action_sheet: Pass/use whole-page context in show{Message,Topic}Actio…

…nSheet

lib/widgets/action_sheet.dart

@@ -163,11 +163,16 @@ class ActionSheetCancelButton extends StatelessWidget {
 }
 
 /// Show a sheet of actions you can take on a topic.
-void showTopicActionSheet(BuildContext context, {
+///
+/// [pageContext] should be the context of the whole page in the nav,
+/// not of the specific element that was long-pressed.
+/// The long-pressed element live-updates on server events,
+/// so it might unmount before the action-sheet buttons have finished using it.
+void showTopicActionSheet(BuildContext pageContext, {
   required int channelId,
   required TopicName topic,
 }) {
-  final store = PerAccountStoreWidget.of(context);
+  final store = PerAccountStoreWidget.of(pageContext);
   final subscription = store.subscriptions[channelId];
 
   final optionButtons = <ActionSheetMenuItemButton>[];
@@ -237,7 +242,7 @@ void showTopicActionSheet(BuildContext context, {
       currentVisibilityPolicy: visibilityPolicy,
       newVisibilityPolicy: to,
       narrow: TopicNarrow(channelId, topic),
-      pageContext: context);
+      pageContext: pageContext);
   }));
 
   if (optionButtons.isEmpty) {
@@ -250,7 +255,7 @@ void showTopicActionSheet(BuildContext context, {
     return;
   }
 
-  _showActionSheet(context, optionButtons: optionButtons);
+  _showActionSheet(pageContext, optionButtons: optionButtons);
 }
 
 class UserTopicUpdateButton extends ActionSheetMenuItemButton {
@@ -390,6 +395,9 @@ void showMessageActionSheet({required BuildContext context, required Message mes
   final markAsUnreadSupported = store.connection.zulipFeatureLevel! >= 155; // TODO(server-6)
   final showMarkAsUnreadButton = markAsUnreadSupported && isMessageRead;
 
+  // TODO like in showTopicActionSheet, don't pass buttons a BuildContext
+  //   for live-updating UI that could unmount before it's finished being used.
+
   final optionButtons = [
     ReactionButtons(message: message, pageContext: context),
     StarButton(message: message, pageContext: context),

lib/widgets/inbox.dart

@@ -13,14 +13,34 @@ import 'text.dart';
 import 'theme.dart';
 import 'unread_count_badge.dart';
 
+
+/// The interface for the state of an [InboxPageBody].
+///
+/// To obtain one of these, see [InboxPageBody.ancestorOf].
+abstract class InboxPageState {
+  BuildContext get context;
+}
+
 class InboxPageBody extends StatefulWidget {
   const InboxPageBody({super.key});
 
+  /// The [InboxPageState] above this context in the tree.
+  ///
+  /// Uses the inefficient [BuildContext.findAncestorStateOfType];
+  /// don't call this in a build method.
+  // If we do find ourselves wanting this in a build method, it won't be hard
+  // to enable that: we'd just need to add an [InheritedWidget] here.
+  static InboxPageState ancestorOf(BuildContext context) {
+    final state = context.findAncestorStateOfType<_InboxPageState>();
+    assert(state != null, 'No InboxPageBody ancestor');
+    return state!;
+  }
+
   @override
   State<InboxPageBody> createState() => _InboxPageState();
 }
 
-class _InboxPageState extends State<InboxPageBody> with PerAccountStoreAwareStateMixin<InboxPageBody> {
+class _InboxPageState extends State<InboxPageBody> with PerAccountStoreAwareStateMixin<InboxPageBody> implements InboxPageState {
   Unreads? unreadsModel;
   RecentDmConversationsView? recentDmConversationsModel;
 
@@ -516,7 +536,8 @@ class _TopicItem extends StatelessWidget {
           Navigator.push(context,
             MessageListPage.buildRoute(context: context, narrow: narrow));
         },
-        onLongPress: () => showTopicActionSheet(context,
+        onLongPress: () => showTopicActionSheet(
+          InboxPageBody.ancestorOf(context).context,
           channelId: streamId, topic: topic),
         child: ConstrainedBox(constraints: const BoxConstraints(minHeight: 34),
           child: Row(crossAxisAlignment: CrossAxisAlignment.center, children: [

lib/widgets/message_list.dart

@@ -183,6 +183,8 @@ abstract class MessageListPageState {
   ///
   /// This is null if [MessageList] has not mounted yet.
   MessageListView? get model;
+
+  BuildContext get context;
 }
 
 class MessageListPage extends StatefulWidget {
@@ -400,7 +402,8 @@ class MessageListAppBarTitle extends StatelessWidget {
           width: double.infinity,
           child: GestureDetector(
             behavior: HitTestBehavior.translucent,
-            onLongPress: () => showTopicActionSheet(context,
+            onLongPress: () => showTopicActionSheet(
+              MessageListPage.ancestorOf(context).context,
               channelId: streamId, topic: topic),
             child: Column(
               crossAxisAlignment: willCenterTitle ? CrossAxisAlignment.center
@@ -1112,7 +1115,8 @@ class StreamMessageRecipientHeader extends StatelessWidget {
       onTap: () => Navigator.push(context,
         MessageListPage.buildRoute(context: context,
           narrow: TopicNarrow.ofMessage(message))),
-      onLongPress: () => showTopicActionSheet(context,
+      onLongPress: () => showTopicActionSheet(
+        MessageListPage.ancestorOf(context).context,
         channelId: message.streamId, topic: topic),
       child: ColoredBox(
         color: backgroundColor,