Optimize channel list scrolling performance

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/ChatClient.kt

@@ -247,6 +247,7 @@ import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.job
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.plus
+import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 import kotlinx.coroutines.withTimeout
@@ -422,18 +423,13 @@ internal constructor(
         "This method is used to avoid race-condition between plugin initialization and dependency resolution.",
     )
     public fun awaitInitializationState(timeoutMilliseconds: Long): InitializationState? {
-        var initState: InitializationState? = clientState.initializationState.value
-        var spendTime = 0L
-        inheritScope { Job(it) }.launch {
-            initState = withTimeoutOrNull(timeoutMilliseconds) {
-                clientState.initializationState.first { it == InitializationState.COMPLETE }
+        val currentState = clientState.initializationState.value
+        if (currentState != InitializationState.INITIALIZING) return currentState
+        return runBlocking {
+            withTimeoutOrNull(timeoutMilliseconds) {
+                clientState.initializationState.first { it != InitializationState.INITIALIZING }
             }
         }
-        while (initState == InitializationState.INITIALIZING && spendTime < timeoutMilliseconds) {
-            java.lang.Thread.sleep(INITIALIZATION_DELAY)
-            spendTime += INITIALIZATION_DELAY
-        }
-        return initState
     }
 
     /**

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/extensions/internal/Channel.kt

@@ -265,7 +265,7 @@ public fun Collection<Channel>.updateUsers(users: Map<String, User>): List<Chann
  * pinnedMessages of channel instance.
  */
 internal fun Channel.updateUsers(users: Map<String, User>): Channel {
-    return if (users().map(User::id).any(users::containsKey)) {
+    return if (users().any { user -> users[user.id]?.let { it != user } == true }) {
         copy(
             messages = messages.updateUsers(users),
             members = members.updateUsers(users).toList(),

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/internal/offline/repository/domain/user/internal/DatabaseUserRepository.kt

@@ -25,6 +25,8 @@ import io.getstream.chat.android.models.Mute
 import io.getstream.chat.android.models.User
 import io.getstream.log.taggedLogger
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
@@ -42,6 +44,9 @@ internal class DatabaseUserRepository(
     private val userCache = LruCache<String, User>(cacheSize)
     private val latestUsersFlow: MutableStateFlow<Map<String, User>> = MutableStateFlow(emptyMap())
     private val dbMutex = Mutex()
+    private val pendingEntities = mutableListOf<UserEntity>()
+    private val pendingMutex = Mutex()
+    private var flushJob: Job? = null
 
     override fun observeLatestUsers(): StateFlow<Map<String, User>> = latestUsersFlow
 
@@ -62,11 +67,29 @@ internal class DatabaseUserRepository(
             .filter { it != userCache[it.id] }
             .map { it.toEntity() }
         cacheUsers(users)
-        scope.launchWithMutex(dbMutex) {
-            logger.v { "[insertUsers] inserting ${usersToInsert.size} entities on DB, updated ${users.size} on cache" }
-            usersToInsert
-                .takeUnless { it.isEmpty() }
-                ?.let { userDao.insertMany(it) }
+        if (usersToInsert.isEmpty()) return
+        pendingMutex.withLock {
+            pendingEntities.addAll(usersToInsert)
+            if (flushJob?.isActive != true) {
+                flushJob = scope.launch {
+                    delay(BATCH_FLUSH_DELAY_MS)
+                    flushPendingUsers()
+                }
+            }
+        }
+    }
+
+    private suspend fun flushPendingUsers() {
+        val snapshot = pendingMutex.withLock {
+            val copy = pendingEntities.toList()
+            pendingEntities.clear()
+            copy
+        }
+        if (snapshot.isEmpty()) return
+        val deduped = snapshot.associateBy { it.id }.values.toList()
+        logger.v { "[insertUsers] batch flushing ${deduped.size} entities to DB (from ${snapshot.size} enqueued)" }
+        dbMutex.withLock {
+            userDao.insertMany(deduped)
         }
     }
 
@@ -112,10 +135,16 @@ internal class DatabaseUserRepository(
     }
 
     private fun cacheUsers(users: Collection<User>) {
-        for (userEntity in users) {
-            userCache.put(userEntity.id, userEntity)
+        var changed = false
+        for (user in users) {
+            if (userCache[user.id] != user) {
+                userCache.put(user.id, user)
+                changed = true
+            }
+        }
+        if (changed) {
+            scope.launch { latestUsersFlow.value = userCache.snapshot() }
         }
-        scope.launch { latestUsersFlow.value = userCache.snapshot() }
     }
 
     private fun User.toEntity(): UserEntity =
@@ -162,5 +191,6 @@ internal class DatabaseUserRepository(
 
     companion object {
         private const val ME_ID = "me"
+        private const val BATCH_FLUSH_DELAY_MS = 3_000L
     }
 }

stream-chat-android-client/src/main/java/io/getstream/chat/android/client/internal/state/event/handler/internal/EventHandlerSequential.kt

@@ -526,7 +526,9 @@ internal class EventHandlerSequential(
         )
         pollEvents.forEach { batchBuilder.addPollToFetch(it.poll.id) }
 
-        val users: List<User> = events.filterIsInstance<UserEvent>().map { it.user } +
+        val users: List<User> = events.filterIsInstance<UserEvent>()
+            .filterNot { it is UserStartWatchingEvent || it is UserStopWatchingEvent }
+            .map { it.user } +
             events.filterIsInstance<HasOwnUser>().map { it.me }
 
         batchBuilder.addUsers(users)

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/channels/list/ChannelItem.kt

@@ -240,6 +240,7 @@ internal fun RowScope.DefaultChannelItemCenterContent(
     }
 }
 
+@Suppress("LongMethod")
 @Composable
 private fun TitleRow(
     channelItemState: ItemState.ChannelItemState,
@@ -260,11 +261,15 @@ private fun TitleRow(
             verticalAlignment = Alignment.CenterVertically,
             horizontalArrangement = Arrangement.spacedBy(StreamTokens.spacing2xs),
         ) {
+            val channelNameFormatter = ChatTheme.channelNameFormatter
+            val formattedChannelName = remember(channel, currentUser, channelNameFormatter) {
+                channelNameFormatter.formatChannelName(channel, currentUser)
+            }
             Text(
                 modifier = Modifier
                     .testTag("Stream_ChannelName")
                     .weight(1f, fill = false),
-                text = ChatTheme.channelNameFormatter.formatChannelName(channel, currentUser),
+                text = formattedChannelName,
                 style = ChatTheme.typography.headingSmall,
                 maxLines = 1,
                 overflow = TextOverflow.Ellipsis,
@@ -306,6 +311,7 @@ private fun TitleRow(
     }
 }
 
+@Suppress("LongMethod")
 @Composable
 private fun MessageRow(
     channelItemState: ItemState.ChannelItemState,
@@ -334,14 +340,22 @@ private fun MessageRow(
                 )
             }
 
-            val lastMessageText =
+            val messagePreviewFormatter = ChatTheme.messagePreviewFormatter
+            val lastMessageText = remember(
+                channelItemState.draftMessage,
+                lastMessage,
+                currentUser,
+                isDirectMessaging,
+                messagePreviewFormatter,
+            ) {
                 channelItemState.draftMessage
-                    ?.let { ChatTheme.messagePreviewFormatter.formatDraftMessagePreview(it) }
+                    ?.let { messagePreviewFormatter.formatDraftMessagePreview(it) }
                     ?: lastMessage?.let {
-                        ChatTheme.messagePreviewFormatter.formatMessagePreview(
+                        messagePreviewFormatter.formatMessagePreview(
                             it, currentUser, isDirectMessaging,
                         )
                     }
+            }
 
             Text(
                 modifier = Modifier

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/channels/list/ChannelList.kt

@@ -140,7 +140,6 @@ public fun ChannelList(
         }
     },
     channelContent: @Composable LazyItemScope.(ItemState.ChannelItemState) -> Unit = { itemState ->
-        val user by viewModel.user.collectAsState()
         val selectedCid = viewModel.selectedChannel.value?.cid
         val enrichedItemState = if (selectedCid != null && itemState.channel.cid == selectedCid) {
             itemState.copy(isSelected = true)
@@ -150,18 +149,17 @@ public fun ChannelList(
         with(ChatTheme.componentFactory) {
             ChannelListItemContent(
                 channelItem = enrichedItemState,
-                currentUser = user,
+                currentUser = viewModel.user.value,
                 onChannelClick = onChannelClick,
                 onChannelLongClick = onChannelLongClick,
             )
         }
     },
     searchResultContent: @Composable LazyItemScope.(ItemState.SearchResultItemState) -> Unit = { itemState ->
-        val user by viewModel.user.collectAsState()
         with(ChatTheme.componentFactory) {
             SearchResultItemContent(
                 searchResultItem = itemState,
-                currentUser = user,
+                currentUser = viewModel.user.value,
                 onSearchResultClick = onSearchResultClick,
             )
         }

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/channels/list/Channels.kt

@@ -90,6 +90,7 @@ public fun Channels(
             itemsIndexed(
                 items = channelItems,
                 key = { _, item -> item.key },
+                contentType = { _, item -> item::class },
             ) { index, item ->
                 itemContent(item)
 

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/components/Timestamp.kt

@@ -18,6 +18,7 @@ package io.getstream.chat.android.compose.ui.components
 
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.platform.testTag
@@ -54,10 +55,12 @@ public fun Timestamp(
     val timestamp = if (LocalInspectionMode.current) {
         "13:49"
     } else {
-        when (formatType) {
-            TIME -> formatter.formatTime(date)
-            DATE -> formatter.formatDate(date)
-            RELATIVE -> formatter.formatRelativeTime(date)
+        remember(date, formatType) {
+            when (formatType) {
+                TIME -> formatter.formatTime(date)
+                DATE -> formatter.formatDate(date)
+                RELATIVE -> formatter.formatRelativeTime(date)
+            }
         }
     }
 

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/components/avatar/Avatar.kt

@@ -16,7 +16,6 @@
 
 package io.getstream.chat.android.compose.ui.components.avatar
 
-import androidx.compose.animation.Crossfade
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
@@ -55,17 +54,15 @@ internal fun Avatar(
         content = { state ->
             val painter = (state as? AsyncImagePainter.State.Success)?.painter
 
-            Crossfade(targetState = painter) { painter ->
-                if (painter == null) {
-                    fallback()
-                } else {
-                    Image(
-                        modifier = Modifier.fillMaxSize(),
-                        contentScale = ContentScale.Crop,
-                        painter = painter,
-                        contentDescription = null,
-                    )
-                }
+            if (painter == null) {
+                fallback()
+            } else {
+                Image(
+                    modifier = Modifier.fillMaxSize(),
+                    contentScale = ContentScale.Crop,
+                    painter = painter,
+                    contentDescription = null,
+                )
             }
         },
     )

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/viewmodel/channels/ChannelListViewModel.kt

@@ -53,6 +53,7 @@ import io.getstream.chat.android.ui.common.state.channels.actions.ChannelAction
 import io.getstream.chat.android.ui.common.utils.extensions.defaultChannelListFilter
 import io.getstream.log.taggedLogger
 import io.getstream.result.call.toUnitCall
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancelChildren
@@ -62,9 +63,11 @@ import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.debounce
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.job
@@ -234,6 +237,8 @@ public class ChannelListViewModel(
      */
     private val searchMessageState: MutableStateFlow<SearchMessageState?> = MutableStateFlow(null)
 
+    private var previousChannelItems: Map<String, ItemState.ChannelItemState> = emptyMap()
+
     private var lastNextQuery: QueryChannelsRequest? = null
 
     /**
@@ -452,7 +457,9 @@ public class ChannelListViewModel(
                             )
                         }
                     }
-                }.collectLatest { newState -> channelsState = newState }
+                }.flowOn(Dispatchers.Default)
+                    .debounce(CHANNEL_LIST_DEBOUNCE_MS)
+                    .collectLatest { newState -> channelsState = newState }
             }
         }
     }.onFailure {
@@ -747,12 +754,16 @@ public class ChannelListViewModel(
     ): List<ItemState.ChannelItemState> {
         val mutedChannelIds = channelMutes.map { channelMute -> channelMute.channel?.cid }.toSet()
         return channels.map {
-            ItemState.ChannelItemState(
+            val newItem = ItemState.ChannelItemState(
                 channel = it,
                 isMuted = it.cid in mutedChannelIds,
                 typingUsers = typingEvents[it.cid]?.users ?: emptyList(),
                 draftMessage = draftMessages[it.cid],
             )
+            val previous = previousChannelItems[newItem.key]
+            if (previous != null && previous == newItem) previous else newItem
+        }.also { items ->
+            previousChannelItems = items.associateBy { it.key }
         }
     }
 
@@ -771,6 +782,12 @@ public class ChannelListViewModel(
          * Minimum length of the search query to start searching for channels.
          */
         private const val MIN_CHANNEL_SEARCH_QUERY_LENGTH = 3
+
+        /**
+         * Debounce for channel list state updates. Collapses rapid WebSocket events
+         * (e.g. 30 user.watching.start events) into fewer UI updates.
+         */
+        private const val CHANNEL_LIST_DEBOUNCE_MS = 100L
     }
 
     private data class SearchMessageState(