Write some documentation for the LocalObserver

kifu/gtk/src/lib.rs

@@ -39,12 +39,19 @@ where
     result
 }
 
+/// LocalObserver creates a task on the current thread which watches the specified observer for notifications and calls the handler function with each one.
+///
+/// The LocalObserver starts a task which listens for notifications during the constructor. When the observer goes out of scope, it will make a point of aborting the task. This combination means that anything which uses the observer can create it, hold on to a reference of it, and then drop it when done, and not have to do anything else with the observer object.
 struct LocalObserver<T> {
     join_handle: glib::JoinHandle<()>,
     handler: Rc<dyn Fn(T)>,
 }
 
 impl<T: 'static> LocalObserver<T> {
+    /// Construct a new LocalObserver and start it running.
+    ///
+    /// observable -- any object which emits events
+    /// handler -- a function which can process events
     fn new(observable: &dyn Observable<T>, handler: impl Fn(T) + 'static) -> Self {
         let listener = observable.subscribe();
         let handler = Rc::new(handler);
@@ -54,8 +61,9 @@ impl<T: 'static> LocalObserver<T> {
                 loop {
                     match listener.recv().await {
                         Ok(msg) => handler(msg),
-                        Err(err) => {
+                        Err(_) => {
-                            unimplemented!("Should display an error message in the UI: {}", err)
+                            // recv only fails if the channel has been closed and no other notifications are pending. This will break out of the loop and terminate the observer.
+                            return;
                         }
                     }
                     yield_now().await;
@@ -71,6 +79,7 @@ impl<T: 'static> LocalObserver<T> {
 
 impl<T> Drop for LocalObserver<T> {
     fn drop(&mut self) {
+        // Abort the task when the observer goes out of scope.
         self.join_handle.abort();
     }
 }

kifu/gtk/src/view_models/home_view_model.rs

@@ -17,7 +17,7 @@ You should have received a copy of the GNU General Public License along with Kif
 use crate::LocalObserver;
 use kifu_core::{Core, CoreNotification};
 
-/// DatabaseViewModel controls the view that the user sees when starting the application if the application has been configured and if there are no games in progress. It provides a window into the database, showing a list of recently recorded games (whether from this app or from a main database). It also provides the UI for starting a new game. This will render an empty database view if the user hasn't configured a database yet.
+/// Home controls the view that the user sees when starting the application if there are no games in progress. It provides a window into the database, showing a list of recently recorded games. It also provides the UI for starting a new game. This will render an empty database view if the user hasn't configured a database yet.
 pub struct HomeViewModel {
     core: Core,
     notification_observer: LocalObserver<CoreNotification>,