content: sub Init()
  	? "[MainScene] init"
  	' store loadingIndicator node to m
      m.loadingIndicator = m.top.FindNode("loadingIndicator")
      InitScreenStack()
      ShowGridScreen()
      RunContentTask() ' retrieving content
  end sub
  
  function onKeyEvent(key, press) as Boolean
  	? "[MainScene] onKeyEvent", key, press
  	result = false
      if press
          ' handle "back" key press
          if key = "back"
              numberOfScreens = m.screenStack.Count()
              ' close top screen if there are two or more screens in the screen stack
              if numberOfScreens > 1
                  CloseScreen(invalid)
                  result = true
              end if
          end if
      end if
      ' The OnKeyEvent() function must return true if the component handled the event,
      ' or false if it did not handle the event.
      return result
  end function