Discussion on: A historical introduction to the Compose reactive state model

That’s true, and my wording wasn’t as precise as it should have been. You are correct that effects can already be used to run code in parallel to composition.

What I intended that sentence to mean was that Compose can perform composition of multiple composables in parallel. It does not currently do this - when preparing a frame, all invalidated composable functions are currently recomposed in a loop on the main thread. Experimental support for parallel recomposition is already present but you have to opt in to it using fairly low level APIs.

So, for example, in this code, when state is changed, the lambdas passed to box 1 and box 2 would both be invalidated, and then they could both be re-executed on different background threads. Right now they’d be executed serially on the main thread.

@Composable fun Root() {
  val state by remember { mutableStateOf(…) }
  Column {
    // Box 1
    Box {
      println(state)
    }
    // Box 2
    Box {
      println(state)
    }
  }
}