Dfci was not designed to be used in this way, and the mode initialization actually sets the character, but in the future it could make many other dynamic tests/checks if needed. So I don't think we should modify it to work the other way you suggest, because for menit is not general enough. But I will follow the Eli's suggestions in this aspects more than my own opinion. 
Any way, if you want to use the mode in this way (for now) you can/need to set the display-fill-column-indicator-character to your desired value and it should work as it is now. But I can't promise that it will work the same way in the future.
But again, probably Eli will suggest a better solution for your use case.


On August 4, 2019 9:39:06 PM GMT+02:00, Juri Linkov <juri@linkov.net> wrote:
>> Hi, sorry, I don't understand actually why is so complex this
>provided code
>> in the email. The initialization for display-fill-column-indicator
>makes
>> some checks to set the default character as described in the
>documentation,
>> so no extra code is needed for that in the user side.
>> In the initialization I see in this mail, they just set the column's
>value
>> to 78 which can be done also using the variable fill-column for the
>whole
>> major mode too. And actually dfci will recognize it by default and
>other
>> functionalities too so in the general scenario is better to use that
>one.
>>
>> (setq fill-column 78)
>> (display-fill-column-indicator t)
>>
>> Should work no matters the order. Maybe as you were setting the
>mode's
>> variable instead of calling the function with the same name; the mode
>> was not properly initialized.
>
>The problem is that is when the need is to enable dfci, it is simpler
>to avoid eval to enable this mode because dfci works fine without using
>dfci-mode, i.e. when only variables are set in Local Variables:
>
>  ;;; Local Variables:
>  ;;; display-fill-column-indicator: t
>  ;;; display-fill-column-indicator-column: 78
>  ;;; End:
>
>or in .dir-locals.el:
>
>  (display-fill-column-indicator . t)
>  (display-fill-column-indicator-column . 78)
>
>But the display-fill-column-indicator-character can't be set
>in Local Variables because its value depends on the current display:
>either U+2502 or ?| if the font does not support Unicode characters.
>
>Do you think it would be possible to set the default value of
>display-fill-column-indicator-character without calling
>display-fill-column-indicator-mode?

-- 
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