feat(gui): desktop notification when a viewer joins or leaves

The host screen pops a desktop notification on each viewer join/leave,
so you know someone connected while the window is in the background.

Fired on a detached thread (the D-Bus call never touches the egui
frame) and gated on the same viewer-list transitions, so stopping the
host — which drops the child and stops pumping events — doesn't spray a
notification per remaining viewer.

notify-rust's default features give the pure-Rust zbus backend, so this
adds no system libdbus dependency and no GTK event loop (gui feature
only; the headless build is untouched).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.toml

@@ -34,9 +34,9 @@ ureq = { version = "3", default-features = false, features = ["rustls"] }
 toml = "1"
 chrono = { version = "0.4", default-features = false, features = ["clock", "serde"] }
 eframe = { version = "0.34.2", default-features = false, features = ["glow", "default_fonts", "wayland", "x11"], optional = true }
-tray-icon = { version = "0.24.0", optional = true }
+# Desktop notifications on viewer join/leave. Default features give the
-notify-rust = { version = "4.17.0", optional = true }
+# pure-Rust zbus backend (no system libdbus, no image crate).
-gtk = { version = "0.18.2", optional = true }
+notify-rust = { version = "4", optional = true }
 
 [profile.release]
 lto = "thin"
@@ -46,4 +46,4 @@ strip = "symbols"
 [features]
 # Opt-in graphical front-end (pixelpass --gui). Default-off so the headless
 # build never pulls the GUI toolkit tree.
-gui = ["dep:eframe", "dep:tray-icon", "dep:notify-rust", "dep:gtk"]
+gui = ["dep:eframe", "dep:notify-rust"]

src/common/output.rs

@@ -22,7 +22,11 @@ pub fn set_json(enabled: bool) {
     JSON_ENABLED.store(enabled, Ordering::Relaxed);
 }
 
-fn json_enabled() -> bool {
+/// Whether the JSON event stream is on — i.e. we're being driven by a
+/// machine front-end (the `--gui` shell-out) rather than a human terminal.
+/// Gates features that only make sense under that front-end, like the
+/// stdin command channel the host reads `kick` requests from.
+pub fn json_enabled() -> bool {
     JSON_ENABLED.load(Ordering::Relaxed)
 }
 
@@ -42,9 +46,11 @@ pub enum Event<'a> {
         max_viewers: u32,
         max_viewers_source: &'a str,
     },
-    /// A new viewer joined.
+    /// A viewer joined. `id` is the viewer's endpoint id; `active` is the new
+    /// total after the join.
     ViewerJoined { id: &'a str, active: u32, max: u32 },
-    /// A viewer disconnected.
+    /// A viewer left — disconnected on their own or kicked by the host. `id`
+    /// is the viewer's endpoint id; `active` is the new total after.
     ViewerLeft { id: &'a str, active: u32, max: u32 },
     /// Capture pipeline lifecycle (spawned on first viewer, torn down on last).
     Capture { state: CaptureState },

src/gui/child.rs

@@ -6,8 +6,8 @@
 //! egui app drains each frame. stderr is captured into a small ring so a
 //! failed launch (e.g. a missing gst plugin) can be surfaced in the window.
 
-use std::io::{BufRead, BufReader};
+use std::io::{BufRead, BufReader, Write};
-use std::process::{Child, Command, Stdio};
+use std::process::{Child, ChildStdin, Command, Stdio};
 use std::sync::mpsc::Receiver;
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
@@ -69,7 +69,9 @@ pub struct ChildProc {
     child: Child,
     pub rx: Receiver<ChildEvent>,
     stderr_tail: Arc<Mutex<Vec<String>>>,
-    stdin: std::process::ChildStdin,
+    /// Write end of the child's stdin, for the line-based command channel
+    /// (see [`ChildProc::send_command`]). `None` once it's been closed.
+    stdin: Option<ChildStdin>,
 }
 
 impl ChildProc {
@@ -79,13 +81,15 @@ impl ChildProc {
         let exe = std::env::current_exe()?;
         let mut child = Command::new(exe)
             .args(args)
+            // Piped so we can send line commands (e.g. `kick <id>`); the host
+            // only reads it when driven this way (`--output json`).
             .stdin(Stdio::piped())
             .stdout(Stdio::piped())
             .stderr(Stdio::piped())
             .spawn()?;
 
+        let stdin = child.stdin.take();
         let (tx, rx) = std::sync::mpsc::channel();
-        let stdin = child.stdin.take().expect("stdin piped");
         let stdout = child.stdout.take().expect("stdout piped");
         std::thread::spawn(move || {
             let reader = BufReader::new(stdout);
@@ -126,6 +130,19 @@ impl ChildProc {
         })
     }
 
+    /// Send one newline-terminated command to the child over its stdin (the
+    /// host parses these as `kick <endpoint-id>`). Best-effort: a closed pipe
+    /// (child already gone) just drops the command.
+    pub fn send_command(&mut self, cmd: &str) {
+        let Some(stdin) = self.stdin.as_mut() else {
+            return;
+        };
+        if let Err(e) = writeln!(stdin, "{cmd}") {
+            tracing::warn!("failed to send command to host child: {e}");
+            self.stdin = None; // pipe is dead; stop trying
+        }
+    }
+
     /// Whether the child is still running.
     pub fn is_alive(&mut self) -> bool {
         matches!(self.child.try_wait(), Ok(None))
@@ -136,14 +153,6 @@ impl ChildProc {
         self.stderr_tail.lock().unwrap().join("\n")
     }
 
-    /// Send a newline-terminated command to the child.
-    pub fn send_command(&mut self, cmd: &str) {
-        use std::io::Write;
-        if let Err(e) = writeln!(self.stdin, "{cmd}") {
-            tracing::warn!("failed to send command to child: {e}");
-        }
-    }
-
     /// Gracefully stop the child: SIGINT (so the host runs its ctrl-c teardown
     /// — tears down capture, closes the endpoint), with a ~2 s grace period
     /// before a hard kill. Idempotent.
@@ -222,7 +231,7 @@ mod tests {
     }
 
     #[test]
-    fn viewer_events_round_trips() {
+    fn viewer_join_leave_round_trip() {
         assert!(matches!(
             parse(Event::ViewerJoined { id: "nodeXYZ", active: 2, max: 4 }),
             ChildEvent::ViewerJoined { id, active: 2, max: 4 } if id == "nodeXYZ"

src/gui/mod.rs

@@ -78,6 +78,23 @@ fn short_id(id: &str) -> String {
     }
 }
 
+/// Fire a desktop notification, on a detached thread so the D-Bus round-trip
+/// can't stall the egui frame. Best-effort: with no notification daemon it
+/// just does nothing. (notify-rust talks D-Bus via pure-Rust zbus, so this
+/// needs no system libdbus and no GTK event loop.)
+fn notify(summary: &'static str, body: String) {
+    std::thread::spawn(move || {
+        if let Err(e) = notify_rust::Notification::new()
+            .appname("PixelPass")
+            .summary(summary)
+            .body(&body)
+            .show()
+        {
+            tracing::warn!("desktop notification failed: {e}");
+        }
+    });
+}
+
 /// Which screen the single window is currently showing.
 #[derive(Default, PartialEq)]
 enum Screen {
@@ -168,8 +185,9 @@ struct HostState {
     copied: bool,
     last_refusal: Option<String>,
     error: Option<String>,
+    /// Endpoint ids of the currently-connected viewers, in arrival order.
+    /// Drives the per-viewer list and its Kick buttons.
     viewers: Vec<String>,
-    tray_icon: Option<tray_icon::TrayIcon>,
 }
 
 impl Default for HostState {
@@ -189,7 +207,6 @@ impl Default for HostState {
             last_refusal: None,
             error: None,
             viewers: Vec::new(),
-            tray_icon: None,
         }
     }
 }
@@ -235,11 +252,6 @@ impl eframe::App for PixelPassApp {
         self.pump_host_events();
         self.pump_viewer_events();
 
-        if let Ok(_event) = tray_icon::menu::MenuEvent::receiver().try_recv() {
-            // Only one menu item right now: "Stop Hosting"
-            self.stop_host();
-        }
-
         match self.screen {
             Screen::Menu => self.menu(ui),
             Screen::Host => self.host(ui),
@@ -370,18 +382,22 @@ impl PixelPassApp {
 
         ui.add_space(6.0);
         ui.label(format!("Viewers: {} / {}", self.host.active, self.host.max));
-        if !self.host.viewers.is_empty() {
+
-            ui.add_space(4.0);
+        // Per-viewer list with a Kick button each. Collect the click first so
-            for id in &self.host.viewers.clone() {
+        // we're not borrowing self.host.viewers while we reach for the child.
+        let mut kick: Option<String> = None;
+        for id in &self.host.viewers {
             ui.horizontal(|ui| {
-                    ui.label(format!("• {}", short_id(id)));
+                ui.label(format!("• endpoint {}", short_id(id)));
-                    if ui.button("Kick").clicked() {
+                if ui.small_button("Kick").clicked() {
-                        if let Some(p) = &mut self.host.proc {
+                    kick = Some(id.clone());
-                            p.send_command(&format!("kick {id}"));
-                        }
                 }
             });
         }
+        if let Some(id) = kick
+            && let Some(p) = &mut self.host.proc
+        {
+            p.send_command(&format!("kick {id}"));
         }
 
         if let Some(info) = &self.host.info {
@@ -474,6 +490,7 @@ impl PixelPassApp {
         self.host.max = 0;
         self.host.capturing = false;
         self.host.copied = false;
+        self.host.viewers.clear();
 
         let mut args = vec![
             "--host".to_string(),
@@ -494,28 +511,7 @@ impl PixelPassApp {
         }
 
         match ChildProc::spawn(&args, ctx) {
-            Ok(p) => {
+            Ok(p) => self.host.proc = Some(p),
-                self.host.proc = Some(p);
-
-                #[cfg(target_os = "linux")]
-                if let Err(e) = gtk::init() {
-                    tracing::warn!("Failed to initialize GTK for system tray: {e}");
-                }
-
-                use tray_icon::{TrayIconBuilder, menu::{Menu, MenuItem}};
-                let menu = Menu::new();
-                let _ = menu.append(&MenuItem::new("Stop Hosting", true, None));
-                let icon = tray_icon::Icon::from_rgba(vec![255, 0, 0, 255], 1, 1).unwrap();
-                if let Ok(tray) = TrayIconBuilder::new()
-                    .with_title("PixelPass")
-                    .with_tooltip("PixelPass Screen Sharing")
-                    .with_icon(icon)
-                    .with_menu(Box::new(menu))
-                    .build()
-                {
-                    self.host.tray_icon = Some(tray);
-                }
-            }
             Err(e) => self.host.error = Some(format!("Couldn't start host: {e}")),
         }
     }
@@ -527,7 +523,6 @@ impl PixelPassApp {
         self.host.ticket = None;
         self.host.copied = false;
         self.host.viewers.clear();
-        self.host.tray_icon = None;
     }
 
     /// Drain the host child's event channel into state, and detect an
@@ -592,21 +587,23 @@ impl PixelPassApp {
                 self.host.active = active;
                 self.host.max = max;
                 if !self.host.viewers.contains(&id) {
-                    self.host.viewers.push(id.clone());
+                    notify(
-                    let _ = notify_rust::Notification::new()
+                        "PixelPass — viewer connected",
-                        .summary("PixelPass Viewer Connected")
+                        format!("endpoint {} is now watching ({active}/{max})", short_id(&id)),
-                        .body(&format!("Viewer {} joined the stream.", short_id(&id)))
+                    );
-                        .show();
+                    self.host.viewers.push(id);
                 }
             }
             ChildEvent::ViewerLeft { id, active, max } => {
                 self.host.active = active;
                 self.host.max = max;
+                if self.host.viewers.iter().any(|v| v == &id) {
+                    notify(
+                        "PixelPass — viewer disconnected",
+                        format!("endpoint {} left ({active}/{max})", short_id(&id)),
+                    );
                     self.host.viewers.retain(|v| v != &id);
-                let _ = notify_rust::Notification::new()
+                }
-                    .summary("PixelPass Viewer Disconnected")
-                    .body(&format!("Viewer {} left the stream.", short_id(&id)))
-                    .show();
             }
             ChildEvent::Capture { state } => {
                 self.host.capturing = matches!(state, child::CaptureState::Started);

src/host/mod.rs

@@ -12,7 +12,6 @@ use iroh::{Endpoint, EndpointAddr};
 use iroh_tickets::endpoint::EndpointTicket;
 use std::collections::HashMap;
 use std::time::Duration;
-use tokio::io::{AsyncBufReadExt, BufReader};
 use tokio::sync::{mpsc, oneshot};
 use tokio_util::sync::CancellationToken;
 
@@ -25,11 +24,16 @@ use crate::common::{
 use self::pipeline::CaptureHandle;
 use self::quality::EffectiveQuality;
 
-/// Messages from per-viewer tasks to the capture supervisor.
+/// Messages from per-viewer tasks (and the GUI command channel) to the
+/// capture supervisor.
+// The shared `Viewer` suffix is the point — these are all viewer lifecycle
+// messages — so keep the descriptive names.
+#[allow(clippy::enum_variant_names)]
 enum SupervisorMsg {
-    /// A new viewer wants in. Supervisor replies with the local capture
+    /// A new viewer wants in. Supervisor replies with the local capture HTTP
-    /// HTTP port to connect to, or an error string if the host is full or
+    /// port to connect to, or an error string if the host is full or capture
-    /// capture spawn failed.
+    /// spawn failed. `cancel` is the viewer's own token — the supervisor keeps
+    /// it so a later `KickViewer` can tear this viewer's stream down.
     AddViewer {
         id: String,
         cancel: CancellationToken,
@@ -38,7 +42,9 @@ enum SupervisorMsg {
     /// A viewer's session ended. Supervisor decrements the count and tears
     /// down capture if it just hit zero.
     RemoveViewer { id: String },
-    /// Request to kick a specific viewer.
+    /// Host asked (via the GUI command channel) to disconnect a viewer by
+    /// endpoint id. Cancels that viewer's token; the normal teardown path then
+    /// emits the `ViewerLeft`.
     KickViewer { id: String },
 }
 
@@ -121,16 +127,14 @@ pub async fn run(opts: HostOpts) -> Result<()> {
         sup_rx,
     ));
 
-    // Stdin listener for "kick <id>"
+    // Command channel for the GUI front-end: read `kick <endpoint-id>` lines
-    let stdin_sup_tx = sup_tx.clone();
+    // off stdin. Only when machine-driven (`--output json`) — a human host has
-    tokio::spawn(async move {
+    // nothing to type here, and we don't want to swallow terminal input. Runs
-        let mut lines = BufReader::new(tokio::io::stdin()).lines();
+    // on a plain OS thread (not a tokio task) so a read parked on stdin can't
-        while let Ok(Some(line)) = lines.next_line().await {
+    // hold up runtime shutdown on Ctrl+C; the thread dies with the process.
-            if let Some(id) = line.strip_prefix("kick ") {
+    if output::json_enabled() {
-                let _ = stdin_sup_tx.send(SupervisorMsg::KickViewer { id: id.trim().to_string() }).await;
+        spawn_kick_listener(sup_tx.clone());
     }
-        }
-    });
 
     accept_loop(&endpoint, sup_tx.clone(), cancel.clone()).await;
 
@@ -178,11 +182,18 @@ async fn handle_peer(
     cancel: CancellationToken,
 ) {
     let remote = conn.remote_id();
-    let id_str = remote.to_string();
+    let id = remote.to_string();
+    // This viewer's own kill switch: the supervisor holds a clone so a `kick`
+    // can cancel it, and the stream select! below watches it.
     let peer_cancel = CancellationToken::new();
 
     let (reply_tx, reply_rx) = oneshot::channel();
-    if sup_tx.send(SupervisorMsg::AddViewer { id: id_str.clone(), cancel: peer_cancel.clone(), reply: reply_tx }).await.is_err() {
+    let add = SupervisorMsg::AddViewer {
+        id: id.clone(),
+        cancel: peer_cancel.clone(),
+        reply: reply_tx,
+    };
+    if sup_tx.send(add).await.is_err() {
         tracing::warn!(%remote, "supervisor channel closed; dropping peer");
         return;
     }
@@ -203,7 +214,7 @@ async fn handle_peer(
         Ok(s) => s,
         Err(e) => {
             tracing::warn!(%remote, "accept_bi failed: {e:#}");
-            let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id: id_str }).await;
+            let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id }).await;
             return;
         }
     };
@@ -214,7 +225,7 @@ async fn handle_peer(
         Ok(t) => t,
         Err(e) => {
             tracing::warn!(%remote, "connect_to_capture failed: {e:#}");
-            let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id: id_str }).await;
+            let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id }).await;
             return;
         }
     };
@@ -234,7 +245,28 @@ async fn handle_peer(
     }
 
     eprintln!("[pixelpass] viewer disconnected: {remote}");
-    let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id: id_str }).await;
+    let _ = sup_tx.send(SupervisorMsg::RemoveViewer { id }).await;
+}
+
+/// Read `kick <endpoint-id>` lines off stdin and forward them to the
+/// supervisor. Runs on a detached OS thread (see the call site for why). Ends
+/// when stdin hits EOF (the GUI closed the pipe) or the supervisor is gone.
+fn spawn_kick_listener(sup_tx: mpsc::Sender<SupervisorMsg>) {
+    use std::io::BufRead;
+    std::thread::spawn(move || {
+        let stdin = std::io::stdin();
+        for line in stdin.lock().lines().map_while(Result::ok) {
+            let Some(id) = line.trim().strip_prefix("kick ") else {
+                continue;
+            };
+            let msg = SupervisorMsg::KickViewer { id: id.trim().to_string() };
+            // blocking_send is valid here: this is a plain thread, not inside
+            // the tokio runtime. An Err means the supervisor closed — stop.
+            if sup_tx.blocking_send(msg).is_err() {
+                break;
+            }
+        }
+    });
 }
 
 /// Owns the single shared CaptureHandle and the active viewer count. Spawns
@@ -249,12 +281,15 @@ async fn supervise(
     mut rx: mpsc::Receiver<SupervisorMsg>,
 ) {
     let mut handle: Option<CaptureHandle> = None;
-    let mut count: u32 = 0;
+    // Active viewers, keyed by endpoint id, holding each one's kill switch.
+    // The count is just `viewers.len()`. (A given endpoint connecting twice is
+    // a non-case here: each viewer process uses a fresh ephemeral identity.)
     let mut viewers: HashMap<String, CancellationToken> = HashMap::new();
 
     while let Some(msg) = rx.recv().await {
         match msg {
             SupervisorMsg::AddViewer { id, cancel, reply } => {
+                let count = viewers.len() as u32;
                 if count >= max_viewers {
                     let reason =
                         format!("host is full ({count} of {max_viewers} viewers connected)");
@@ -280,18 +315,22 @@ async fn supervise(
                 }
 
                 let port = handle.as_ref().expect("handle was just set").local_port();
-                count += 1;
                 viewers.insert(id.clone(), cancel);
+                let active = viewers.len() as u32;
                 let _ = reply.send(Ok(port));
-                output::emit(output::Event::ViewerJoined { id: &id, active: count, max: max_viewers });
+                output::emit(output::Event::ViewerJoined { id: &id, active, max: max_viewers });
-                tracing::info!(active = count, cap = max_viewers, "viewer joined");
+                tracing::info!(active, cap = max_viewers, "viewer joined");
             }
             SupervisorMsg::RemoveViewer { id } => {
-                viewers.remove(&id);
+                // A given viewer task only ever sends RemoveViewer once, but the
-                count = count.saturating_sub(1);
+                // map remove is the source of truth either way.
-                output::emit(output::Event::ViewerLeft { id: &id, active: count, max: max_viewers });
+                if viewers.remove(&id).is_none() {
-                tracing::info!(active = count, cap = max_viewers, "viewer left");
+                    continue;
-                if count == 0
+                }
+                let active = viewers.len() as u32;
+                output::emit(output::Event::ViewerLeft { id: &id, active, max: max_viewers });
+                tracing::info!(active, cap = max_viewers, "viewer left");
+                if active == 0
                     && let Some(h) = handle.take()
                 {
                     tracing::info!("last viewer left — tearing down capture");
@@ -302,10 +341,15 @@ async fn supervise(
                 }
             }
             SupervisorMsg::KickViewer { id } => {
-                if let Some(cancel) = viewers.get(&id) {
+                match viewers.get(&id) {
+                    // Cancel the viewer's token; its handle_peer select! wakes,
+                    // sends RemoveViewer, and the leave is emitted there.
+                    Some(cancel) => {
                         tracing::info!(%id, "kicking viewer");
                         cancel.cancel();
                     }
+                    None => tracing::debug!(%id, "kick for unknown/already-gone viewer"),
+                }
             }
         }
     }