macOS: QtQuick ItemView sometimes stuck at currentItem whilst scrolling

If a currentItem/currentIndex exists the ItemViews (noticed with ListView) can sometimes get stuck to the current item whilst scrolling after a currentIndex is set.

This happens when you:

• click some item in the example (to set currentIndex and moveReason to SetIndex)
• scroll down really slowy (I'm using a Mac with an Apple Magic Mouse)

QQuickListView::viewportMoved uses vData.flicking und vData.moving (and hData counterparts) to detect mouse interaction. When scrolling slowly those properties are all "false" so moveReason is kept at SetIndex.

In this situation QQuickItemView::refill -> visibleItemsChanged -> updateHighlight -> updateTrackedItem -> trackedPositionChanged sometimes calls QQuickItem::setPosition with the currentItem's position which clashes with the scroll positioning.

The two changes for -----QTBUG-62864----- seem to have made this bug more obvious as they both remove lines that reset moveReason.

Looks like this is related to the changes introduced in ae01e0dbf50cb6da1967e10eb95d63313dc5aa7a (QTBUG-63026).

import QtQuick 2.10
import QtQuick.Window 2.10

Window {
  visible: true
  width: 640
  height: 480
  title: qsTr("Hello World")

  ListView {
    id: view
    anchors.fill: parent
    model: 10000
    cacheBuffer: 0
    keyNavigationEnabled: true
    focus: true

    delegate: Rectangle {
      id: delegate
      width: 300
      height: 30
      Text {
        anchors.centerIn: parent
        text: modelData
      }
      color: ListView.isCurrentItem ? "green" : "white"
      MouseArea {
        anchors.fill: parent
        onClicked: view.currentIndex = model.index
      }
    }
  }
}