[Interest] Rotating objects in QML are killing performance

[Sletta Gunnar]

On 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.

Is vsync enabled in your driver? Sounds like it might not be. If not, then Qt Quick 2.0 will render at 100% cpu rendering maybe many thousands of frames per second, even though you only see 60 of them.

cheers,
Gunnar

> 
> 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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