feat(client): add subscribe_with_options

This commit adds a new method, subscribe_with_options to
komorebi-client.

The first option introduced is to tell komorebi to only send
notifications when the window manager state has been changed during the
processing of an event.

This new subscription option is now used with komorebi-bar to improve
rendering and update performance.

komorebi/src/lib.rs

@@ -177,6 +177,8 @@ lazy_static! {
         Arc::new(Mutex::new(HashMap::new()));
     pub static ref SUBSCRIPTION_SOCKETS: Arc<Mutex<HashMap<String, PathBuf>>> =
         Arc::new(Mutex::new(HashMap::new()));
+    pub static ref SUBSCRIPTION_SOCKET_OPTIONS: Arc<Mutex<HashMap<String, SubscribeOptions>>> =
+        Arc::new(Mutex::new(HashMap::new()));
     static ref TCP_CONNECTIONS: Arc<Mutex<HashMap<String, TcpStream>>> =
         Arc::new(Mutex::new(HashMap::new()));
     static ref HIDING_BEHAVIOUR: Arc<Mutex<HidingBehaviour>> =
@@ -297,18 +299,34 @@ pub struct Notification {
     pub state: State,
 }
 
-pub fn notify_subscribers(notification: &str) -> Result<()> {
+pub fn notify_subscribers(notification: Notification, state_has_been_modified: bool) -> Result<()> {
+    let is_subscription_event = matches!(
+        notification.event,
+        NotificationEvent::Socket(SocketMessage::AddSubscriberSocket(_))
+            | NotificationEvent::Socket(SocketMessage::AddSubscriberSocketWithOptions(_, _))
+    );
+
+    let notification = &serde_json::to_string(&notification)?;
     let mut stale_sockets = vec![];
     let mut sockets = SUBSCRIPTION_SOCKETS.lock();
+    let options = SUBSCRIPTION_SOCKET_OPTIONS.lock();
 
     for (socket, path) in &mut *sockets {
-        match UnixStream::connect(path) {
-            Ok(mut stream) => {
-                tracing::debug!("pushed notification to subscriber: {socket}");
-                stream.write_all(notification.as_bytes())?;
-            }
-            Err(_) => {
-                stale_sockets.push(socket.clone());
+        let apply_state_filter = (*options)
+            .get(socket)
+            .copied()
+            .unwrap_or_default()
+            .filter_state_changes;
+
+        if !apply_state_filter || state_has_been_modified || is_subscription_event {
+            match UnixStream::connect(path) {
+                Ok(mut stream) => {
+                    tracing::debug!("pushed notification to subscriber: {socket}");
+                    stream.write_all(notification.as_bytes())?;
+                }
+                Err(_) => {
+                    stale_sockets.push(socket.clone());
+                }
             }
         }
     }