Eli Zaretskii <eliz@gnu.org> writes:

> I see your change adds a post-command-hook, but when and how is that
> hook removed?

The hook is removed when display-fill-column-indicator-mode is turn-off,
i forgot to remove the hook in the submitted patch, I've fixed it.

>> I also wanted to do the same for indicator character but I couldn't find
>> a way to implement it.
>
> What do you mean by "indicator character"?

i meant `display-fill-column-indicator-character', I wanted to
allow changing its character to a custom one.

example: use this `┃' character (or one chosen by the user)
instead default `│' when changing the fill-column-indicator face.

>> +(defcustom display-fill-column-indicator-warning nil
>> +  "Highlight fill-column-indicator when cursor is above `fill-column'.
>> +Non-nil means highlight fill-column-indicator when cursor is
>> +above `fill-column'."
>> +  :type 'boolean)
>
> This lacks a :version tag.
>
> Also, what do you mean by "cursor is above `fill-column'"?  The
> "above" part confuses me.

I updated the patch to clarify this part.