mark_btn = new JButton( "LabelMark" );
mark_btn.setMargin( btn_insets );
mark_btn.setToolTipText( "Mark the timelines" );
// mark_btn.setPreferredSize( btn_dim );
mark_btn.addActionListener(
new ActionTimelineMark( root_window, this, y_tree ) );
super.add( mark_btn );
icon_URL = getURL( Const.IMG_PATH + "Paste24.gif" );
if ( icon_URL != null )
move_btn = new JButton( new ImageIcon( icon_URL ) );