Change the main app's position and size.
Mostly used for transparent apps.
Example - SetPosition
function OnStart()
{
app.SetPosition( 0.2, 0.2, .6, .6 );
lay = app.CreateLayout( "linear", "VCenter,fillxy" );
lay.SetBackColor("blue")
btn = app.CreateButton( "Hello World", 0.3, 0.1 );
lay.AddChild( btn );
app.AddLayout( lay );
}