eintr: Text and Auto-fill
16.4 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 two 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 '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.
How Major Modes are Chosen (emacs)Choosing Modes.
Local Variables in Files (emacs)File Variables.
Now, back to the ‘.emacs’ file.
Here is the line again; how does it work?
(setq 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,
‘major-mode’, to the subsequent value, which is ‘text-mode’. The
single-quote before ‘text-mode’ tells Emacs to deal directly with the
‘text-mode’ symbol, not with whatever it might stand for. Setting
the Value of a Variable set & setq, 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 is the next line:
(add-hook 'text-mode-hook 'turn-on-auto-fill)
In this line, the ‘add-hook’ command 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.
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, a first non-blank line, or
local variables to 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 line 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)
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