#MSGF_MENU = 2

Procedure WindowCallback(hWnd.l,uMsg.l,wParam.l,lParam.l)
  Select uMsg
    Case #WM_ENTERIDLE
      If wParam = #MSGF_MENU
        GetClientRect_(lParam,mrc.RECT) 
        SetGadgetText(1,"Breite: "+Str(mrc\right))
        SetGadgetText(2,"Höhe: "+Str(mrc\bottom))
      EndIf
  EndSelect
  ProcedureReturn #PB_ProcessPureBasicEvents
EndProcedure

If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  TextGadget(1,200,10,100,20,"Breite: 0",0)
  TextGadget(2,200,30,100,20,"Höhe: 0",0)
  
  If CreateMenu(0,WindowID(0))
    MenuTitle("Test-Menü 1")
      For a=1 To 5
        MenuItem(a,"Menuitem "+Str(a),0)
      Next
    MenuTitle("Test-Menü 2")
      For a=1 To 10
        MenuItem(a,"Test-Menuitem "+Str(a),0)
      Next
  EndIf
  
  SetWindowCallback(@WindowCallback())
  
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf