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added last-picture option to stop-when

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svn: r15739
This commit is contained in:
Matthias Felleisen 2009-08-14 23:15:01 +00:00
parent cd1d7d3985
commit 6514185518
1 changed files with 18 additions and 4 deletions
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22
collects/teachpack/2htdp/scribblings/universe.scrbl
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@ -170,7 +170,7 @@ The design of a world program demands that you come up with a data
(on-mouse key-expr)
(on-draw draw-expr)
(on-draw draw-expr width-expr height-expr)
(stop-when stop-expr)
(stop-when stop-expr) (stop-when stop-expr last-scene-expr)
(check-with world?-expr)
(record? boolean-expr)
(on-receive rec-expr)
@ -403,8 +403,7 @@ All @tech{MouseEvent}s are represented via strings:
tell DrScheme to use a @scheme[width-expr] by @scheme[height-expr]
canvas instead of one determine by the first generated @tech{scene}.
}
}
}}
@item{
@ -417,7 +416,22 @@ All @tech{MouseEvent}s are represented via strings:
tick events, @tech{KeyEvent}s, or @tech{MouseEvent}s are forwarded to
the respective handlers. The @scheme[big-bang] expression returns this
last world.
}}
}
@defform/none[#:literals (stop-when)
(stop-when last-world? last-picture)
#:contracts
([last-world? (-> (unsyntax @tech{WorldState}) boolean?)]
[last-picture (-> (unsyntax @tech{WorldState}) scene?)])]{
tell DrScheme to call the @scheme[last-world?] function whenever the canvas is
drawn. If this call produces @scheme[true], the world program is shut
down after displaying the world one last time, this time using the scene
rendered with @scheme[last-picture]. Specifically, the clock is stopped; no more
tick events, @tech{KeyEvent}s, or @tech{MouseEvent}s are forwarded to
the respective handlers. The @scheme[big-bang] expression returns this
last world.
}
}
@item{