if( !insertSpan.isEmpty() ) {
edit.addPerform( TimelineVisualEdit.select( this, Session.this, insertSpan ));
edit.addPerform( TimelineVisualEdit.position( this, Session.this, insertSpan.stop ));
}
edit.perform();
edit.end();
getUndoManager().addEdit( edit );
} else {
edit.cancel();
}
}