SnappingScrollBar.qml

import QtQuick.Controls 2.0
import QtQuick 2.7
import QtQml 2.2

ScrollBar {
    id: scrollBar
    property ListView listView: parent
    stepSize: 1 / listView.count
    property real effectiveStep: stepSize * (1 - 0)
    size: listView.visibleArea.heightRatio
    active: listView.moving || pressed
    anchors {
        top: parent.top
        bottom: parent.bottom
        right: parent.right
    }
    Binding on position {
        when: !scrollBar.pressed
        value: listView.visibleArea.yPosition
    }
    Binding {
        when: scrollBar.pressed
        target: listView
        property: "contentY"
        value: scrollBar.stepSize ? Math.round(scrollBar.position/effectiveStep) * scrollBar.effectiveStep * listView.contentHeight : scrollBar.position * listView.contentHeight
    }
}