add word-evt

scribblings/lux.scrbl

@@ -72,6 +72,11 @@ Returns a label for @racket[w] that could use @racket[frame-time] to
 show the performance of the @tech{word} rendering. By default, returns
 @racket[(lux-standard-label "Lux" frame-time)].}
 
+@defproc[(word-evt [w word?]) evt?]{
+
+Returns a synchronizable event that the @tech{word} @racket[w]
+requires notification of. By default, returns @racket[never-evt].}
+
 @defproc[(word-event [w word?] [e any/c]) word?]{
 
 Returns a @tech{word} based on @racket[w] that integrates the

word.rkt

@@ -10,6 +10,7 @@
 (define-generics word
   (word-fps word)
   (word-label word frame-time)
+  (word-evt word)
   (word-event word evt)
   (word-tick word)
   (word-output word)
@@ -19,6 +20,8 @@
      60.0)
    (define (word-label w frame-time)
      (lux-standard-label "Lux" frame-time))
+   (define (word-evt w)
+     never-evt)
    (define (word-event w e) w)
    (define (word-tick w) w)
    (define (word-output w) #f)
@@ -74,7 +77,8 @@
   (define (body next-time w)
     (define input-evt
       (handle-evt
-       (chaos-event c)
+       (choice-evt (word-evt w)
+                   (chaos-event c))
        (λ (e)
          (update-word w
                       (λ (w)