calm-evt: event wrapper that calms an event’s delivery.

(require (planet "calm-evt.ss" ("dyoo" "calm-evt.plt" 1 0)))

calm-evt wraps around events and calms them down. It’s meant to be similar to the behavior of calm-e in the Flapjax language.

1 Example

Examples:

> (module exercise-calm-evt mzscheme       (require (lib "mred.ss" "mred")                (lib "class.ss")                (lib "async-channel.ss")                (planet "calm-evt.ss" ("dyoo" "calm-evt.plt" 1)))            (provide test)            (define text%/changed-notification         (class text%           (inherit get-text)           (define notify-channel (make-async-channel))                (define/public (get-notify-channel)             notify-channel)                (define/augment (after-insert pos len)             (inner (void) after-insert pos len)             (async-channel-put notify-channel (get-text)))                (define/augment (after-delete pos len)             (inner (void) after-delete pos len)             (async-channel-put notify-channel (get-text)))                (super-new)))                 (define (test)         (parameterize ([current-eventspace (make-eventspace)])           (define f (new frame% [label ""]))           (define t (new text%/changed-notification))           (define c (new editor-canvas%                          [parent f]                          [editor t]))           (send f show #t)                (thread            (lambda ()              (define delayed-change-evt                (make-calm-evt (send t get-notify-channel)))              (let loop ()                (sync (handle-evt delayed-change-evt                                  (lambda (val)                                    (printf "~s~n" val))))                (loop))))           (void))))

Run the test function, and then start typing in the new frame. Changes in the text will be printed out, but only after a period of inactivity.

2 API

A calm-evt can be used as an argument to sync. Its result is the result of the event that it wraps.

(make-calm-evt   wrapped-evt            [ delay-in-milliseconds])   →   calm-evt?

wrapped-evt : evt?

delay-in-milliseconds : natural-number/c = 1000

Creates a new calm-evt that wraps around the wrapped-evt.

(calm-evt? datum) → boolean?

datum : any/c

Returns true if the datum is a calm-evt.