use proper css styling for the font colors

Previously the Hello handler in `ListenTask` echoed our local commit
back but deliberately threw away the peer's, on the assumption that
the outgoing connect-side path (`connect.rs:278-279` →
`set_peer_commit`) would always populate the visible state for any
bidirectionally-configured peer.

That assumption breaks any time the *outgoing* TCP/DTLS direction is
broken even though the inbound direction is fine — happened just now
when the peer Mac's daemon stopped listening on 4242 (DHCP-renewed
IP, daemon crashed, asymmetric NAT, …). Mac was still happily
connecting in the other direction and sending events, including the
initial Hello, but Linux silently displayed "peer version unknown"
because the listen side dropped Mac's commit on the floor.

Add a `PeerHello { addr, commit }` EmulationEvent variant fired from
the listen-side Hello handler. The service maps `addr → ClientHandle`
via `client_manager.get_client(addr)` and calls `set_peer_commit` +
`broadcast_client` exactly like the connect path does. The connect
path remains the primary source for symmetric setups; this is the
defensive fallback so version visibility doesn't depend on outbound
reachability.

Skips silently when no outgoing client is configured for the peer's
addr (incoming-only setup) — there's no UI row to update in that
case anyway.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lan-mouse-gtk/resources/resources.gresource.xml

@@ -6,6 +6,7 @@
     <file compressed="true" preprocess="xml-stripblanks">fingerprint_window.ui</file>
     <file compressed="true" preprocess="xml-stripblanks">client_row.ui</file>
     <file compressed="true" preprocess="xml-stripblanks">key_row.ui</file>
+    <file compressed="true">style.css</file>
   </gresource>
   <gresource prefix="/de/feschber/LanMouse/icons">
     <file compressed="true" preprocess="xml-stripblanks">de.feschber.LanMouse.svg</file>

lan-mouse-gtk/resources/style.css

@@ -0,0 +1,12 @@
+.peer-match > box > list .subtitle {
+    color: @success_color;
+}
+
+.peer-mismatch > box > list .subtitle {
+    font-weight: bold;
+    color: @warning_color;
+}
+
+.peer-unknown > box > list .subtitle {
+    color: @warning_color;
+}

lan-mouse-gtk/src/client_object.rs

@@ -26,6 +26,7 @@ impl ClientObject {
                     .collect::<Vec<_>>(),
             )
             .property("resolving", state.resolving)
+            .property("peer-commit", peer_commit_to_string(state.peer_commit))
             .build()
     }
 
@@ -34,6 +35,14 @@ impl ClientObject {
     }
 }
 
+/// Render the 8-byte ASCII commit hash carried in
+/// [`lan_mouse_ipc::ClientState::peer_commit`] as a `String`. `None`
+/// in → `None` out (peer hasn't sent a Hello yet, or speaks an older
+/// proto).
+pub fn peer_commit_to_string(commit: Option<[u8; 8]>) -> Option<String> {
+    commit.and_then(|c| std::str::from_utf8(&c).ok().map(str::to_string))
+}
+
 #[derive(Default, Clone)]
 pub struct ClientData {
     pub handle: ClientHandle,
@@ -43,4 +52,5 @@ pub struct ClientData {
     pub position: String,
     pub resolving: bool,
     pub ips: Vec<String>,
+    pub peer_commit: Option<String>,
 }

lan-mouse-gtk/src/client_object/imp.rs

@@ -19,6 +19,7 @@ pub struct ClientObject {
     #[property(name = "position", get, set, type = String, member = position)]
     #[property(name = "resolving", get, set, type = bool, member = resolving)]
     #[property(name = "ips", get, set, type = Vec<String>, member = ips)]
+    #[property(name = "peer-commit", get, set, type = Option<String>, member = peer_commit)]
     pub data: RefCell<ClientData>,
 }
 

lan-mouse-gtk/src/client_row.rs

@@ -123,6 +123,12 @@ impl ClientRow {
         bindings.push(position_binding);
         bindings.push(resolve_binding);
         bindings.push(ip_binding);
+
+        // Render the initial collapsed subtitle from whatever
+        // peer_commit the ClientObject was created with. Subsequent
+        // changes are pushed by `Window::update_client_state` calling
+        // `refresh_version_status` after writing the new property.
+        self.refresh_version_status();
     }
 
     pub fn unbind(&self) {
@@ -150,4 +156,40 @@ impl ClientRow {
     pub fn set_dns_state(&self, resolved: bool) {
         self.imp().set_dns_state(resolved);
     }
+
+    /// Recompute the collapsed subtitle (Pango markup) based on the
+    /// current `peer-commit` property and the local build's commit.
+    /// Soft-warn semantics: a missing or mismatched peer commit
+    /// surfaces as orange text but never blocks traffic. Called by
+    /// the window after `update_client_state` writes the new
+    /// `peer-commit`. The dns-status icon is left to its existing
+    /// `set_dns_state` handler so the two indicators don't fight
+    /// for the same CSS class.
+    pub fn refresh_version_status(&self) {
+        let peer: Option<String> = self
+            .imp()
+            .client_object
+            .borrow()
+            .as_ref()
+            .and_then(|co| co.property::<Option<String>>("peer-commit"));
+        let local = crate::local_commit_str();
+        let markup = match peer.as_deref() {
+            None => format!("Peer version: unknown · Ours: {local}"),
+            Some(p) if p == local.as_str() => {
+                format!("Peer version: {p} · matched")
+            }
+            Some(p) => {
+                format!("Peer version: {p} · Ours: {local}")
+            }
+        };
+        self.remove_css_class("peer-mismatch");
+        self.remove_css_class("peer-match");
+        self.remove_css_class("peer-unknown");
+        match peer.as_deref() {
+            Some(p) if p == local.as_str() => self.add_css_class("peer-match"),
+            Some(_) => self.add_css_class("peer-mismatch"),
+            None => self.add_css_class("peer-unknown"),
+        };
+        self.set_subtitle(&markup);
+    }
 }

lan-mouse-gtk/src/lib.rs

@@ -10,10 +10,28 @@ mod macos_privacy;
 mod macos_status_item;
 mod window;
 
-use std::{env, process, str};
+use std::{env, process, str, sync::OnceLock};
 
+use gtk::CssProvider;
 use window::Window;
 
+/// Local build's commit hash, set once by [`run`] before the GTK
+/// main loop starts. Read by per-row UI to compare against each
+/// peer's [`lan_mouse_ipc::ClientState::peer_commit`] for the
+/// soft-warn version-mismatch indicator.
+pub(crate) static LOCAL_COMMIT: OnceLock<[u8; 8]> = OnceLock::new();
+
+/// Convenience: returns the local commit as an 8-char ASCII string,
+/// or a placeholder if unset (which would indicate a programmer
+/// error since [`run`] always sets it).
+pub(crate) fn local_commit_str() -> String {
+    LOCAL_COMMIT
+        .get()
+        .and_then(|c| std::str::from_utf8(c).ok())
+        .unwrap_or("????????")
+        .to_string()
+}
+
 use lan_mouse_ipc::FrontendEvent;
 
 use adw::Application;
@@ -31,8 +49,12 @@ pub enum GtkError {
     NonZeroExitCode(i32),
 }
 
-pub fn run() -> Result<(), GtkError> {
+pub fn run(local_commit: [u8; 8]) -> Result<(), GtkError> {
     log::debug!("running gtk frontend");
+    LOCAL_COMMIT
+        .set(local_commit)
+        .expect("local_commit set once");
+
     #[cfg(windows)]
     let ret = std::thread::Builder::new()
         .stack_size(8 * 1024 * 1024) // https://gitlab.gnome.org/GNOME/gtk/-/commit/52dbb3f372b2c3ea339e879689c1de535ba2c2c3 -> caused crash on windows
@@ -64,6 +86,7 @@ fn gtk_main() -> glib::ExitCode {
         .build();
 
     app.connect_startup(|app| {
+        load_css();
         load_icons();
         setup_actions(app);
         setup_menu(app);
@@ -132,6 +155,16 @@ fn configure_macos_bundle_environment() {
     );
 }
 
+fn load_css() {
+    let provider = CssProvider::default();
+    provider.load_from_resource("de/feschber/LanMouse/style.css");
+    gtk::style_context_add_provider_for_display(
+        &Display::default().expect("Could not connect to a display"),
+        &provider,
+        gtk::STYLE_PROVIDER_PRIORITY_APPLICATION,
+    );
+}
+
 fn load_icons() {
     let display = &Display::default().expect("Could not connect to a display.");
     let icon_theme = IconTheme::for_display(display);

lan-mouse-gtk/src/window.rs

@@ -365,6 +365,13 @@ impl Window {
             .map(|ip| ip.to_string())
             .collect::<Vec<_>>();
         client_object.set_ips(ips);
+
+        /* peer build version (drives the version-match indicator) */
+        client_object.set_property(
+            "peer-commit",
+            crate::client_object::peer_commit_to_string(state.peer_commit),
+        );
+        row.refresh_version_status();
     }
 
     fn client_object_for_handle(&self, handle: ClientHandle) -> Option<ClientObject> {

lan-mouse-ipc/src/lib.rs

@@ -176,6 +176,12 @@ pub struct ClientState {
     pub has_pressed_keys: bool,
     /// dns resolving in progress
     pub resolving: bool,
+    /// Peer's build short commit hash from the [`Hello`] proto
+    /// event. `None` means we haven't received a Hello yet — either
+    /// the connection is fresh, or the peer is on an older build
+    /// that predates the Hello event. The frontend uses this to
+    /// soft-warn on version mismatch.
+    pub peer_commit: Option<[u8; 8]>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

lan-mouse-proto/src/lib.rs

@@ -63,6 +63,15 @@ pub enum ProtoEvent {
     Ping,
     /// Response to [`ProtoEvent::Ping`], true if emulation is enabled / available
     Pong(bool),
+    /// Build identification for the sending peer. Sent by the
+    /// connect side once after the connection authenticates, and
+    /// echoed back by the listen side in reply, so each end can
+    /// display the peer's build hash and warn (soft) on mismatch.
+    /// `commit` is the 8-byte ASCII short commit hash from
+    /// `shadow_rs`'s `SHORT_COMMIT`. Old peers that don't
+    /// recognize the event type silently skip it per the
+    /// forward-compat handling in the receive loop.
+    Hello { commit: [u8; 8] },
 }
 
 impl Display for ProtoEvent {
@@ -80,6 +89,10 @@ impl Display for ProtoEvent {
                     if *alive { "alive" } else { "not available" }
                 )
             }
+            ProtoEvent::Hello { commit } => {
+                let s = std::str::from_utf8(commit).unwrap_or("????????");
+                write!(f, "Hello({s})")
+            }
         }
     }
 }
@@ -98,6 +111,7 @@ pub enum EventType {
     Enter,
     Leave,
     Ack,
+    Hello,
 }
 
 impl ProtoEvent {
@@ -120,6 +134,7 @@ impl ProtoEvent {
             ProtoEvent::Enter(_) => EventType::Enter,
             ProtoEvent::Leave(_) => EventType::Leave,
             ProtoEvent::Ack(_) => EventType::Ack,
+            ProtoEvent::Hello { .. } => EventType::Hello,
         }
     }
 }
@@ -174,6 +189,13 @@ impl TryFrom<[u8; MAX_EVENT_SIZE]> for ProtoEvent {
             EventType::Enter => Ok(Self::Enter(decode_u8(&mut buf)?.try_into()?)),
             EventType::Leave => Ok(Self::Leave(decode_u32(&mut buf)?)),
             EventType::Ack => Ok(Self::Ack(decode_u32(&mut buf)?)),
+            EventType::Hello => {
+                let mut commit = [0u8; 8];
+                for b in commit.iter_mut() {
+                    *b = decode_u8(&mut buf)?;
+                }
+                Ok(Self::Hello { commit })
+            }
         }
     }
 }
@@ -238,6 +260,11 @@ impl From<ProtoEvent> for ([u8; MAX_EVENT_SIZE], usize) {
                 ProtoEvent::Enter(pos) => encode_u8(buf, len, pos as u8),
                 ProtoEvent::Leave(serial) => encode_u32(buf, len, serial),
                 ProtoEvent::Ack(serial) => encode_u32(buf, len, serial),
+                ProtoEvent::Hello { commit } => {
+                    for b in commit.iter() {
+                        encode_u8(buf, len, *b);
+                    }
+                }
             }
         }
         (buf, len)

src/client.rs

@@ -282,6 +282,12 @@ impl ClientManager {
         }
     }
 
+    pub(crate) fn set_peer_commit(&self, handle: ClientHandle, commit: Option<[u8; 8]>) {
+        if let Some((_, s)) = self.clients.borrow_mut().get_mut(handle as usize) {
+            s.peer_commit = commit;
+        }
+    }
+
     pub(crate) fn active_addr(&self, handle: ClientHandle) -> Option<SocketAddr> {
         self.clients
             .borrow()

src/config.rs

@@ -28,6 +28,18 @@ use shadow_rs::shadow;
 
 shadow!(build);
 
+/// Local build's 8-byte ASCII short commit hash, suitable for use
+/// in [`lan_mouse_proto::ProtoEvent::Hello`]. Pads with `'?'` if
+/// shadow_rs returns an unexpected length so the field is always
+/// well-formed on the wire.
+pub fn local_commit() -> [u8; 8] {
+    let bytes = build::SHORT_COMMIT.as_bytes();
+    let mut out = [b'?'; 8];
+    let n = bytes.len().min(8);
+    out[..n].copy_from_slice(&bytes[..n]);
+    out
+}
+
 const CONFIG_FILE_NAME: &str = "config.toml";
 const CERT_FILE_NAME: &str = "lan-mouse.pem";
 

src/connect.rs

@@ -1,4 +1,5 @@
 use crate::client::ClientManager;
+use crate::config::local_commit;
 use lan_mouse_ipc::{ClientHandle, DEFAULT_PORT};
 use lan_mouse_proto::{MAX_EVENT_SIZE, ProtoEvent};
 use local_channel::mpsc::{Receiver, Sender, channel};
@@ -197,6 +198,19 @@ async fn connect_to_handle(
         conns.lock().await.insert(addr, conn.clone());
         connecting.lock().await.remove(&handle);
 
+        // Best-effort version handshake. Send our commit hash once
+        // immediately after the DTLS handshake; the listen side
+        // mirrors a Hello back so the receive loop can populate
+        // `peer_commit`. Old peers will silently skip this event
+        // per the forward-compat handler in [`receive_loop`].
+        let (buf, len) = ProtoEvent::Hello {
+            commit: local_commit(),
+        }
+        .into();
+        if let Err(e) = conn.send(&buf[..len]).await {
+            log::debug!("hello send to {addr} failed: {e}");
+        }
+
         // poll connection for active
         spawn_local(ping_pong(addr, conn.clone(), ping_response.clone()));
 
@@ -255,16 +269,26 @@ async fn receive_loop(
 ) {
     let mut buf = [0u8; MAX_EVENT_SIZE];
     while conn.recv(&mut buf).await.is_ok() {
-        if let Ok(event) = buf.try_into() {
+        match buf.try_into() {
-            log::trace!("{addr} <==<==<== {event}");
+            Ok(event) => {
-            match event {
+                log::trace!("{addr} <==<==<== {event}");
-                ProtoEvent::Pong(b) => {
+                match event {
-                    client_manager.set_active_addr(handle, Some(addr));
+                    ProtoEvent::Pong(b) => {
-                    client_manager.set_alive(handle, b);
+                        client_manager.set_active_addr(handle, Some(addr));
-                    ping_response.borrow_mut().insert(addr);
+                        client_manager.set_alive(handle, b);
+                        ping_response.borrow_mut().insert(addr);
+                    }
+                    ProtoEvent::Hello { commit } => {
+                        client_manager.set_peer_commit(handle, Some(commit));
+                    }
+                    event => tx.send((handle, event)).expect("channel closed"),
                 }
-                event => tx.send((handle, event)).expect("channel closed"),
             }
+            // Skip undecodable datagrams without dropping the
+            // connection. Each DTLS recv is one framed message, so
+            // skipping is safe and keeps us forward-compatible with
+            // peers that send event types we don't yet know about.
+            Err(e) => log::debug!("ignoring undecodable event from {addr}: {e}"),
         }
     }
     log::warn!("recv error");
@@ -280,6 +304,7 @@ async fn disconnect(
     log::warn!("client ({handle}) @ {addr} connection closed");
     conns.lock().await.remove(&addr);
     client_manager.set_active_addr(handle, None);
+    client_manager.set_peer_commit(handle, None);
     let active: Vec<SocketAddr> = conns.lock().await.keys().copied().collect();
     log::info!("active connections: {active:?}");
 }

src/emulation.rs

@@ -1,3 +1,4 @@
+use crate::config::local_commit;
 use crate::listen::{LanMouseListener, ListenEvent, ListenerCreationError};
 use futures::StreamExt;
 use input_emulation::{EmulationHandle, InputEmulation, InputEmulationError};
@@ -52,6 +53,17 @@ pub(crate) enum EmulationEvent {
     EmulationEnabled,
     /// capture should be released
     ReleaseNotify,
+    /// peer sent us a Hello with its build commit hash. Used to
+    /// populate `client_manager.peer_commit` from the listen side
+    /// too — without this, peer-version visibility silently fails
+    /// whenever the outgoing connection in the *other* direction is
+    /// broken (one-way setups, asymmetric NAT, peer's TCP listener
+    /// down). The connect-side path stays as the primary source;
+    /// this is the defensive fallback.
+    PeerHello {
+        addr: SocketAddr,
+        commit: [u8; 8],
+    },
 }
 
 enum EmulationRequest {
@@ -150,6 +162,21 @@ impl ListenTask {
                             }
                             ProtoEvent::Input(event) => self.emulation_proxy.consume(event, addr),
                             ProtoEvent::Ping => self.listener.reply(addr, ProtoEvent::Pong(self.emulation_proxy.emulation_active.get())).await,
+                            // Peer's version handshake. Echo our own
+                            // commit back so the peer's connect-side
+                            // receive_loop populates its `peer_commit`,
+                            // AND publish a PeerHello upward so our
+                            // service can populate ours from the listen
+                            // side too — the connect side is the primary
+                            // path, but if the outbound direction is
+                            // broken (one-way setup, NAT, peer's TCP
+                            // listener down) the version display would
+                            // otherwise silently say "unknown" while
+                            // the peer is in fact happily talking to us.
+                            ProtoEvent::Hello { commit } => {
+                                self.listener.reply(addr, ProtoEvent::Hello { commit: local_commit() }).await;
+                                self.event_tx.send(EmulationEvent::PeerHello { addr, commit }).expect("channel closed");
+                            }
                             _ => {}
                         }
                     }

src/listen.rs

@@ -259,8 +259,16 @@ async fn read_loop(
                 .send(ListenEvent::Msg { event, addr })
                 .expect("channel closed"),
             Err(e) => {
-                log::warn!("error receiving event: {e}");
+                // Skip the malformed/unknown datagram and keep
-                break;
+                // listening. Each DTLS recv returns one full
+                // datagram, so a parse error here can't desync a
+                // stream; the next call gets a fresh, framed
+                // message. This makes the protocol forward-
+                // compatible: a peer running a newer Lan Mouse
+                // version can introduce additional event types
+                // and old peers will simply ignore them rather
+                // than dropping the connection.
+                log::debug!("ignoring undecodable event from {addr}: {e}");
             }
         }
     }

src/main.rs

@@ -74,7 +74,7 @@ fn run() -> Result<(), LanMouseError> {
             #[cfg(feature = "gtk")]
             {
                 let mut service = start_service()?;
-                let res = lan_mouse_gtk::run();
+                let res = lan_mouse_gtk::run(config::local_commit());
                 #[cfg(unix)]
                 {
                     // on unix we give the service a chance to terminate gracefully

src/service.rs

@@ -319,6 +319,17 @@ impl Service {
             EmulationEvent::Connected { addr, fingerprint } => {
                 self.notify_frontend(FrontendEvent::DeviceConnected { addr, fingerprint });
             }
+            EmulationEvent::PeerHello { addr, commit } => {
+                // Map the peer's source addr back to its client handle
+                // and stamp the commit. Skip if we don't have an
+                // outgoing client configured for this peer (incoming-
+                // only setup) — there's nowhere to display the version
+                // in that case anyway.
+                if let Some(handle) = self.client_manager.get_client(addr) {
+                    self.client_manager.set_peer_commit(handle, Some(commit));
+                    self.broadcast_client(handle);
+                }
+            }
         }
     }