action_sheet: Add 'Channel feed' button to channel action sheet

assets/l10n/app_en.arb

@@ -116,6 +116,10 @@
   "@actionSheetOptionListOfTopics": {
     "description": "Label for navigating to a channel's topic-list page."
   },
+  "actionSheetOptionChannelFeed": "Channel feed",
+  "@actionSheetOptionChannelFeed": {
+    "description": "Label for navigating to a channel's channel-feed page."
+  },
   "actionSheetOptionUnsubscribe": "Unsubscribe",
   "@actionSheetOptionUnsubscribe": {
     "description": "Label in the channel action sheet for unsubscribing from the channel."

lib/generated/l10n/zulip_localizations.dart

@@ -275,7 +275,7 @@ abstract class ZulipLocalizations {
   /// **'To upload files, please grant Zulip additional permissions in Settings.'**
   String get permissionsDeniedReadExternalStorage;
 
-  /// Label in the channel context menu for subscribing to the channel.
+  /// Label in the channel action sheet for subscribing to the channel.
   ///
   /// In en, this message translates to:
   /// **'Subscribe'**
@@ -305,7 +305,13 @@ abstract class ZulipLocalizations {
   /// **'List of topics'**
   String get actionSheetOptionListOfTopics;
 
-  /// Label in the channel context menu for unsubscribing from the channel.
+  /// Label for navigating to a channel's channel-feed page.
+  ///
+  /// In en, this message translates to:
+  /// **'Channel feed'**
+  String get actionSheetOptionChannelFeed;
+
+  /// Label in the channel action sheet for unsubscribing from the channel.
   ///
   /// In en, this message translates to:
   /// **'Unsubscribe'**

lib/generated/l10n/zulip_localizations_ar.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsAr extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_de.dart

@@ -104,6 +104,9 @@ class ZulipLocalizationsDe extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Themenliste';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_en.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsEn extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_fr.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsFr extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_it.dart

@@ -103,6 +103,9 @@ class ZulipLocalizationsIt extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Elenco degli argomenti';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_ja.dart

@@ -101,6 +101,9 @@ class ZulipLocalizationsJa extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'トピック一覧';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_nb.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsNb extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_pl.dart

@@ -104,6 +104,9 @@ class ZulipLocalizationsPl extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Lista wątków';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_ru.dart

@@ -104,6 +104,9 @@ class ZulipLocalizationsRu extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Список тем';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_sk.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsSk extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_sl.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsSl extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Seznam tem';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_uk.dart

@@ -105,6 +105,9 @@ class ZulipLocalizationsUk extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'Список тем';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/generated/l10n/zulip_localizations_zh.dart

@@ -102,6 +102,9 @@ class ZulipLocalizationsZh extends ZulipLocalizations {
   @override
   String get actionSheetOptionListOfTopics => 'List of topics';
 
+  @override
+  String get actionSheetOptionChannelFeed => 'Channel feed';
+
   @override
   String get actionSheetOptionUnsubscribe => 'Unsubscribe';
 

lib/widgets/action_sheet.dart

@@ -239,11 +239,18 @@ enum BottomSheetDismissButtonStyle {
 /// Show a sheet of actions you can take on a channel.
 ///
 /// Needs a [PageRoot] ancestor.
+/// May or may not have a [MessageListPage] ancestor;
+/// some callers are on that page and some aren't.
 void showChannelActionSheet(BuildContext context, {
   required int channelId,
 }) {
   final pageContext = PageRoot.contextOf(context);
   final store = PerAccountStoreWidget.of(pageContext);
+  final messageListPageState = MessageListPage.maybeAncestorOf(pageContext);
+
+  final messageListPageNarrow = messageListPageState?.narrow;
+  final isOnChannelFeed = messageListPageNarrow is ChannelNarrow
+    && messageListPageNarrow.streamId == channelId;
 
   final unreadCount = store.unreads.countInChannelNarrow(channelId);
   final isSubscribed = store.subscriptions[channelId] != null;
@@ -255,6 +262,8 @@ void showChannelActionSheet(BuildContext context, {
       if (unreadCount > 0)
         MarkChannelAsReadButton(pageContext: pageContext, channelId: channelId),
       TopicListButton(pageContext: pageContext, channelId: channelId),
+      if (!isOnChannelFeed)
+        ChannelFeedButton(pageContext: pageContext, channelId: channelId),
       CopyChannelLinkButton(channelId: channelId, pageContext: pageContext)
     ],
     if (isSubscribed)
@@ -355,6 +364,30 @@ class TopicListButton extends ActionSheetMenuItemButton {
   }
 }
 
+class ChannelFeedButton extends ActionSheetMenuItemButton {
+  const ChannelFeedButton({
+    super.key,
+    required this.channelId,
+    required super.pageContext,
+  });
+
+  final int channelId;
+
+  @override
+  IconData get icon => ZulipIcons.message_feed;
+
+  @override
+  String label(ZulipLocalizations zulipLocalizations) {
+    return zulipLocalizations.actionSheetOptionChannelFeed;
+  }
+
+  @override
+  void onPressed() {
+    Navigator.push(pageContext,
+      MessageListPage.buildRoute(context: pageContext, narrow: ChannelNarrow(channelId)));
+  }
+}
+
 class CopyChannelLinkButton extends ActionSheetMenuItemButton {
   const CopyChannelLinkButton({
     super.key,

lib/widgets/message_list.dart

@@ -197,14 +197,30 @@ class MessageListPage extends StatefulWidget {
   ///
   /// 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.
+  ///
+  /// See also:
+  ///  * [maybeAncestorOf], which returns null instead of throwing
+  ///    when an ancestor [MessageListPageState] is not found.
   static MessageListPageState ancestorOf(BuildContext context) {
-    final state = context.findAncestorStateOfType<_MessageListPageState>();
+    final state = maybeAncestorOf(context);
     assert(state != null, 'No MessageListPage ancestor');
     return state!;
   }
 
+  /// The [MessageListPageState] above this context in the tree, if any.
+  ///
+  /// Uses the inefficient [BuildContext.findAncestorStateOfType];
+  /// don't call this in a build method.
+  ///
+  /// See also:
+  ///  * [ancestorOf], which throws instead of returning null
+  ///    when an ancestor [MessageListPageState] is not found.
+  // 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 MessageListPageState? maybeAncestorOf(BuildContext context) {
+    return context.findAncestorStateOfType<_MessageListPageState>();
+  }
+
   final Narrow initNarrow;
   final int? initAnchorMessageId; // TODO(#1564) highlight target upon load