bug#2473: usability issues on emacs's describe-mode

[xah lee <xah@xahlee.org>]

hi guys,

Some problem i think on emacs describe-mode.

   http://xahlee.org/emacs/modernization_mode_doc.html

Here's a plain text version. Following the text is some proposed code  
solution (beta) that fixes 2 of the issues.

--------------------------

Usability Problems Of Emacs's Mode Documentation

Xah Lee, 2009-02-06

This page details some usability problems of Emacs's inline  
documentation for its major-mode.

Emacs has a command describe-mode (Ctrl+h m) that shows the inline  
doc for the current mode. For example, if you are coding in  
javascript, html, perl, or python, you can type “Ctrl+h m” to  
quickly see a summarization of what functionalities you have while  
coding in that lang, and what are the keyboard shortcuts.

This is really a wonderful feature, but it is a shame that it has  
some major usability problem, almost making this feature not usable.  
The following gives some details.

For example, when in w3m mode, which is a mode that allows you to  
browse the web pages, i type “Ctrl+h m” to read the online doc  
about the mode's features. The result page starts like this:

     Enabled minor modes: Abbrev Auto-Compression Blink-Cursor
     Command-Frequency Command-Frequency-Autosave Delete-Selection
     Desktop-Save Encoded-Kbd File-Name-Shadow Font-Lock Global-Font- 
Lock
     Line-Number Menu-Bar Mouse-Wheel Recentf Shell-Dirtrack Show-Paren
     Tooltip Transient-Mark Unify-8859-On-Encoding Utf-Translate-Cjk

     (Information about these minor modes follows the major mode info.)

It began by listing “minor-modes”. (What Emacs calls “minor  
modes”, is similar in concept to modern app's preference settings  
and add-ons features.)

Here's a excerpt of the minor mode doc that comes after the major  
mode doc:

     ^L
     Abbrev minor mode (indicator Abbrev):
     Toggle Abbrev mode in the current buffer.
     With optional argument ARG, turn abbrev mode on if ARG is
     positive, otherwise turn it off.  In Abbrev mode, inserting an
     abbreviation causes it to expand and be replaced by its expansion.
     ^L
     Auto-Compression minor mode (no indicator):
     Toggle automatic file compression and uncompression.
     With prefix argument ARG, turn auto compression on if positive,  
else off.
     Return the new status of auto compression (non-nil means on).
     ^L
     Blink-Cursor minor mode (no indicator):
     Toggle blinking cursor mode.
     With a numeric argument, turn blinking cursor mode on if ARG is  
positive,
     otherwise turn it off.  When blinking cursor mode is enabled, the
     cursor of the selected window blinks.

     Note that this command is effective only when Emacs
     displays through a window system, because then Emacs does its own
     cursor display.  On a text-only terminal, this is not implemented.
     ^L
     Cua minor mode (no indicator):
     Toggle CUA key-binding mode.
     When enabled, using shifted movement keys will activate the
     region (and highlight the region using `transient-mark-mode'),
     and typed text replaces the active selection.

Most of the minor modes, filled with emacs-specific technicalities  
and terminologies, are not something emacs users need to know daily.  
When user calls describe-mode, most of the time she really want to  
know what functionality and shortcuts the major mode provides. But  
these minor modes often fills more than 60% of the page.

To me, it is really a pain to read (a emacs user for 10 years), and i  
have learned the habit not even seeing them. I imagine it is very  
confusing to new emacs users.

Imagine, it has to annoy users about discussion such as Blink-Cursor,  
Tooltip, Menu-Bar, Mouse-Wheel, Transient-Mark, Delete-Selection,  
Font-Lock, Line-Number. Each of these is at least one paragraph long,  
and some are emacs's non-intuitive and weired tech jargons. For  
example, the standard feature of having selected text highlighted, is  
in emacs called transient-mark-mode. The standard feature of typing  
overriding selected text, is in emacs tech jargon called delete- 
selection-mode. The standard feature of copy/cut/paste keys, is in  
emacs called cua-mode. Syntax highlighting is called font-lock-mode.

Does user really need to know, that he has Blinking Cursor on? And a  
user needs to be told of the fact he has mouse wheel support on? And  
menu bar, tooltip, syntax highlighting? Do users need explanation  
what these do too?

The emacs minor mode, also includes proper features such as: Show- 
Paren, Recentf, Desktop-Save, Abbrev, Yas/Minor ... etc. For example,  
show-paren-mode highlight matching parenthesis. “recentf-mode”  
lets user open recently opened files. “desktop-save-mode”  
preserves opened files when emacs restarts.

It is nice to be able to see what features are currently on, and what  
extra functionality it supports, but perhaps a separate command  
describe-minor-modes would be better.

Minor mode listing also include a bunch that shows some technical  
issues of emacs's current state that has little to do with daily use  
of emacs. For example, it shows Shell-Dirtrack, Auto-Compression,  
Encoded-Kbd, File-Name-Shadow, Unify-8859-On-Encoding, Utf-Translate- 
Cjk. I have used emacs daily for 10 years, half of the minor mode  
showing up in describe-mode i don't even know what exactly they are.

Also, the page litters “^L” char (ascii 12) through out. The  
“^L” is a page break marker. Such practice is a convention in the  
1980s. Almost no software today does this, and very few professional  
programers today understand what it is. This adds to the  
incomprehensibility.

I think the major usability problem with describe-mode is the listing  
of minor modes. Though, the major mode's inline doc could also use  
some improvement. Here's a excerpt of the inline doc for w3m:

     w3m mode:
     Major mode for browsing web.

     RET     Display the page pointed to by the link under point.   
You may use
             the prefix arg `2' or `C-u C-u' to make a new session.

             If w3m-use-form is t, `RET' and `<mouse-2>' enable you  
to enter forms.
             You may use the prefix arg `2' or `C-u C-u' to make a  
new session.

     <S-kp-enter>
             Display the page of the link in a new session.
             If the region is active, visit all the links within the  
region.

     <S-mouse-2>
             Display the page of the link in a new session by mouse.

     C-c C-c  Submit the form at point.

     R        Reload the current page.
     r        Redisplay the current page.
     C t      Redisplay the page, specifying a content type.
     C c      Redisplay the current page, specifying a charset.
     C C      Redisplay the current page and reset the user-specified  
charset and
              content type.

The notation for keyboard shortcuts, such as “C-u C-u”, “RET”,  
are hard to read. It becomes more confusing when there are shortcuts  
that doesn't use a modifier such as “C t”. The “<mouse-2>”  
and “S-kp-enter” are especially cryptic.
Suggestions

     * describe-mode should just show the inline doc for the major mode.
     * Add a link to the bottom that point to the full doc of the  
mode, if it exists. (the link may be to info doc, or call browse-url  
to open a html doc on local disk, or to a url online of the mode's  
doc website)
     * Get rid of convention of using ^L (ascii 12) for page break  
marker.
     * Add a link at the bottom, to a page that shows inline doc of  
minor modes.
     * Use curly quotes “” instead of the 1980's ascii kludge `'.

For detail about the key notation that adds up readability, see:  
Emacs's M-‹key› Notation vs Alt+‹key› Notation.

The use of backtick char ` and single quote char ' for “matching  
quotes” is a 1980's kludge. They also adds to the readability problem.

It would also be helpful, if the keys are rendered as buttons. Note  
that the button rendering is used in the help files in MS Windows and  
Mac OS X too. And in Wikipedia's articles related to keys, it is also  
used thru-out. e.g. Table of keyboard shortcuts.

Here's a sample output for comparison:

     w3m mode:
     Major mode for browsing web.

     Enter	Display the page pointed to by the link under point.
     You may use the prefix arg “2” or “Ctrl+u Ctrl+u” to make  
a new session.
     If w3m-use-form is t, “Enter” and “mouse middle button”  
enable you to enter forms.
     You may use the prefix arg “2” or “Ctrl+u Ctrl+u” to make  
a new session.
     Keypad Shift+Enter	Display the page of the link in a new session.
     If the region is active, visit all the links within the region.
     Shift+Mouse Middle Button	Display the page of the link in a new  
session by mouse.
     Ctrl+c Ctrl+c	Submit the form at point.
     R	Reload the current page.
     r	Redisplay the current page.
     C t	Redisplay the page, specifying a content type.
     C c	Redisplay the current page, specifying a charset.
     C C	Redisplay the current page and reset the user-specified  
charset and content type.


-------------------------

;; code by Kevin Rodgers. 2009-02-25
(defun describe-major-mode ()
   "Show inline doc for current major-mode."
   (interactive)
   (describe-function major-mode))

;; display page delimiter “^L” as a horizontal line. Code by  
Sébastien Vauban. 2009-02-25
(or standard-display-table
     (setq
      standard-display-table (make-display-table)))
(aset standard-display-table ?\f (vconcat "\n" (make-vector 60 ?-) "^L 
\n"))

;; Display the “^L” page break mark as a horizontal line
;; from http://www.emacswiki.org/emacs/OverlayControlL , 2009-02-25
;; code by Andre Riemann
(add-hook
  'after-change-major-mode-hook
  (lambda ()
    (font-lock-add-keywords nil
     `((,page-delimiter ;; variable with the regexp (usually "^\f" or  
"^^L")
         0
         (prog1 nil
           ;; don't display ^L
           (compose-region (match-beginning 0) (match-end 0) "")
           ;; make an overlay (like in hl-line)
           (let ((pdl (make-overlay (line-beginning-position)
                                    (line-beginning-position 2))))
             ;; :background has to be different from the background  
color
             ;; gray1 here is just a little different from black
             (overlay-put pdl 'face '(:underline "gray30" :background  
"gray1"))
             (overlay-put pdl 'modification-hooks
                          ;; these arguments are received from  
modification-hooks
                          '((lambda (overlay after-p begin end  
&optional length)
                              (delete-overlay overlay))))
             (overlay-put pdl 'insert-in-front-hooks
                          '((lambda (overlay after-p begin end  
&optional length)
                              (delete-overlay overlay)))))) t)))))

   Xah
∑ http://xahlee.org/

☄