Fix chat not scrolling to end rotating/fullscreen

lib/screens/channel/chat/chat.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/scheduler.dart';
 import 'package:flutter_mobx/flutter_mobx.dart';
 import 'package:frosty/screens/channel/chat/emote_menu/emote_menu.dart';
 import 'package:frosty/screens/channel/chat/widgets/chat_bottom_bar.dart';
@@ -14,10 +13,6 @@ class Chat extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    // Add a post-frame callback to scroll to bottom when rotating or entering full-screen.
-    SchedulerBinding.instance?.addPostFrameCallback((_) {
-      if (chatStore.scrollController.hasClients) chatStore.resumeScroll();
-    });
     return Observer(
       builder: (context) => Column(
         children: [

lib/screens/channel/stores/chat_store.dart

@@ -76,7 +76,7 @@ abstract class _ChatStoreBase with Store {
   @readonly
   var _userState = const USERSTATE();
 
-  late final ReactionDisposer disposeEmoteMenuReaction;
+  final reactions = <ReactionDisposer>[];
 
   _ChatStoreBase({
     required this.auth,
@@ -90,11 +90,20 @@ abstract class _ChatStoreBase with Store {
     // Create a reaction where anytime the emote menu is shown or hidden,
     // scroll to the bottom of the list. This will prevent the emote menu
     // from covering the latest messages when summoned.
-    disposeEmoteMenuReaction = reaction((_) => assetsStore.showEmoteMenu, (_) {
-      SchedulerBinding.instance?.addPostFrameCallback((_) {
+    reactions.add(reaction(
+      (_) => assetsStore.showEmoteMenu,
+      (_) => SchedulerBinding.instance?.addPostFrameCallback((_) {
         if (scrollController.hasClients) scrollController.jumpTo(scrollController.position.maxScrollExtent);
-      });
-    });
+      }),
+    ));
+
+    // Create a reaction for scrolling to bottom when exiting fullscreen.
+    reactions.add(reaction(
+      (_) => settings.fullScreen,
+      (_) => SchedulerBinding.instance?.addPostFrameCallback((_) {
+        if (scrollController.hasClients) scrollController.jumpTo(scrollController.position.maxScrollExtent);
+      }),
+    ));
 
     assetsStore.init();
 
@@ -337,7 +346,10 @@ abstract class _ChatStoreBase with Store {
     _channel?.sink.close(1001);
     _channel = null;
 
-    disposeEmoteMenuReaction();
+    for (final reactionDisposer in reactions) {
+      reactionDisposer();
+    }
+
     textController.dispose();
     scrollController.dispose();
     assetsStore.dispose();

lib/screens/channel/video_chat.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_mobx/flutter_mobx.dart';
 import 'package:frosty/api/twitch_api.dart';
@@ -25,6 +26,7 @@ class VideoChat extends StatefulWidget {
 
 class _VideoChatState extends State<VideoChat> {
   final _videoKey = GlobalKey();
+  final _chatKey = GlobalKey();
 
   @override
   Widget build(BuildContext context) {
@@ -88,7 +90,10 @@ class _VideoChatState extends State<VideoChat> {
       ),
     );
 
-    final chat = Chat(chatStore: chatStore);
+    final chat = Chat(
+      key: _chatKey,
+      chatStore: chatStore,
+    );
 
     final appBar = AppBar(
       title: Text(
@@ -115,7 +120,13 @@ class _VideoChatState extends State<VideoChat> {
       body: OrientationBuilder(
         builder: (context, orientation) {
           if (orientation == Orientation.landscape) {
+            // Add a post-frame callback to scroll to bottom when rotating.
+            SchedulerBinding.instance?.addPostFrameCallback((_) {
+              if (chatStore.scrollController.hasClients) chatStore.scrollController.jumpTo(chatStore.scrollController.position.maxScrollExtent);
+            });
+
             SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersiveSticky);
+
             return Observer(
               builder: (context) => ColoredBox(
                 color: settingsStore.showVideo ? Colors.black : Theme.of(context).scaffoldBackgroundColor,
@@ -123,7 +134,16 @@ class _VideoChatState extends State<VideoChat> {
                   bottom: false,
                   child: settingsStore.showVideo
                       ? settingsStore.fullScreen
-                          ? video
+                          ? Stack(
+                              children: [
+                                Visibility(
+                                  visible: false,
+                                  maintainState: true,
+                                  child: chat,
+                                ),
+                                video,
+                              ],
+                            )
                           : Row(
                               children: [
                                 Flexible(