#lang racket/gui

;;; scroll-fac-gui.rkt - Les barres de defilement sont automatiques (exercice 14.5.4 page 338)
;;; Chapitre 14 (Objets et API graphique)
;;; Livre PCPS : "Premiers Cours de Programmation avec Scheme"
;;; Langage determine par le source

"INTERFACE GRAPHIQUE : LA FACTORIELLE AVEC SCROLLING VERTICAL"

(define FRAME (new frame% 
                   (label "Factorielle") (stretchable-height #f)))

(define VPANEL (new vertical-panel% 
                    (parent FRAME) 
                    (alignment '(left center))))

(define (fac n)
  (apply * (build-list n add1)))

(define (updateText1 n)
  (send TEXT lock #f)
  (send TEXT erase)
  (send TEXT insert (format "Sa factorielle vaut ~a" (fac n)))
  (send TEXT lock #t)
  (send TEXT hide-caret #t))

(define TEXT-FIELD (new text-field% 
                        (parent VPANEL) (min-width 300) (stretchable-width #f)
                        (label "Donnez la valeur de n : ")
                        (init-value "1")
                        (callback (lambda (obj evt)
                                    (when (equal? (send evt get-event-type) 'text-field-enter)
                                      (let ((n (string->number (send TEXT-FIELD get-value))))
                                        (printf "Dans le text-field : ~a\n" n)
                                        (updateText1 n)))))))

(define TEXT (new text%))
(send TEXT lock #t)
(send TEXT hide-caret #t)

(define ECANVAS (new editor-canvas% (parent FRAME) (min-height 50) (editor TEXT)))

(send TEXT insert "Sa factorielle vaut 1")

(define HPANEL (new horizontal-panel% (parent VPANEL) (alignment '(center center))))

(define BOUTON (new button% 
                    (parent HPANEL) 
                    (label "Random")
                    ;(style '(border))     ; Attention : ceci capturerait l'evenement 'text-field-enter !
                    (callback (lambda (obj evt)
                                (let ((n (+ 2 (random 40))))
                                  (send TEXT-FIELD set-value (number->string n))
                                  (updateText1 n))))))

(send FRAME show #t)