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[gnu-emacs] / lisp / mouse-sel.el

;;; mouse-sel.el --- multi-click selection support

;; Copyright (C) 1993, 1994, 1995, 2001, 2002, 2003, 2004, 2005, 2006,
;;   2007, 2008, 2009, 2010, 2011, 2012  Free Software Foundation, Inc.

;; Author: Mike Williams <mdub@bigfoot.com>
;; Keywords: mouse

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This module provides multi-click mouse support for GNU Emacs versions
;; 19.18 and later.  I've tried to make it behave more like standard X
;; clients (eg. xterm) than the default Emacs 19 mouse selection handlers.
;; Basically:
;;
;;   * Clicking mouse-1 starts (cancels) selection, dragging extends it.
;;
;;   * Clicking or dragging mouse-3 extends the selection as well.
;;
;;   * Double-clicking on word constituents selects words.
;;     Double-clicking on symbol constituents selects symbols.
;;     Double-clicking on quotes or parentheses selects sexps.
;;     Double-clicking on whitespace selects whitespace.
;;     Triple-clicking selects lines.
;;     Quad-clicking selects paragraphs.
;;
;;   * Selecting sets the region & X primary selection, but does NOT affect
;;     the kill-ring.  Because the mouse handlers set the primary selection
;;     directly, mouse-sel sets the variables interprogram-cut-function
;;     and interprogram-paste-function to nil.
;;
;;   * Clicking mouse-2 inserts the contents of the primary selection at
;;     the mouse position (or point, if mouse-yank-at-point is non-nil).
;;
;;   * Pressing mouse-2 while selecting or extending copies selection
;;     to the kill ring.  Pressing mouse-1 or mouse-3 kills it.
;;
;;   * Double-clicking mouse-3 also kills selection.
;;
;;   * M-mouse-1, M-mouse-2 & M-mouse-3 work similarly to mouse-1, mouse-2
;;     & mouse-3, but operate on the X secondary selection rather than the
;;     primary selection and region.
;;
;; This module requires my thingatpt.el module, which it uses to find the
;; bounds of words, lines, sexps, etc.
;;
;; Thanks to KevinB@bartley.demon.co.uk for his useful input.
;;
;;--- Customisation -------------------------------------------------------
;;
;; * You may want to use none or more of following:
;;
;;      ;; Enable region highlight
;;      (transient-mark-mode 1)
;;
;;      ;; But only in the selected window
;;      (setq highlight-nonselected-windows nil)
;;
;;      ;; Enable pending-delete
;;      (delete-selection-mode 1)
;;
;; * You can control the way mouse-sel binds its keys by setting the value
;;   of mouse-sel-default-bindings before loading mouse-sel.
;;
;;   (a) If mouse-sel-default-bindings = t (the default)
;;
;;       Mouse sets and insert selection
;;         mouse-1              mouse-select
;;         mouse-2              mouse-insert-selection
;;         mouse-3              mouse-extend
;;
;;       Selection/kill-ring interaction is disabled
;;         interprogram-cut-function   = nil
;;         interprogram-paste-function = nil
;;
;;   (b) If mouse-sel-default-bindings = 'interprogram-cut-paste
;;
;;       Mouse sets selection, and pastes from kill-ring
;;         mouse-1              mouse-select
;;         mouse-2              mouse-insert-selection
;;         mouse-3              mouse-extend
;;       In this mode, mouse-insert-selection just calls mouse-yank-at-click.
;;
;;       Selection/kill-ring interaction is retained
;;         interprogram-cut-function   = x-select-text
;;         interprogram-paste-function = x-cut-buffer-or-selection-value
;;
;;       What you lose is the ability to select some text in
;;       delete-selection-mode and yank over the top of it.
;;
;;   (c) If mouse-sel-default-bindings = nil, no bindings are made.
;;
;; * By default, mouse-insert-selection (mouse-2) inserts the selection at
;;   the mouse position.  You can tell it to insert at point instead with:
;;
;;     (setq mouse-yank-at-point t)
;;
;; * I like to leave point at the end of the region nearest to where the
;;   mouse was, even though this makes region highlighting mis-leading (the
;;   cursor makes it look like one extra character is selected).  You can
;;   disable this behavior with:
;;
;;     (setq mouse-sel-leave-point-near-mouse nil)
;;
;; * By default, mouse-select cycles the click count after 4 clicks.  That
;;   is, clicking mouse-1 five times has the same effect as clicking it
;;   once, clicking six times has the same effect as clicking twice, etc.
;;   Disable this behavior with:
;;
;;     (setq mouse-sel-cycle-clicks nil)
;;
;; * The variables mouse-sel-{set,get}-selection-function control how the
;;   selection is handled.  Under X Windows, these variables default so
;;   that the X primary selection is used.  Under other windowing systems,
;;   alternate functions are used, which simply store the selection value
;;   in a variable.
;;
;; * You can change the selection highlight face by altering the properties
;;   of mouse-drag-overlay, eg.
;;
;;     (overlay-put mouse-drag-overlay 'face 'bold)

;;; Code:

(require 'mouse)
(require 'thingatpt)

(eval-when-compile
  (require 'cl))

;;=== User Variables ======================================================

(defgroup mouse-sel nil
  "Mouse selection enhancement."
  :group 'mouse)

(defcustom mouse-sel-leave-point-near-mouse t
  "Leave point near last mouse position.
If non-nil, \\[mouse-select] and \\[mouse-extend] will leave point at the end
of the region nearest to where the mouse last was.
If nil, point will always be placed at the beginning of the region."
  :type 'boolean
  :group 'mouse-sel)

(defcustom mouse-sel-cycle-clicks t
  "If non-nil, \\[mouse-select] cycles the click-counts after 4 clicks."
  :type 'boolean
  :group 'mouse-sel)

(defcustom mouse-sel-default-bindings t
  "Control mouse bindings."
  :type '(choice (const :tag "none" nil)
                 (const :tag "cut and paste" interprogram-cut-paste)
                 (other :tag "default bindings" t))
  :group 'mouse-sel)

;;=== Key bindings ========================================================

(defconst mouse-sel-bound-events
  '(;; Primary selection bindings.
    ;;
    ;; Bind keys to `ignore' instead of unsetting them because modes may
    ;; bind `down-mouse-1', for instance, without binding `mouse-1'.
    ;; If we unset `mouse-1', this leads to a bitch_at_user when the
    ;; mouse goes up because no matching binding is found for that.
    ([mouse-1]          . ignore)
    ([drag-mouse-1]     . ignore)
    ([mouse-3]          . ignore)
    ([down-mouse-1]     . mouse-select)
    ([down-mouse-3]     . mouse-extend)
    ([mouse-2]          . mouse-insert-selection)
    ;; Secondary selection bindings.
    ([M-mouse-1]        . ignore)
    ([M-drag-mouse-1]   . ignore)
    ([M-mouse-3]        . ignore)
    ([M-down-mouse-1]   . mouse-select-secondary)
    ([M-mouse-2]        . mouse-insert-secondary)
    ([M-down-mouse-3]   . mouse-extend-secondary))
  "An alist of events that `mouse-sel-mode' binds.")

;;=== User Command ========================================================

(defvar mouse-sel-has-been-enabled nil
  "Non-nil if Mouse Sel mode has been enabled at least once.")

(defvar mouse-sel-original-bindings nil)
(defvar mouse-sel-original-interprogram-cut-function nil)
(defvar mouse-sel-original-interprogram-paste-function nil)

;;;###autoload
(define-minor-mode mouse-sel-mode
  "Toggle Mouse Sel mode.
With prefix ARG, turn Mouse Sel mode on if and only if ARG is positive.
Returns the new status of Mouse Sel mode (non-nil means on).

When Mouse Sel mode is enabled, mouse selection is enhanced in various ways:

- Clicking mouse-1 starts (cancels) selection, dragging extends it.

- Clicking or dragging mouse-3 extends the selection as well.

- Double-clicking on word constituents selects words.
Double-clicking on symbol constituents selects symbols.
Double-clicking on quotes or parentheses selects sexps.
Double-clicking on whitespace selects whitespace.
Triple-clicking selects lines.
Quad-clicking selects paragraphs.

- Selecting sets the region & X primary selection, but does NOT affect
the `kill-ring', nor do the kill-ring functions change the X selection.
Because the mouse handlers set the primary selection directly,
mouse-sel sets the variables `interprogram-cut-function' and
`interprogram-paste-function' to nil.

- Clicking mouse-2 inserts the contents of the primary selection at
the mouse position (or point, if `mouse-yank-at-point' is non-nil).

- Pressing mouse-2 while selecting or extending copies selection
to the kill ring.  Pressing mouse-1 or mouse-3 kills it.

- Double-clicking mouse-3 also kills selection.

- M-mouse-1, M-mouse-2 & M-mouse-3 work similarly to mouse-1, mouse-2
& mouse-3, but operate on the X secondary selection rather than the
primary selection and region."
  :global t
  :group 'mouse-sel
  (if mouse-sel-mode
      (progn
        ;; If mouse-2 has never been done by the user, initialize the
        ;; `event-kind' property to ensure that `follow-link' clicks
        ;; are interpreted correctly.
        (put 'mouse-2 'event-kind 'mouse-click)
        (add-hook 'x-lost-selection-functions 'mouse-sel-lost-selection-hook)
        (when mouse-sel-default-bindings
          ;; Save original bindings and replace them with new ones.
          (setq mouse-sel-original-bindings
                (mapcar (lambda (binding)
                          (let ((event (car binding)))
                            (prog1 (cons event (lookup-key global-map event))
                              (global-set-key event (cdr binding)))))
                        mouse-sel-bound-events))
          ;; Update interprogram functions.
          (setq mouse-sel-original-interprogram-cut-function
                interprogram-cut-function
                mouse-sel-original-interprogram-paste-function
                interprogram-paste-function
                mouse-sel-has-been-enabled t)
          (unless (eq mouse-sel-default-bindings 'interprogram-cut-paste)
            (setq interprogram-cut-function nil
                  interprogram-paste-function nil))))

    ;; Restore original bindings
    (remove-hook 'x-lost-selection-functions 'mouse-sel-lost-selection-hook)
    (dolist (binding mouse-sel-original-bindings)
      (global-set-key (car binding) (cdr binding)))
    ;; Restore the old values of these variables,
    ;; only if they were actually saved previously.
    (if mouse-sel-has-been-enabled
        (setq interprogram-cut-function
              mouse-sel-original-interprogram-cut-function
              interprogram-paste-function
              mouse-sel-original-interprogram-paste-function))))

;;=== Internal Variables/Constants ========================================

(defvar mouse-sel-primary-thing nil
  "Type of PRIMARY selection in current buffer.")
(make-variable-buffer-local 'mouse-sel-primary-thing)

(defvar mouse-sel-secondary-thing nil
  "Type of SECONDARY selection in current buffer.")
(make-variable-buffer-local 'mouse-sel-secondary-thing)

;; Ensure that secondary overlay is defined
(unless (overlayp mouse-secondary-overlay)
  (setq mouse-secondary-overlay (make-overlay 1 1))
  (overlay-put mouse-secondary-overlay 'face 'secondary-selection))

(defconst mouse-sel-selection-alist
  '((PRIMARY mouse-drag-overlay mouse-sel-primary-thing)
    (SECONDARY mouse-secondary-overlay mouse-sel-secondary-thing))
  "Alist associating selections with variables.
Each element is of the form:

   (SELECTION-NAME OVERLAY-SYMBOL SELECTION-THING-SYMBOL)

where   SELECTION-NAME          = name of selection
        OVERLAY-SYMBOL          = name of variable containing overlay to use
        SELECTION-THING-SYMBOL  = name of variable where the current selection
                                  type for this selection should be stored.")

(declare-function x-select-text "term/x-win" (text &optional push))

(defvar mouse-sel-set-selection-function
  (if (eq mouse-sel-default-bindings 'interprogram-cut-paste)
      'x-set-selection
    (lambda (selection value)
      (if (eq selection 'PRIMARY)
          (x-select-text value)
        (x-set-selection selection value))))
  "Function to call to set selection.
Called with two arguments:

  SELECTION, the name of the selection concerned, and
  VALUE, the text to store.

This sets the selection as well as the cut buffer for the older applications,
unless `mouse-sel-default-bindings' is `interprogram-cut-paste'.")

(declare-function x-cut-buffer-or-selection-value "term/x-win" ())

(defvar mouse-sel-get-selection-function
  (lambda (selection)
    (if (eq selection 'PRIMARY)
        (or (x-cut-buffer-or-selection-value)
            (bound-and-true-p x-last-selected-text)
            (bound-and-true-p x-last-selected-text-primary))
      (x-get-selection selection)))
  "Function to call to get the selection.
Called with one argument:

   SELECTION: the name of the selection concerned.")

;;=== Support/access functions ============================================

(defun mouse-sel-determine-selection-thing (nclicks)
  "Determine what `thing' `mouse-sel' should operate on.
The first argument is NCLICKS, is the number of consecutive
mouse clicks at the same position.

Double-clicking on word constituents selects words.
Double-clicking on symbol constituents selects symbols.
Double-clicking on quotes or parentheses selects sexps.
Double-clicking on whitespace selects whitespace.
Triple-clicking selects lines.
Quad-clicking selects paragraphs.

Feel free to re-define this function to support your own desired
multi-click semantics."
  (let* ((next-char (char-after (point)))
         (char-syntax (if next-char (char-syntax next-char))))
    (if mouse-sel-cycle-clicks
        (setq nclicks (1+ (% (1- nclicks) 4))))
    (cond
     ((= nclicks 1) nil)
     ((= nclicks 3) 'line)
     ((>= nclicks 4) 'paragraph)
     ((memq char-syntax '(?\( ?\) ?\" ?')) 'sexp)
     ((memq next-char '(?\s ?\t ?\n)) 'whitespace)
     ((eq char-syntax ?_) 'symbol)
     ((eq char-syntax ?w) 'word))))

(defun mouse-sel-set-selection (selection value)
  "Set the specified SELECTION to VALUE."
  (if mouse-sel-set-selection-function
      (funcall mouse-sel-set-selection-function selection value)
    (put 'mouse-sel-internal-selection selection value)))

(defun mouse-sel-get-selection (selection)
  "Get the value of the specified SELECTION."
  (if mouse-sel-get-selection-function
      (funcall mouse-sel-get-selection-function selection)
    (get 'mouse-sel-internal-selection selection)))

(defun mouse-sel-selection-overlay (selection)
  "Return overlay corresponding to SELECTION."
  (let ((symbol (nth 1 (assoc selection mouse-sel-selection-alist))))
    (or symbol (error "No overlay corresponding to %s selection" selection))
    (symbol-value symbol)))

(defun mouse-sel-selection-thing (selection)
  "Return overlay corresponding to SELECTION."
  (let ((symbol (nth 2 (assoc selection mouse-sel-selection-alist))))
    (or symbol (error "No symbol corresponding to %s selection" selection))
    symbol))

(defun mouse-sel-region-to-primary (orig-window)
  "Convert region to PRIMARY overlay and deactivate region.
Argument ORIG-WINDOW specifies the window the cursor was in when the
originating command was issued, and is used to determine whether the
region was visible or not."
  (if transient-mark-mode
      (let ((overlay (mouse-sel-selection-overlay 'PRIMARY)))
        (cond
         ((and mark-active
               (or highlight-nonselected-windows
                   (eq orig-window (selected-window))))
          ;; Region was visible, so convert region to overlay
          (move-overlay overlay (region-beginning) (region-end)
                        (current-buffer)))
         ((eq orig-window (selected-window))
          ;; Point was visible, so set overlay at point
          (move-overlay overlay (point) (point) (current-buffer)))
         (t
          ;; Nothing was visible, so remove overlay
          (delete-overlay overlay)))
        (setq mark-active nil))))

(defun mouse-sel-primary-to-region (&optional direction)
  "Convert PRIMARY overlay to region.
Optional argument DIRECTION specifies the mouse drag direction: a value of
1 indicates that the mouse was dragged left-to-right, otherwise it was
dragged right-to-left."
  (let* ((overlay (mouse-sel-selection-overlay 'PRIMARY))
         (start (overlay-start overlay))
         (end (overlay-end overlay)))
    (if (eq start end)
        (progn
          (if start (goto-char start))
          (deactivate-mark))
      (if (and mouse-sel-leave-point-near-mouse (eq direction 1))
          (progn
            (goto-char end)
            (push-mark start 'nomsg 'active))
        (goto-char start)
        (push-mark end 'nomsg 'active)))
    (if transient-mark-mode (delete-overlay overlay))))

(defmacro mouse-sel-eval-at-event-end (event &rest forms)
  "Evaluate forms at mouse position.
Move to the end position of EVENT, execute FORMS, and restore original
point and window."
  `(let ((posn (event-end ,event)))
    (if posn (mouse-minibuffer-check ,event))
    (if (and posn (not (windowp (posn-window posn))))
        (error "Cursor not in text area of window"))
    (let (orig-window orig-point-marker)
      (setq orig-window (selected-window))
      (if posn (select-window (posn-window posn)))
      (setq orig-point-marker (point-marker))
      (if (and posn (numberp (posn-point posn)))
          (goto-char (posn-point posn)))
      (unwind-protect
           (progn
             ,@forms)
        (goto-char (marker-position orig-point-marker))
        (move-marker orig-point-marker nil)
        (select-window orig-window)))))

(put 'mouse-sel-eval-at-event-end 'lisp-indent-hook 1)

;;=== Select ==============================================================

(defun mouse-select (event)
  "Set region/selection using the mouse.

Click sets point & mark to click position.
Dragging extends region/selection.

Multi-clicking selects word/lines/paragraphs, as determined by
'mouse-sel-determine-selection-thing.

Clicking mouse-2 while selecting copies selected text to the kill-ring.
Clicking mouse-1 or mouse-3 kills the selected text.

This should be bound to a down-mouse event."
  (interactive "@e")
  (let (select)
    (unwind-protect
        (setq select (mouse-select-internal 'PRIMARY event))
      (if (and select (listp select))
          (push (cons 'mouse-2 (cdr event)) unread-command-events)
        (mouse-sel-primary-to-region select)))))

(defun mouse-select-secondary (event)
  "Set secondary selection using the mouse.

Click sets the start of the secondary selection to click position.
Dragging extends the secondary selection.

Multi-clicking selects word/lines/paragraphs, as determined by
'mouse-sel-determine-selection-thing.

Clicking mouse-2 while selecting copies selected text to the kill-ring.
Clicking mouse-1 or mouse-3 kills the selected text.

This should be bound to a down-mouse event."
  (interactive "e")
  (mouse-select-internal 'SECONDARY event))

(defun mouse-select-internal (selection event)
  "Set SELECTION using the mouse, with EVENT as the initial down-event.
Normally, this returns the direction in which the selection was
made: a value of 1 indicates that the mouse was dragged
left-to-right, otherwise it was dragged right-to-left.

However, if `mouse-1-click-follows-link' is non-nil and the
subsequent mouse events specify following a link, this returns
the final mouse-event.  In that case, the selection is not set."
  (mouse-sel-eval-at-event-end event
    (let ((thing-symbol (mouse-sel-selection-thing selection))
          (overlay (mouse-sel-selection-overlay selection)))
      (set thing-symbol
           (mouse-sel-determine-selection-thing (event-click-count event)))
      (let ((object-bounds (bounds-of-thing-at-point
                            (symbol-value thing-symbol))))
        (if object-bounds
            (progn
              (move-overlay overlay
                            (car object-bounds) (cdr object-bounds)
                            (current-buffer)))
          (move-overlay overlay (point) (point) (current-buffer)))))
    (catch 'follow-link
      (mouse-extend-internal selection event t))))

;;=== Extend ==============================================================

(defun mouse-extend (event)
  "Extend region/selection using the mouse."
  (interactive "e")
  (let ((orig-window (selected-window))
        direction)
    (select-window (posn-window (event-end event)))
    (unwind-protect
        (progn
          (mouse-sel-region-to-primary orig-window)
          (setq direction (mouse-extend-internal 'PRIMARY event)))
      (mouse-sel-primary-to-region direction))))

(defun mouse-extend-secondary (event)
  "Extend secondary selection using the mouse."
  (interactive "e")
  (save-window-excursion
    (mouse-extend-internal 'SECONDARY event)))

(defun mouse-extend-internal (selection &optional initial-event no-process)
  "Extend specified SELECTION using the mouse.
Track mouse-motion events, adjusting the SELECTION appropriately.
Optional argument INITIAL-EVENT specifies an initial down-mouse event.
Optional argument NO-PROCESS means not to process the initial
event.

See documentation for mouse-select-internal for more details."
  (mouse-sel-eval-at-event-end initial-event
    (let ((orig-cursor-type
           (cdr (assoc 'cursor-type (frame-parameters (selected-frame))))))
      (unwind-protect

          (let* ((thing-symbol (mouse-sel-selection-thing selection))
                 (overlay (mouse-sel-selection-overlay selection))
                 (orig-window (selected-window))
                 (orig-window-frame (window-frame orig-window))
                 (top (nth 1 (window-edges orig-window)))
                 (bottom (nth 3 (window-edges orig-window)))
                 (mark-active nil)      ; inhibit normal region highlight
                 (echo-keystrokes 0)    ; don't echo mouse events
                 min max
                 direction
                 event)

            ;; Get current bounds of overlay
            (if (eq (overlay-buffer overlay) (current-buffer))
                (setq min (overlay-start overlay)
                      max (overlay-end overlay))
              (setq min (point)
                    max min)
              (set thing-symbol nil))


            ;; Bar cursor
            (if (fboundp 'modify-frame-parameters)
                (modify-frame-parameters (selected-frame)
                                         '((cursor-type . bar))))

            ;; Handle dragging
            (track-mouse

              (while (if (and initial-event (not no-process))
                         ;; Use initial event
                         (prog1
                             (setq event initial-event)
                           (setq initial-event nil))
                       (setq event (read-event))
                       (and (consp event)
                            (memq (car event) '(mouse-movement switch-frame))))

                (let ((selection-thing (symbol-value thing-symbol))
                      (end (event-end event)))

                  (cond

                   ;; Ignore any movement outside the frame
                   ((eq (car-safe event) 'switch-frame) nil)
                   ((and (posn-window end)
                         (not (eq (let ((posn-w (posn-window end)))
                                    (if (windowp posn-w)
                                        (window-frame posn-w)
                                      posn-w))
                                  (window-frame orig-window)))) nil)

                   ;; Different window, same frame
                   ((not (eq (posn-window end) orig-window))
                    (let ((end-row (cdr (cdr (mouse-position)))))
                      (cond
                       ((and end-row (not (bobp)) (< end-row top))
                        (mouse-scroll-subr orig-window (- end-row top)
                                           overlay max))
                       ((and end-row (not (eobp)) (>= end-row bottom))
                        (mouse-scroll-subr orig-window (1+ (- end-row bottom))
                                           overlay min))
                       )))

                   ;; On the mode line
                   ((eq (posn-point end) 'mode-line)
                    (mouse-scroll-subr orig-window 1 overlay min))

                   ;; In original window
                   (t (goto-char (posn-point end)))

                   )

                  ;; Determine direction of drag
                  (cond
                   ((and (not direction) (not (eq min max)))
                    (setq direction (if (< (point) (/ (+ min max) 2)) -1 1)))
                   ((and (not (eq direction -1)) (<= (point) min))
                    (setq direction -1))
                   ((and (not (eq direction 1)) (>= (point) max))
                    (setq direction 1)))

                  (if (not selection-thing) nil

                    ;; If dragging forward, goal is next character
                    (if (and (eq direction 1) (not (eobp))) (forward-char 1))

                    ;; Move to start/end of selected thing
                    (let ((goal (point)))
                      (goto-char (if (eq 1 direction) min max))
                      (condition-case nil
                          (progn
                            (while (> (* direction (- goal (point))) 0)
                              (forward-thing selection-thing direction))
                            (let ((end (point)))
                              (forward-thing selection-thing (- direction))
                              (goto-char
                               (if (> (* direction (- goal (point))) 0)
                                   end (point)))))
                        (error))))

                  ;; Move overlay
                  (move-overlay overlay
                                (if (eq 1 direction) min (point))
                                (if (eq -1 direction) max (point))
                                (current-buffer))

                  )))                   ; end track-mouse

            ;; Detect follow-link events
            (when (mouse-sel-follow-link-p initial-event event)
              (throw 'follow-link event))

            ;; Finish up after dragging
            (let ((overlay-start (overlay-start overlay))
                  (overlay-end (overlay-end overlay)))

              ;; Set selection
              (if (not (eq overlay-start overlay-end))
                  (mouse-sel-set-selection
                   selection
                   (buffer-substring overlay-start overlay-end)))

              ;; Handle copy/kill
              (let (this-command)
                (cond
                 ((eq (event-basic-type last-input-event) 'mouse-2)
                  (copy-region-as-kill overlay-start overlay-end)
                  (read-event) (read-event))
                 ((and (memq (event-basic-type last-input-event)
                             '(mouse-1 mouse-3))
                       (memq 'down (event-modifiers last-input-event)))
                  (kill-region overlay-start overlay-end)
                  (move-overlay overlay overlay-start overlay-start)
                  (read-event) (read-event))
                 ((and (eq (event-basic-type last-input-event) 'mouse-3)
                       (memq 'double (event-modifiers last-input-event)))
                  (kill-region overlay-start overlay-end)
                  (move-overlay overlay overlay-start overlay-start)))))

            direction)

        ;; Restore cursor
        (if (fboundp 'modify-frame-parameters)
            (modify-frame-parameters
             (selected-frame) (list (cons 'cursor-type orig-cursor-type))))

        ))))

(defun mouse-sel-follow-link-p (initial final)
  "Return t if we should follow a link, given INITIAL and FINAL mouse events.
See `mouse-1-click-follows-link' for details.  Currently, Mouse
Sel mode does not support using a `double' value to follow links
using double-clicks."
  (and initial final mouse-1-click-follows-link
       (eq (car initial) 'down-mouse-1)
       (mouse-on-link-p (event-start initial))
       (= (posn-point (event-start initial))
          (posn-point (event-end final)))
       (= (event-click-count initial) 1)
       (or (not (integerp mouse-1-click-follows-link))
           (let ((t0 (posn-timestamp (event-start initial)))
                 (t1 (posn-timestamp (event-end final))))
             (and (integerp t0) (integerp t1)
                  (if (> mouse-1-click-follows-link 0)
                      (<= (- t1 t0) mouse-1-click-follows-link)
                    (< (- t0 t1) mouse-1-click-follows-link)))))))

;;=== Paste ===============================================================

(defun mouse-insert-selection (event arg)
  "Insert the contents of the PRIMARY selection at mouse click.
If `mouse-yank-at-point' is non-nil, insert at point instead."
  (interactive "e\nP")
  (if (eq mouse-sel-default-bindings 'interprogram-cut-paste)
      (mouse-yank-at-click event arg)
    (mouse-insert-selection-internal 'PRIMARY event)))

(defun mouse-insert-secondary (event)
  "Insert the contents of the SECONDARY selection at mouse click.
If `mouse-yank-at-point' is non-nil, insert at point instead."
  (interactive "e")
  (mouse-insert-selection-internal 'SECONDARY event))

(defun mouse-insert-selection-internal (selection event)
  "Insert the contents of the named SELECTION at mouse click.
If `mouse-yank-at-point' is non-nil, insert at point instead."
  (unless mouse-yank-at-point
    (mouse-set-point event))
  (when mouse-sel-get-selection-function
    (push-mark (point) 'nomsg)
  (insert-for-yank
   (or (funcall mouse-sel-get-selection-function selection) ""))))

;;=== Handle loss of selections ===========================================

(defun mouse-sel-lost-selection-hook (selection)
  "Remove the overlay for a lost selection."
  (let ((overlay (mouse-sel-selection-overlay selection)))
    (delete-overlay overlay)))

(provide 'mouse-sel)

;;; mouse-sel.el ends here