[Interest] Rotating objects in QML are killing performance

[Aleix Pol]

I can confirm this. We have the same problem as well in KDE4 (that is Qt4),
so it's not a regression, but something that hasn't been fixed. (I once
even spent some time trying to figure out if it was fixable).

I guess you should report it here:
https://bugreports.qt-project.org/secure/Dashboard.jspa

Aleix


On Thu, Apr 11, 2013 at 6:31 PM, Michael Andersen <michael at steelcode.com>wrote:

> Hi list,
>
> I have a loading throbber in my application that is completely killing the
> performance. If it is rotating then the application does not repaint while
> it is being dragged and if more than two or three copies of the application
> are running then it starts lagging Unity. I'm on Ubuntu 12.04 with Qt 5.0.1
> 64-bit. I was going to wait until 5.2 was out and check again, but it's
> taking a little longer than I expected for a stable version to be released.
>
> Here is a simple reproducer of the problem, I create a QtQuick2
> application in Qt Creator 2.7. I adjust the QML to look like this:
>
> import QtQuick 2.0
>
> Rectangle {
>     width: 400
>     height: 400
>     Rectangle {
>         id: redsquare
>         color: "red"
>         width: 50
>         height: 50
>         x: 50
>         y: 50
>     }
>     RotationAnimation {
>         loops: Animation.Infinite
>         target: redsquare
>         properties: "rotation"
>         from: 0
>         to: 360
>         duration: 300*5
>         direction: RotationAnimation.Clockwise
>         running: true
>     }
> }
>
> My main.cpp is the default, but that looks like this:
>
> #include <QtGui/QGuiApplication>
> #include "qtquick2applicationviewer.h"
>
> int main(int argc, char *argv[])
> {
>     QGuiApplication app(argc, argv);
>
>     QtQuick2ApplicationViewer viewer;
>     viewer.setMainQmlFile(QStringLiteral("qml/SimpleRotator/main.qml"));
>     viewer.showExpanded();
>
>     return app.exec();
> }
>
> I am new to Qt, so perhaps I am doing something wrong with my animation,
> but I have tried a couple other methods of animating and they all lag
> equally badly. The PC I develop on is quite a monster, so if it is lagging
> on this, I hate to think what it's going to do on my clients' laptops.
>
> Anyone have any ideas?
>
> Regards
> Michael
>
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