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  1. Qt
  2. QTBUG-79017

on iOS, Animation in QML decreases accuracy of Timers by 15%

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    • iOS/tvOS/watchOS

    Description

      I have the following Main.qml

      import QtQuick 2.0
import QtQuick.Window 2.10

Window {
    id: app
    visible: true
    width: 640
    height: 480

    Rectangle {
        id: btn
        anchors.fill: parent
        color: "green"
        SequentialAnimation {
            running: true
            loops: Animation.Infinite
            NumberAnimation {target: btn; property: "width"; to: 60; duration: 1000}
            NumberAnimation {target: btn; property: "width"; to: 70; duration: 1000}
        }
        Timer {
            interval: 10000
            running: true
            repeat: true
            onTriggered: console.log("*** timer  ")
        }
    }
}

      When running this on iOS (on a recent iPhone XR), I get the following logs (I installed my own message handler to add timestamps)

      13:50:41.250 Debug: *** timer   
13:50:52.749 Debug: *** timer   
13:51:04.486 Debug: *** timer   
13:51:16.378 Debug: *** timer

      As you can see, the 10s timer fires only after about 11.5s.

      When changing `running` to false, or `Window` to `Item`, the timer fires accurately again.  This problem is not seen on Mac, Linux or Android

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            vestbo Tor Arne Vestbø
            vdaele vdaele
            Veli-Pekka Heinonen Veli-Pekka Heinonen
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              Updated:

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