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(emacs-lisp-intro.info)Text and Auto-fill

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Text and Auto Fill Mode
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   Now we come to the part that `turns on' Text mode and Auto Fill mode.

     ;;; Text mode and Auto Fill mode
     ; The next three lines put Emacs into Text mode
     ; and Auto Fill mode, and are for writers who
     ; want to start writing prose rather than code.
     
     (setq default-major-mode 'text-mode)
     (add-hook 'text-mode-hook 'text-mode-hook-identify)
     (add-hook 'text-mode-hook 'turn-on-auto-fill)

   Here is the first part of this `.emacs' file that does something
besides remind a forgetful human!

   The first of the two lines in parentheses tells Emacs to turn on Text
mode when you find a file, _unless_ that file should go into some other
mode, such as C mode.

   When Emacs reads a file, it looks at the extension to the file name,
if any.  (The extension is the part that comes after a `.'.)  If the
file ends with a `.c' or `.h' extension then Emacs turns on C mode.
Also, Emacs looks at first nonblank line of the file; if the line says
`-*- C -*-', Emacs turns on C mode.  Emacs possesses a list of
extensions and specifications that it uses automatically.  In addition,
Emacs looks near the last page for a per-buffer, "local variables
list", if any.

   Note: How Major Modes are Chosen.

   Note: Local Variables in Files.

   Now, back to the `.emacs' file.

   Here is the line again; how does it work?

     (setq default-major-mode 'text-mode)

This line is a short, but complete Emacs Lisp expression.

   We are already familiar with `setq'.  It sets the following variable,
`default-major-mode', to the subsequent value, which is `text-mode'.
The single quote mark before `text-mode' tells Emacs to deal directly
with the `text-mode' variable, not with whatever it might stand for.
Note: Setting the Value of a Variable, for a reminder of
how `setq' works.  The main point is that there is no difference
between the procedure you use to set a value in your `.emacs' file and
the procedure you use anywhere else in Emacs.

   Here are the next two lines:

     (add-hook 'text-mode-hook 'text-mode-hook-identify)
     (add-hook 'text-mode-hook 'turn-on-auto-fill)

In these two lines, the `add-hook' command first adds
`text-mode-hook-identify' to the variable called `text-mode-hook' and
then adds `turn-on-auto-fill' to the variable.

   `turn-on-auto-fill' is the name of a program, that, you guessed it!,
turns on Auto Fill mode.  `text-mode-hook-identify' is a function that
tells `toggle-text-mode-auto-fill' which buffers are in Text mode.

   Every time Emacs turns on Text mode, Emacs runs the commands `hooked'
onto Text mode.  So every time Emacs turns on Text mode, Emacs also
turns on Auto Fill mode.

   In brief, the first line causes Emacs to enter Text mode when you
edit a file, unless the file name extension, first non-blank line, or
local variables tell Emacs otherwise.

   Text mode among other actions, sets the syntax table to work
conveniently for writers.  In Text mode, Emacs considers an apostrophe
as part of a word like a letter; but Emacs does not consider a period
or a space as part of a word.  Thus, `M-f' moves you over `it's'.  On
the other hand, in C mode, `M-f' stops just after the `t' of `it's'.

   The second and third lines causes Emacs to turn on Auto Fill mode
when it turns on Text mode.  In Auto Fill mode, Emacs automatically
breaks a line that is too wide and brings the excessively wide part of
the line down to the next line.  Emacs breaks lines between words, not
within them.

   When Auto Fill mode is turned off, lines continue to the right as you
type them.  Depending on how you set the value of `truncate-lines', the
words you type either disappear off the right side of the screen, or
else are shown, in a rather ugly and unreadable manner, as a
continuation line on the screen.

   In addition, in this part of my `.emacs' file, I tell the Emacs fill
commands to insert two spaces after a colon:

     (setq colon-double-space t)