30.5.1 Auto Fill Mode
Auto Fill mode is a minor mode in which lines are broken
automatically when they become too wide. Breaking happens only when
you type a <SPC> or <RET>.
- M-x auto-fill-mode
- Enable or disable Auto Fill mode.
- In Auto Fill mode, break lines when appropriate.
M-x auto-fill-mode turns Auto Fill mode on if it was off, or off
if it was on. With a positive numeric argument it always turns Auto
Fill mode on, and with a negative argument always turns it off. You can
see when Auto Fill mode is in effect by the presence of the word
‘Fill’ in the mode line, inside the parentheses. Auto Fill mode is
a minor mode which is enabled or disabled for each buffer individually.
See Minor Modes.
In Auto Fill mode, lines are broken automatically at spaces when they
get longer than the desired width. Line breaking and rearrangement
takes place only when you type <SPC> or <RET>. If you wish to
insert a space or newline without permitting line-breaking, type
C-q <SPC> or C-q C-j (recall that a newline is really a
control-J). Also, C-o inserts a newline without line breaking.
Auto Fill mode works well with programming-language modes, because it
indents new lines with <TAB>. If a line ending in a comment gets
too long, the text of the comment is split into two comment lines.
Optionally, new comment delimiters are inserted at the end of the first
line and the beginning of the second so that each line is a separate
comment; the variable
comment-multi-line controls the choice
Adaptive filling (see Adaptive Fill) works for Auto Filling as
well as for explicit fill commands. It takes a fill prefix
automatically from the second or first line of a paragraph.
Auto Fill mode does not refill entire paragraphs; it can break lines but
cannot merge lines. So editing in the middle of a paragraph can result in
a paragraph that is not correctly filled. The easiest way to make the
paragraph properly filled again is usually with the explicit fill commands.
Many users like Auto Fill mode and want to use it in all text files.
The section on init files says how to arrange this permanently for yourself.
See Init File.