double-click.rkt

#lang scratch

(define will-text%
  (class text%
    (inherit get-start-position)
    (super-new)
    (define DOUBLE-CLICK-DELTA 500)
    (define last-click 0)
    (define/private (select-word)
      (define s (box (get-start-position)))
      (define e (box (get-start-position)))
      (send text find-wordbreak s e 'selection)
      (send text set-position (unbox s) (unbox e)))
    (define/override (on-event evt)
      (super on-event evt)
      (when (eq? 'left-down (send evt get-event-type))
        (define new-click (send evt get-time-stamp))
        (when (<= (- new-click last-click) DOUBLE-CLICK-DELTA)
          (select-word))
        (set! last-click new-click)))))

(define f (new frame% [label "HI"]
               [min-width 500]
               [min-height 500]))

(define text (new will-text%))
(send text insert "This is just a small snip of text.")

(new editor-canvas% [parent f]
     [editor text])
(send f show #t)