30.5.3 Explicit Fill Commands

M-q

Fill current paragraph (fill-paragraph).

C-x f

Set the fill column (set-fill-column).

M-x fill-region

Fill each paragraph in the region (fill-region).

M-x fill-region-as-paragraph

Fill the region, considering it as one paragraph.

M-s

Center a line.

To refill a paragraph, use the command M-q (fill-paragraph). This operates on the paragraph that point is inside, or the one after point if point is between paragraphs. Refilling works by removing all the line-breaks, then inserting new ones where necessary.

To refill many paragraphs, use M-x fill-region, which divides the region into paragraphs and fills each of them.

M-q and fill-region use the same criteria as M-h for finding paragraph boundaries (see Paragraphs). For more control, you can use M-x fill-region-as-paragraph, which refills everything between point and mark. This command deletes any blank lines within the region, so separate blocks of text end up combined into one block.

A numeric argument to M-q causes it to justify the text as well as filling it. This means that extra spaces are inserted to make the right margin line up exactly at the fill column. To remove the extra spaces, use M-q with no argument. (Likewise for fill-region.) Another way to control justification, and choose other styles of filling, is with the justification text property; see Format Justification.

The command M-s (center-line) centers the current line within the current fill column. With an argument n, it centers n lines individually and moves past them. This binding is made by Text mode and is available only in that and related modes (see Text Mode).

The maximum line width for filling is in the variable fill-column. Altering the value of fill-column makes it local to the current buffer; until that time, the default value is in effect. The default is initially 70. See Locals. The easiest way to set fill-column is to use the command C-x f (set-fill-column). With a numeric argument, it uses that as the new fill column. With just C-u as argument, it sets fill-column to the current horizontal position of point.

Emacs commands normally consider a period followed by two spaces or by a newline as the end of a sentence; a period followed by just one space indicates an abbreviation and not the end of a sentence. To preserve the distinction between these two ways of using a period, the fill commands do not break a line after a period followed by just one space.

If the variable sentence-end-double-space is nil, the fill commands expect and leave just one space at the end of a sentence. Ordinarily this variable is t, so the fill commands insist on two spaces for the end of a sentence, as explained above. See Sentences.

If the variable colon-double-space is non-nil, the fill commands put two spaces after a colon.

Some languages do not use period to indicate end of sentence. For example, a sentence in Thai text ends with double space but without a period. Set the variable sentence-end-without-period to t to tell the sentence commands that a period is not necessary.

The variable fill-nobreak-predicate specifies additional conditions for where line-breaking is allowed. Its value is either nil or a Lisp function; the function is called with no arguments, and if it returns a non-nil value, then point is not a good place to break the line. Two standard functions you can use are fill-single-word-nobreak-p (don't break after the first word of a sentence or before the last) and fill-french-nobreak-p (don't break after ‘(’ or before ‘)’, ‘:’ or ‘?’).