[raystatic]

Uses Nav3's ListDetailSceneStrategy (for an adaptive list-detail layout.

• Wide windows (tablets, unfolded foldables in landscape): the chat list is the
  list pane, the conversation the detail pane, and profiles open in the extra
  pane. The drawer is disabled there; the list pane takes its place.
• Single-pane windows: unchanged - ModalNavigationDrawer, the channel name
  opens it.
• Tapping the channel name on wide windows pops a profile that hides the list.
• Channels get their own fake data; droidcon-nyc shows an empty state instead
  of duplicating #composers (behaviour change vs main, where both channels
  showed the same messages).
• Keyboard is only shown when the input is tapped

Screenshots

Folded phone (compact, unchanged)
Conversation	Drawer (channel name opens it)	Profile

Unfolded phone (expanded, 2 panes)
Chat list + conversation	Profile replaces the list (channel name brings it back)

Tablet (large, 3 panes)
Chat list + conversation	Chat list + conversation + profile

[compose-devrel-github-bot]

⚡ Jetpack Compose Performance Review

No Jetpack Compose performance issues were found in the changed code.

Summary of Analyzed Changes

• JetchatApp.kt:
  • directive calculation is properly memoized with explicit calculation keys using remember(windowAdaptiveInfo).
  • Coroutine effect LaunchedEffect(isMultiPane) correctly wraps suspending operation drawerState.close().
  • selectedKey = backStack.last() is cached in a local variable, avoiding duplicate snapshot state reads.
  • Scene strategies and adaptive pane layout decorators adhere to Navigation 3 and Material 3 Adaptive best practices.
• Conversation.kt:
  • Direct condition check uiState.messages.isEmpty() avoids unnecessary derivedStateOf overhead for collection emptiness inspection.
• JetchatAppBar.kt & JetchatScaffold.kt:
  • Nullability check if (onNavIconPressed != null) guards composable instantiation cleanly.
• ConversationViewModel.kt, UserInput.kt, FakeData.kt, JetchatNavKeys.kt, NavigationTest.kt:
  • Non-composable configurations, data models, and test updates with no performance impact on Compose frame phases.

[compose-devrel-github-bot]

⚡ Jetpack Compose Performance Review

Finding 1: Uncached Snapshot Collection Filtering and Loss of Instance Equality for Skippability

• File: Jetchat/app/src/main/java/com/example/compose/jetchat/JetchatApp.kt
• Lines: 106–114
• Category: Category 1: State, snapshots, and stability & Category 5: Effects, lifecycle, and threading
• Impact:
  1. backStack is a mutable snapshot collection (SnapshotStateList). In single-pane window mode (!isMultiPane), backStack.filter { it !is ChatList } executes directly within the body of JetchatApp on every recomposition pass (e.g., whenever drawerState.isOpen changes or during drawer swipe gestures). This causes repetitive collection iterations and allocates a new ArrayList on each recomposition.
  2. Because a new List instance is produced on every recomposition (displayBackStack !== previousDisplayBackStack), passing it downstream to NavDisplay(backStack = displayBackStack, ...) breaks the === instance equality check for unstable/collection parameters under Strong Skipping Mode. This prevents NavDisplay from skipping recomposition when JetchatApp recomposes for unrelated state changes.
• Recommendation:
  Wrap the derivation in remember(isMultiPane) { derivedStateOf { ... } }. derivedStateOf tracks mutations to backStack and caches the resulting list instance across recompositions of JetchatApp, preserving instance equality (===) and avoiding unnecessary allocations:

    // On single-pane windows the chat list is shown in the drawer instead of a screen. The
    // conversation is never popped, so the displayed back stack is never empty.
    val displayBackStack by remember(isMultiPane) {
        derivedStateOf {
            if (isMultiPane) {
                backStack
            } else {
                backStack.filter { it !is ChatList }.also {
                    check(it.isNotEmpty()) { "A conversation must always be on the back stack" }
                }
            }
        }
    }

---

Finding 2: Shape Re-allocation in Composition & Redundant Clipping Layer on Surface

• File: Jetchat/app/src/main/java/com/example/compose/jetchat/conversation/Conversation.kt
• Lines: 374–387
• Category: Category 2: Layouts and measurement optimization & Category 5: Effects, lifecycle, and threading
• Impact:
  1. val shape = RoundedCornerShape(20.dp) is allocated directly inside the title composable slot of ChannelNameBar. Because ChannelNameBar is a top app bar linked to scrollBehavior, scrolling the conversation triggers recompositions of the app bar, re-allocating a new RoundedCornerShape instance on every scroll frame.
  2. Applying Modifier.clip(shape) to Surface(shape = shape, ...) introduces a redundant clipping graphics layer node into the layout hierarchy. Surface already handles shape clipping and background shaping internally using its shape parameter.
• Recommendation:
  Hoist RoundedCornerShape(20.dp) to a top-level constant outside the composable, and remove the redundant Modifier.clip(shape) from the modifier chain passed to Surface:

private val ChannelNameBarShape = RoundedCornerShape(20.dp)

        title = {
            Surface(
                modifier = if (onNavIconPressed != null) {
                    Modifier
                        .clickable(onClick = onNavIconPressed)
                        .semantics { contentDescription = navIconContentDescription }
                } else {
                    Modifier
                },
                shape = ChannelNameBarShape,
                color = MaterialTheme.colorScheme.surface.copy(alpha = 0.65f),
            ) {

---

Finding 3: Redundant Layout Wrapper Node in Placeholder

• File: Jetchat/app/src/main/java/com/example/compose/jetchat/JetchatApp.kt
• Lines: 231–245
• Category: Category 2: Layouts and measurement optimization
• Impact:
  ChatPlaceholder nests a Box(contentAlignment = Alignment.Center) inside an outer Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.surfaceContainer). Surface introduces an extra layout node solely to apply the background color and fill size. Wrapping layout nodes increases layout tree depth and measurement/placement overhead.
• Recommendation:
  Collapse the nested Surface + Box hierarchy into a single Box with Modifier.background:

/** Shown in the detail pane when no conversation is selected. */
@Composable
private fun ChatPlaceholder() {
    Box(
        modifier = Modifier
            .fillMaxSize()
            .background(MaterialTheme.colorScheme.surfaceContainer),
        contentAlignment = Alignment.Center,
    ) {
        Text(
            text = stringResource(R.string.select_a_chat),
            style = MaterialTheme.typography.bodyLarge,
            color = MaterialTheme.colorScheme.onSurfaceVariant,
            modifier = Modifier.padding(24.dp),
        )
    }
}

[riggaroo]

I dont think this pattern is generally encouraged, I would rather pass an empty navigationIcon instead of checking this is null

[riggaroo]

Does this need to be done twice?

[riggaroo]

@dturner or @bsagmoe Could you review this usage of Nav3?

[compose-devrel-github-bot]

⚡ Jetpack Compose Performance Review

No Jetpack Compose performance issues were found in the changed code.

Audit Summary

• State, Snapshots & Stability: State derivations and pane scaffold transition states (targetState) are read appropriately in the relevant scopes. windowAdaptiveInfo is explicitly passed as a key to remember when computing scaffold directives. Repeated reads of backStack.last() are hoisted cleanly into a local variable. No collection models were annotated with unnecessary stability markers.
• Layouts & Measurements: No onGloballyPositioned observers, layout-to-composition feedback loops, or redundant wrapper layouts were introduced.
• Lazy Layouts: Direct list size and emptiness queries (uiState.messages.isEmpty()) access standard properties without redundant derivedStateOf wrappers. Existing item keys and content types are preserved.
• Effects & Lifecycle: LaunchedEffect(isMultiPane) wraps suspending work (drawerState.close()) guarded by conditional checks without cycling effect keys during animations or scrolls.
• Graphics & Custom Drawing: No un-cached drawing allocations, canvas nodes, or unoptimized image decoders were introduced in the diff.