Initial commit

breadgreet/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "breadgreet"
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+authors = ["Breadway <rileyhorsham@gmail.com>"]
+description = "Graphical greetd greeter for Hyprland / Wayland"
+
+[[bin]]
+name = "breadgreet"
+path = "src/main.rs"
+
+[dependencies]
+breadlock-ui = { path = "../breadlock-ui" }
+bread-theme = { workspace = true, features = ["gtk"] }
+gtk4 = { version = "0.11", features = ["v4_12"] }
+relm4 = { version = "0.11", features = ["macros"] }
+greetd_ipc = { version = "0.10", default-features = false, features = ["tokio-codec"] }
+chrono = "0.4"
+tokio.workspace = true
+serde.workspace = true
+toml.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+thiserror.workspace = true

breadgreet/src/config.rs

@@ -0,0 +1,63 @@
+use breadlock_ui::config::Appearance;
+use serde::Deserialize;
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Default, Deserialize)]
+#[serde(default)]
+pub struct Config {
+    #[serde(flatten)]
+    pub appearance: Appearance,
+    pub sessions: Sessions,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(default)]
+pub struct Sessions {
+    pub wayland_dirs: Vec<String>,
+    pub xsessions_dirs: Vec<String>,
+    /// `.desktop` file stem (without extension) to auto-select.
+    pub default: String,
+}
+
+impl Default for Sessions {
+    fn default() -> Self {
+        Self {
+            wayland_dirs: vec!["/usr/share/wayland-sessions".to_string()],
+            xsessions_dirs: vec!["/usr/share/xsessions".to_string()],
+            default: "hyprland".to_string(),
+        }
+    }
+}
+
+/// `breadgreet` commonly runs as the dedicated `greeter` system user (per
+/// BOS's `/etc/greetd/config.toml` `user = "greeter"`), so a fixed system
+/// path is checked first; XDG is the fallback for local dev/testing under a
+/// normal user session.
+pub fn load() -> Config {
+    let system_path = std::path::Path::new("/etc/greetd/breadgreet.toml");
+    if system_path.exists() {
+        return breadlock_ui::config::load_or_default(system_path);
+    }
+    breadlock_ui::config::load_or_default(&xdg_config_path())
+}
+
+fn xdg_config_path() -> PathBuf {
+    let base = std::env::var_os("XDG_CONFIG_HOME")
+        .map(PathBuf::from)
+        .or_else(|| std::env::var_os("HOME").map(|h| PathBuf::from(h).join(".config")))
+        .unwrap_or_else(|| PathBuf::from("."));
+    base.join("breadgreet").join("breadgreet.toml")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn default_sessions_match_standard_greetd_dirs() {
+        let s = Sessions::default();
+        assert_eq!(s.wayland_dirs, vec!["/usr/share/wayland-sessions"]);
+        assert_eq!(s.xsessions_dirs, vec!["/usr/share/xsessions"]);
+        assert_eq!(s.default, "hyprland");
+    }
+}

breadgreet/src/greetd/client.rs

@@ -0,0 +1,250 @@
+//! Thin async wrapper around `greetd_ipc`'s wire protocol — connects to
+//! `$GREETD_SOCK`, and turns greetd's `Request`/`Response` enums into a
+//! small state machine ([`Outcome`]) the UI drives.
+
+use greetd_ipc::codec::TokioCodec;
+use greetd_ipc::{AuthMessageType, ErrorType, Request, Response};
+use tokio::net::UnixStream;
+
+#[derive(Debug, thiserror::Error)]
+pub enum GreetdError {
+    #[error("$GREETD_SOCK is not set — breadgreet must be launched by greetd")]
+    NoSocketEnv,
+    #[error("failed to connect to greetd socket: {0}")]
+    Connect(#[source] std::io::Error),
+    #[error("greetd IPC error: {0}")]
+    Codec(#[from] greetd_ipc::codec::Error),
+    #[error("{description}")]
+    Greetd {
+        description: String,
+        is_auth_error: bool,
+    },
+}
+
+/// One step of a PAM conversation, as relayed by greetd.
+#[derive(Debug, Clone)]
+pub enum AuthPrompt {
+    /// Answer should be shown as typed (e.g. a username confirmation).
+    Visible(String),
+    /// Answer should be masked (a password).
+    Secret(String),
+    /// Informational message — no answer needed, just display and continue.
+    Info(String),
+    /// Non-fatal error message from a PAM module — display and continue.
+    Error(String),
+}
+
+#[derive(Debug, Clone)]
+pub enum Outcome {
+    /// Login flow complete — call [`Client::start_session`] next.
+    Success,
+    /// Another prompt to answer via [`Client::respond`].
+    Prompt(AuthPrompt),
+}
+
+#[derive(Debug)]
+pub struct Client {
+    stream: UnixStream,
+}
+
+impl Client {
+    /// Connects to the Unix socket greetd set in `$GREETD_SOCK` when it
+    /// launched this process.
+    pub async fn connect() -> Result<Self, GreetdError> {
+        let path = std::env::var_os("GREETD_SOCK").ok_or(GreetdError::NoSocketEnv)?;
+        Self::connect_to(path).await
+    }
+
+    /// Connects to an explicit socket path, bypassing `$GREETD_SOCK` —
+    /// used directly by tests against a mock server so they don't need to
+    /// mutate process-global environment state (which parallel `cargo test`
+    /// threads would race on).
+    async fn connect_to(path: impl AsRef<std::path::Path>) -> Result<Self, GreetdError> {
+        let stream = UnixStream::connect(path)
+            .await
+            .map_err(GreetdError::Connect)?;
+        Ok(Self { stream })
+    }
+
+    /// Starts a login attempt for `username`. Answer any resulting
+    /// [`Outcome::Prompt`] via [`Self::respond`] until [`Outcome::Success`].
+    pub async fn create_session(&mut self, username: &str) -> Result<Outcome, GreetdError> {
+        let req = Request::CreateSession {
+            username: username.to_string(),
+        };
+        self.roundtrip(req).await
+    }
+
+    /// Answers the most recent [`AuthPrompt`]. `None` for prompts that don't
+    /// need an answer (info/error messages).
+    pub async fn respond(&mut self, answer: Option<String>) -> Result<Outcome, GreetdError> {
+        self.roundtrip(Request::PostAuthMessageResponse { response: answer })
+            .await
+    }
+
+    /// Hands the chosen session off to greetd, which execs it and owns the
+    /// VT switch away from the greeter. Only valid after an [`Outcome::Success`].
+    pub async fn start_session(
+        &mut self,
+        cmd: Vec<String>,
+        env: Vec<String>,
+    ) -> Result<(), GreetdError> {
+        Request::StartSession { cmd, env }
+            .write_to(&mut self.stream)
+            .await?;
+        match Response::read_from(&mut self.stream).await? {
+            Response::Success => Ok(()),
+            Response::Error {
+                error_type,
+                description,
+            } => Err(GreetdError::Greetd {
+                description,
+                is_auth_error: matches!(error_type, ErrorType::AuthError),
+            }),
+            Response::AuthMessage { .. } => Err(GreetdError::Greetd {
+                description: "greetd sent an unexpected auth message after StartSession"
+                    .to_string(),
+                is_auth_error: false,
+            }),
+        }
+    }
+
+    /// Aborts an in-progress login flow (e.g. the user hit Escape). Per the
+    /// protocol this can only be called before `StartSession` — best-effort,
+    /// errors here don't matter to the caller since the flow is being torn
+    /// down either way.
+    pub async fn cancel_session(&mut self) {
+        let _ = Request::CancelSession.write_to(&mut self.stream).await;
+        let _ = Response::read_from(&mut self.stream).await;
+    }
+
+    async fn roundtrip(&mut self, req: Request) -> Result<Outcome, GreetdError> {
+        req.write_to(&mut self.stream).await?;
+        match Response::read_from(&mut self.stream).await? {
+            Response::Success => Ok(Outcome::Success),
+            Response::AuthMessage {
+                auth_message_type,
+                auth_message,
+            } => Ok(Outcome::Prompt(match auth_message_type {
+                AuthMessageType::Visible => AuthPrompt::Visible(auth_message),
+                AuthMessageType::Secret => AuthPrompt::Secret(auth_message),
+                AuthMessageType::Info => AuthPrompt::Info(auth_message),
+                AuthMessageType::Error => AuthPrompt::Error(auth_message),
+            })),
+            Response::Error {
+                error_type,
+                description,
+            } => Err(GreetdError::Greetd {
+                description,
+                is_auth_error: matches!(error_type, ErrorType::AuthError),
+            }),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    //! Exercises the framing/state-machine logic against a mock Unix-socket
+    //! server speaking the real greetd_ipc wire format — no real greetd or
+    //! PAM involved. This is the safe way to test this module: a bug here
+    //! just fails a test, it can never affect a real login.
+    use super::*;
+    use tokio::net::UnixListener;
+
+    async fn mock_server(path: std::path::PathBuf, script: Vec<Response>) {
+        let listener = UnixListener::bind(&path).unwrap();
+        let (mut stream, _) = listener.accept().await.unwrap();
+        for response in script {
+            // Drain the request that prompted this response — we don't need
+            // to inspect it, just keep the framing in lockstep.
+            let _ = Request::read_from(&mut stream).await;
+            response.write_to(&mut stream).await.unwrap();
+        }
+    }
+
+    fn socket_path(name: &str) -> std::path::PathBuf {
+        std::env::temp_dir().join(format!(
+            "breadgreet-test-{name}-{}.sock",
+            std::process::id()
+        ))
+    }
+
+    #[tokio::test]
+    async fn create_session_success_flows_straight_through() {
+        let path = socket_path("success");
+        std::fs::remove_file(&path).ok();
+        let server = tokio::spawn(mock_server(path.clone(), vec![Response::Success]));
+
+        // Give the listener a moment to bind before connecting.
+        tokio::time::sleep(std::time::Duration::from_millis(20)).await;
+        let mut client = Client::connect_to(&path).await.unwrap();
+        let outcome = client.create_session("bob").await.unwrap();
+        assert!(matches!(outcome, Outcome::Success));
+
+        server.await.unwrap();
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[tokio::test]
+    async fn create_session_prompts_for_password_then_succeeds() {
+        let path = socket_path("prompt");
+        std::fs::remove_file(&path).ok();
+        let server = tokio::spawn(mock_server(
+            path.clone(),
+            vec![
+                Response::AuthMessage {
+                    auth_message_type: AuthMessageType::Secret,
+                    auth_message: "Password:".to_string(),
+                },
+                Response::Success,
+            ],
+        ));
+
+        tokio::time::sleep(std::time::Duration::from_millis(20)).await;
+        let mut client = Client::connect_to(&path).await.unwrap();
+
+        let outcome = client.create_session("bob").await.unwrap();
+        let Outcome::Prompt(AuthPrompt::Secret(msg)) = outcome else {
+            panic!("expected a secret prompt, got {outcome:?}");
+        };
+        assert_eq!(msg, "Password:");
+
+        let outcome = client.respond(Some("hunter2".to_string())).await.unwrap();
+        assert!(matches!(outcome, Outcome::Success));
+
+        server.await.unwrap();
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[tokio::test]
+    async fn auth_error_is_reported_as_such() {
+        let path = socket_path("autherr");
+        std::fs::remove_file(&path).ok();
+        let server = tokio::spawn(mock_server(
+            path.clone(),
+            vec![Response::Error {
+                error_type: ErrorType::AuthError,
+                description: "denied".to_string(),
+            }],
+        ));
+
+        tokio::time::sleep(std::time::Duration::from_millis(20)).await;
+        let mut client = Client::connect_to(&path).await.unwrap();
+
+        let err = client.create_session("bob").await.unwrap_err();
+        match err {
+            GreetdError::Greetd { is_auth_error, .. } => assert!(is_auth_error),
+            other => panic!("expected a greetd auth error, got {other:?}"),
+        }
+
+        server.await.unwrap();
+        std::fs::remove_file(&path).ok();
+    }
+
+    #[tokio::test]
+    async fn connect_without_greetd_sock_env_fails_cleanly() {
+        std::env::remove_var("GREETD_SOCK");
+        let err = Client::connect().await.unwrap_err();
+        assert!(matches!(err, GreetdError::NoSocketEnv));
+    }
+}

breadgreet/src/greetd/mod.rs

@@ -0,0 +1,3 @@
+mod client;
+
+pub use client::{AuthPrompt, Client, Outcome};

breadgreet/src/main.rs

@@ -0,0 +1,304 @@
+mod config;
+mod greetd;
+mod sessions;
+mod theme;
+
+use greetd::{AuthPrompt, Client, Outcome};
+use gtk4::prelude::*;
+use relm4::prelude::*;
+use tokio::sync::mpsc;
+
+/// Commands sent from the UI thread to the greetd actor task (see
+/// [`spawn_greetd_actor`]), which owns the single stateful connection to
+/// `$GREETD_SOCK` for the lifetime of one login attempt.
+enum GreetdCommand {
+    CreateSession(String),
+    Respond(Option<String>),
+    StartSession { cmd: Vec<String>, env: Vec<String> },
+}
+
+#[derive(Debug, Clone)]
+enum Stage {
+    /// Waiting for a username in `entry`.
+    Username,
+    /// greetd/PAM asked a question; `entry` holds the answer (masking is
+    /// applied imperatively on the entry widget when the prompt arrives).
+    Prompt,
+    /// A request is in flight — input is disabled so a second Enter can't
+    /// race it.
+    Working,
+}
+
+#[derive(Debug)]
+enum AppInput {
+    ClockTick,
+    /// Enter pressed in the entry — behavior depends on `Stage`.
+    Submit,
+    Outcome(Outcome),
+    Error(String),
+    SessionStarted,
+}
+
+struct App {
+    clock_lbl: gtk4::Label,
+    status_lbl: gtk4::Label,
+    entry: gtk4::Entry,
+    stage: Stage,
+    username: String,
+    session: Option<sessions::Session>,
+    clock_format: String,
+    cmd_tx: mpsc::UnboundedSender<GreetdCommand>,
+}
+
+#[relm4::component]
+impl SimpleComponent for App {
+    type Init = ();
+    type Input = AppInput;
+    type Output = ();
+
+    view! {
+        gtk4::ApplicationWindow {
+            add_css_class: "breadgreet",
+            set_title: Some("breadgreet"),
+
+            #[name = "root_box"]
+            gtk4::Box {
+                set_orientation: gtk4::Orientation::Vertical,
+                set_halign: gtk4::Align::Center,
+                set_valign: gtk4::Align::Center,
+            }
+        }
+    }
+
+    fn init(
+        _init: Self::Init,
+        root: Self::Root,
+        sender: ComponentSender<Self>,
+    ) -> ComponentParts<Self> {
+        root.fullscreen();
+
+        let config = config::load();
+        let session = sessions::discover(
+            &config.sessions.wayland_dirs,
+            &config.sessions.xsessions_dirs,
+            &config.sessions.default,
+        );
+
+        let clock_lbl = gtk4::Label::new(None);
+        clock_lbl.add_css_class("login-clock");
+
+        let entry = gtk4::Entry::new();
+        entry.add_css_class("login-entry");
+        entry.set_placeholder_text(Some("Username"));
+        entry.set_width_chars(24);
+        {
+            let sender = sender.clone();
+            entry.connect_activate(move |_| sender.input(AppInput::Submit));
+        }
+
+        let status_lbl = gtk4::Label::new(None);
+        status_lbl.add_css_class("login-status");
+
+        let session_lbl = gtk4::Label::new(session.as_ref().map(|s| s.name.as_str()));
+        session_lbl.add_css_class("login-session");
+        if session.is_none() {
+            session_lbl.set_label("No session found — cannot log in");
+        }
+
+        let card = gtk4::Box::new(gtk4::Orientation::Vertical, 8);
+        card.add_css_class("login-card");
+        card.append(&entry);
+        card.append(&status_lbl);
+        card.append(&session_lbl);
+
+        let widgets = view_output!();
+        widgets.root_box.append(&clock_lbl);
+        widgets.root_box.append(&card);
+
+        let (cmd_tx, cmd_rx) = mpsc::unbounded_channel();
+        spawn_greetd_actor(cmd_rx, sender.clone());
+
+        theme::apply();
+        spawn_clock_ticker(sender.clone());
+
+        let model = App {
+            clock_lbl,
+            status_lbl,
+            entry,
+            stage: Stage::Username,
+            username: String::new(),
+            session,
+            clock_format: config.appearance.clock.format.clone(),
+            cmd_tx,
+        };
+        model
+            .clock_lbl
+            .set_label(&current_time(&model.clock_format));
+
+        ComponentParts { model, widgets }
+    }
+
+    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
+        match msg {
+            AppInput::ClockTick => {
+                self.clock_lbl.set_label(&current_time(&self.clock_format));
+            }
+            AppInput::Submit => self.handle_submit(),
+            AppInput::Outcome(Outcome::Success) => self.start_session(),
+            AppInput::Outcome(Outcome::Prompt(prompt)) => self.handle_prompt(prompt),
+            AppInput::Error(description) => {
+                self.status_lbl.set_label(&description);
+                self.status_lbl.add_css_class("error");
+                self.entry.set_text("");
+                self.entry.set_visibility(true);
+                self.entry.set_placeholder_text(Some("Username"));
+                self.entry.set_sensitive(true);
+                self.stage = Stage::Username;
+                self.username.clear();
+            }
+            AppInput::SessionStarted => {
+                // greetd now owns the VT switch to the started session —
+                // nothing left for the greeter to do.
+                self.status_lbl.set_label("Starting session…");
+            }
+        }
+    }
+}
+
+impl App {
+    fn handle_submit(&mut self) {
+        if matches!(self.stage, Stage::Working) {
+            return;
+        }
+        let text = self.entry.text().to_string();
+
+        match &self.stage {
+            Stage::Username => {
+                if text.is_empty() {
+                    return;
+                }
+                self.username = text;
+                self.entry.set_text("");
+                self.entry.set_sensitive(false);
+                self.stage = Stage::Working;
+                let _ = self
+                    .cmd_tx
+                    .send(GreetdCommand::CreateSession(self.username.clone()));
+            }
+            Stage::Prompt => {
+                self.entry.set_text("");
+                self.entry.set_sensitive(false);
+                self.stage = Stage::Working;
+                let answer = if text.is_empty() { None } else { Some(text) };
+                let _ = self.cmd_tx.send(GreetdCommand::Respond(answer));
+            }
+            Stage::Working => {}
+        }
+    }
+
+    fn handle_prompt(&mut self, prompt: AuthPrompt) {
+        self.status_lbl.remove_css_class("error");
+        match prompt {
+            AuthPrompt::Info(message) | AuthPrompt::Error(message) => {
+                // No answer needed — display and immediately continue the
+                // conversation with an empty response.
+                self.status_lbl.set_label(&message);
+                let _ = self.cmd_tx.send(GreetdCommand::Respond(None));
+            }
+            AuthPrompt::Visible(message) => {
+                self.status_lbl.set_label(&message);
+                self.entry.set_visibility(true);
+                self.entry.set_placeholder_text(Some(&message));
+                self.entry.set_sensitive(true);
+                self.entry.grab_focus();
+                self.stage = Stage::Prompt;
+            }
+            AuthPrompt::Secret(message) => {
+                self.status_lbl.set_label(&message);
+                self.entry.set_visibility(false);
+                self.entry.set_placeholder_text(Some(&message));
+                self.entry.set_sensitive(true);
+                self.entry.grab_focus();
+                self.stage = Stage::Prompt;
+            }
+        }
+    }
+
+    fn start_session(&mut self) {
+        let Some(session) = &self.session else {
+            self.status_lbl.set_label("No session available to start");
+            self.status_lbl.add_css_class("error");
+            return;
+        };
+        self.status_lbl.set_label("Starting session…");
+        let _ = self.cmd_tx.send(GreetdCommand::StartSession {
+            cmd: session.exec.clone(),
+            env: Vec::new(),
+        });
+    }
+}
+
+/// Owns the single stateful connection to `$GREETD_SOCK` for one login
+/// attempt and translates the UI's [`GreetdCommand`]s into greetd IPC
+/// round-trips, forwarding each outcome back as an [`AppInput`].
+fn spawn_greetd_actor(
+    mut cmd_rx: mpsc::UnboundedReceiver<GreetdCommand>,
+    sender: ComponentSender<App>,
+) {
+    relm4::spawn(async move {
+        let mut client = match Client::connect().await {
+            Ok(client) => client,
+            Err(err) => {
+                sender.input(AppInput::Error(format!("Cannot reach greetd: {err}")));
+                return;
+            }
+        };
+
+        while let Some(cmd) = cmd_rx.recv().await {
+            let result = match cmd {
+                GreetdCommand::CreateSession(username) => client.create_session(&username).await,
+                GreetdCommand::Respond(answer) => client.respond(answer).await,
+                GreetdCommand::StartSession { cmd, env } => {
+                    match client.start_session(cmd, env).await {
+                        Ok(()) => {
+                            sender.input(AppInput::SessionStarted);
+                            continue;
+                        }
+                        Err(err) => Err(err),
+                    }
+                }
+            };
+
+            match result {
+                Ok(outcome) => sender.input(AppInput::Outcome(outcome)),
+                Err(err) => {
+                    tracing::warn!(%err, "greetd reported an error");
+                    client.cancel_session().await;
+                    sender.input(AppInput::Error(err.to_string()));
+                }
+            }
+        }
+    });
+}
+
+fn spawn_clock_ticker(sender: ComponentSender<App>) {
+    relm4::spawn(async move {
+        loop {
+            tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+            sender.input(AppInput::ClockTick);
+        }
+    });
+}
+
+fn current_time(format: &str) -> String {
+    chrono::Local::now().format(format).to_string()
+}
+
+fn main() {
+    tracing_subscriber::fmt()
+        .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
+        .init();
+
+    let app = RelmApp::new("sh.breadway.breadgreet");
+    app.run::<App>(());
+}

breadgreet/src/sessions.rs

@@ -0,0 +1,94 @@
+//! Session discovery: scans the standard greetd-greeter session directories
+//! for `.desktop` entries. BOS effectively ships one session (Hyprland via
+//! `bos-session`), so v1 has no picker UI — it just auto-selects the
+//! configured default (or the only entry found) and resolves its `Exec=`
+//! line to hand to `greetd`'s `StartSession`.
+
+use breadlock_ui::desktop_entry::{scan_dir, DesktopEntry};
+use std::path::Path;
+
+pub struct Session {
+    pub name: String,
+    pub exec: Vec<String>,
+}
+
+/// Scans `wayland_dirs` then `xsessions_dirs` (in that order) and returns
+/// the entry matching `default` (by `.desktop` file stem), falling back to
+/// the first entry found in either directory. `None` if nothing is
+/// installed — the greeter has no session to offer.
+pub fn discover(
+    wayland_dirs: &[String],
+    xsessions_dirs: &[String],
+    default: &str,
+) -> Option<Session> {
+    let mut all: Vec<(String, DesktopEntry)> = Vec::new();
+    for dir in wayland_dirs.iter().chain(xsessions_dirs) {
+        all.extend(scan_dir(Path::new(dir)));
+    }
+
+    let chosen = all
+        .iter()
+        .find(|(stem, _)| stem == default)
+        .or_else(|| all.first())?;
+
+    Some(Session {
+        name: chosen.1.name.clone(),
+        exec: split_exec(&chosen.1.exec),
+    })
+}
+
+/// Splits a `.desktop` `Exec=` line into an argv. Only handles plain
+/// whitespace-separated commands (BOS's own `hyprland.desktop` is
+/// `Exec=Hyprland`) — full field-code (`%f`, `%u`, …) and quoting support
+/// isn't needed for a greeter that never launches file-manager-style
+/// entries.
+fn split_exec(exec: &str) -> Vec<String> {
+    exec.split_whitespace()
+        .filter(|arg| !arg.starts_with('%'))
+        .map(str::to_string)
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn split_exec_drops_field_codes() {
+        assert_eq!(split_exec("Hyprland"), vec!["Hyprland"]);
+        assert_eq!(split_exec("gnome-session %U"), vec!["gnome-session"]);
+    }
+
+    #[test]
+    fn discover_returns_none_when_no_directories_exist() {
+        assert!(discover(
+            &["/nonexistent/a".to_string()],
+            &["/nonexistent/b".to_string()],
+            "hyprland"
+        )
+        .is_none());
+    }
+
+    #[test]
+    fn discover_prefers_configured_default_over_first_entry() {
+        let dir = std::env::temp_dir().join("breadgreet-test-sessions-discover");
+        std::fs::create_dir_all(&dir).unwrap();
+        std::fs::write(
+            dir.join("aaa.desktop"),
+            "[Desktop Entry]\nName=A\nExec=a-cmd\n",
+        )
+        .unwrap();
+        std::fs::write(
+            dir.join("hyprland.desktop"),
+            "[Desktop Entry]\nName=Hyprland\nExec=Hyprland\n",
+        )
+        .unwrap();
+
+        let dir_str = dir.to_str().unwrap().to_string();
+        let session = discover(&[dir_str], &[], "hyprland").unwrap();
+        assert_eq!(session.name, "Hyprland");
+        assert_eq!(session.exec, vec!["Hyprland"]);
+
+        std::fs::remove_dir_all(&dir).ok();
+    }
+}

breadgreet/src/theme.rs

@@ -0,0 +1,35 @@
+use bread_theme::{gtk as bgtk, ink_on, load_palette};
+use gtk4::CssProvider;
+use std::cell::RefCell;
+
+thread_local! {
+    static USER_PROVIDER: RefCell<Option<CssProvider>> = const { RefCell::new(None) };
+}
+
+fn load_css() -> String {
+    let p = load_palette();
+    format!(
+        "window.breadgreet {{ background-color: {bg}; color: {on_bg}; }}\
+         .login-card {{ background: {surface}; color: {on_surface}; border-radius: 8px;\
+             padding: 20px; min-width: 320px; }}\
+         .login-clock {{ font-size: 48px; font-weight: bold; margin-bottom: 20px; }}\
+         .login-entry {{ font-size: 14px; }}\
+         .login-status {{ font-size: 12px; opacity: 0.75; margin-top: 8px; }}\
+         .login-status.error {{ color: {red}; opacity: 1; }}\
+         .login-session {{ font-size: 12px; opacity: 0.6; margin-top: 12px; }}",
+        bg = p.background,
+        surface = p.color0,
+        red = p.color1,
+        on_bg = ink_on(&p.background),
+        on_surface = ink_on(&p.color0),
+    )
+}
+
+pub fn apply() {
+    bgtk::apply_shared();
+    bgtk::apply_app_css(load_css);
+
+    let home = std::env::var("HOME").unwrap_or_default();
+    let user_path = std::path::PathBuf::from(format!("{home}/.config/breadgreet/style.css"));
+    USER_PROVIDER.with(|cell| bgtk::apply_user_css(&user_path, cell));
+}