Redirecting to openjfx-dev which is the right list to discuss technical
issues such as this.
-- Kevin
On 9/20/2025 8:02 PM, Michael Zucchi wrote:
Morning list!
I hit the above bug[1] a little while ago while using a Transition for
timing on a couple of GNU/Linux systems [2,3]. Basically it runs
flat-chat because each interpolation call makes changes which triggers
a new render pass which then re-runs the animators if they're active,
which retriggers another render pass and so on. Trivial example that
demonstrated is below. If you set a specific frame-rate in the
constructor then it doesn't occur. None of the related system
properties seem to have any effect. Tracing through the code I
couldn't see how this doesn't always happen with X11/OpenGL, plus
there seems to be a bunch of stale/unfinished frame throttling code
that never gets run. I also noticed that gdk_timer was used for frame
timing, but this is documented as not being suitable for this task -
it lacks suitable resolution and must be reset each call guaranteeing
drift. And in any event timing unlinked from the display will never
be accurate.
I developed a small patch to use GLX_SGI_video_sync to synchronise to
the actual video frame-rate. It's probably hooked into the wrong
place but i'm not very familiar with the code and couldn't find much
documentation on the internals of prism and quantum toolkit; I've
attached it as a matter of interest. With this patch enabled multiple
windows will render smoothly matching the video frame rate exactly and
the animation calculations are only invoked once per frame apart from
wrap-around of cyclic animations (I've only tested with simple scenes).
The main drawback is added latency for low-frame rate monitors (I've
tested with a system that can do anything from 25 to 150), and the
'animation now timestamp' is calculated ad-hoc rather than syncing to
the expected presentation time. Having to call glXMakeContext extra
times isn't very cheap either, but it's already being called a lot.
With some guidance/pointers I can look further if it would be of use
to the project.
Regards,
Michael Z
[1] https://bugs.openjdk.org/browse/JDK-8210547
[2] gentoo, liunux 6.12.36, AMD Ryzen 4700U APU.
[3] slackare64-current linux 6.12.29, Ryzen 3900X, Radeon HD7970.
--
Group g = new Group(new Text("Hello"));
g.setTranslateX(100);
g.setTranslateY(100);
root.getChildren().setAll(g);
Transition anim = new Transition() {
double arg = 0;
{
setCycleCount(INDEFINITE);
setCycleDuration(Duration.seconds(1));
}
@Override
protected void interpolate(double frac) {
g.setRotate(arg++);
}
};
anim.play();
