Merge pull request #3735 from vitorpamplona/fix/community-tab-first-frame

fix(chats): render the community tab correct on its first frame

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/navs/Nav.kt

@@ -94,10 +94,18 @@ class Nav(
                 // Clear sibling bottom-nav entries but keep Home (the start
                 // destination) below, so back-swipe from any tab returns to
                 // Home and back-swipe from Home leaves the app.
+                //
+                // saveState/restoreState is what makes a tab survive being left. Without them the
+                // popped entry is DESTROYED, taking its ViewModelStore with it — so every return to
+                // a tab rebuilt its screen-scoped ViewModels from nothing and re-fetched. On the
+                // Buzz community tab that is a visible ~1s of empty Direct Messages plus a channel
+                // list that reshuffles as data lands; other tabs pay it as lost scroll position.
                 popUpTo(Route.Home) {
                     inclusive = false
+                    saveState = true
                 }
                 launchSingleTop = true
+                restoreState = true
             }
             // Mark this entry as a tab root: hides the back arrow in canPop
             // and skips the horizontal slide in composableFromEnd.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/buzz/BuzzDmListViewModel.kt

@@ -23,6 +23,7 @@ package com.vitorpamplona.amethyst.ui.screen.loggedIn.buzz
 import androidx.compose.runtime.Immutable
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import com.vitorpamplona.amethyst.commons.model.buzz.BuzzDmChannels
 import com.vitorpamplona.amethyst.commons.model.buzz.BuzzDmRegistry
 import com.vitorpamplona.amethyst.commons.model.buzz.BuzzRelayDialect
 import com.vitorpamplona.amethyst.commons.model.buzz.BuzzWorkspaces
@@ -126,10 +127,39 @@ class BuzzDmListViewModel : ViewModel() {
         // challenge was spent unauthenticated, so reconnect to re-challenge and authenticate.
         if (newlyJoined) account.client.reconnect(onlyIfChanged = false, ignoreRetryDelays = true)
 
+        // Paint from cache BEFORE any network work. [discoverMemberChannels] learns the channel ids
+        // from a relay round-trip, so waiting on it left the Direct Messages section visibly empty
+        // for about a second on every visit — even though the always-on [BuzzDmDiscovery] already
+        // recorded those ids process-wide and [rebuildRows] reads nothing but caches. Seeding from
+        // that registry makes the first frame the right frame; the refresh below still runs and
+        // corrects anything stale.
+        seedFromDiscovery(account, relay)
+
         refresh()
         startLive()
     }
 
+    /**
+     * Fills [memberChannels] from the app-wide [BuzzDmChannels] registry (scoped to this community's
+     * relay) and projects the rows straight away, so the inbox renders from cache instead of after a
+     * fetch. A no-op the first time a viewer ever opens a Buzz relay, when discovery genuinely has
+     * nothing yet.
+     */
+    private fun seedFromDiscovery(
+        account: Account,
+        relay: NormalizedRelayUrl,
+    ) {
+        val known = BuzzDmChannels.channelsFor(account.userProfile().pubkeyHex)
+        var seeded = false
+        known.forEach { (channelId, discoveredOn) ->
+            if (discoveredOn == relay) {
+                memberChannels[channelId] = discoveredOn
+                seeded = true
+            }
+        }
+        if (seeded) rebuildRows(account)
+    }
+
     fun refresh() {
         val account = account ?: return
         viewModelScope.launch(Dispatchers.IO) {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/RelayGroupChannelListScreen.kt

@@ -216,20 +216,30 @@ fun RelayGroupChannelListScreen(
         }
 
     fun buzzTypeOf(groupId: GroupId): String? = channelsById[groupId.id]?.event?.buzzChannelType()
-    // Starred channels float to the top of their section (stable sort keeps the alphabetical order
-    // within the starred and unstarred buckets).
+
+    // Starred channels float to the top of their section, then alphabetical.
+    //
+    // The name is the tie-break on purpose: [buzzGroupIds] is in *arrival* order (membership ids as
+    // the ViewModel emitted them, then directory ids), so sorting on `starred` alone — a stable sort
+    // over a boolean — left the underlying order at the mercy of whatever landed first. The list
+    // visibly reshuffled in the second after opening, and came back differently each visit. Ordering
+    // by a property of the channel instead makes the first frame the final order; a channel whose
+    // 39000 hasn't arrived sorts by its id until the name lands.
     val starred by BuzzChannelStars.flow.collectAsStateWithLifecycle()
+
+    fun buzzSortKey(groupId: GroupId): String = channelsById[groupId.id]?.toBestDisplayName()?.lowercase() ?: groupId.id
+
     val buzzChatChannels =
         remember(buzzGroupIds, channelsById, starred) {
             buzzGroupIds
                 .filter { buzzTypeOf(it).let { t -> t != BUZZ_CHANNEL_TYPE_FORUM && t != BUZZ_CHANNEL_TYPE_DM } }
-                .sortedByDescending { it.id in starred }
+                .sortedWith(compareByDescending<GroupId> { it.id in starred }.thenBy { buzzSortKey(it) })
         }
     val buzzForumChannels =
         remember(buzzGroupIds, channelsById, starred) {
             buzzGroupIds
                 .filter { buzzTypeOf(it) == BUZZ_CHANNEL_TYPE_FORUM }
-                .sortedByDescending { it.id in starred }
+                .sortedWith(compareByDescending<GroupId> { it.id in starred }.thenBy { buzzSortKey(it) })
         }
 
     // Which sections the user has collapsed (session-scoped). Keyed by section id below.