content: ' Function called when the screen is displayed by the screen manager
  ' It is expected that screens override this function to handle focus
  ' managmenet and any other actions required on screen shown
  sub OnScreenShown()
      if m.top.lastFocus <> invalid
          m.top.lastFocus.setFocus(true)
      else
          m.top.setFocus(true)
      end if
  end sub
  
  ' Function called when the screen is hidden by the screen manager
  ' It is expected that screens override this function if required,
  ' to handle focus any actions required on the screen being hidden
  sub OnScreenHidden()
  end sub