70 lines
2.2 KiB

;;;; STk adaptation of the Tk widget demo.
;;;; This demonstration script creates a simple canvas that can be
;;;; scrolled in two dimensions.
(require "Tk-classes")
(define canv-old-fill "")
(define canv-current-item #f)
(define (demo-cscroll)
(define w (make-demo-toplevel "cscroll"
"Scrollable Canvas Demonstration"
"This window displays a canvas widget that can be scrolled either using the scrollbars or by dragging with button 2 in the canvas. If you click button 1 on one of the rectangles, its indices will be printed on stdout."))
(define (scroll-enter)
(let* ((item (car (find-items c 'with 'current)))
(rect (if (is-a? item <Rectangle>)
(Cid->instance c (- (Cid item) 1)))))
(set! canv-current-item rect)
(when (> (winfo 'depth c) 1)
(set! canv-old-fill (fill rect))
(set! (fill rect) "RoyalBlue1"))))
(define (scroll-leave)
(when (and canv-current-item (> (winfo 'depth c) 1))
(set! (fill canv-current-item) canv-old-fill)
(set! canv-current-item #f)))
(define (scroll-button)
(let* ((item (car (find-items c 'with 'current)))
(txt (if (is-a? item <Text-item>)
(Cid->instance c (+ (Cid item) 1)))))
(format #t "You buttoned at ~A\n" (text-of txt))))
(define c (make <Scroll-Canvas> :parent w :scroll-region '(-11c -11c 20c 20c)
:h-scroll-side "bottom" :border-width 2 :relief "raised"))
;; Make internal objects
(let ((bg (background c)))
(dotimes (i 10)
(let ((x (+ -10 (* 3 i)))
(y -10))
(dotimes (j 10)
(make <Rectangle> :parent c
:ouline "black" :fill bg :tags "rect"
:coords (read-from-string (format #f "(~Ac ~Ac ~Ac ~Ac)"
x y (+ x 2) (+ y 2))))
(make <Text-item> :parent c :text (cons i j) :anchor 'center
:font '(Courier -12)
:tags "text" :coords (read-from-string
(format #f "(~Ac ~Ac)"
(+ x 1) (+ y 1))))
(set! y (+ y 3))))))
;; Pack canvas
(pack c :fill "both" :expand #t)
;; Some bindings
(bind c "all" "<Any-Enter>" scroll-enter)
(bind c "all" "<Any-Leave>" scroll-leave)
(bind c "all" "<1>" scroll-button)
(bind c "<2>" (lambda (x y) (scan c 'mark x y)))
(bind c "<B2-Motion>" (lambda (x y) (scan c 'dragto x y))))