[Development] ListView.positionViewAtIndex() seems to be unreliable during object initialization

[Baldo Davide]

Hello,

I'm having in issue with ListView.positionViewAtIndex(), i'm changing the
index with the last selection of the user in Component.onCompleted(),
but positionViewAtIndex() seems to behave randomly: sometime the listview
is moved correctly, sometime is off by 1 or 2 items.
I've been having this issue since 5.0 and i can still reproduce it on 5.3,
i spent several hours trying to debug it but without luck, in the end i
added a workaround:

Timer {

    interval: 100

    repeat: false

    running: true

    onTriggered: {

      main.alignIndex()

    }

 }.
but it's really a bad solution, and it's even visible.

Is it wrong to call positionViewAtIndex() inside Component.onCompleted()?
If so, when should i call it?

The component is a simple digit selector.

--- CODE ---

import QtQuick 2.0


Rectangle {

  id: main

  width: 60

  height: 180

  color: "transparent"

  border.color: "black"

  border.width: 3

  radius: 3

  clip: true


  property int initialDigit: 0;

  property int digit: 0;

  property string textColor: "violet";


  function alignIndex()

  {

    var newIndex = main.digit + 50

    listView.positionViewAtIndex(newIndex,ListView.Center);

  }


  /** workaround, force refresh after initialization **/

  Timer {

    interval: 100

    repeat: false

    running: true

    onTriggered: {

      main.alignIndex()

    }

  }


  onDigitChanged: {

    if( main.digit >= 10 ) {

      main.digit = main.digit % 10

    }

    main.alignIndex()

  }


  Component.onCompleted: {

    for( var i = 0; i < 10; i +=1 )

    {

      for( var n = 0; n < 10; n += 1 )

      {

        listModel.append({

          digit: n

        })

      }

    }


    //console.log("initial digit: "+initialDigit)

    digit = initialDigit

    alignIndex();

  }


  Timer {

    running: true

    repeat: false

    interval: 1

    onTriggered: {

      main.alignIndex()

    }

  }


  ListView {

    id: listView

    anchors.fill: parent


    snapMode: ListView.SnapPosition


    Rectangle {

      anchors.left: listView.left

      anchors.right: listView.right

      anchors.margins: 3

      height: 60 * 0.8

      y: main.height/2.0 - height/2.0 - 3

      color: "#37ffffff"

    }


    onMovementEnded: {

      main.digit = listView.indexAt(

        listView.contentX,

        listView.contentY + main.height/2.0

      ) % 10

    }


    model: ListModel {

      id: listModel

    }


    orientation: ListView.Vertical


    delegate: Component

    {

      id: digitDelegate;

      Item

      {

        height: 60

        width: main.width

        Text {

          id: digitText

          anchors.fill: parent

          text: digit

          font.pixelSize: parent.height * 0.8

          verticalAlignment: Text.Center

          horizontalAlignment: Text.Center


          Component.onCompleted: {

            digitText.color = main.textColor

          }

        }

      }

    }

  }

}



-- 
Regards,
Davide Baldo
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