-- a simple demo for checkbuttons in the Tk library

import Tk

cb_widget =
     TkCol [] [
       TkLabel [TkText "CheckButton Demo:"],
       TkEntry [TkRef vresult, TkText "off", TkBackground "yellow"],
       TkRow [] [TkCheckButton [TkText "Check1", TkInit "1", TkRef vc1,
                                TkCmd showChecks],
                 TkCheckButton [TkText "Check2", TkRef vc2,
                                TkCmd showChecks],
                 TkButton tkExit [TkText "Stop"]]]
  where vc1, vc2, vresult free

        showChecks wp =
         do c1 <- tkGetValue vc1 wp
            c2 <- tkGetValue vc2 wp
            tkSetValue vresult ("Check 1: "++c1++" / Check 2: "++c2) wp


main = runWidget "CheckButton Demo" cb_widget