I am just trying to get my head around compose-desktop. How would you create a time based, multi-platform animation of some complex graphics. The state of the graphics is computed based on the current time. So the graphics should be rendered constantly as fast as possible (capped to 60 fps). The examples that I have seen seem to use some Android features which are not available on desktop. The JavaFX equivalent of what I am looking for would be an AnimationTimer. Any help is appreciated.

cc @Doris Liu @Adam Powell

I think the common approach is to start an animation and then make it's animated value a part of the composition: I was trying to make a 3d renderer: https://github.com/sigurdurrafn/compose3d/ and the best examples seemed to use that: https://github.com/adibfara/ComposeClock You can then animate arbitrary values, while never having direct control, e.g calling

invalidate()

directly

The core primitive used for this is the

withFrameNanos

suspend function. Its operation is synchronized to the target framerate of the composition when running in a

CoroutineScope

obtained from

LaunchedEffect

or

rememberCoroutineScope

.

Note, that we should use

CoroutineScope

only obtained from

LaunchedEffect

 or 

rememberCoroutineScope

(not hand-created independent CoroutineScope). Because it contains the local timer (

coroutineContext[MonotonicFrameClock]

) for the current display (we can have multiple displays with different refresh rate). Currently

withFrameNanos

timer uses default display's refresh rate, but soon there will be a fix in Compose for Desktop (

withFrameNanos

will use the local display timer).

I got this working according to Siggis proposal although I feel that is not the right way to do it. I have to admit that I don’t (yet) understand what Adam and Igor are saying. Do you have an example?

Which timer will it use if my drawing is on two or more screens at the same time

It will use timer with refresh rate of display on which the window is currently running. If we move window to another display - it will use different timer. This is how it will work soon. Now timer uses only default's display refresh rate.