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document unexpected mouse event reporting; Closes PR 12278

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Matthias Felleisen 2011-10-12 09:36:39 -04:00
parent 8c2dc5ccb7
commit 8cdbd3285b
1 changed files with 8 additions and 2 deletions
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collects/teachpack/2htdp/scribblings/universe.scrbl
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@ -442,10 +442,16 @@ All @tech{MouseEvent}s are represented via strings:
coordinates may be negative or larger than the (implicitly) specified coordinates may be negative or larger than the (implicitly) specified
width and height. width and height.
Note: the computer's software doesn't really notice every single movement @bold{Note 1}: the operating system doesn't really notice every single movement
of the mouse (across the mouse pad). Instead it samples the movements and of the mouse (across the mouse pad). Instead it samples the movements and
signals most of them.} signals most of them.}
}
@bold{Note 2}: while mouse events are usually reported in the expected
manner, the operating system doesn't necessarily report them in the
expected order. For example, the Windows operating system insists on
signaling a @racket["move"] event immediately after a @racket["button-up"]
event is discovered. Programmers must design the @racket[on-mouse]
handler to handle any possible mouse event at any moment. }
@item{ @item{