model/views: Support event-triggered callback from views.

This commit adds two new functions in model.py:
- register_callback(): That registers callbacks for UI
elements and stores them in model.callbacks data-structure.
- process_callback(): That processes the corresponding callback
that are already registered after getting triggered from events.

These combined allow us to dynamically update the checkboxes in
stream_info popup after receiving events.

Fixes #747.

Author: zee-bit

zulipterminal/model.py

@@ -98,6 +98,8 @@ def __init__(self, controller: Any) -> None:
 
         self._notified_user_of_notification_failure = False
 
+        self.callbacks: Dict[str, Any] = {}
+
         # Events fetched once at startup
         self.initial_data_to_fetch: List[str] = [
             "realm",
@@ -178,6 +180,28 @@ def __init__(self, controller: Any) -> None:
         self.new_user_input = True
         self._start_presence_updates()
 
+    def register_callback(
+        self, obj: Any, event: str, callback: Callable[[Any], None]
+    ) -> None:
+        """
+        Registers a callback from UI elements that needs
+        to be triggered on events.
+        """
+        if event not in self.callbacks:
+            self.callbacks[event] = {}
+        self.callbacks[event] = (obj, callback)
+
+    def process_callback(self, event: str, stream_id: Optional[int]) -> None:
+        """
+        This function processes and calls the callback function that
+        was registered in self.callbacks and is recently triggered.
+        """
+        if event in self.callbacks and event == "stream_info_open":
+            caller = self.callbacks[event]
+            if caller[0].stream_id == stream_id:
+                callback = caller[1]
+                callback()
+
     def get_focus_in_current_narrow(self) -> Union[int, Set[None]]:
         """
         Returns the focus in the current narrow.
@@ -954,7 +978,6 @@ def get_stream_by_id(streams: List[StreamData], stream_id: int) -> StreamData:
                         self.muted_streams.add(stream_id)
                         self.unread_counts["all_msg"] -= unread_count
                         stream_button.mark_muted()
-                    self.controller.update_screen()
                 elif event.get("property", None) == "pin_to_top":
                     stream_id = event["stream_id"]
 
@@ -974,7 +997,8 @@ def get_stream_by_id(streams: List[StreamData], stream_id: int) -> StreamData:
                     sort_streams(self.unpinned_streams)
                     sort_streams(self.pinned_streams)
                     self.controller.view.left_panel.update_stream_view()
-                    self.controller.update_screen()
+                self.process_callback("stream_info_open", event.get("stream_id", None))
+                self.controller.update_screen()
         elif event["op"] in ("peer_add", "peer_remove"):
             # NOTE: ZFL 35 commit was not atomic with API change
             #       (ZFL >=35 can use new plural style)

zulipterminal/ui_tools/views.py

@@ -1242,6 +1242,10 @@ def __init__(self, controller: Any, stream_id: int) -> None:
 
         self.widgets.append(muted_setting)
         self.widgets.append(pinned_setting)
+
+        self.controller.model.register_callback(
+            self, "stream_info_open", self.update_checkboxes_from_events
+        )
         super().__init__(controller, self.widgets, "STREAM_DESC", popup_width, title)
 
     def toggle_mute_status(self, button: Any, new_state: bool) -> None: