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module tut9_1_1
// ********************************************************************************
// Clean tutorial example program.
//
// This program creates a window that displays growing concentric circles.
// For this purpose it uses a timer.
// ********************************************************************************
import StdEnv, StdIO
:: TimerState = { nrCircles :: Int,
equiDistance :: Int,
minRadius :: Int }
Start :: *World -> *World
Start world = circles (openId world)
circles :: (Id, *World) -> *World
circles (wid, world) = startIO SDI Void (snd o seqList [openWindow Void wdef, openMenu Void mdef, openTimer initTimerState tdef]) [] world
where
windowEdge = 200
viewDomain = { corner1 = {x= ~windowEdge/2, y= ~windowEdge/2},
corner2 = {x= windowEdge/2, y= windowEdge/2} }
wdef = Window "Circles" NilLS [ WindowId wid,
WindowViewSize (rectangleSize viewDomain),
WindowViewDomain viewDomain ]
mdef = Menu "&Circles" (MenuItem "&Quit" [MenuFunction (noLS closeProcess), MenuShortKey 'q']) []
tdef = Timer (ticksPerSecond/20) NilLS [TimerFunction timer]
initTimerState = { nrCircles = 4,
equiDistance = 2,
minRadius = 0 }
timer _ (lst=:{nrCircles,equiDistance,minRadius},pst)
| minRadius < windowEdge/2
# lst = {lst & minRadius = minRadius + equiDistance}
newRadius = minRadius + nrCircles * equiDistance
# pst = appPIO (appWindowPicture wid (draw {oval_rx=newRadius, oval_ry=newRadius}
o undraw {oval_rx=minRadius, oval_ry=minRadius})) pst
= (lst,pst)
| otherwise
# pst = appPIO (appWindowPicture wid (unfill viewDomain)) pst
= (initTimerState, pst)
|
