blob: 5ac8a8dc48f637331031b4421a225bddfc2d28e4 [file] [log] [blame]
;; Copyright 2017 The Go Authors. All rights reserved.
;; Use of this source code is governed by a BSD-style
;; license that can be found in the LICENSE file.
;; This makes fill-paragraph (M-q) add line breaks at sentence
;; boundaries in addition to normal wrapping. This is the style for Go
;; proposals.
;; Loading this script automatically enables this for markdown-mode
;; buffers in the go-design/proposal directory. It can also be
;; manually enabled with M-x enable-fill-split-sentences.
;; This is sensitive to the setting of `sentence-end-double-space`,
;; which defaults to t. If `sentence-end-double-space` is t, but a
;; paragraph only a single space between sentences, this will not
;; insert line breaks where expected.
(defun fill-split-sentences (&optional justify)
"Fill paragraph at point, breaking lines at sentence boundaries."
;; Do a trial fill and get the fill prefix for this paragraph.
(let ((prefix (or (fill-paragraph) ""))
(end (progn (fill-forward-paragraph 1) (point)))
(beg (progn (fill-forward-paragraph -1) (point))))
(narrow-to-region (line-beginning-position) end)
;; Unfill the paragraph.
(let ((fill-column (point-max)))
(fill-region beg end))
;; Fill each sentence.
(goto-char (point-min))
(while (not (eobp))
(if (bobp)
;; Skip over initial prefix.
(goto-char beg)
;; Clean up space between sentences.
(skip-chars-forward " \t")
(delete-horizontal-space 'backward-only)
(insert "\n" prefix))
(let ((sbeg (point))
(fill-prefix prefix))
(fill-region-as-paragraph sbeg (point)))))
(defun enable-fill-split-sentences ()
"Make fill break lines at sentence boundaries in this buffer."
(setq-local fill-paragraph-function #'fill-split-sentences))
(defun proposal-enable-fill-split ()
(when (string-match "go-proposal/design/" (buffer-file-name))
;; Enable sentence splitting in new proposal buffers.
(add-hook 'markdown-mode-hook #'proposal-enable-fill-split)
;; Enable sentence splitting in this buffer, in case the user loaded
;; fill.el when already in a buffer.
(when (eq major-mode 'markdown-mode)