Reduce Compose overhead on lower-end device.

Co-authored-by: Greyson Parrelli <greyson@signal.org>

app/src/main/java/org/thoughtcrime/securesms/main/CallsNavHost.kt

@@ -21,6 +21,8 @@ import org.thoughtcrime.securesms.serialization.JsonSerializableNavType
 import org.thoughtcrime.securesms.service.webrtc.links.CallLinkRoomId
 import kotlin.reflect.typeOf
 
+private val callLinkRoomIdType = typeOf<CallLinkRoomId>()
+
 fun NavGraphBuilder.callNavGraphBuilder(navHostController: NavHostController) {
   composable<MainNavigationDetailLocation.Empty> {
     EmptyDetailScreen()
@@ -28,7 +30,7 @@ fun NavGraphBuilder.callNavGraphBuilder(navHostController: NavHostController) {
 
   composable<MainNavigationDetailLocation.Calls.CallLinks.CallLinkDetails>(
     typeMap = mapOf(
-      typeOf<CallLinkRoomId>() to JsonSerializableNavType(CallLinkRoomId.serializer())
+      callLinkRoomIdType to JsonSerializableNavType(CallLinkRoomId.serializer())
     )
   ) {
     informNavigatorWeAreReady()
@@ -40,7 +42,7 @@ fun NavGraphBuilder.callNavGraphBuilder(navHostController: NavHostController) {
 
   composable<MainNavigationDetailLocation.Calls.CallLinks.EditCallLinkName>(
     typeMap = mapOf(
-      typeOf<CallLinkRoomId>() to JsonSerializableNavType(CallLinkRoomId.serializer())
+      callLinkRoomIdType to JsonSerializableNavType(CallLinkRoomId.serializer())
     )
   ) {
     informNavigatorWeAreReady()

app/src/main/java/org/thoughtcrime/securesms/main/ChatsNavHost.kt

@@ -62,6 +62,10 @@ import org.thoughtcrime.securesms.window.AppScaffoldAnimationState
 import kotlin.reflect.typeOf
 import kotlin.time.Duration.Companion.milliseconds
 
+private val conversationArgsType = typeOf<ConversationArgs>()
+private val recipientIdType = typeOf<RecipientId>()
+private val messageIdType = typeOf<MessageId>()
+
 fun NavGraphBuilder.chatNavGraphBuilder(
   chatNavGraphState: ChatNavGraphState
 ) {
@@ -71,7 +75,7 @@ fun NavGraphBuilder.chatNavGraphBuilder(
 
   composable<MainNavigationDetailLocation.Chats.Conversation>(
     typeMap = mapOf(
-      typeOf<ConversationArgs>() to JsonSerializableNavType(ConversationArgs.serializer())
+      conversationArgsType to JsonSerializableNavType(ConversationArgs.serializer())
     )
   ) { navBackStackEntry ->
     val route = navBackStackEntry.toRoute<MainNavigationDetailLocation.Chats.Conversation>()
@@ -147,8 +151,8 @@ fun NavGraphBuilder.chatNavGraphBuilder(
 
   composable<MainNavigationDetailLocation.Chats.MessageDetails>(
     typeMap = mapOf(
-      typeOf<RecipientId>() to JsonSerializableNavType(RecipientId.serializer()),
-      typeOf<MessageId>() to MessageId.NavType()
+      recipientIdType to JsonSerializableNavType(RecipientId.serializer()),
+      messageIdType to MessageId.NavType()
     )
   ) { navBackStackEntry ->
     val context = LocalContext.current
@@ -173,7 +177,7 @@ fun NavGraphBuilder.chatNavGraphBuilder(
 
   composable<MainNavigationDetailLocation.Chats.ConversationSettings>(
     typeMap = mapOf(
-      typeOf<RecipientId>() to JsonSerializableNavType(RecipientId.serializer())
+      recipientIdType to JsonSerializableNavType(RecipientId.serializer())
     )
   ) { navBackStackEntry ->
 

app/src/main/java/org/thoughtcrime/securesms/window/AppScaffold.kt

@@ -5,8 +5,16 @@
 
 package org.thoughtcrime.securesms.window
 
+import android.os.Build
+import androidx.activity.compose.BackHandler
+import androidx.compose.animation.AnimatedContent
 import androidx.compose.animation.EnterTransition
 import androidx.compose.animation.ExitTransition
+import androidx.compose.animation.SizeTransform
+import androidx.compose.animation.core.snap
+import androidx.compose.animation.slideInHorizontally
+import androidx.compose.animation.slideOutHorizontally
+import androidx.compose.animation.togetherWith
 import androidx.compose.foundation.background
 import androidx.compose.foundation.interaction.MutableInteractionSource
 import androidx.compose.foundation.layout.Box
@@ -24,6 +32,7 @@ import androidx.compose.material3.Text
 import androidx.compose.material3.adaptive.ExperimentalMaterial3AdaptiveApi
 import androidx.compose.material3.adaptive.currentWindowAdaptiveInfo
 import androidx.compose.material3.adaptive.layout.AnimatedPane
+import androidx.compose.material3.adaptive.layout.PaneAdaptedValue
 import androidx.compose.material3.adaptive.layout.PaneExpansionState
 import androidx.compose.material3.adaptive.layout.ThreePaneScaffoldScope
 import androidx.compose.material3.adaptive.layout.defaultDragHandleSemantics
@@ -31,6 +40,7 @@ import androidx.compose.material3.adaptive.layout.rememberPaneExpansionState
 import androidx.compose.material3.adaptive.navigation.NavigableListDetailPaneScaffold
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clipToBounds
@@ -41,13 +51,14 @@ import androidx.compose.ui.layout.layout
 import androidx.compose.ui.platform.LocalConfiguration
 import androidx.compose.ui.platform.LocalResources
 import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.zIndex
+import kotlinx.coroutines.launch
 import org.signal.core.ui.WindowBreakpoint
 import org.signal.core.ui.compose.AllDevicePreviews
 import org.signal.core.ui.compose.Previews
 import org.signal.core.ui.getWindowBreakpoint
-import org.signal.core.ui.isSplitPane
 import org.signal.core.ui.isWidthExpanded
 import org.signal.core.ui.rememberIsSplitPane
 import org.thoughtcrime.securesms.main.MainFloatingActionButtonsCallback
@@ -87,6 +98,11 @@ enum class NavigationType {
  * A top-level scaffold that automatically adapts its layout based on the device's window size class. It is a generic container designed to handle the
  * arrangement of navigation rails, top/bottom bars, and list-detail pane management for both compact and large screens.
  *
+ * On phone-class layouts (single horizontal partition) running on devices that predate predictive back (API < 33),
+ * this dispatches to [SinglePaneAppScaffold], which skips [NavigableListDetailPaneScaffold] / [ThreePaneScaffold] and
+ * its lookahead measurement pass. The scaffold's seek-driven predictive back animation never fires on those devices,
+ * so we pay no UX cost for the simpler implementation.
+ *
  * @param topBarContent An optional top bar that spans across all panes.
  *
  * @param primaryContent The main content, which is typically the detail view in a split-pane layout.
@@ -95,10 +111,10 @@ enum class NavigationType {
  * @param navRailContent The side navigation rail, shown on medium and larger screen sizes.
  * @param bottomNavContent The bottom navigation bar, shown on compact screen sizes.
  *
- * @param paneExpansionState Manages the position and expansion of the panes in a list-detail layout.
- * @param paneExpansionDragHandle An optional drag handle used to resize panes in the list-detail layout.
+ * @param paneExpansionState Manages the position and expansion of the panes in a list-detail layout. Ignored by [SinglePaneAppScaffold].
+ * @param paneExpansionDragHandle An optional drag handle used to resize panes in the list-detail layout. Ignored by [SinglePaneAppScaffold].
  *
- * @param animatorFactory Provides animations to control how panes enter and exit the screen during navigation.
+ * @param animatorFactory Provides animations to control how panes enter and exit the screen during navigation. Ignored by [SinglePaneAppScaffold].
  */
 @OptIn(ExperimentalMaterial3AdaptiveApi::class)
 @Composable
@@ -115,6 +131,52 @@ fun AppScaffold(
   snackbarHost: @Composable () -> Unit = {},
   contentWindowInsets: WindowInsets = WindowInsets.systemBars,
   animatorFactory: AppScaffoldAnimationStateFactory = AppScaffoldAnimationStateFactory.Default
+) {
+  val useSimpleScaffold = navigator.scaffoldDirective.maxHorizontalPartitions == 1 && Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU
+  if (useSimpleScaffold) {
+    SinglePaneAppScaffold(
+      navigator = navigator,
+      modifier = modifier,
+      topBarContent = topBarContent,
+      primaryContent = primaryContent,
+      secondaryContent = secondaryContent,
+      bottomNavContent = bottomNavContent,
+      snackbarHost = snackbarHost,
+      contentWindowInsets = contentWindowInsets
+    )
+  } else {
+    AdaptiveAppScaffold(
+      navigator = navigator,
+      modifier = modifier,
+      topBarContent = topBarContent,
+      primaryContent = primaryContent,
+      secondaryContent = secondaryContent,
+      navRailContent = navRailContent,
+      bottomNavContent = bottomNavContent,
+      paneExpansionState = paneExpansionState,
+      paneExpansionDragHandle = paneExpansionDragHandle,
+      snackbarHost = snackbarHost,
+      contentWindowInsets = contentWindowInsets,
+      animatorFactory = animatorFactory
+    )
+  }
+}
+
+@OptIn(ExperimentalMaterial3AdaptiveApi::class)
+@Composable
+private fun AdaptiveAppScaffold(
+  navigator: AppScaffoldNavigator<Any>,
+  modifier: Modifier = Modifier,
+  topBarContent: @Composable () -> Unit = {},
+  primaryContent: @Composable () -> Unit = {},
+  secondaryContent: @Composable () -> Unit,
+  navRailContent: @Composable () -> Unit = {},
+  bottomNavContent: @Composable () -> Unit = {},
+  paneExpansionState: PaneExpansionState = rememberPaneExpansionState(),
+  paneExpansionDragHandle: (@Composable ThreePaneScaffoldScope.(PaneExpansionState) -> Unit)? = null,
+  snackbarHost: @Composable () -> Unit = {},
+  contentWindowInsets: WindowInsets = WindowInsets.systemBars,
+  animatorFactory: AppScaffoldAnimationStateFactory = AppScaffoldAnimationStateFactory.Default
 ) {
   val minPaneWidth = navigator.scaffoldDirective.defaultPanePreferredWidth
   val navigationState = navigator.state
@@ -229,6 +291,67 @@ fun AppScaffold(
   }
 }
 
+/**
+ * Phone-only scaffold that swaps content between [secondaryContent] and [primaryContent] without using
+ * [NavigableListDetailPaneScaffold]. Avoids the lookahead measurement pass and deep adaptive layout tree
+ * that drives ANR on low-end devices.
+ *
+ */
+@OptIn(ExperimentalMaterial3AdaptiveApi::class)
+@Composable
+private fun SinglePaneAppScaffold(
+  navigator: AppScaffoldNavigator<Any>,
+  modifier: Modifier = Modifier,
+  topBarContent: @Composable () -> Unit = {},
+  primaryContent: @Composable () -> Unit = {},
+  secondaryContent: @Composable () -> Unit,
+  bottomNavContent: @Composable () -> Unit = {},
+  snackbarHost: @Composable () -> Unit = {},
+  contentWindowInsets: WindowInsets = WindowInsets.systemBars
+) {
+  val showDetail = navigator.scaffoldValue.primary == PaneAdaptedValue.Expanded
+  val coroutineScope = rememberCoroutineScope()
+
+  BackHandler(enabled = navigator.canNavigateBack()) {
+    coroutineScope.launch { navigator.navigateBack() }
+  }
+
+  Scaffold(
+    containerColor = Color.Transparent,
+    contentWindowInsets = contentWindowInsets,
+    topBar = topBarContent,
+    snackbarHost = snackbarHost,
+    modifier = modifier
+  ) { paddingValues ->
+    AnimatedContent(
+      targetState = showDetail,
+      transitionSpec = {
+        val transform = if (targetState) {
+          slideInHorizontally(animationSpec = AppScaffoldAnimationDefaults.tween()) { fullWidth -> fullWidth } togetherWith
+            slideOutHorizontally(animationSpec = AppScaffoldAnimationDefaults.tween()) { fullWidth -> -fullWidth }
+        } else {
+          slideInHorizontally(animationSpec = AppScaffoldAnimationDefaults.tween()) { fullWidth -> -fullWidth } togetherWith
+            slideOutHorizontally(animationSpec = AppScaffoldAnimationDefaults.tween()) { fullWidth -> fullWidth }
+        }
+        transform using SizeTransform(clip = false) { _, _ -> snap() }
+      },
+      modifier = Modifier.padding(paddingValues),
+      label = "SimpleAppScaffold"
+    ) { isDetail ->
+      if (isDetail) {
+        primaryContent()
+      } else {
+        Column(modifier = Modifier.fillMaxSize()) {
+          Box(modifier = Modifier.weight(1f)) {
+            secondaryContent()
+          }
+          bottomNavContent()
+        }
+      }
+    }
+  }
+}
+
 @Composable
 private fun ListAndNavigation(
   topBarContent: @Composable () -> Unit,