;;; linum-ex.el --- Display line numbers to the left of buffers

;; originally derived from linum.el, which is
;; Copyright (C) 2007, 2008  Markus Triska

;; modifications in linum-ex.el provided by: Dino Chiesa

;; Author: Markus Triska <markus.triska@gmx.at>
;; Last saved: <2011-May-23 12:47:18>
;;
;; Keywords: convenience

;; This file 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, or (at your option)
;; any later version.

;; This file 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; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; Display line numbers for the current buffer. Copy linum-ex.el to your
;; load-path and add to your .emacs:

;;    (require 'linum-ex)

;; Then toggle display of line numbers with M-x linum-mode. To enable
;; line numbering in all buffers, use M-x global-linum-mode.

;; =======================================================
;;
;; Dino Chiesa Mon, 23 May 2011  12:00
;;
;; notes on changes.
;;
;; The problem with the original linum module is that it updated the
;; line numbers after every scroll and possibly every command. This
;; works for small files but not for files with 100,000+ lines. Even
;; with linum-delay turned on, linum had the effect of "Freezing" the
;; display when the user was continuously scrolling.  It also introduced
;; noticeable delays when scrolling only momentarily.
;;
;; One idea for working around that is to use run-with-idle-timer, and
;; only update the line numbers when emacs is idle. One can set a single
;; timer, for, say 0.1s, and then when emacs goes idle for that period,
;; the line numbers will be updated. Seems like the perfect fit,
;; but there's a problem: a timer created via run-with-idle-timer
;; gets canceled after being delayed 10 times.
;;
;; So if the after-scroll event sets up a timer via run-with-idle-timer,
;; only when no timer has been set, the timer may get canceled silently,
;; by timer.el . Look at `timer-max-repeats'.
;;
;; This happens if emacs is busy for 1s, as for example when the user is
;; holding pgdn to continuously scroll through a large document.  If the
;; timer doesn't fire, then the line numbers don't ever get updated.
;;
;; To avoid that pitfall, this code can set run-with-idle-timer for
;; every scroll event, and handle the delay explicitly, right here.  The
;; way to do it is, within the after-scroll event, store the "last
;; scrolled" time, and then call `run-with-idle-timer'. There may be
;; other outstanding timer events, but we don't care.  In the function
;; that gets called when the timer fires, check to see if a reasonable
;; interval (Say 0.1s) has elapsed since the last scroll event. If so,
;; do linum-update. If not, it means scrolling is still happening, so,
;; do nothing. All this applies only if linum-delay is non-nil.
;;
;; The result is that timers fire constantly while the user is
;; continuously scrolling, but the line numbers get updated only after
;; the user stops scrolling.  The user experiences no delay while
;; scrolling, but (unfortunately) gets no line numbers either.  The user
;; sees updated line numbers immediately when he stops.
;;
;; =======================================================


;;; Code:

(require 'timer)

(defconst linum-version "0.991")

(defvar linum-overlays nil "Overlays used in this buffer.")
(defvar linum-available nil "Overlays available for reuse.")
(defvar linum-before-numbering-hook nil
  "Functions run in each buffer before line numbering starts.")

(mapc #'make-variable-buffer-local '(linum-overlays linum-available))

(defgroup linum nil
  "Show line numbers to the left of buffers"
  :group 'convenience)

;;;###autoload
(defcustom linum-format 'dynamic
  "Format used to display line numbers. Either a format string
like \"%7d\", 'dynamic to adapt the width as needed, or a
function that is called with a line number as its argument and
should evaluate to a string to be shown on that line. See also
`linum-before-numbering-hook'."
  :group 'linum
  :type 'sexp)

(defface linum
  '((t :inherit (shadow default)))
  "Face for displaying line numbers in the display margin."
  :group 'linum)

(defcustom linum-eager t
  "Whether line numbers should be updated after each command.
The conservative setting `nil' might miss some buffer changes,
and you have to scroll or press C-l to update the numbers."
  :group 'linum
  :type 'boolean)

(defcustom linum-delay nil
  "Delay updates to give Emacs a chance for other changes."
  :group 'linum
  :type 'boolean)

(defvar linum--delay-time 0.1
  "Delay time.  See also `linum-delay'")

(defvar linum--last-scroll nil
  "Time of last scroll event. See also `linum-delay'")

(defvar linum--last-cmd nil
  "Time of last command. See also `linum-delay'")

(defvar linum--win nil
  "Window of the last scroll event. See also `linum-delay'")


;;;###autoload
(define-minor-mode linum-mode
  "Toggle display of line numbers in the left marginal area."
  :lighter ""                           ; for desktop.el
  (if linum-mode
      (progn
        (if linum-eager
            (add-hook 'post-command-hook 'linum-post-command)
          (add-hook 'after-change-functions 'linum-after-change nil t))
        (add-hook 'window-scroll-functions 'linum-after-scroll nil t)
        ;; mistake in Emacs: window-size-change-functions cannot be local
        (add-hook 'window-size-change-functions 'linum-after-size)
        (add-hook 'change-major-mode-hook 'linum-delete-overlays nil t)
        (add-hook 'window-configuration-change-hook
                  'linum-after-config nil t)
        (set (make-local-variable 'linum--win) nil)
        (set (make-local-variable 'linum--last-scroll) nil)
        (set (make-local-variable 'linum--last-cmd) nil)
        (linum-update-current))
    (remove-hook 'post-command-hook 'linum-post-command t)
    (remove-hook 'window-size-change-functions 'linum-after-size)
    (remove-hook 'window-scroll-functions 'linum-after-scroll t)
    (remove-hook 'after-change-functions 'linum-after-change t)
    (remove-hook 'window-configuration-change-hook 'linum-after-config t)
    (remove-hook 'change-major-mode-hook 'linum-delete-overlays t)
    (linum-delete-overlays)))

;;;###autoload
(define-globalized-minor-mode global-linum-mode linum-mode linum-on)

(defun linum-on ()
  (unless (minibufferp)
    (linum-mode 1)))

(defun linum-delete-overlays ()
  "Delete all overlays displaying line numbers for this buffer."
  (mapc #'delete-overlay linum-overlays)
  (setq linum-overlays nil)
  (dolist (w (get-buffer-window-list (current-buffer) nil t))
    (set-window-margins w 0)))

(defun linum-update-current ()
  "Update line numbers for the current buffer."
  (linum-update (current-buffer)))

(defun linum-update (buffer)
  "Update line numbers for all windows displaying BUFFER."
  (with-current-buffer buffer
    (when linum-mode
      (setq linum-available linum-overlays)
      (setq linum-overlays nil)
      (save-excursion
        (mapc #'linum-update-window
              (get-buffer-window-list buffer nil 'visible)))
      (mapc #'delete-overlay linum-available)
      (setq linum-available nil
            linum--last-cmd nil
            linum--last-scroll nil))))


(defun linum-update-window (win)
  "Update line numbers for the portion visible in window WIN."
  (goto-char (window-start win))
  (let ((line (line-number-at-pos))
        (limit (window-end win t))
        (fmt (cond ((stringp linum-format) linum-format)
                   ((eq linum-format 'dynamic)
                    (let ((w (length (number-to-string
                                      (count-lines (point-min) (point-max))))))
                      (concat "%" (number-to-string w) "d")))))
        (width 0))
    (run-hooks 'linum-before-numbering-hook)
    ;; Create an overlay (or reuse an existing one) for each
    ;; line visible in this window, if necessary.
    (while (and (not (eobp)) (<= (point) limit))
      (let* ((str (if fmt
                      (propertize (format fmt line) 'face 'linum)
                    (funcall linum-format line)))
             (visited (catch 'visited
                        (dolist (o (overlays-in (point) (point)))
                          (when (string= (overlay-get o 'linum-str) str)
                            (unless (memq o linum-overlays)
                              (push o linum-overlays))
                            (setq linum-available (delete o linum-available))
                            (throw 'visited t))))))
        (setq width (max width (length str)))
        (unless visited
          (let ((ov (if (null linum-available)
                        (make-overlay (point) (point))
                      (move-overlay (pop linum-available) (point) (point)))))
            (push ov linum-overlays)
            (overlay-put ov 'before-string
                         (propertize " " 'display `((margin left-margin) ,str)))
            (overlay-put ov 'linum-str str))))
      (forward-line)
      (setq line (1+ line)))
    (set-window-margins win width)))

(defun linum-after-change (beg end len)
  ;; update overlays on deletions, and after newlines are inserted
  (when (or (= beg end)
            (= end (point-max))
            ;; TODO: use string-match-p with CVS or new release
            (string-match "\n" (buffer-substring-no-properties beg end)))
    (linum-update-current)))

(defun linum--after-scroll-fired ()
  (if linum--last-scroll
      (let ((now  (current-time))
            (one-moment-after-scroll (timer-relative-time linum--last-scroll linum--delay-time)))
        (if (time-less-p one-moment-after-scroll now)
            (linum-update linum--win)))))

(defun linum-after-scroll (win start)
  (if linum-delay
      (progn
        (setq linum--win (window-buffer win))
        (setq linum--last-scroll (current-time))
        (run-with-idle-timer linum--delay-time nil 'linum--after-scroll-fired))
    (linum-update (window-buffer win))))


(defun linum--post-command-fired ()
  (if linum--last-cmd
      (let ((now  (current-time))
            (one-moment-after-cmd (timer-relative-time linum--last-cmd linum--delay-time)))
        (if (time-less-p one-moment-after-cmd now)
            (linum-update-current)))))

(defun linum-post-command ()
  (if linum-delay
      (progn
        (setq linum--win (window-buffer win))
        (setq linum--last-cmd (current-time))
        (run-with-idle-timer linum--delay-time nil 'linum--post-command-fired))
    (linum-update-current)))

(defun linum-after-size (frame)
  (linum-after-config))

(defun linum-after-config ()
  (walk-windows (lambda (w) (linum-update (window-buffer w))) nil 'visible))


(provide 'linum-ex)
;;; linum-ex.el ends here