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NOTE: Racket GUI 避免重複開啟視窗

 2 years ago
source link: https://dannypsnl.github.io/blog/2021/03/06/cs/racket-gui-avoid-retrigger-frame/
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NOTE: Racket GUI 避免重複開啟視窗

首先用 define/augment 往 on-close 附加一些額外的控制程式碼

(define open? #f)

(define custom-frame%
  (class frame%
    (super-new [label "test"]
               [width 300] [height 300])

    (define/augment (on-close)
      (set! open? #f))

    (set! open? #t)))

接著設計一個只有當 flag 被設定好時才會開啟視窗（frame）的函數

(define (show-it!)
  (unless open?
    (define f (new custom-frame%))
    (send f show #t)
    (send f center)))

最後就可以得到重複觸發也不會重複開啟的視窗啦！

(show-it!)
(show-it!)

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