;;; display-line-numbers.el --- interface for display-line-numbers -*- lexical-binding: t -*-
;; Copyright (C) 2017-2024 Free Software Foundation, Inc.
;; Maintainer: emacs-devel@gnu.org
;; Keywords: convenience
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Provides a minor mode interface for `display-line-numbers'.
;;
;; Toggle display of line numbers with M-x display-line-numbers-mode.
;; To enable line numbering in all buffers, use M-x
;; global-display-line-numbers-mode. To change the default type of
;; line numbers displayed, customize display-line-numbers-type.
;; NOTE: Customization variables for `display-line-numbers' itself are
;; defined in cus-start.el.
;;; Code:
(defgroup display-line-numbers nil
"Display line numbers in the buffer."
:group 'convenience
:group 'display)
(defcustom display-line-numbers-type t
"The default type of line numbers to use in `display-line-numbers-mode'.
See `display-line-numbers' for value options."
:group 'display-line-numbers
:type '(choice (const :tag "Relative line numbers" relative)
(const :tag "Relative visual line numbers" visual)
(other :tag "Absolute line numbers" t))
:version "26.1")
(defcustom display-line-numbers-grow-only nil
"If non-nil, do not shrink line number width."
:group 'display-line-numbers
:type 'boolean
:version "26.1")
(defcustom display-line-numbers-width-start nil
"If non-nil, count number of lines to use for line number width.
When `display-line-numbers-mode' is turned on, if this option is
non-nil, `display-line-numbers-width' is set up front to a width
necessary to display all line numbers in the buffer. If the value
is a positive number, it is interpreted as extra lines to account
for when computing the required width; this should be set to the
number of lines in the tallest window in which you want to prevent
the line-number width from changing."
:group 'display-line-numbers
:type '(choice (boolean :tag "Minimum width for buffer's line count")
(integer :tag "Number of extra lines to account for"))
:version "28.1")
(defun display-line-numbers-update-width ()
"Prevent the line number width from shrinking."
(let ((width (line-number-display-width)))
(when (> width (or display-line-numbers-width 1))
(setq display-line-numbers-width width))))
;;;###autoload
(define-minor-mode display-line-numbers-mode
"Toggle display of line numbers in the buffer.
This uses `display-line-numbers' internally.
To change the type of line numbers displayed by default,
customize `display-line-numbers-type'. To change the type while
the mode is on, set `display-line-numbers' directly."
:lighter nil
(if display-line-numbers-mode
(progn
(when display-line-numbers-width-start
(setq display-line-numbers-width
(length (number-to-string
(+ (count-lines (point-min) (point-max))
(if (and (numberp display-line-numbers-width-start)
(> display-line-numbers-width-start 0))
display-line-numbers-width-start
0))))))
(when display-line-numbers-grow-only
(add-hook 'pre-command-hook #'display-line-numbers-update-width nil t))
(setq display-line-numbers display-line-numbers-type))
(remove-hook 'pre-command-hook #'display-line-numbers-update-width t)
(setq display-line-numbers nil)))
(defun display-line-numbers--turn-on ()
"Turn on `display-line-numbers-mode'."
(unless (minibufferp)
(display-line-numbers-mode)))
;;;###autoload
(define-globalized-minor-mode global-display-line-numbers-mode
display-line-numbers-mode display-line-numbers--turn-on)
;;;###autoload
(defvar header-line-indent ""
"String of spaces to indent the beginning of header-line due to line numbers.
This is intended to be used in `header-line-format', and requires
the `header-line-indent-mode' to be turned on, in order for the width
of this string to be kept updated when the line-number width changes
on display. An example of a `header-line-format' that uses this
variable might look like this:
(\"\" header-line-indent THE-REST...)
where THE-REST is the format string which produces the actual text
of the header-line.
Also see `header-line-indent-width'.")
;;;###autoload
(defvar header-line-indent-width 0
"The width of the current line number display in the window.
This is measured in units of the frame's canonical columns.
This is updated when `header-line-indent-mode' is switched on,
and is intended for use in `:align-to' display specifications
that are part of `header-line-format', when portions of header-line
text should be aligned to respective parts of buffer text.
Also see `header-line-indent'.")
(defun header-line-indent--line-number-width ()
"Return the width taken by `display-line-numbers' in the current buffer."
;; line-number-display-width returns the value for the selected
;; window, which might not be the window in which the current buffer
;; is displayed.
(if (not display-line-numbers)
0
(let ((cbuf-window (get-buffer-window (current-buffer) t)))
(if (window-live-p cbuf-window)
(with-selected-window cbuf-window
(truncate (line-number-display-width 'columns)))
4))))
(defun header-line-indent--watch-line-number-width (_window)
(let ((width (header-line-indent--line-number-width)))
(setq header-line-indent-width width)
(unless (= (length header-line-indent) width)
(setq header-line-indent (make-string width ?\s)))))
(defun header-line-indent--window-scroll-function (window _start)
(let ((width (with-selected-window window
(truncate (line-number-display-width 'columns)))))
(setq header-line-indent-width width)
(unless (= (length header-line-indent) width)
(setq header-line-indent (make-string width ?\s)))))
;;;###autoload
(define-minor-mode header-line-indent-mode
"Minor mode to help with alignment of header line when line numbers are shown.
This minor mode should be turned on in buffers which display header-line
that needs to be aligned with buffer text when `display-line-numbers-mode'
is turned on in the buffer.
Buffers that have this switched on should have a `header-line-format'
that uses the `header-line-indent' or the `header-line-indent-width'
variables, which this mode will keep up-to-date with the current
display of line numbers. For example, a `header-line-format' that
looks like this:
(\"\" header-line-indent THE-REST...)
will make sure the text produced by THE-REST (which should be
a header-line format string) is always indented to be aligned on
display with the first column of buffer text.
The `header-line-indent-width' variable is also kept updated,
and can be used, for instance, in `:align-to' specs as part
of `header-line-format', like this:
(space :align-to (+ header-line-indent-width 10))
See also `line-number-display-width'."
:lighter nil
(if header-line-indent-mode
(progn
(setq-local header-line-indent ""
header-line-indent-width 0)
(add-hook 'pre-redisplay-functions
#'header-line-indent--watch-line-number-width nil t)
(add-hook 'window-scroll-functions
#'header-line-indent--window-scroll-function nil t))
(setq-local header-line-indent ""
header-line-indent-width 0)
(remove-hook 'pre-redisplay-functions
#'header-line-indent--watch-line-number-width t)
(remove-hook 'window-scroll-functions
#'header-line-indent--window-scroll-function t)))
(provide 'display-line-numbers)
;;; display-line-numbers.el ends here