`ComposeScene` has the `hasInvalidations` function...

# compose-desktop

[Jakob K]

ComposeScene has the hasInvalidations function, which I currently check periodically. Is there a way to setup a callback which will be executed if this value changes to true?

[Igor Demin]

ComposeScene has invalidate callback in its constructor, which will be called, when ComposeScene should be rerendered

[Jakob K]

And how can I make sure that calling scene.render(canvas, System.nanoTime()) inside that invalidate callback does not lead to concurrency issues?

[Igor Demin]

You shouldn't call render in it. You should schedule a new frame inside your rendering loop, render should be called inside it. See the example

[Jakob K]

I assume that in this example GlfwCoroutineDispatcher() (and using that for the FrameDispatcher) is the important part, because it is only single threaded, am I right?

[Igor Demin]

Yes, it is important that it is single threaded. It is mostly for `LaunchedEffect`'s, which can't perform in parallel with ComposeScene methods. Sorry, it is not true, `LaunchedEffect`'s theoretically can launch in parallel. It also used for other things, like recompositions, and scheduling callbacks.