BackdropScaffold

@Composable
@OptIn(ExperimentalMaterialApi::class)
fun BackdropScaffoldSample() {
    val scope = rememberCoroutineScope()
    val selection = remember { mutableStateOf(1) }
    val scaffoldState = rememberBackdropScaffoldState(BackdropValue.Concealed)
    LaunchedEffect(scaffoldState) {
        scaffoldState.reveal()
    }
    BackdropScaffold(
        scaffoldState = scaffoldState,
        appBar = {
            TopAppBar(
                title = { Text("Backdrop scaffold") },
                navigationIcon = {
                    if (scaffoldState.isConcealed) {
                        IconButton(onClick = { scope.launch { scaffoldState.reveal() } }) {
                            Icon(Icons.Default.Menu, contentDescription = "Localized description")
                        }
                    } else {
                        IconButton(onClick = { scope.launch { scaffoldState.conceal() } }) {
                            Icon(Icons.Default.Close, contentDescription = "Localized description")
                        }
                    }
                },
                actions = {
                    var clickCount by remember { mutableStateOf(0) }
                    IconButton(
                        onClick = {
                            // show snackbar as a suspend function
                            scope.launch {
                                scaffoldState.snackbarHostState
                                    .showSnackbar("Snackbar #${++clickCount}")
                            }
                        }
                    ) {
                        Icon(Icons.Default.Favorite, contentDescription = "Localized description")
                    }
                },
                elevation = 0.dp,
                backgroundColor = Color.Transparent
            )
        },
        backLayerContent = {
            LazyColumn {
                items(if (selection.value >= 3) 3 else 5) {
                    ListItem(
                        Modifier.clickable {
                            selection.value = it
                            scope.launch { scaffoldState.conceal() }
                        },
                        text = { Text("Select $it") }
                    )
                }
            }
        },
        frontLayerContent = {
            Text("Selection: ${selection.value}")
            LazyColumn {
                items(50) {
                    ListItem(
                        text = { Text("Item $it") },
                        icon = {
                            Icon(
                                Icons.Default.Favorite,
                                contentDescription = "Localized description"
                            )
                        }
                    )
                }
            }
        }
    )
}