Send writing messages event

lib/helpers/conversations_helper.dart

@@ -404,6 +404,10 @@ class ConversationsHelper {
     }
   }
 
+  /// Send a notification to inform that the user is writing a message
+  static Future<void> sendWritingEvent(int convID) async =>
+      await ws("conversations/is_writing", {"convID": convID});
+
   /// Turn an API response into a ConversationMessage object
   static ConversationMessage apiToConversationMessage(
     Map<String, dynamic> map,

lib/ui/screens/conversation_screen.dart

@@ -66,6 +66,8 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   ScrollWatcher _scrollController;
   _OlderMessagesLevel _loadingOlderMessages = _OlderMessagesLevel.NONE;
 
+  int _lastWritingEventSent = 0;
+
   CancelToken _sendCancel;
   double _sendProgress;
 
@@ -533,7 +535,10 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
                     style: TextStyle(
                       color: darkTheme() ? Colors.white : Colors.black,
                     ),
-                    onChanged: (s) => setState(() {}),
+                    onChanged: (s) {
+                      _sendWritingEvent();
+                      setState(() {});
+                    },
                     decoration: InputDecoration(
                       hintText: tr("New message..."),
                       hintStyle: TextStyle(
@@ -650,6 +655,21 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
     );
   }
 
+  void _sendWritingEvent() async {
+    try {
+      if (textMessage.isEmpty) return;
+      final t = time();
+
+      if (t - _lastWritingEventSent <
+          srvConfig.conversationsPolicy.writingEventInterval) return;
+
+      _lastWritingEventSent = t;
+      await ConversationsHelper.sendWritingEvent(_conversation.id);
+    } catch (e, s) {
+      logError(e, s);
+    }
+  }
+
   /// Request message statistics
   void _requestMessageStats(ConversationMessage message) async {
     MainController.of(context)