Drag and Drop support for TreeView

[bidjiz]

Hi everyone, I'm trying to implement drag and drop for TreeView. I've ended up with the following QML code for my view:

TreeView {

	id: tree_view

	model: root.m_model // defined in C++

	selectionModel: ItemSelectionModel {
		id: selection_model
	}

	DropArea {
		id: drop_area
		anchors.fill: parent
		
		onDropped: (drag) => { // <-- never called
			console.log('DropArea onDropped');
			var from = drag.sourceDelegate.visualIndex;
			var to = visualIndex;
			root.m_model.move(from, to);
		}
	}

	delegate: TreeViewDelegate {

		id: tree_delegate

		Drag.source: drag_handler
		Drag.active: drag_handler.active

		DragHandler {
			id: drag_handler
			target: parent
			cursorShape: Qt.ClosedHandCursor
			
			onActiveChanged: {

				console.log('onActiveChanged ', active);

				if (drag_handler.active)
					drag_handler.parent.Drag.drop()
			}
		}
	}
}

The problem is that onDropped() is never called. Thus moving tree elements does nothing. I'm missing something obvious here, but what exactly? My Qt version is 6.4.