Hide first or last item in PathView - qt

Question

I wrote a simple carousel in QML. I run Qt 6.2.0 under Ubuntu 20.04.
import QtQuick
PathView {
id: view
property int item_width: 864
property int item_gap: 250
anchors.fill: parent
anchors.bottomMargin: 150
anchors.topMargin: 50
pathItemCount: 3
preferredHighlightBegin: 0.5
preferredHighlightEnd: 0.5
highlightRangeMode: PathView.StrictlyEnforceRange
highlightMoveDuration: 1000
snapMode: PathView.SnapToItem
rotation: -90
model: modelContent
delegate: DelegateContent { }
path: Path {
startX: -item_gap; startY: view.height / 2
PathAttribute { name: "iconScale"; value: 0.7 }
PathAttribute { name: "iconOpacity"; value: 0.1 }
PathAttribute { name: "iconOrder"; value: 0 }
PathLine {x: view.width / 2; y: view.height / 2; }
PathAttribute { name: "iconScale"; value: 1 }
PathAttribute { name: "iconOpacity"; value: 1 }
PathAttribute { name: "iconOrder"; value: 9 }
PathLine {x: view.width + item_gap; y: view.height / 2; }
}
Component.onCompleted: {
gesture.gestureFired.connect(gestureFired)
}
onCurrentIndexChanged: {
itemAtIndex(0).visible = currentIndex < (count - 1)
}
function gestureFired(type) {
switch (type) {
case 1:
if (view.currentIndex > 0) view.decrementCurrentIndex();
break;
case 2:
if (view.currentIndex < view.count - 1) view.incrementCurrentIndex();
break;
}
}
}
It works very well. The change of the current index is done programmatically only (gestureFired signal from C++). As you can see there is no circular behavior.
Hence, I want to hide the first item (when the last one is selected) or the last item (when the first is selected).
I tried with the code above:
onCurrentIndexChanged: {
itemAtIndex(0).visible = currentIndex < (count - 1)
}
The idea is: if the currentIndex is the last element ( = count - 1) the visible property of the first item should be false.
But it does not work:
TypeError: Value is null and could not be converted to an object
Which "Value" is it talking about?
I debugged the currentIndex and count and they are both valid (4 and 5).
Which is the correct way to achieve such a behavior?

Answer 1

A simple solution is to do the binding in the delegate:
import QtQuick
Column {
id: root
required property int index
// mapping model roles
required property string name
visible: _internals.calculateVisibility()
QtObject {
id: _internals
function calculateVisibility() {
console.log(index, root.PathView.isCurrentItem, root.PathView.view.currentIndex)
if ((root.index === (root.PathView.view.count - 1)) && (root.PathView.view.currentIndex === 0))
return false;
else if ((root.index === 0) && (root.PathView.view.currentIndex === (root.PathView.view.count - 1)))
return false;
return true;
}
}
Text {
id: nameText
text: root.name
font.pointSize: 16
color: root.PathView.isCurrentItem ? "red" : "blue"
}
}