Re: Customizing the mode line

[M Jared Finder <jared@hpalace.com>]

Eli Zaretskii wrote:
>> From: Richard Stallman <rms@gnu.org>
>> CC: emacs-devel@gnu.org
>> Date: Sat, 31 Oct 2009 07:07:44 -0400
>>
>> I don't think that a better UI for customizing the mode line is a
>> really important place to improve.  Customizing it is not that hard to
>> do.
> 
> ??? Really?  Then please describe how to do that.  What user options
> are available for that, and what values one should give them for the
> following use-cases:

The first two are easy.

>  . Show only the major mode, not the minor modes.

(setq minor-mode-alist nil) or customize mode-line-modes

>  . Remove the percent/All/Top/Bot part.

Remove the first two entries of mode-line-position


>  . Display the load-average and the Mail notification between the line
>    number and the major/minor mode indicator.

Reordering the mode line is much harder (and would be greatly 
appreciated by me).  I think if you cleaned up mode-line-format so that 
it only included VARIABLES, then this would be clear as day.  Right now 
mode-line-format's default value is big and scary (note, from Emacs22):

("%e"
  #("-" 0 1
    (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0"))
  mode-line-mule-info mode-line-modified mode-line-frame-identification 
mode-line-buffer-identification
  #("   " 0 3
    (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0"))
  mode-line-position
  (vc-mode vc-mode)
  #("  " 0 2
    (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0"))
  mode-line-modes
  (which-func-mode
   ("" which-func-format
    #("--" 0 2
      (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0"))))
  (global-mode-string
   (#("--" 0 2
      (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0"))
    global-mode-string))
  #("-%-" 0 3
    (help-echo "mouse-1: select (drag to resize), mouse-2 = C-x 1, 
mouse-3 = C-x 0")))

You could clean this up to be a lot clearer.  Part of it is the pretty 
printer is doing an awful job, part of it is the explicit propertized 
strings.  Imagine if it was like this:

(mode-line-mem-info
  (:propertize "-" (mode-line-default-props))
  mode-line-mule-info
  mode-line-modified
  mode-line-frame-identification
  (:propertize "    " (mode-line-default-props))
  mode-line-position
  mode-line-vc-info
  mode-line-modes
  mode-line-which-func-info
  global-mode-string
  (:propertize "-%-" (mode-line-default-props)))

And then you could expose this in Customize as a reorder-able list!

In short, I have four proposals:

1. Change mode-line-format to not include ANY explicitly propertized 
strings.  Use :eval and :propertize.
2. Remove condition branching in mode-line-format.  Just variables with 
formatting info should be there, put the branching in those variables.
3. Change the pretty-printer used by C-h v to somehow recognize that 
mode-line-format should be formatted with a newline after every element.
4. Change the customize option for mode-line-format to display it as a 
reorderable list, like c-mode-hook.

   -- MJF