title: How to improve ListView performance during scrolling in qt/qml
body: <p>I am facing serious issues while scolling ListView when there is costly delegate.
  When i am scrolling listview, its jerky.</p>
  
  <p>Some once please help on this.</p>
  
  <p>Here is my sample code</p>
  
  <p>/<em>LIstview with some dummy costly delegate, I tried using loader to load the delegate then its a bit better but still its jerky</em>/</p>
  
  <pre><code>import QtQuick 2.9
  import QtQuick.Controls 2.2
  import QtQuick.Window 2.2
  
  ApplicationWindow {
      visible: true
      width: Screen.width
      height: Screen.height
  
      ListView {
          width: Screen.width
          height: Screen.height
  
          model: 500
          spacing: 10
  
          highlightMoveVelocity: 50
  
          flickDeceleration: 500
          delegate: Loader{
              asynchronous: true
              sourceComponent: Image {
                  width: Screen.width
                  asynchronous: true
                  height: index %2 === 0 ? 500: 200
                  source: "file:///home/Downloads/4k.jpg"
  
                 ///Just for show
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
                  Image {
                      anchors.fill: parent
                      asynchronous: true
                      source: "file:///home/Downloads/4k.jpg"
                  }
  
              }
          }
      }
  }
  </code></pre>