Post-ignore_user pagination does work to refill the cleared timeline.

But, there are still a couple of things we need to fix up:
* saving which event ID is currently shown on each timeline,
  such that we can jump back to displaying that event after the
  timelines get cleared and then refilled.
* subscribing to an ignored user stream, such that we can receive
  an update when the current logged-in user (un)ignores someone
  from a different client that we do not control.
  * See `Client::subscribe_to_ignore_user_list_changes()`:
    <https://matrix-org.github.io/matrix-rust-sdk/matrix_sdk/struct.Client.html#method.subscribe_to_ignore_user_list_changes>

src/home/room_screen.rs

@@ -995,6 +995,7 @@ impl Widget for Timeline {
                         if clear_cache {
                             tl.content_drawn_since_last_update.clear();
                             tl.profile_drawn_since_last_update.clear();
+                            tl.fully_paginated = false;
                         } else {
                             tl.content_drawn_since_last_update.remove(changed_indices.clone());
                             tl.profile_drawn_since_last_update.remove(changed_indices.clone());

src/sliding_sync.rs

@@ -388,11 +388,26 @@ async fn async_worker(mut receiver: UnboundedReceiver<MatrixRequest>) -> Result<
                                 if new_room_member.is_ignored() { "" } else { "un" },
                             );
                             enqueue_user_profile_update(UserProfileUpdate::RoomMemberOnly {
-                                room_id,
+                                room_id: room_id.clone(),
                                 room_member: new_room_member,
                             });
                         }
                     }
+
+                    // After a successful (un)ignore operation, all timelines get completely cleared,
+                    // so we must re-fetch all timelines for all rooms.
+                    // Start with the current room, since that's the one being displayed.
+                    for room_id_to_paginate in client.get_room(&room_id)
+                        .into_iter()
+                        .chain(client.joined_rooms())
+                        .map(|room| room.room_id().to_owned())
+                    {
+                        submit_async_request(MatrixRequest::PaginateRoomTimeline {
+                            room_id: room_id_to_paginate,
+                            num_events: 50,
+                            forwards: false,
+                        });
+                    }
                 });
             }