Merge "Mark scenes as ready in a LaunchedEffect" into main

                    BackHandler { onChangeScene(backScene) }

                }

                Box(

                    Modifier.drawWithContent {

                        drawContent()

                        // At this point, all scenes in scenesToCompose are fully laid out so they

                        // are marked as ready. This is necessary because the animation code needs

                        // to know the position and size of the elements in each scenes they are in,

                        // so [readyScenes] will be used to decide whether the transition is ready

                        // (see isTransitionReady() below).

                        //

                        // We can't do that in a DisposableEffect or SideEffect because those are

                        // run between composition and layout. LaunchedEffect could work and might

                        // be better, but it looks like launched effects run a frame later than this

                        // code so doing this here seems better for performance.

                        scenesToCompose.fastForEach { readyScenes[it.key] = true }

                    }

                ) {

                Box {

                    scenesToCompose.fastForEach { scene ->

                        val key = scene.key

                        key(key) {

                            // Mark this scene as ready once it has been composed, laid out and

                            // drawn the first time. We have to do this in a LaunchedEffect here

                            // because DisposableEffect runs between composition and layout.

                            LaunchedEffect(key) { readyScenes[key] = true }

                            DisposableEffect(key) { onDispose { readyScenes.remove(key) } }

                            scene.Content(