contextMenu( event, items ) {
		event.preventDefault();
		event.stopImmediatePropagation();

		const menu = getOwner( this ).lookup( "nwjs:menu" );
		menu.items.pushObjects( items );
		menu.menu.popup( Math.round( event.clientX ), Math.round( event.clientY ) );
	}
@param {MouseEvent} event
@param {nw.MenuItem[]} items