message_list: Avoid rerender of user sidebar when adding msgs.

Added methods to live update user sidebar when messages are
added or removed from the message list without doing a complete
rerender.

web/src/activity_ui.ts

@@ -10,6 +10,7 @@ import * as buddy_data from "./buddy_data.ts";
 import {buddy_list} from "./buddy_list.ts";
 import * as keydown_util from "./keydown_util.ts";
 import {ListCursor} from "./list_cursor.ts";
+import * as narrow_state from "./narrow_state.ts";
 import * as people from "./people.ts";
 import * as pm_list from "./pm_list.ts";
 import * as popovers from "./popovers.ts";
@@ -96,6 +97,14 @@ export function redraw_user(user_id: number): void {
     update_presence_indicators();
 }
 
+export function rerender_user_sidebar_participants(): void {
+    if (!narrow_state.stream_id() || !narrow_state.topic()) {
+        return;
+    }
+
+    buddy_list.rerender_participants();
+}
+
 export function check_should_redraw_new_user(user_id: number): boolean {
     if (realm.realm_presence_disabled) {
         return false;

web/src/buddy_list.ts

@@ -983,6 +983,24 @@ export class BuddyList extends BuddyListConf {
                 is_participant_user: all_participant_ids.has(user_id),
             });
         }
+
+        this.display_or_hide_sections();
+        this.render_section_headers();
+    }
+
+    rerender_participants(): void {
+        const all_participant_ids = this.render_data.get_all_participant_ids();
+        const users_to_remove = this.participant_user_ids.filter(
+            (user_id) => !all_participant_ids.has(user_id),
+        );
+        const users_to_add = [...all_participant_ids].filter(
+            (user_id) => !this.participant_user_ids.includes(user_id),
+        );
+
+        // We are just moving the users around since we still want to show the
+        // user in buddy list regardless of if they are a participant, so we
+        // call `insert_or_move` on both `users_to_remove` and `users_to_add`.
+        this.insert_or_move([...users_to_remove, ...users_to_add]);
     }
 
     fill_screen_with_content(): void {

web/src/message_list.ts

@@ -8,7 +8,6 @@ import * as compose_tooltips from "./compose_tooltips.ts";
 import type {MessageListData} from "./message_list_data.ts";
 import * as message_list_tooltips from "./message_list_tooltips.ts";
 import {MessageListView} from "./message_list_view.ts";
-import * as message_lists from "./message_lists.ts";
 import type {Message} from "./message_store.ts";
 import * as narrow_banner from "./narrow_banner.ts";
 import * as narrow_state from "./narrow_state.ts";
@@ -216,6 +215,7 @@ export class MessageList {
 
         if (interior_messages.length > 0) {
             this.view.rerender_preserving_scrolltop(true);
+            this.update_user_sidebar_participants();
             return {need_user_to_scroll: true};
         }
         if (top_messages.length > 0) {
@@ -244,11 +244,7 @@ export class MessageList {
             this.select_id(first_unread_message_id, {then_scroll: true, use_closest: true});
         }
 
-        // Rebuild message list, since we might need to shuffle around the participant users.
+        this.update_user_sidebar_participants();
-        if (this === message_lists.current && narrow_state.stream_sub() && narrow_state.topic()) {
-            activity_ui.build_user_sidebar();
-        }
-
         return render_info;
     }
 
@@ -503,14 +499,16 @@ export class MessageList {
 
     remove_and_rerender(message_ids: number[]): void {
         const should_rerender = this.data.remove(message_ids);
+        this.update_user_sidebar_participants();
         if (!should_rerender) {
             return;
         }
         this.rerender();
-        // Rebuild message list if we're deleting messages from the current list,
+    }
-        // since we might need to remove a participant user.
+
+    update_user_sidebar_participants(): void {
         if (this.is_current_message_list()) {
-            activity_ui.build_user_sidebar();
+            activity_ui.rerender_user_sidebar_participants();
         }
     }
 
@@ -616,6 +614,11 @@ export class MessageList {
         // But in any case, we need to rerender the list for user muting,
         // to make sure only the right messages are hidden.
         this.rerender();
+
+        // While this can have changed the conversation's visible
+        // participants, we don't need to call
+        // this.update_user_sidebar_participants, because changing a
+        // muted user's state already does a full sidebar redraw.
     }
 
     all_messages(): Message[] {

web/tests/buddy_data.test.cjs

@@ -5,15 +5,21 @@ const assert = require("node:assert/strict");
 const _ = require("lodash");
 
 const {mock_esm, zrequire} = require("./lib/namespace.cjs");
-const {run_test} = require("./lib/test.cjs");
+const {noop, run_test} = require("./lib/test.cjs");
 const {page_params} = require("./lib/zpage_params.cjs");
 
 mock_esm("../src/settings_data", {
     user_can_access_all_other_users: () => true,
 });
 const timerender = mock_esm("../src/timerender");
+mock_esm("../src/buddy_list", {
+    buddy_list: {
+        rerender_participants: noop,
+    },
+});
 
 const compose_fade_helper = zrequire("compose_fade_helper");
+const activity_ui = zrequire("activity_ui");
 const muted_users = zrequire("muted_users");
 const narrow_state = zrequire("narrow_state");
 const peer_data = zrequire("peer_data");
@@ -435,6 +441,7 @@ test("get_conversation_participants", ({override_rewire}) => {
     override_rewire(narrow_state, "stream_id", () => rome_sub.stream_id);
     override_rewire(narrow_state, "topic", () => "Foo");
 
+    activity_ui.rerender_user_sidebar_participants();
     assert.deepEqual(
         buddy_data.get_conversation_participants_callback()(),
         new Set([selma.user_id]),

web/tests/message_list.test.cjs

@@ -52,7 +52,7 @@ const current_user = {};
 set_current_user(current_user);
 
 run_test("basics", ({override}) => {
-    override(activity_ui, "build_user_sidebar", noop);
+    override(activity_ui, "rerender_user_sidebar_participants", noop);
     const filter = new Filter([]);
 
     const list = new MessageList({
@@ -451,7 +451,7 @@ run_test("bookend", ({override}) => {
 });
 
 run_test("add_remove_rerender", ({override}) => {
-    override(activity_ui, "build_user_sidebar", noop);
+    override(activity_ui, "rerender_user_sidebar_participants", noop);
 
     const filter = new Filter([]);
     const list = new MessageList({