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;;; mouse.el --- window system-independent mouse support  -*- lexical-binding: t -*-
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;; Copyright (C) 1993-1995, 1999-2014 Free Software Foundation, Inc.
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: hardware, mouse
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;; Package: emacs
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
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;; 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.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:

;; This package provides various useful commands (including help
;; system access) through the mouse.  All this code assumes that mouse
;; interpretation has been abstracted into Emacs input events.

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;;; Code:

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;;; Utility functions.
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;; Indent track-mouse like progn.
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(put 'track-mouse 'lisp-indent-function 0)
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(defcustom mouse-yank-at-point nil
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  "If non-nil, mouse yank commands yank at point instead of at click."
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  :type 'boolean
  :group 'mouse)
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(defcustom mouse-drag-copy-region nil
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  "If non-nil, copy to kill-ring upon mouse adjustments of the region.

This affects `mouse-save-then-kill' (\\[mouse-save-then-kill]) in
addition to mouse drags."
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  :type 'boolean
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  :version "24.1"
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  :group 'mouse)

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(defcustom mouse-1-click-follows-link 450
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  "Non-nil means that clicking Mouse-1 on a link follows the link.
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With the default setting, an ordinary Mouse-1 click on a link
performs the same action as Mouse-2 on that link, while a longer
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Mouse-1 click \(hold down the Mouse-1 button for more than 450
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milliseconds) performs the original Mouse-1 binding \(which
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typically sets point where you click the mouse).

If value is an integer, the time elapsed between pressing and
releasing the mouse button determines whether to follow the link
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or perform the normal Mouse-1 action (typically set point).
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The absolute numeric value specifies the maximum duration of a
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\"short click\" in milliseconds.  A positive value means that a
short click follows the link, and a longer click performs the
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normal action.  A negative value gives the opposite behavior.
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If value is `double', a double click follows the link.

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Otherwise, a single Mouse-1 click unconditionally follows the link.
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Note that dragging the mouse never follows the link.

This feature only works in modes that specifically identify
clickable text as links, so it may not work with some external
packages.  See `mouse-on-link-p' for details."
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  :version "22.1"
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  :type '(choice (const :tag "Disabled" nil)
		 (const :tag "Double click" double)
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                 (number :tag "Single click time limit" :value 450)
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                 (other :tag "Single click" t))
  :group 'mouse)

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(defcustom mouse-1-click-in-non-selected-windows t
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  "If non-nil, a Mouse-1 click also follows links in non-selected windows.
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If nil, a Mouse-1 click on a link in a non-selected window performs
the normal mouse-1 binding, typically selects the window and sets
point at the click position."
  :type 'boolean
  :version "22.1"
  :group 'mouse)

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(defun mouse--down-1-maybe-follows-link (&optional _prompt)
  "Turn `mouse-1' events into `mouse-2' events if follows-link.
Expects to be bound to `down-mouse-1' in `key-translation-map'."
  (if (or (null mouse-1-click-follows-link)
          (not (eq (if (eq mouse-1-click-follows-link 'double)
                       'double-down-mouse-1 'down-mouse-1)
                   (car-safe last-input-event)))
          (not (mouse-on-link-p (event-start last-input-event)))
          (and (not mouse-1-click-in-non-selected-windows)
               (not (eq (selected-window)
                        (posn-window (event-start last-input-event))))))
      nil
    (let ((this-event last-input-event)
          (timedout
           (sit-for (if (numberp mouse-1-click-follows-link)
                     (/ (abs mouse-1-click-follows-link) 1000.0)
                     0))))
      (if (if (and (numberp mouse-1-click-follows-link)
                   (>= mouse-1-click-follows-link 0))
              timedout (not timedout))
          nil

        (let ((event (read-event)))
          (if (eq (car-safe event) (if (eq mouse-1-click-follows-link 'double)
                                       'double-mouse-1 'mouse-1))
              ;; Turn the mouse-1 into a mouse-2 to follow links.
              (let ((newup (if (eq mouse-1-click-follows-link 'double)
                                'double-mouse-2 'mouse-2))
                    (newdown (if (eq mouse-1-click-follows-link 'double)
                                 'double-down-mouse-2 'down-mouse-2)))
                ;; If mouse-2 has never been done by the user, it doesn't have
                ;; the necessary property to be interpreted correctly.
                (put newup 'event-kind (get (car event) 'event-kind))
                (put newdown 'event-kind (get (car this-event) 'event-kind))
                (push (cons newup (cdr event)) unread-command-events)
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                ;; Modify the event in place, so read-key-sequence doesn't
                ;; generate a second fake prefix key (see fake_prefixed_keys in
                ;; src/keyboard.c).
                (setcar this-event newdown)
                (vector this-event))
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            (push event unread-command-events)
            nil))))))

(define-key key-translation-map [down-mouse-1]
  #'mouse--down-1-maybe-follows-link)
(define-key key-translation-map [double-down-mouse-1]
  #'mouse--down-1-maybe-follows-link)
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;; Provide a mode-specific menu on a mouse button.

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(defun minor-mode-menu-from-indicator (indicator)
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  "Show menu for minor mode specified by INDICATOR.
Interactively, INDICATOR is read using completion.
If there is no menu defined for the minor mode, then create one with
items `Turn Off' and `Help'."
  (interactive
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   (list (completing-read
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	  "Minor mode indicator: "
	  (describe-minor-mode-completion-table-for-indicator))))
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  (let* ((minor-mode (lookup-minor-mode-from-indicator indicator))
         (mm-fun (or (get minor-mode :minor-mode-function) minor-mode)))
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    (unless minor-mode (error "Cannot find minor mode for `%s'" indicator))
    (let* ((map (cdr-safe (assq minor-mode minor-mode-map-alist)))
           (menu (and (keymapp map) (lookup-key map [menu-bar]))))
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      (setq menu
            (if menu
                (mouse-menu-non-singleton menu)
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	      `(keymap
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                ,indicator
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                (turn-off menu-item "Turn Off minor mode" ,mm-fun)
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                (help menu-item "Help for minor mode"
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                      (lambda () (interactive)
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                        (describe-function ',mm-fun))))))
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      (popup-menu menu))))
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(defun mouse-minor-mode-menu (event)
  "Show minor-mode menu for EVENT on minor modes area of the mode line."
  (interactive "@e")
  (let ((indicator (car (nth 4 (car (cdr event))))))
    (minor-mode-menu-from-indicator indicator)))

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(defun mouse-menu-major-mode-map ()
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  (run-hooks 'activate-menubar-hook 'menu-bar-update-hook)
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  (let* (;; Keymap from which to inherit; may be null.
	 (ancestor (mouse-menu-non-singleton
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		    (and (current-local-map)
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			 (local-key-binding [menu-bar]))))
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	 ;; Make a keymap in which our last command leads to a menu or
	 ;; default to the edit menu.
	 (newmap (if ancestor
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		     (make-sparse-keymap (concat (format-mode-line mode-name)
                                                 " Mode"))
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		   menu-bar-edit-menu)))
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    (if ancestor
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	(set-keymap-parent newmap ancestor))
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    newmap))
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(defun mouse-menu-non-singleton (menubar)
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  "Return menu keybar MENUBAR, or a lone submenu inside it.
If MENUBAR defines exactly one submenu, return just that submenu.
Otherwise, return MENUBAR."
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  (if menubar
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      (let (submap)
        (map-keymap
         (lambda (k v) (setq submap (if submap t (cons k v))))
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         (keymap-canonicalize menubar))
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        (if (eq submap t)
            menubar
          (lookup-key menubar (vector (car submap)))))))
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(defun mouse-menu-bar-map ()
  "Return a keymap equivalent to the menu bar.
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The contents are the items that would be in the menu bar whether or
not it is actually displayed."
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  (run-hooks 'activate-menubar-hook 'menu-bar-update-hook)
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  (let* ((local-menu (and (current-local-map)
			  (lookup-key (current-local-map) [menu-bar])))
	 (global-menu (lookup-key global-map [menu-bar]))
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	 ;; If a keymap doesn't have a prompt string (a lazy
	 ;; programmer didn't bother to provide one), create it and
	 ;; insert it into the keymap; each keymap gets its own
	 ;; prompt.  This is required for non-toolkit versions to
	 ;; display non-empty menu pane names.
	 (minor-mode-menus
	  (mapcar
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           (lambda (menu)
             (let* ((minor-mode (car menu))
                    (menu (cdr menu))
                    (title-or-map (cadr menu)))
               (or (stringp title-or-map)
                   (setq menu
                         (cons 'keymap
                               (cons (concat
                                      (capitalize (subst-char-in-string
                                                   ?- ?\s (symbol-name
                                                           minor-mode)))
                                      " Menu")
                                     (cdr menu)))))
               menu))
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	   (minor-mode-key-binding [menu-bar])))
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	 (local-title-or-map (and local-menu (cadr local-menu)))
	 (global-title-or-map (cadr global-menu)))
    (or (null local-menu)
	(stringp local-title-or-map)
	(setq local-menu (cons 'keymap
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			       (cons (concat (format-mode-line mode-name)
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                                             " Mode Menu")
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				     (cdr local-menu)))))
    (or (stringp global-title-or-map)
	(setq global-menu (cons 'keymap
			        (cons "Global Menu"
				      (cdr global-menu)))))
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    ;; Supplying the list is faster than making a new map.
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    ;; FIXME: We have a problem here: we have to use the global/local/minor
    ;; so they're displayed in the expected order, but later on in the command
    ;; loop, they're actually looked up in the opposite order.
    (apply 'append
           global-menu
           local-menu
           minor-mode-menus)))

(defun mouse-major-mode-menu (event &optional prefix)
  "Pop up a mode-specific menu of mouse commands.
Default to the Edit menu if the major mode doesn't define a menu."
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  (declare (obsolete mouse-menu-major-mode-map "23.1"))
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  (interactive "@e\nP")
  (run-hooks 'activate-menubar-hook 'menu-bar-update-hook)
  (popup-menu (mouse-menu-major-mode-map) event prefix))

(defun mouse-popup-menubar (event prefix)
  "Pop up a menu equivalent to the menu bar for keyboard EVENT with PREFIX.
The contents are the items that would be in the menu bar whether or
not it is actually displayed."
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  (declare (obsolete mouse-menu-bar-map "23.1"))
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  (interactive "@e \nP")
  (run-hooks 'activate-menubar-hook 'menu-bar-update-hook)
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  (popup-menu (mouse-menu-bar-map) (unless (integerp event) event) prefix))
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(defun mouse-popup-menubar-stuff (event prefix)
  "Popup a menu like either `mouse-major-mode-menu' or `mouse-popup-menubar'.
Use the former if the menu bar is showing, otherwise the latter."
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  (declare (obsolete nil "23.1"))
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  (interactive "@e\nP")
  (run-hooks 'activate-menubar-hook 'menu-bar-update-hook)
  (popup-menu
   (if (zerop (or (frame-parameter nil 'menu-bar-lines) 0))
       (mouse-menu-bar-map)
     (mouse-menu-major-mode-map))
   event prefix))
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;; Commands that operate on windows.

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(defun mouse-minibuffer-check (event)
  (let ((w (posn-window (event-start event))))
    (and (window-minibuffer-p w)
	 (not (minibuffer-window-active-p w))
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	 (user-error "Minibuffer window is not active")))
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  ;; Give temporary modes such as isearch a chance to turn off.
  (run-hooks 'mouse-leave-buffer-hook))
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(defun mouse-delete-window (click)
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  "Delete the window you click on.
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Do nothing if the frame has just one window.
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This command must be bound to a mouse click."
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  (interactive "e")
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  (unless (one-window-p t)
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    (mouse-minibuffer-check click)
    (delete-window (posn-window (event-start click)))))
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(defun mouse-select-window (click)
  "Select the window clicked on; don't move point."
  (interactive "e")
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  (mouse-minibuffer-check click)
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  (let ((oframe (selected-frame))
	(frame (window-frame (posn-window (event-start click)))))
    (select-window (posn-window (event-start click)))
    (raise-frame frame)
    (select-frame frame)
    (or (eq frame oframe)
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	(set-mouse-position (selected-frame) (1- (frame-width)) 0))))
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(defun mouse-tear-off-window (click)
  "Delete the window clicked on, and create a new frame displaying its buffer."
  (interactive "e")
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  (mouse-minibuffer-check click)
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  (let* ((window (posn-window (event-start click)))
	 (buf (window-buffer window))
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	 (frame (make-frame)))
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    (select-frame frame)
    (switch-to-buffer buf)
    (delete-window window)))

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(defun mouse-delete-other-windows ()
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  "Delete all windows except the one you click on."
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  (interactive "@")
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  (delete-other-windows))
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(defun mouse-split-window-vertically (click)
  "Select Emacs window mouse is on, then split it vertically in half.
The window is split at the line clicked on.
This command must be bound to a mouse click."
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  (interactive "@e")
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  (mouse-minibuffer-check click)
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  (let ((start (event-start click)))
    (select-window (posn-window start))
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    (let ((new-height (1+ (cdr (posn-col-row (event-end click)))))
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	  (first-line window-min-height)
	  (last-line (- (window-height) window-min-height)))
      (if (< last-line first-line)
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	  (error "Window too short to split")
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	(split-window-vertically
	 (min (max new-height first-line) last-line))))))
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(defun mouse-split-window-horizontally (click)
  "Select Emacs window mouse is on, then split it horizontally in half.
The window is split at the column clicked on.
This command must be bound to a mouse click."
  (interactive "@e")
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  (mouse-minibuffer-check click)
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  (let ((start (event-start click)))
    (select-window (posn-window start))
    (let ((new-width (1+ (car (posn-col-row (event-end click)))))
	  (first-col window-min-width)
	  (last-col (- (window-width) window-min-width)))
      (if (< last-col first-col)
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	  (error "Window too narrow to split")
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	(split-window-horizontally
	 (min (max new-width first-col) last-col))))))
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;; `mouse-drag-line' is now the common routine for handling all line
;; dragging events combining the earlier `mouse-drag-mode-line-1' and
;; `mouse-drag-vertical-line'.  It should improve the behavior of line
;; dragging wrt Emacs 23 as follows:

;; (1) Gratuitous error messages and restrictions have been (hopefully)
;; removed.  (The help-echo that dragging the mode-line can resize a
;; one-window-frame's window will still show through via bindings.el.)

;; (2) No gratuitous selection of other windows should happen.  (This
;; has not been completely fixed for mouse-autoselected windows yet.)

;; (3) Mouse clicks below a scroll-bar should pass through via unread
;; command events.

;; Note that `window-in-direction' replaces `mouse-drag-window-above'
;; and `mouse-drag-vertical-line-rightward-window' with Emacs 24.1.
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(defun mouse-drag-line (start-event line)
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  "Drag a mode line, header line, or vertical line with the mouse.
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START-EVENT is the starting mouse-event of the drag action.  LINE
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must be one of the symbols `header', `mode', or `vertical'."
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  ;; Give temporary modes such as isearch a chance to turn off.
  (run-hooks 'mouse-leave-buffer-hook)
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  (let* ((echo-keystrokes 0)
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	 (start (event-start start-event))
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	 (window (posn-window start))
	 (frame (window-frame window))
	 (minibuffer-window (minibuffer-window frame))
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	 (side (and (eq line 'vertical)
		    (or (cdr (assq 'vertical-scroll-bars
				   (frame-parameters frame)))
			'right)))
	 (draggable t)
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	 height finished event position growth dragged)
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    (cond
     ((eq line 'header)
      ;; Check whether header-line can be dragged at all.
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      (if (window-at-side-p window 'top)
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	  (setq draggable nil)
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	(setq height (/ (window-header-line-height window) 2))
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	(setq window (window-in-direction 'above window t))))
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     ((eq line 'mode)
      ;; Check whether mode-line can be dragged at all.
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      (if (and (window-at-side-p window 'bottom)
	       ;; Allow resizing the minibuffer window if it's on the same
	       ;; frame as and immediately below the clicked window, and
	       ;; it's active or `resize-mini-windows' is nil.
	       (not (and (eq (window-frame minibuffer-window) frame)
			 (= (nth 1 (window-pixel-edges minibuffer-window))
			    (nth 3 (window-pixel-edges window)))
			 (or (not resize-mini-windows)
			     (eq minibuffer-window
				 (active-minibuffer-window))))))
	  (setq draggable nil)
	(setq height (/ (window-mode-line-height window) 2))))
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     ((eq line 'vertical)
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      ;; Get the window to adjust for the vertical case.  If the scroll
      ;; bar is on the window's right or we drag a vertical divider,
      ;; adjust the window where the start-event occurred.  If the
      ;; scroll bar is on the start-event window's left or there are no
      ;; scrollbars, adjust the window on the left of it.
      (unless (or (eq side 'right)
		  (not (zerop (window-right-divider-width window))))
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	(setq window (window-in-direction 'left window t)))))
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    ;; Start tracking.
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    (track-mouse
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      ;; Loop reading events and sampling the position of the mouse.
      (while (not finished)
	(setq event (read-event))
	(setq position (mouse-pixel-position))
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	;; Do nothing if
	;;   - there is a switch-frame event.
	;;   - the mouse isn't in the frame that we started in
	;;   - the mouse isn't in any Emacs frame
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	;; Drag if
	;;   - there is a mouse-movement event
	;;   - there is a scroll-bar-movement event (Why? -- cyd)
	;;     (same as mouse movement for our purposes)
	;; Quit if
	;;   - there is a keyboard event or some other unknown event.
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	(cond
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	 ((not (consp event))
	  (setq finished t))
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	 ((memq (car event) '(switch-frame select-window))
	  nil)
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	 ((not (memq (car event) '(mouse-movement scroll-bar-movement)))
	  (when (consp event)
	    ;; Do not unread a drag-mouse-1 event to avoid selecting
	    ;; some other window.  For vertical line dragging do not
	    ;; unread mouse-1 events either (but only if we dragged at
	    ;; least once to allow mouse-1 clicks get through).
	    (unless (and dragged
			 (if (eq line 'vertical)
			     (memq (car event) '(drag-mouse-1 mouse-1))
			   (eq (car event) 'drag-mouse-1)))
	      (push event unread-command-events)))
	  (setq finished t))
	 ((not (and (eq (car position) frame)
		    (cadr position)))
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	  nil)
	 ((eq line 'vertical)
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	  ;; Drag vertical divider.  This must be probably fixed like
	  ;; for the mode-line.
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	  (setq growth (- (cadr position)
			  (if (eq side 'right) 0 2)
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			  (nth 2 (window-pixel-edges window))
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			  -1))
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	  (unless (zerop growth)
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	    (setq dragged t)
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	    (adjust-window-trailing-edge window growth t t)))
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	 (draggable
	  ;; Drag horizontal divider.
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	  (setq growth
		(if (eq line 'mode)
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		    (- (+ (cddr position) height)
		       (nth 3 (window-pixel-edges window)))
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		  ;; The window's top includes the header line!
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		  (- (+ (nth 3 (window-pixel-edges window)) height)
		     (cddr position))))
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	  (unless (zerop growth)
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	    (setq dragged t)
	    (adjust-window-trailing-edge
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	     window (if (eq line 'mode) growth (- growth)) nil t))))))))
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(defun mouse-drag-mode-line (start-event)
  "Change the height of a window by dragging on the mode line."
  (interactive "e")
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  (mouse-drag-line start-event 'mode))
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(defun mouse-drag-header-line (start-event)
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  "Change the height of a window by dragging on the header line."
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  (interactive "e")
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  (mouse-drag-line start-event 'header))
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(defun mouse-drag-vertical-line (start-event)
  "Change the width of a window by dragging on the vertical line."
  (interactive "e")
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  (mouse-drag-line start-event 'vertical))
504

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(defun mouse-set-point (event)
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  "Move point to the position clicked on with the mouse.
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This should be bound to a mouse click event type."
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  (interactive "e")
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  (mouse-minibuffer-check event)
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  ;; Use event-end in case called from mouse-drag-region.
  ;; If EVENT is a click, event-end and event-start give same value.
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  (posn-set-point (event-end event)))
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(defvar mouse-last-region-beg nil)
(defvar mouse-last-region-end nil)
(defvar mouse-last-region-tick nil)

(defun mouse-region-match ()
  "Return non-nil if there's an active region that was set with the mouse."
  (and (mark t) mark-active
       (eq mouse-last-region-beg (region-beginning))
       (eq mouse-last-region-end (region-end))
       (eq mouse-last-region-tick (buffer-modified-tick))))

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(defun mouse-set-region (click)
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  "Set the region to the text dragged over, and copy to kill ring.
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This should be bound to a mouse drag event.
See the `mouse-drag-copy-region' variable to control whether this
command alters the kill ring or not."
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  (interactive "e")
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  (mouse-minibuffer-check click)
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  (select-window (posn-window (event-start click)))
  (let ((beg (posn-point (event-start click)))
	(end (posn-point (event-end click))))
    (and mouse-drag-copy-region (integerp beg) (integerp end)
	 ;; Don't set this-command to `kill-region', so a following
	 ;; C-w won't double the text in the kill ring.  Ignore
	 ;; `last-command' so we don't append to a preceding kill.
	 (let (this-command last-command deactivate-mark)
	   (copy-region-as-kill beg end)))
    (if (numberp beg) (goto-char beg))
    ;; On a text terminal, bounce the cursor.
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    (or transient-mark-mode
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	(window-system)
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	(sit-for 1))
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    (push-mark)
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    (set-mark (point))
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    (if (numberp end) (goto-char end))
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    (mouse-set-region-1)))

(defun mouse-set-region-1 ()
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  ;; Set transient-mark-mode for a little while.
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  (unless (eq (car-safe transient-mark-mode) 'only)
    (setq transient-mark-mode
	  (cons 'only
		(unless (eq transient-mark-mode 'lambda)
		  transient-mark-mode))))
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  (setq mouse-last-region-beg (region-beginning))
  (setq mouse-last-region-end (region-end))
  (setq mouse-last-region-tick (buffer-modified-tick)))
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(defcustom mouse-scroll-delay 0.25
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  "The pause between scroll steps caused by mouse drags, in seconds.
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If you drag the mouse beyond the edge of a window, Emacs scrolls the
window to bring the text beyond that edge into view, with a delay of
this many seconds between scroll steps.  Scrolling stops when you move
the mouse back into the window, or release the button.
This variable's value may be non-integral.
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Setting this to zero causes Emacs to scroll as fast as it can."
  :type 'number
  :group 'mouse)
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(defcustom mouse-scroll-min-lines 1
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  "The minimum number of lines scrolled by dragging mouse out of window.
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Moving the mouse out the top or bottom edge of the window begins
scrolling repeatedly.  The number of lines scrolled per repetition
is normally equal to the number of lines beyond the window edge that
the mouse has moved.  However, it always scrolls at least the number
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of lines specified by this variable."
  :type 'integer
  :group 'mouse)
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(defun mouse-scroll-subr (window jump &optional overlay start)
  "Scroll the window WINDOW, JUMP lines at a time, until new input arrives.
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If OVERLAY is an overlay, let it stretch from START to the far edge of
the newly visible text.
Upon exit, point is at the far edge of the newly visible text."
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  (cond
   ((and (> jump 0) (< jump mouse-scroll-min-lines))
    (setq jump mouse-scroll-min-lines))
   ((and (< jump 0) (< (- jump) mouse-scroll-min-lines))
    (setq jump (- mouse-scroll-min-lines))))
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  (let ((opoint (point)))
    (while (progn
	     (goto-char (window-start window))
	     (if (not (zerop (vertical-motion jump window)))
		 (progn
		   (set-window-start window (point))
		   (if (natnump jump)
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		       (if (window-end window)
			   (progn
			     (goto-char (window-end window))
			     ;; window-end doesn't reflect the window's new
			     ;; start position until the next redisplay.
			     (vertical-motion (1- jump) window))
			 (vertical-motion (- (window-height window) 2)))
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		     (goto-char (window-start window)))
		   (if overlay
		       (move-overlay overlay start (point)))
		   ;; Now that we have scrolled WINDOW properly,
		   ;; put point back where it was for the redisplay
		   ;; so that we don't mess up the selected window.
		   (or (eq window (selected-window))
		       (goto-char opoint))
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		   (sit-for mouse-scroll-delay)))))
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    (or (eq window (selected-window))
	(goto-char opoint))))
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(defvar mouse-selection-click-count 0)
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(defvar mouse-selection-click-count-buffer nil)

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(defun mouse-drag-region (start-event)
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  "Set the region to the text that the mouse is dragged over.
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Highlight the drag area as you move the mouse.
This must be bound to a button-down mouse event.
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In Transient Mark mode, the highlighting remains as long as the mark
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remains active.  Otherwise, it remains until the next input event.

If the click is in the echo area, display the `*Messages*' buffer."
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  (interactive "e")
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  ;; Give temporary modes such as isearch a chance to turn off.
  (run-hooks 'mouse-leave-buffer-hook)
  (mouse-drag-track start-event t))
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(defun mouse-posn-property (pos property)
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  "Look for a property at click position.
POS may be either a buffer position or a click position like
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those returned from `event-start'.  If the click position is on
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a string, the text property PROPERTY is examined.
If this is nil or the click is not on a string, then
the corresponding buffer position is searched for PROPERTY.
If PROPERTY is encountered in one of those places,
its value is returned."
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  (if (consp pos)
      (let ((w (posn-window pos)) (pt (posn-point pos))
	    (str (posn-string pos)))
	(or (and str
		 (get-text-property (cdr str) property (car str)))
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            ;; FIXME: mouse clicks on the mode-line come with a position in
            ;; (nth 5).  Maybe we should change the C code instead so that
            ;; mouse-clicks don't include a position there!
	    (and pt (not (memq (posn-area pos) '(mode-line header-line)))
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		 (get-char-property pt property w))))
    (get-char-property pos property)))

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(defun mouse-on-link-p (pos)
  "Return non-nil if POS is on a link in the current buffer.
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POS must be a buffer position in the current buffer or a mouse
event location in the selected window (see `event-start').
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However, if `mouse-1-click-in-non-selected-windows' is non-nil,
POS may be a mouse event location in any window.
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A clickable link is identified by one of the following methods:

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- If the character at POS has a non-nil `follow-link' text or
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overlay property, the value of that property determines what to do.
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- If there is a local key-binding or a keybinding at position POS
for the `follow-link' event, the binding of that event determines
what to do.
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The resulting value determine whether POS is inside a link:

- If the value is `mouse-face', POS is inside a link if there
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is a non-nil `mouse-face' property at POS.  Return t in this case.

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- If the value is a function, FUNC, POS is inside a link if
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the call \(FUNC POS) returns non-nil.  Return the return value
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from that call.  Arg is \(posn-point POS) if POS is a mouse event.
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- Otherwise, return the value itself.
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The return value is interpreted as follows:

- If it is a string, the mouse-1 event is translated into the
first character of the string, i.e. the action of the mouse-1
click is the local or global binding of that character.

- If it is a vector, the mouse-1 event is translated into the
first element of that vector, i.e. the action of the mouse-1
click is the local or global binding of that event.

- Otherwise, the mouse-1 event is translated into a mouse-2 event
at the same position."
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  (let ((action
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	 (and (or (not (consp pos))
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		  mouse-1-click-in-non-selected-windows
		  (eq (selected-window) (posn-window pos)))
	      (or (mouse-posn-property pos 'follow-link)
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                  (let ((area (posn-area pos)))
                    (when area
                      (key-binding (vector area 'follow-link) nil t pos)))
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		  (key-binding [follow-link] nil t pos)))))
    (cond
     ((eq action 'mouse-face)
      (and (mouse-posn-property pos 'mouse-face) t))
     ((functionp action)
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      ;; FIXME: This seems questionable if the click is not in a buffer.
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      ;; Should we instead decide that `action' takes a `posn'?
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      (if (consp pos)
	  (with-current-buffer (window-buffer (posn-window pos))
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	    (funcall action (posn-point pos)))
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	(funcall action pos)))
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     (t action))))
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(defun mouse-fixup-help-message (msg)
  "Fix help message MSG for `mouse-1-click-follows-link'."
  (let (mp pos)
    (if (and mouse-1-click-follows-link
	     (stringp msg)
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	     (string-match-p "\\`mouse-2" msg)
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	     (setq mp (mouse-pixel-position))
	     (consp (setq pos (cdr mp)))
	     (car pos) (>= (car pos) 0)
	     (cdr pos) (>= (cdr pos) 0)
	     (setq pos (posn-at-x-y (car pos) (cdr pos) (car mp)))
	     (windowp (posn-window pos)))
	(with-current-buffer (window-buffer (posn-window pos))
	  (if (mouse-on-link-p pos)
	      (setq msg (concat
		    (cond
		     ((eq mouse-1-click-follows-link 'double) "double-")
		     ((and (integerp mouse-1-click-follows-link)
			   (< mouse-1-click-follows-link 0)) "Long ")
		     (t ""))
		    "mouse-1" (substring msg 7)))))))
  msg)
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(defun mouse-drag-track (start-event  &optional
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				      do-mouse-drag-region-post-process)
    "Track mouse drags by highlighting area between point and cursor.
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The region will be defined with mark and point.
DO-MOUSE-DRAG-REGION-POST-PROCESS should only be used by
`mouse-drag-region'."
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  (mouse-minibuffer-check start-event)
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  (setq mouse-selection-click-count-buffer (current-buffer))
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  (deactivate-mark)
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  (let* ((scroll-margin 0) ; Avoid margin scrolling (Bug#9541).
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         ;; We've recorded what we needed from the current buffer and
         ;; window, now let's jump to the place of the event, where things
         ;; are happening.
         (_ (mouse-set-point start-event))
         (echo-keystrokes 0)
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	 (start-posn (event-start start-event))
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	 (start-point (posn-point start-posn))
	 (start-window (posn-window start-posn))
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	 (start-window-start (window-start start-window))
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	 (start-hscroll (window-hscroll start-window))
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	 (bounds (window-edges start-window))
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	 (make-cursor-line-fully-visible nil)
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	 (top (nth 1 bounds))
	 (bottom (if (window-minibuffer-p start-window)
		     (nth 3 bounds)
		   ;; Don't count the mode line.
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		   (1- (nth 3 bounds))))
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	 (click-count (1- (event-click-count start-event)))
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	 ;; Suppress automatic hscrolling, because that is a nuisance
	 ;; when setting point near the right fringe (but see below).
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	 (auto-hscroll-mode-saved auto-hscroll-mode)
	 (auto-hscroll-mode nil)
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	 moved-off-start event end end-point)
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    (setq mouse-selection-click-count click-count)
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    ;; In case the down click is in the middle of some intangible text,
    ;; use the end of that text, and put it in START-POINT.
    (if (< (point) start-point)
	(goto-char start-point))
    (setq start-point (point))
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    ;; Activate the region, using `mouse-start-end' to determine where
    ;; to put point and mark (e.g., double-click will select a word).
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    (setq transient-mark-mode
	  (if (eq transient-mark-mode 'lambda)
	      '(only)
	    (cons 'only transient-mark-mode)))
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    (let ((range (mouse-start-end start-point start-point click-count)))
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      (push-mark (nth 0 range) t t)
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      (goto-char (nth 1 range)))
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    ;; Track the mouse until we get a non-movement event.
    (track-mouse
      (while (progn
	       (setq event (read-event))
	       (or (mouse-movement-p event)
		   (memq (car-safe event) '(switch-frame select-window))))
	(unless (memq (car-safe event) '(switch-frame select-window))
	  ;; Automatic hscrolling did not occur during the call to
	  ;; `read-event'; but if the user subsequently drags the
	  ;; mouse, go ahead and hscroll.
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	  (let ((auto-hscroll-mode auto-hscroll-mode-saved))
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	    (redisplay))
	  (setq end (event-end event)
		end-point (posn-point end))
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	  ;; Note whether the mouse has left the starting position.
	  (unless (eq end-point start-point)
	    (setq moved-off-start t))
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	  (if (and (eq (posn-window end) start-window)
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		   (integer-or-marker-p end-point))
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	      (mouse--drag-set-mark-and-point start-point
					      end-point click-count)
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	    (let ((mouse-row (cdr (cdr (mouse-position)))))
	      (cond
	       ((null mouse-row))
	       ((< mouse-row top)
		(mouse-scroll-subr start-window (- mouse-row top)
				   nil start-point))
	       ((>= mouse-row bottom)
		(mouse-scroll-subr start-window (1+ (- mouse-row bottom))
				   nil start-point))))))))

    ;; Handle the terminating event if possible.
    (when (consp event)
      ;; Ensure that point is on the end of the last event.
      (when (and (setq end-point (posn-point (event-end event)))
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		 (eq (posn-window end) start-window)
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		 (integer-or-marker-p end-point)
		 (/= start-point end-point))
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	(mouse--drag-set-mark-and-point start-point
					end-point click-count))

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      ;; Find its binding.
      (let* ((fun (key-binding (vector (car event))))
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	     ;; FIXME This doesn't make sense, because
	     ;; event-click-count always returns something >= 1.
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	     (do-multi-click (and (> (event-click-count event) 0)
				  (functionp fun)
				  (not (memq fun '(mouse-set-point
						   mouse-set-region))))))
	(if (and (/= (mark) (point))
		 (not do-multi-click))
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	    ;; If point has moved, finish the drag.
	    (let* (last-command this-command)
	      (and mouse-drag-copy-region
		   do-mouse-drag-region-post-process
		   (let (deactivate-mark)
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		     (copy-region-as-kill (mark) (point)))))
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	  ;; Otherwise, run binding of terminating up-event.
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          (deactivate-mark)
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	  (if do-multi-click
	      (goto-char start-point)
	    (unless moved-off-start
	      (pop-mark)))

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	  (when (and (functionp fun)
		     (= start-hscroll (window-hscroll start-window))
		     ;; Don't run the up-event handler if the window
		     ;; start changed in a redisplay after the
		     ;; mouse-set-point for the down-mouse event at
		     ;; the beginning of this function.  When the
		     ;; window start has changed, the up-mouse event
		     ;; contains a different position due to the new
		     ;; window contents, and point is set again.
		     (or end-point
			 (= (window-start start-window)
			    start-window-start)))
	    (push event unread-command-events)))))))

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(defun mouse--drag-set-mark-and-point (start click click-count)
  (let* ((range (mouse-start-end start click click-count))
	 (beg (nth 0 range))
	 (end (nth 1 range)))
    (cond ((eq (mark) beg)
	   (goto-char end))
	  ((eq (mark) end)
	   (goto-char beg))
	  ((< click (mark))
	   (set-mark end)
	   (goto-char beg))
	  (t
	   (set-mark beg)
	   (goto-char end)))))

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;; Commands to handle xterm-style multiple clicks.
(defun mouse-skip-word (dir)
  "Skip over word, over whitespace, or over identical punctuation.
If DIR is positive skip forward; if negative, skip backward."
  (let* ((char (following-char))
	 (syntax (char-to-string (char-syntax char))))
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    (cond ((string= syntax "w")
	   ;; Here, we can't use skip-syntax-forward/backward because
	   ;; they don't pay attention to word-separating-categories,
	   ;; and thus they will skip over a true word boundary.  So,
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	   ;; we simulate the original behavior by using forward-word.
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	   (if (< dir 0)
	       (if (not (looking-at "\\<"))
		   (forward-word -1))
	     (if (or (looking-at "\\<") (not (looking-at "\\>")))
		 (forward-word 1))))
	  ((string= syntax " ")
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	   (if (< dir 0)
	       (skip-syntax-backward syntax)
	     (skip-syntax-forward syntax)))
	  ((string= syntax "_")
	   (if (< dir 0)
	       (skip-syntax-backward "w_")
	     (skip-syntax-forward "w_")))
	  ((< dir 0)
	   (while (and (not (bobp)) (= (preceding-char) char))