IssueTracker

Adding a scrollBehavior to a TopAppBar causes the innerPadding property to recompose with the layout changes of the appbar. The innerPadding propery is then passed into the content lambda, which is read in composition and therefore recomposing the content on every frame causing huge performance issue given Scaffold is used usually per-screen.

Deferring reading the innerPadding in the userland code doesn't fix the issue.

Reproducible snippet:

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun InnerPaddingRecomposingWholeContent() {
    val scrollBehavior = TopAppBarDefaults.enterAlwaysScrollBehavior()

    Scaffold(
        topBar = {
            TopAppBar(
                colors = TopAppBarDefaults.topAppBarColors(containerColor = MaterialTheme.colorScheme.primary),
                title = { Text("hello") },
                scrollBehavior = scrollBehavior
            )
        },
        modifier = Modifier
            .nestedScroll(scrollBehavior.nestedScrollConnection)
    ) { innerPadding ->
        // Here the innerPadding causes huge number of recompositions of the whole lambda with LazyColumn.
        // This causes extreme jank in cases of somewhat complex screen (reported by X).
        LazyColumn(
            modifier = Modifier
                // Our standard recommended solution
                .padding(innerPadding)
                // deferring the innerPadding this way won't work, because the innerPadding is read in composition and passed to the lambda as a value
                // .offset { IntOffset(0, innerPadding.calculateTopPadding().roundToPx()) }
        ) {
            items(100) { index ->
                ListItem(headlineContent = { Text(text = "Hello $index!") })
            }
        }
    }
}

This behavior also affects material.Scaffold, which can be fixed as well.