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)