[Development] clunky-animations-issue in Qt5 scenegraph

[André Bergner]

Hi All,

I'm currently playing around with simple QML test programs in order to
evaluate the smoothness of animated QtQuickItems.

As mentioned in the blog entry here
http://labs.qt.nokia.com/2011/05/31/qml-scene-graph-in-master/ in Qt4 the
drawing update and render calls have not been synced, which led to jerky
animations. Apparently this is supposed to be solved in Qt5. Comparing a
simple QML-test app (rectangle moving with constant velocity) between Qt4
and Qt5 there are some obvious improvement in the animations quality.

However, with Qt5 I still perceive some occasional jumps in the animation,
more rarely, though, hinting to some timing issue still existing. These
jumps can be perceived in several testing environments: Mac, Windows, Linux
(x86 as well as embedded ARM). I'm using the current Qt alpha release to
run those tests. I'v also compared to other test apps using directx or
opengl running the same test perfectly smooth. Apparently these jumps seem
to originate in the opengl render call not synced to vsync.

Is this an issue the Qt-devs are aware of? And if yes, is this going to be
solved, or am I'm doing something wrong (some missing switch for instance)?
In the source file
Qt5/qtdeclarative/src/quick/items/qquickwindowmanager.cpp it says "OpenGL
pipeline will not block for vsync in swap". Does that mean Qt scenegraphs
render calls are not synced to vsync? And if yes: WHY?

*watinting for enlightment*
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