30.5.6 Long Lines Mode

Long Lines mode is a minor mode for word wrapping; it lets you edit “unfilled” text files, which Emacs would normally display as a bunch of extremely long lines. Many text editors, such as those built into many web browsers, normally do word wrapping.

To enable Long Lines mode, type M-x longlines-mode. If the text is full of long lines, this will “wrap” them immediately—i.e., break up to fit in the window. As you edit the text, Long Lines mode automatically re-wraps lines by inserting or deleting soft newlines as necessary (see Hard and Soft Newlines.) These soft newlines won't show up when you save the buffer into a file, or when you copy the text into the kill ring, clipboard, or a register.

Word wrapping is not the same as ordinary filling (see Fill Commands). It does not contract multiple spaces into a single space, recognize fill prefixes (see Fill Prefix), or perform adaptive filling (see Adaptive Fill). The reason for this is that a wrapped line is still, conceptually, a single line. Each soft newline is equivalent to exactly one space in that long line, and vice versa. However, you can still call filling functions such as M-q, and these will work as expected, inserting soft newlines that won't show up on disk or when the text is copied. You can even rely entirely on the normal fill commands by turning off automatic line wrapping, with C-u M-x longlines-auto-wrap. To turn automatic line wrapping back on, type M-x longlines-auto-wrap.

Whenever you type RET, you are inserting a hard newline. If you want to see where all the hard newlines are, type M-x longlines-show-hard-newlines. This will mark each hard newline with a special symbol. The same command with a prefix argument turns this display off.

Long Lines mode does not change normal text files that are already filled, since the existing newlines are considered hard newlines. Before Long Lines can do anything, you need to transform each paragraph into a long line. One way is to set fill-column to a large number (e.g., C-u 9999 C-x f), re-fill all the paragraphs, and then set fill-column back to its original value.