recent dms [nfc]: Allow onDmSelect callback, notifying the selected DM

This will be used soon to provide a specific behaviour when
selecting a DM, where if specified it will replace the default
behaviour of routing to the message list page of the selected DM
narrow.

Author: rajveermalviya

lib/widgets/new_dm_sheet.dart

@@ -6,14 +6,14 @@ import '../model/narrow.dart';
 import '../model/store.dart';
 import 'color.dart';
 import 'icons.dart';
-import 'message_list.dart';
 import 'page.dart';
+import 'recent_dm_conversations.dart';
 import 'store.dart';
 import 'text.dart';
 import 'theme.dart';
 import 'user.dart';
 
-void showNewDmSheet(BuildContext context) {
+void showNewDmSheet(BuildContext context, OnDmSelectCallback onDmSelect) {
   final pageContext = PageRoot.contextOf(context);
   final store = PerAccountStoreWidget.of(context);
   showModalBottomSheet<void>(
@@ -29,12 +29,14 @@ void showNewDmSheet(BuildContext context) {
       padding: EdgeInsets.only(bottom: MediaQuery.viewInsetsOf(context).bottom),
       child: PerAccountStoreWidget(
         accountId: store.accountId,
-        child: NewDmPicker())));
+        child: NewDmPicker(onDmSelect: onDmSelect))));
 }
 
 @visibleForTesting
 class NewDmPicker extends StatefulWidget {
-  const NewDmPicker({super.key});
+  const NewDmPicker({super.key, required this.onDmSelect});
+
+  final OnDmSelectCallback onDmSelect;
 
   @override
   State<NewDmPicker> createState() => _NewDmPickerState();
@@ -132,7 +134,7 @@ class _NewDmPickerState extends State<NewDmPicker> with PerAccountStoreAwareStat
   @override
   Widget build(BuildContext context) {
     return Column(crossAxisAlignment: CrossAxisAlignment.stretch, children: [
-      _NewDmHeader(selectedUserIds: selectedUserIds),
+      _NewDmHeader(selectedUserIds: selectedUserIds, onDmSelect: widget.onDmSelect),
       _NewDmSearchBar(
         controller: searchController,
         selectedUserIds: selectedUserIds,
@@ -148,9 +150,10 @@ class _NewDmPickerState extends State<NewDmPicker> with PerAccountStoreAwareStat
 }
 
 class _NewDmHeader extends StatelessWidget {
-  const _NewDmHeader({required this.selectedUserIds});
+  const _NewDmHeader({required this.selectedUserIds, required this.onDmSelect});
 
   final Set<int> selectedUserIds;
+  final OnDmSelectCallback onDmSelect;
 
   Widget _buildCancelButton(BuildContext context) {
     final designVariables = DesignVariables.of(context);
@@ -178,8 +181,7 @@ class _NewDmHeader extends StatelessWidget {
         final narrow = DmNarrow.withUsers(
           selectedUserIds.toList(),
           selfUserId: store.selfUserId);
-        Navigator.pushReplacement(context,
-          MessageListPage.buildRoute(context: context, narrow: narrow));
+        onDmSelect(narrow);
       },
       child: Text(zulipLocalizations.newDmSheetComposeButtonLabel,
         style: TextStyle(

lib/widgets/recent_dm_conversations.dart

@@ -14,14 +14,22 @@ import 'theme.dart';
 import 'unread_count_badge.dart';
 import 'user.dart';
 
+typedef OnDmSelectCallback = void Function(DmNarrow narrow);
+
 class RecentDmConversationsPageBody extends StatefulWidget {
   const RecentDmConversationsPageBody({
     super.key,
     this.hideDmsIfUserCantPost = false,
+    this.onDmSelect,
   });
 
   final bool hideDmsIfUserCantPost;
 
+  /// Callback to invoke when the user selects a DM conversation from the list.
+  ///
+  /// If null, the default behavior is to navigate to the DM conversation.
+  final OnDmSelectCallback? onDmSelect;
+
   @override
   State<RecentDmConversationsPageBody> createState() => _RecentDmConversationsPageBodyState();
 }
@@ -55,6 +63,18 @@ class _RecentDmConversationsPageBodyState extends State<RecentDmConversationsPag
     });
   }
 
+  void _handleDmSelect(DmNarrow narrow) {
+    Navigator.push(context,
+      MessageListPage.buildRoute(context: context,
+        narrow: narrow));
+  }
+
+  void _handleDmSelectForNewDms(DmNarrow narrow) {
+    Navigator.pushReplacement(context,
+      MessageListPage.buildRoute(context: context,
+        narrow: narrow));
+  }
+
   @override
   Widget build(BuildContext context) {
     final store = PerAccountStoreWidget.of(context);
@@ -91,11 +111,20 @@ class _RecentDmConversationsPageBodyState extends State<RecentDmConversationsPag
                 }
                 return RecentDmConversationsItem(
                   narrow: narrow,
-                  unreadCount: unreadsModel!.countInDmNarrow(narrow));
+                  unreadCount: unreadsModel!.countInDmNarrow(narrow),
+                  onDmSelect: widget.onDmSelect ?? _handleDmSelect);
               })),
         Positioned(
           bottom: 21,
-          child: _NewDmButton()),
+          child: _NewDmButton(onDmSelect: (narrow) {
+            if (widget.onDmSelect case final onDmSelect?) {
+              // Pop the new DMs action sheet.
+              Navigator.pop(context);
+              onDmSelect(narrow);
+            } else {
+              _handleDmSelectForNewDms(narrow);
+            }
+          })),
       ]);
   }
 }
@@ -105,10 +134,12 @@ class RecentDmConversationsItem extends StatelessWidget {
     super.key,
     required this.narrow,
     required this.unreadCount,
+    required this.onDmSelect,
   });
 
   final DmNarrow narrow;
   final int unreadCount;
+  final OnDmSelectCallback onDmSelect;
 
   static const double _avatarSize = 32;
 
@@ -151,10 +182,7 @@ class RecentDmConversationsItem extends StatelessWidget {
     return Material(
       color: backgroundColor,
       child: InkWell(
-        onTap: () {
-          Navigator.push(context,
-            MessageListPage.buildRoute(context: context, narrow: narrow));
-        },
+        onTap: () => onDmSelect(narrow),
         child: ConstrainedBox(constraints: const BoxConstraints(minHeight: 48),
           child: Row(crossAxisAlignment: CrossAxisAlignment.center, children: [
             Padding(padding: const EdgeInsetsDirectional.fromSTEB(12, 8, 0, 8),
@@ -188,7 +216,11 @@ class RecentDmConversationsItem extends StatelessWidget {
 }
 
 class _NewDmButton extends StatefulWidget {
-  const _NewDmButton();
+  const _NewDmButton({
+    required this.onDmSelect,
+  });
+
+  final OnDmSelectCallback onDmSelect;
 
   @override
   State<_NewDmButton> createState() => _NewDmButtonState();
@@ -210,7 +242,7 @@ class _NewDmButtonState extends State<_NewDmButton> {
       : designVariables.fabLabel;
 
     return GestureDetector(
-      onTap: () => showNewDmSheet(context),
+      onTap: () => showNewDmSheet(context, widget.onDmSelect),
       onTapDown: (_) => setState(() => _pressed = true),
       onTapUp: (_) => setState(() => _pressed = false),
       onTapCancel: () => setState(() => _pressed = false),