RE: usability problem of emacs describe-mode

["Drew Adams" <drew.adams@oracle.com>]

> > > >     * Get rid of convention of using ^L (ascii 12) for 
> > > >       page break marker.
> >
> > > Is there a way to draw a sort of horizontal line for the ASCII 12
> > > symbol instead of printing "^L"? I'm talking about X version.
> >
> > Yes.
> > Code:http://www.emacswiki.org/emacs/pp-c-l.el
> > Description:http://www.emacswiki.org/emacs/PrettyControlL
> > You can customize the appearance.
> > The screenshot shows the default appearance.
> 
> Thanks Drew.
> I have now tried your code and it's great. I also updated it here:
> 
> . Usability Problems Of Emacs's Mode Documentation
>   http://xahlee.org/emacs/modernization_mode_doc.html
> 
> Btw, when i insert a ^L, it automatically become displayed as
> horizontal line but with the overlay display "Section (Printable
> Page)". Is there a way to turn that off? i.e. i just want a line.


Yes, and it's described in the file and the doc strings of the user options. To
quote:

------8<-------------------
* Option `pp^L-^L-string':

Highlighted string displayed in place of each Control-l (^L) character.
If `pp^L-^L-string-function' is non-nil, then the string that function
returns is used instead of `pp^L-^L-string'.

* Option `pp^L-^L-string-function':

Function to produce string displayed in place of each Control-l (^L) char.
If this is non-nil, then option `pp^L-^L-string' is not used.
You can use this option to have a dynamically defined display string.
For example, with `foo' as the value, and this definition, a
window-width horizontal line is displayed.

  (defun foo () (make-string (window-width) ?_))

In the library's Commentary:

Note: If you use option `pp^L-^L-string-function' to define the ^L
appearance based on the current window (e.g. its width), then you
might want to add command `refresh-pretty-control-l' to variable
`window-configuration-change-hook', to automatically update the ^L
display whenever you resize the window:

 (add-hook 'window-configuration-change-hook
           'refresh-pretty-control-l)
------8<-------------------

So:

* If you want a different static string from the default,
  "          Section (Printable Page)          ", then just
  customize `pp^L-^L-string'.

* If you want a dynamic string, such as a horizontal line for the
  full window width, even as the window is resized, then use
  `pp^L-^L-string-function'. That option can have a function value.
  If it does, then whatever string that function returns is used.

You can also customize the face used, and prefix and suffix strings to bookend
the basic string.