Shows a tooltip message on the screen.
Example - Show Tool-Tip
function OnStart()
{
lay = app.CreateLayout( "linear", "VCenter,FillXY" );
edt = app.CreateTextEdit( "", 0.5 );
lay.AddChild( edt );
app.AddLayout( lay );
var pos = edt.GetPosition( "screen" );
app.ShowTip( "Type some text here", pos.left, pos.top, 3000, "Down" );
}