Looping threw model items with marquee

Alcatraz

MarqueeText.qml
@
import QtQuick 1.0

Rectangle {
width: parent.width
height: marqueeText.height + padding
clip: true

// text to be displayed by the Marquee
property string text

// top/bottom text padding
property int padding : 10

// the font size used by the Marquee
property int fontSize : 16

// the scrolling animation interval
property int interval : 35

// the text color
property color textColor: "black"

Text {
//anchors.verticalCenter: parent.verticalCenter
verticalAlignment: Text.AlignBottom
id: marqueeText
font.pointSize: fontSize
font.bold: true; font.family: "Trebuchet MS"
color: textColor
text: parent.text
x: parent.width
}

Timer {
interval: parent.interval
onTriggered: moveMarquee()
running: true
repeat: true
}

function moveMarquee()
{
if(marqueeText.x + marqueeText.width < 0)
{
    marqueeText.x = marqueeText.parent.width;
}
marqueeText.x -= 1;
}

}

@

@
Com.MarqueeText {
id: runningString
x: 76; y: 9
width:887; height: 31
text: "My Running String Here"
color: "black"; textColor: "white"
}
@

now i want to take the text from the model like XmlRole { name: "runningString"; query: "rString/string()" }

now how can i make this update the text field once its out of scope

like if x = -1 get the next item and if it has no items loop the ones that are there