test-gui.rkt

#lang racket/gui

(let ([new-es (make-eventspace)])
  (parameterize ([current-eventspace new-es])
    
    (define frame (new frame%
                       [label "Bug demo"]))
    (define button (new button%
                        [callback
                         (lambda _
                           (thread
                            (thunk
                             (channel-put result-chan (random)))))]
                        [label "FOOBAR"]
                        [parent frame]))
    (define result-chan (make-channel))
    
    (define (calling-me-should-get-a-number)
      (send frame show #t)
      (define toret (channel-get result-chan))
      (send frame show #f)
      toret)
    
    (send frame show #t) ;; remove me and program doesn't start?!?!
    
    (thread
     (thunk
      (let loop()
        (displayln (calling-me-should-get-a-number))
        ;(sleep 1) ;; uncomment me and program dies after one iteration?!?!
        (loop))))))
  
(sleep 100000000)