bug#44226: display-fill-column-indicator not ready for prime time

[Kévin Le Gouguec]

積丹尼 Dan Jacobson <jidanni@jidanni.org> writes:

> Alas,
> for my average file.txt
> setting display-fill-column-indicator to t did nothing.

What about M-x display-fill-column-indicator-mode?

> OK describe-variable display-fill-column-indicator leads to
> (info "(emacs) Displaying Boundaries")
> OK, starting over, maybe I need to change display-fill-column-indicator-
> character
> user-error: Value ‘|’ does not match type choice of 
> display-fill-column-indicator-character
> user-error: Value ‘x’ does not match type choice of 
> display-fill-column-indicator-character

How did you try to set this?  Based on your error message, I'm guessing
M-x set-variable?

Characters in Elisp must be spelled with a leading '?', e.g. ?| or ?x
(info "(elisp) Basic Char Syntax").  This is a bit tricky to type with
M-x set-variable, since hitting '?' in the value prompt brings up the
variable's *Help* buffer.  You need to type:

M-x set-variable RET display-fill-column-indicator RET C-q ? | RET

>    Documentation:
>    Character to draw the indicator when ‘display-fill-column-indicator’ is 
> non-nil.
>    The default is U+2502 but a good alternative is 
>    ^^^^^^^^^^^SO WHY IS IT STILL NIL?              

Good question (it is nil for me as well right after startup with emacs
-Q).  Maybe it's set when display-fill-column-indicator-mode is called?

>                                                    (ascii 124)
>                                                    ^^^^^^^^^^ ALSO SAY '|'

I agree that either the character, or its name ("VERTICAL LINE") would
be more informative, to save the reader a roundtrip to ascii(7).

> OK, let's try some more.
> user-error: Value ‘U+2502’ does not match type choice of 
> display-fill-column-indicator-character
> user-error: Value ‘│’ does not match type choice of 
> display-fill-column-indicator-character

Cf above: you need to spell this with Elisp's character syntax, so
#x2502 or ?|.