;;;;
;;;; Scrollbars bindings and procs
;;;;
;;;; Copyright © 1993-1996 Erick Gallesio - I3S-CNRS/ESSI <eg@unice.fr>
;;;; 
;;;; Permission to use, copy, and/or distribute this software and its
;;;; documentation for any purpose and without fee is hereby granted, provided
;;;; that both the above copyright notice and this permission notice appear in
;;;; all copies and derived works.  Fees for distribution or use of this
;;;; software or derived works may only be charged with express written
;;;; permission of the copyright holder.  
;;;; This software is provided ``as is'' without express or implied warranty.
;;;;
;;;; This software is a derivative work of other copyrighted softwares; the
;;;; copyright notices of these softwares are placed in the file COPYRIGHTS
;;;;
;;;;
;;;;           Author: Erick Gallesio [eg@unice.fr]
;;;;    Creation date: 17-May-1993 12:35
;;;; Last file update:  2-Jul-1996 19:40
;;;;

(let ()

(define tk::init-pos    "")
(define tk::init-values '())

;; Standard Motif bindings:

(define-binding "Scrollbar" "<Enter>" (|W| x y)
  (when *tk-strict-motif* 
     (set! tk::active-bg (tk-get |W| :activebackground))
     (tk-set! |W| :activebackground (tk-get |W| :background)))
  (|W| 'activate (|W| 'identify x y)))

(define-binding "Scrollbar" "<Motion>" (|W| x y)
  (|W| 'activate (|W| 'identify x y)))

(define-binding "Scrollbar" "<Leave>" (|W|)
  (if *tk-strict-motif* 
      (tk-set! |W| :activebackground tk::active-bg))
  (|W| 'activate ""))

(define-binding "Scrollbar" "<1>" (|W| x y)
  (Tk:scroll-button-down |W| x y))

(define-binding "Scrollbar" "<B1-Motion>" (|W| x y)
  (Tk:scroll-drag |W| x y))

(define-binding "Scrollbar" "<B1-B2-Motion>" (|W| x y)
  (Tk:scroll-drag |W| x y))

(define-binding "Scrollbar" "<ButtonRelease-1>" (|W| x y)
  (Tk:scroll-button-up |W| x y))

(define-binding "Scrollbar" "<B1-Leave>" ()
  ;; Prevents <Leave> binding from being invoked.
  'nop)

(define-binding "Scrollbar" "<B1-Enter>" ()
  ;; Prevents <Enter> binding from being invoked.
  'nop)

(define-binding "Scrollbar" "<2>" (|W| x y)
  (Tk:scroll-button-2-down |W| x y))

(define-binding "Scrollbar" "<B1-2>" ()
  ; Do nothing, since button 1 is already down.
  'nop)

(define-binding "Scrollbar" "<B2-1>" (|W| x y)
  ; Do nothing, since button 2 is already down.
  'nop)

(define-binding "Scrollbar" "<B2-Motion>" (|W| x y)
  (Tk:scroll-drag |W| x y))

(define-binding "Scrollbar" "<ButtonRelease-2>" (|W| x y)
  (Tk:scroll-button-up |W| x y))

(define-binding "Scrollbar" "<B1-ButtonRelease-2>" ()
  ;Do nothing:  B1 release will handle it.
  'nop)

(define-binding "Scrollbar" "<B2-ButtonRelease-1>" ()
  ;Do nothing:  B1 release will handle it.
  'nop)

(define-binding "Scrollbar" "<B2-Leave>" ()
  ;; Prevents <Leave> binding from being invoked.
  'nop)

(define-binding "Scrollbar" "<B2-Enter>" ()
  ;; Prevents <Enter> binding from being invoked.
  'nop)

(define-binding "Scrollbar" "<Control-1>" (|W| x y)
  (Tk:scroll-top-bottom |W| x y))

(define-binding "Scrollbar" "<Control-2>" (|W| x y)
  (Tk:scroll-top-bottom |W| x y))

(define-binding "Scrollbar" "<Up>"            (|W|) (Tk:scroll-by-units |W| 'v -1))
(define-binding "Scrollbar" "<Down>"          (|W|) (Tk:scroll-by-units |W| 'v +1))
(define-binding "Scrollbar" "<Control-Up>"    (|W|) (Tk:scroll-by-pages |W| 'v -1))
(define-binding "Scrollbar" "<Control-Down>"  (|W|) (Tk:scroll-by-pages |W| 'v +1))
(define-binding "Scrollbar" "<Left>" 	      (|W|) (Tk:scroll-by-units |W| 'h -1))
(define-binding "Scrollbar" "<Right>"         (|W|) (Tk:scroll-by-units |W| 'h +1))
(define-binding "Scrollbar" "<Control-Left>"  (|W|) (Tk:scroll-by-pages |W| 'h -1))
(define-binding "Scrollbar" "<Control-Right>" (|W|) (Tk:scroll-by-pages |W| 'hd +1))
(define-binding "Scrollbar" "<Prior>" 	      (|W|) (Tk:scroll-by-pages |W| 'hv -1))
(define-binding "Scrollbar" "<Next>" 	      (|W|) (Tk:scroll-by-pages |W| 'hv +1))

(define-binding "Scrollbar" "<Home>" (|W|)
  (Tk:scroll-to-pos |W| 0))

(define-binding "Scrollbar" "<End>" (|W|)
  (Tk:scroll-to-pos |W| 1))


;; Tk:scroll-button-down --
;; This procedure is invoked when a button is pressed in a scrollbar.
;; It changes the way the scrollbar is displayed and takes actions
;; depending on where the mouse is.
;;
;; w -		The scrollbar widget.
;; x, y -	Mouse coordinates.

(define (Tk:scroll-button-down w x y)
  (let ((element (w 'identify x y)))
    (set! tk::relief (tk-get w :activerelief))
    (tk-set! w :activerelief "sunken")
    (if (equal? element "slider")
	(Tk:scroll-start-drag w x y)
	(Tk:scroll-select w element "initial"))))

;; Tk:scroll-button-up --
;; This procedure is invoked when a button is released in a scrollbar.
;; It cancels scans and auto-repeats that were in progress, and restores
;; the way the active element is displayed.
;;
;; w -		The scrollbar widget.
;; x, y -	Mouse coordinates.

(define (Tk:scroll-button-up w x y)
  (Tk:cancel-repeat)
  (tk-set! w :activerelief tk::relief)
  (Tk:scroll-end-drag w x y)
  (w 'activate (w 'identify x y)))


;; Tk:scroll-select --
;; This procedure is invoked when a button is pressed over the scrollbar.
;; It invokes one of several scrolling actions depending on where in
;; the scrollbar the button was pressed.
;;
;; w -		The scrollbar widget.
;; element -	The element of the scrollbar that was selected, such
;;		as "arrow1" or "trough2".  Shouldn't be "slider".
;; repeat -	Whether and how to auto-repeat the action:  "noRepeat"
;;		means don't auto-repeat, "initial" means this is the
;;		first action in an auto-repeat sequence, and "again"
;;		means this is the second repetition or later.

(define (Tk:scroll-select w element repeat)
  (when (winfo 'exists w)
    (let ((cont (lambda ()
		  (cond
		   ((string=? repeat "again") 
		         (set! tk::after-id
			       (after (tk-get w :repeatinterval)
				      (lambda ()
					(Tk:scroll-select w 
							  element 
							  "again")))))
		   ((string=? repeat "initial")
		         (let ((delay (tk-get w :repeatdelay)))
			   (if (> delay 0)
			       (set! tk::after-id 
				     (after delay
					    (lambda ()
					      (Tk:scroll-select w 
								element 
								"again")))))))))))
      (cond
       ((equal? element "arrow1")  (Tk:scroll-by-units w 'hv -1) (cont))
       ((equal? element "trough1") (Tk:scroll-by-pages w 'hv -1) (cont))
       ((equal? element "trough2") (Tk:scroll-by-pages w 'hv +1) (cont))
       ((equal? element "arrow2")  (Tk:scroll-by-units w 'hv +1) (cont))))))


;; Tk:scroll-start-drag --
;; This procedure is called to initiate a drag of the slider.  It just
;; remembers the starting position of the mouse and slider.
;;
;; w -		The scrollbar widget.
;; x, y -	The mouse position at the start of the drag operation.

(define (Tk:scroll-start-drag w x y)
  (unless (equal? (tk-get w :command) "")
     (set! tk::press-x x)
     (set! tk::press-y y)
     (set! tk::init-values (w 'get))
     (let ((iv0 (car tk::init-values)))
       (if (= (length tk::init-values) 2)
	   (set! tk::init-pos iv0)
	   (if (= iv0 0)
	       (set! tk::init-pos 0.0)
	       (set! tk::init-pos (/ (caddr tk::init-values) 
				     (car tk::init-values))))))))

;; Tk:scroll-drag --
;; This procedure is called for each mouse motion even when the slider
;; is being dragged.  It notifies the associated widget if we're not
;; jump scrolling, and it just updates the scrollbar if we are jump
;; scrolling.
;;
;; w -		The scrollbar widget.
;; x, y -	The current mouse position.

(define (Tk:scroll-drag w x y)
  (unless (equal? tk::init-pos "")
     (let ((delta (w 'delta (- x tk::press-x) (- y tk::press-y))))
       (if (tk-get w :jump)
	     (if (equal? (length tk::init-values) 2)
		 (w 'set (+ (car  tk::init-values) delta)
		         (+ (cadr tk::init-values) delta))
		 (let ((delta (floor (* delta (car tk::init-values)))))
		   (w 'set (car  tk::init-values)
		      	   (cadr tk::init-values)
			   (+ (caddr tk::init-values)  delta)
			   (+ (cadddr tk::init-values) delta))))
	     (Tk:scroll-to-pos w (+ tk::init-pos delta))))))

;; Tk:scroll-end-drag --
;; This procedure is called to end an interactive drag of the slider.
;; It scrolls the window if we're in jump mode, otherwise it does nothing.
;;
;; w -		The scrollbar widget.
;; x, y -	The mouse position at the end of the drag operation.

(define  (Tk:scroll-end-drag w x y)
  (unless (equal? tk::init-pos "")
     (if (tk-get w :jump)
	 (let ((delta (w 'delta (- x tk::press-x) (- y tk::press-y))))
	   (Tk:scroll-to-pos w (+ tk::init-pos delta))))
     (set! Tk::init-pos "")))


;; Tk:scroll-by-units --
;; This procedure tells the scrollbar's associated widget to scroll up
;; or down by a given number of units.  It notifies the associated widget
;; in different ways for old and new command syntaxes.
;;
;; w -		The scrollbar widget.
;; orient -	Which kinds of scrollbars this applies to:  "h" for
;;		horizontal, "v" for vertical, "hv" for both.
;; amount -	How many units to scroll:  typically 1 or -1.

(define (Tk:scroll-by-units w orient amount)
  (let ((cmd     (tk-get w :command))
	(worient (tk-get w :orient)))
    (unless (equal? cmd "")
       (when (or (eq? orient 'hv) 
		 (and (eq? orient 'h) (string=? worient "horizontal"))
		 (and (eq? orient 'v) (string=? worient "vertical")))
	   (let ((info (w 'get)))
	     (if (= (length info) 2)
		 (cmd 'scroll amount 'units)
		 (cmd (+ (caddr info) amount))))))))

;; Tk:scroll-by-pages --
;; This procedure tells the scrollbar's associated widget to scroll up
;; or down by a given number of screenfuls.  It notifies the associated
;; widget in different ways for old and new command syntaxes.
;;
;; Arguments:
;; w -		The scrollbar widget.
;; orient -	Which kinds of scrollbars this applies to:  "h" for
;;		horizontal, "v" for vertical, "hv" for both.
;; amount -	How many screens to scroll:  typically 1 or -1.

(define (Tk:scroll-by-pages w orient amount)
  (let ((cmd     (tk-get w :command))
	(worient (tk-get w :orient)))
    (unless (equal? cmd "")
       (when (or (eq? orient 'hv) 
		 (and (eq? orient 'h) (string=? worient "horizontal"))
		 (and (eq? orient 'v) (string=? worient "vertical")))
	   (let ((info (w 'get)))
	     (if (= (length info) 2)
		 (cmd 'scroll amount 'pages)
		 (cmd (+ (caddr info) (* (cadr info) amount) -1))))))))

;; Tk:scroll-ToPos --
;; This procedure tells the scrollbar's associated widget to scroll to
;; a particular location, given by a fraction between 0 and 1.  It notifies
;; the associated widget in different ways for old and new command syntaxes.
;;
;; Arguments:
;; w -		The scrollbar widget.
;; pos -		A fraction between 0 and 1 indicating a desired position
;;		in the document.

(define (Tk:scroll-to-pos w pos)
  (let ((cmd (tk-get w :command)))
    (unless (equal? cmd "")
	(let ((info (w 'get)))
	  (if (= (length info) 2)
	      (cmd 'moveto pos)
	      (cmd (floor (* (car info) pos))))))))

;; Tk:scroll-top-bottom
;; Scroll to the top or bottom of the document, depending on the mouse
;; position.
;;
;; w -		The scrollbar widget.
;; x, y -	Mouse coordinates within the widget.

(define (Tk:scroll-top-bottom w x y)
  (let ((element (w 'identify x y)))
    (cond
       ((member element '("arrow1" "trough1")) (Tk:scroll-to-pos w 0))
       ((member element '("arrow2" "trough2")) (Tk:scroll-to-pos w 1)))

    ;; Set tk::relief, since it's needed by Tk:scroll-button-up.
    (set! tk::relief (tk-get w :activerelief))))


;; Tk:scroll-button-2-down
;; This procedure is invoked when button 2 is pressed over a scrollbar.
;; If the button is over the trough or slider, it sets the scrollbar to
;; the mouse position and starts a slider drag.  Otherwise it just
;; behaves the same as button 1.
;;
;; Arguments:
;; w -		The scrollbar widget.
;; x, y -	Mouse coordinates within the widget.

(define (Tk:scroll-button-2-down w x y)
  (let ((element (w 'identify x y)))
    (if (or (equal? element "arrow1") (equal? element "arrow2"))
	(Tk:scroll-button-down w x y)
	(begin
	   (Tk:scroll-to-pos w (w 'fraction x y))
	   (set! tk::relief (tk-get w :activerelief))

	   ; Need the "update idletasks" below so that the widget calls us
	   ; back to reset the actual scrollbar position before we start the
	   ; slider drag.
	   (update 'idletasks)
	   (tk-set! w :activerelief "sunken")
	   (w 'activate 'slider)
	   (Tk:scroll-start-drag w x y)))))

)