[Interest] QtQuick 2 performance issue

[Dmitry Volosnykh]

Here is example application:

import QtQuick 2.0

PathView {
    width: 1280
    height: 720
    cacheItemCount: 7
    pathItemCount: 7
    preferredHighlightBegin: 0.5
    preferredHighlightEnd: 0.5
    model: ListModel {
        ListElement {
            color: "orange"
            text: "first"
        }
        ListElement {
            color: "lightgreen"
            text: "second"
        }
        ListElement {
            color: "orchid"
            text: "third"
        }
        ListElement {
            color: "tomato"
            text: "fourth"
        }
        ListElement {
            color: "skyblue"
            text: "fifth"
        }
        ListElement {
            color: "hotpink"
            text: "sixth"
        }
        ListElement {
            color: "darkseagreen"
            text: "seventh"
        }
        ListElement {
            color: "salmon"
            text: "eightth"
        }
        ListElement {
            color: "darkolivegreen"
            text: "nineth"
        }
        ListElement {
            color: "navy"
            text: "tenth"
        }
    }
    delegate: Item {
        width: 150
        height: 150

        Rectangle {
            id: rect
            anchors.fill: parent
            color: model.color
            opacity: 0.8
        }

        Text {
            anchors.centerIn: parent
            text: model.text
            color: "white"
            font.pixelSize: 24
        }
    }
    path: Path {
        startX: -150
        startY: height / 2
        PathLine {
            x: width + 150
            relativeY: 0
        }
    }

    NumberAnimation on offset {
        from: 0
        to: count
        loops: Animation.Infinite
        duration: 4000
        Component.onCompleted: start()
    }
}

On Fri, Dec 26, 2014 at 2:19 PM, Dmitry Volosnykh <
dmitry.volosnykh at gmail.com> wrote:

> Hi,
>
> I've composed a simple example with a set of squares constantly looping
> from left to right. Unfortunately, the do not run smoothly. Jiggling at
> start might seem reasonable due to QML engine performing some kind of
> initialization (do not know its internals). However, after a while when
> initialization seems to be done, motion still gets freezed from time to
> time. As a first guess, I could think that it is the garbage collector
> affecting performance, but since UI structure does not change such
> suggestion might be irrelevant.
>
> I see similar behavior when using qmlscene for Qt versions 5.1.1 and 5.3.2
> (Ubuntu 14.04), and 5.2.1 (embedded Linux).
>
> Can this be related to "QML instantiation performance" discussion happened
> in the beginning of December? Maybe this is related to QTBUG-43096. But in
> this case it should not be reproducible on version 5.1.1.
>
> Regards,
> Dmitry.
>
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