Playing with recomposition to understand the optimistic scenario, I discovered that I can create a simple bouncing ball without any animation api. Just changing mutable state values. Is that a thing to avoid or is perfectly fine? About hardware resources can things like that consume a lot?

This makes sense since, at least right now, there’s a 1:1 relationship between frames and compositions (composition is triggered every frame, and only by the frame), and MutableState changes that happen in one frame will immediately mark the recompose scope as dirty for the next frame, causing a loop. However I think this is probably not great because compositions can fail, and so you could theoretically skip some animation frames if a failed composition causes your code to run multiple times per frame. I’m not sure if you’d ever notice that currently, but I think this could start breaking once composition starts getting automatically split across threads.

This sample I ran first with compose desktop. I didn't saw any frame drops. Then I executed with Android Emulator and I saw some dropped frames when the ball falling. Good to know about 1:1. What is the best way to fix frame drop in the sample?

Well usually you put in a time factor, or something that is based on time. So you don't say 20 pixels per frame as you will not know what your framerate will be, but you can say 200px per second. In that case, you calculate time passed since last frame and multiply it by the 200px per second

Good to know about 1:1

Don’t quote me on that, and don’t rely on it 😜 I think that it’s usually 1:1 currently but I don’t believe that’s part of the contract so it’s not safe to rely on for stuff like this. If you are actually building real animations and not just exploring the tech, definitely use the actual animation apis.

The body of a

Canvas

isn't run during composition, it's run during the drawing phase. It's correct that something might be drawn multiple times for a single frame in some potentially esoteric cases

I think that I'm entering in the advanced compose with

LaunchedEffect

and

withFrameNanos

😅. Constant remembers was a mistake after a refactor. I'll check them out.