off, scrolling through history ends up printing weird mismatched lines.
> 
> Here’s a similar issue discussed in nodejs:
> https://github.com/nodejs/node-v0.x-archive/issues/3860
> 
> Any suggestions where to look for prompt length calculations?
> I flipped through guile-readline/readline.c but didn’t see any obvious places to apply a fix.
> 
> Thanks,
> Matt
> 
> On Feb 25, 2016, at 1:05 PM, Mike Gran <spk121@yahoo.com> wrote:
> 
>> 
>> 
>> 
>> On Thursday, February 25, 2016 9:21 AM, Matthew Keeter <matt.j.keeter@gmail.com> wrote:
>> 
>>> 
>>> Run this and you’ll get a Guile shell.  Into that shell, type
>>> 
>>>   '(1 2 3 4 5 6 7 8 9 10)
>>> 
>>> The final parenthesis will highlight a character midway through the string
>>> (instead of the first parenthesis).
>>> 
>>> The same issues happen if you try to scroll through history: lines end up
>>> overlapping in strange ways.
>>> 
>>> Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
>>> like to have a colored prompt and correct readline behavior.
>>> 
>>> Does anyone have any ideas?
>> 
>> The conflict is likely between your codes and the bounce-parens functionality
>> of the readline prompt.
>> 
>> (readline-set! bounce-parens 0)  should disable that functionality and make the
>> colored prompt work.
>> 
>> To get your escape sequences and bounce-parens working would probably require
>> more thinking...
>> 
>> -Mike
> 


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Re: Readline behavior with colored custom prompt

[Nala Ginrut]

Are you looking for something like guile-colorized?
https://github.com/NalaGinrut/guile-colorized


On Thu, 2016-02-25 at 12:20 -0500, Matthew Keeter wrote:
> Hi all,
> 
> I’m seeing strange behavior with readline's interaction with ANSI codes.
> 
> Here’s a minimal sample script that reproduces the behavior:
> 
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> (use-modules (system repl repl) (system repl common))
> (use-modules (ice-9 readline))
> 
> (define (custom-prompt repl)  "\x1b[34m :D > \x1b[0m")
> 
> (activate-readline)
> (repl-default-option-set! 'prompt custom-prompt)
> 
> (start-repl)
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> 
> Run this and you’ll get a Guile shell.  Into that shell, type
> 
>     '(1 2 3 4 5 6 7 8 9 10)
> 
> The final parenthesis will highlight a character midway through the string
> (instead of the first parenthesis).
> 
> The same issues happen if you try to scroll through history: lines end up
> overlapping in strange ways.
> 
> Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
> like to have a colored prompt and correct readline behavior.
> 
> Does anyone have any ideas?
> 
> Thanks,
> Matt