model: Add footer notification for message.

This commit shows notifications in the footer if a
message sent/edited by user is outside current narrow.
This will give the user a pointer as to why the message
disappeared from the screen. The code is hooked to the
part where message request is sent to the server, hence
preventing check for user_id and message sender_id being
the same.

Fixes #781.

Author: zee-bit

zulipterminal/model.py

@@ -357,6 +357,17 @@ def send_stream_message(self, stream: str, topic: str,
         }
         response = self.client.send_message(request)
         display_error_if_present(response, self.controller)
+
+        curr_narrow = self.narrow
+        view = self.controller.view
+        if ((len(curr_narrow) == 1
+             and curr_narrow[0][1] != request['to'])
+                or (len(curr_narrow) == 2
+                    and (curr_narrow[0][1] != request['to']
+                         or curr_narrow[1][1] != request['subject']))):
+            view.set_footer_text(
+                'Message is sent outside of current narrow.', 3)
+
         return response['result'] == 'success'
 
     def update_private_message(self, msg_id: int, content: str) -> bool:
@@ -381,6 +392,13 @@ def update_stream_message(self, topic: str, message_id: int,
 
         response = self.client.update_message(request)
         display_error_if_present(response, self.controller)
+
+        old_topic = self.index['messages'][message_id].get('subject', None)
+        new_topic = request['topic']
+        view = self.controller.view
+        if old_topic != new_topic:
+            view.set_footer_text('Topic changed', 3)
+
         return response['result'] == 'success'
 
     def fetch_custom_emojis(self) -> NamedEmojiData: