JpGraph :: เอา text ไว้ใน Gantt Graph ให้ ตำแหน่งอยู่ตรงกลางกราฟ ทำอย่างไรค่ะ จากโค้ด

$sql_Master = " SELECT * FROM room_bookings WHERE  active = 'True' AND room_name = 'Master Suite' AND booking_from <= '$today' AND booking_to >= '$fromday'"; 
$query_Master = mysql_query($sql_Master) or die(mysql_error());
$total_Master= mysql_num_rows($query_Master); 
if($total_Master >0)
{
	$i = 0;
	while($row_Master = mysql_fetch_array($query_Master))
	{ 	
		$activity1= new GanttBar(0,"$row_Master[room_name]","$row_Master[booking_from]","$row_Master[booking_to]"," ");	
		//$activity1->title->SetFont(FF_ARIAL,FS_NORMAL,10);
		$activity1->SetPattern(GANTT_DIAGCROSS,"pink");
		$activity1->SetHeight(18);		
		$graph->Add($activity1);
		 $i++; 	
		 
		 //RightMark
		$activity1->rightMark->Show();    
		//$activity1->SetMargin(0,0,0,0);
		//$activity1->rightMark->SetType(MARK_FILLEDCIRCLE);
		//$activity1->rightMark->SetWidth(10);
		//$activity1->rightMark->SetColor('black');
		//$activity1->rightMark->SetFillColor('pink');
		$activity1->rightMark->title->Set("$row_Master[guest_name]");
		$activity1->rightMark->title->SetFont(FF_ARIAL,FS_NORMAL,9);
		$activity1->rightMark->title->SetColor('red');

	}	
}