.

crates/community_ui/src/lib.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 use std::fmt;
 
 use anyhow::Result;
@@ -502,32 +502,7 @@ impl CommunityPanel {
             return;
         }
 
-        let mut index: HashMap<EventId, usize> = self
-            .rows
-            .iter()
-            .enumerate()
-            .map(|(ix, message)| (message.id, ix))
-            .collect();
-
-        let mut added = Vec::new();
-
-        for message in messages {
-            match index.get(&message.id).copied() {
-                Some(ix) => self.rows[ix] = message,
-                None => {
-                    index.insert(message.id, self.rows.len() + added.len());
-                    added.push(message);
-                }
-            }
-        }
-
-        if !added.is_empty() {
-            let at = self.item_count();
-            let count = added.len();
-            self.rows.extend(added);
-            self.list_state.splice(at..at, count);
-        }
-
+        self.merge(messages);
         cx.notify();
     }
 
@@ -537,22 +512,42 @@ impl CommunityPanel {
             return;
         }
 
-        let known: HashSet<EventId> = self.rows.iter().map(|message| message.id).collect();
-        let added: Vec<ChatMessage> = timeline
-            .messages
-            .into_iter()
-            .filter(|message| !known.contains(&message.id))
+        self.has_more = timeline.has_more;
+        self.merge(timeline.messages);
+        cx.notify();
+    }
+
+    /// Fold read rows into what is on screen, keeping the list in time order.
+    fn merge(&mut self, messages: Vec<ChatMessage>) {
+        let mut shown: HashMap<EventId, usize> = self
+            .rows
+            .iter()
+            .enumerate()
+            .map(|(ix, message)| (message.id, ix))
             .collect();
 
-        self.has_more = timeline.has_more;
+        let mut fresh = Vec::new();
 
-        if !added.is_empty() {
-            let count = added.len();
-            self.rows.splice(0..0, added);
-            self.list_state.splice(1..1, count);
+        for message in messages {
+            match shown.get(&message.id).copied() {
+                Some(ix) => self.rows[ix] = message,
+                None => fresh.push(message),
+            }
         }
 
-        cx.notify();
+        for message in fresh {
+            if shown.contains_key(&message.id) {
+                continue;
+            }
+
+            let at = self
+                .rows
+                .partition_point(|row| (row.at_ms, row.id) <= (message.at_ms, message.id));
+
+            shown.insert(message.id, at);
+            self.rows.insert(at, message);
+            self.list_state.splice(at + 1..at + 1, 1);
+        }
     }
 
     fn send(&mut self, window: &mut Window, cx: &mut Context<Self>) {
@@ -567,9 +562,6 @@ impl CommunityPanel {
             return;
         };
 
-        // A rotation that excluded us moved the write plane out of reach, and the
-        // community refuses to seal a message nobody could read. The notice above
-        // the list is what says why.
         if let Some(notice) = self.notice(cx).filter(|notice| !notice.writable()) {
             window.push_notification(Notification::error(notice.to_string()).autohide(false), cx);
             return;