;;; Moving an object on a canvas
;;;   (drag the circle around)

(define last-x 0)
(define last-y 0)

(define (item-start-drag c x y)
  (set! last-x (c 'canvasx x))
  (set! last-y (c 'canvasy y)))

(define (item-drag c x y)
  (set! x (c 'canvasx x))
  (set! y (c 'canvasy y))
  (c 'move 'current (- x last-x) (- y last-y))
  (set! last-x x)
  (set! last-y y))

(pack (canvas '.c1) :expand #t :fill "both")

(.c1 'create 'oval 150 150 170 170 :fill "skyblue" :tag "oval")

;;; Bindings 
(.c1 'bind "oval" "<Any-Enter>"       '(.c1 'itemconfig 'current :fill "red"))
(.c1 'bind "oval" "<Any-Leave>"       '(.c1 'itemconfig 'current :fill "SkyBlue2"))
(.c1 'bind "oval" "<1>" 	      '(item-start-drag .c1 %x %y))
(.c1 'bind "oval" "<B1-Motion>"       '(item-drag .c1 %x %y))
(.c1 'bind "oval" "<ButtonRelease-1>" '(.c1 'dtag 'selected))