Re: emacs settings priority

[crstml]

Eli Zaretskii wrote:
> > From: crstml@libero.it
> > Date: Fri, 5 Apr 2024 18:07:57 +0200
> >
> > Eli Zaretskii wrote:
> > > > I've tried without success to find in the manual information
> > > > about these priorities/precedences.
> > > >
> > > > Is it possible to know how emacs decides what font is used when the
> > > > same font is specified in more places: X resource, command line,
> > > > init file?
> > > Why is it important to know?
> > When a user specify some setting in the command line for example he expects
> > some feedback from the application. If the effect of that setting is not visible
> > the user must understand the cause.
> If you can describe a situation where a setting from the command line
> didn't have any effect, please do.

Of course. Here is my configuration:

---- begin OS Version ----

Distributor ID: Debian
Description:    Debian GNU/Linux 12 (bookworm)
Release:        12
Codename:       bookworm

Basically a clean Debian 12 installation.

---- end OS Version ----



---- begin ~/.emacs ----

(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(default ((t (:inherit nil :extend nil :stipple nil :background "black" :foreground 
"gray" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil 
:slant normal :weight normal :height 113 :width normal))))
 '(font-lock-builtin-face ((t (:foreground "cornflower blue"))))
 '(font-lock-comment-delimiter-face ((default (:inherit 
font-lock-comment-face)) (((class color) (min-colors 16)) nil)))
 '(font-lock-comment-face ((t (:foreground "red"))))
 '(font-lock-function-name-face ((((class color) (min-colors 88) (background dark)) 
(:foreground "gray" :weight bold))))
 '(font-lock-keyword-face ((((class color) (min-colors 88) (background dark)) 
(:foreground "RoyalBlue"))))
 '(font-lock-string-face ((((class color) (min-colors 88) (background dark)) (:foreground 
"orange"))))
 '(font-lock-type-face ((((class color) (min-colors 88) (background dark)) (:foreground 
"darkslategray"))))
 '(font-lock-variable-name-face ((t (:foreground "goldenrod"))))
 '(mode-line ((((class color) (min-colors 88)) (:background "orange" :foreground 
"black")))))

;;No other contents is present in this file
;;

---- end ~/.emacs ----

Here are the tests:

1) Try the following command lines:

    emacs -fn 10x20 &
    emacs -fn lucidasanstypewriter-24 &

    There is no difference between the emacs instances regarding the fonts.

2) Rename the .emacs to .emacs.disabled and run the same commands again.

   mv .emacs .emacs.disabled
   emacs -fn 10x20 &
   emacs -fn lucidasanstypewriter-24 &

   Now without the .emacs file the -fn command line option is taken
   into account.

From these tests it's obvious that -fn has lower precedence than the .emacs
file. It turns that probably I always need to specify an init file in the
command line when I start emacs (if sometimes I want a different behavior).
Not that it's impossible or difficult. But I had to do some experiments to
understand what is going on and in the end I was interested if this stuff
is documented probably with some advice/best practices about how the users
should set up their environments.




> > > Users aren't supposed to specify
> > > contradictory setting via several different means of doing so.
> > Is the fact that the users aren't supposed to specify different settings
> > via several different means an overall design decision? If yes, then the
> > users should be aware of this decision and it should be specified in the
> > manual.
> >
> > But (personal opinion based on my way of using emacs) such a design decision
> > is not very wise. Users must be able to control how the settings are applied
> > or what are the causes of their impossibility of specifying settings.
> >
> > Maybe I want to start an instance of emacs with a different background color
> > and font size in a certain context (using the command line or a context
> > dependent configuration file) and I see that these settings are not applied.
> >
> > How can I understand why not or what can I do?
> Please describe a specific situation where this happens, and let's
> take it from there.  You seem to be talking about some general
> principles, and I'm not sure that is useful.  In general, Emacs does
> sensible things in these cases, so it isn't like the user is
> completely in the dark.