<NME> xserver.rs
<BEF> /*
 * Steps of XWayland server creation
 *
 * Sockets to create:
 * - a pair for XWayland to connect to smithay as a wayland client, we use our
 *   end to insert the XWayland client in the display
 * - a pair for smithay to connect to XWayland as a WM, we give our end to the
 *   WM and it deals with it
 * - 2 listening sockets on which the XWayland server will listen. We need to
 *   bind them ourselves so we know what value put in the $DISPLAY env variable.
 *   This involves some dance with a lockfile to ensure there is no collision with
 *   an other starting xserver
 *   if we listen on display $D, their paths are respectively:
 *   - /tmp/.X11-unix/X$D
 *   - @/tmp/.X11-unix/X$D (abstract socket)
 *
 * The XWayland server is spawned via an intermediate shell
 * -> wlroots does a double-fork while weston a single one, why ??
 *    -> https://stackoverflow.com/questions/881388/
 * -> once it is started, it will check if SIGUSR1 is set to ignored. If so,
 *    if will consider its parent as "smart", and send a SIGUSR1 signal when
 *    startup completes. We want to catch this so we can launch the VM.
 * -> we need to track if the XWayland crashes, to restart it
 *
 *
 */
use std::cell::RefCell;
use std::rc::Rc;
use std::env;
use std::ffi::CString;
use std::os::unix::io::{AsRawFd, IntoRawFd};
use std::os::unix::net::UnixStream;

use nix::{Error as NixError, Result as NixResult};
use nix::errno::Errno;
use nix::unistd::{fork, ForkResult, Pid};
use nix::sys::signal;

use wayland_server::{Client, Display, LoopToken};
use wayland_server::sources::{SignalEvent, Source};

use super::x11_sockets::{X11Lock, prepare_x11_sockets};

/// The XWayland handle
pub struct XWayland<WM: XWindowManager> {
        net::UnixStream,
        process::CommandExt,
    },
    process::{ChildStdout, Command, Stdio},
    sync::{Arc, Mutex},
};

use calloop::{
    channel::{self, sync_channel, Channel, SyncSender},
    generic::Generic,
    Interest, LoopHandle, Mode,
};
use wayland_server::{
    backend::{ClientData, ClientId, DisconnectReason},
    Client, DisplayHandle,
};

use slog::{error, info, o};

use super::x11_sockets::{prepare_x11_sockets, X11Lock};

impl<WM: XWindowManager + 'static> XWayland<WM> {
    /// Start the XWayland server
    pub fn init<L>(
        wm: WM,
        token: LoopToken,
        display: Rc<RefCell<Display>>,
        logger: L,
    ) -> Result<XWayland<WM>, ()>
/// This is a very low-level interface, only notifying you when the connection
/// with XWayland is up, or when it terminates.
///
        let log = ::slog_or_stdlog(logger);
        let inner = Rc::new(RefCell::new(Inner {
            wm,
            token,
            wayland_display: display,
            instance: None,
            log: log.new(o!("smithay_module" => "XWayland")),

        /// The display number the XWayland server is available at.
        ///
        /// This may be used if you wish to set the `DISPLAY` variable manually when spawning processes that
        /// may use XWayland.
        display: u32,
    },

    /// The XWayland server exited
    ///
    /// This event is sent when the [`XWayland`] handle is dropped.
    Exited,
struct XWaylandInstance {
    display_lock: X11Lock,
    wayland_client: Client,
    sigusr1_handler: Option<Source<SignalEvent>>,
    wm_fd: Option<UnixStream>,
    started_at: ::std::time::Instant,
    child_pid: Option<Pid>,
    pub fn new<L>(logger: L, dh: &DisplayHandle) -> (XWayland, XWaylandSource)
    where
// Inner implementation of the XWayland manager
struct Inner<WM: XWindowManager> {
    wm: WM,
    token: LoopToken,
    wayland_display: Rc<RefCell<Display>>,
    instance: Option<XWaylandInstance>,
    log: ::slog::Logger,
            sender,
            dh: dh.clone(),
            log: log.new(o!("smithay_module" => "XWayland")),
        }));
        (XWayland { inner }, XWaylandSource { channel })
    }

    /// Attempt to start the XWayland instance
    ///
    /// If it succeeds, you'll eventually receive an `XWaylandEvent::Ready`
    /// through the source provided by `XWayland::new()` containing an
    /// `UnixStream` representing your WM connection to XWayland, and the
    /// wayland `Client` for XWayland.
    ///
    /// Does nothing if XWayland is already started or starting.
    pub fn start<D>(&self, loop_handle: LoopHandle<'_, D>) -> io::Result<()> {
        let dh = self.inner.lock().unwrap().dh.clone();
        launch(&self.inner, loop_handle, dh)
    }

    /// Shutdown XWayland
    ///
    /// Does nothing if it was not already running, otherwise kills it and you will
    /// later receive a `XWaylandEvent::Exited` event.
    pub fn shutdown(&self) {
        self.inner.lock().unwrap().shutdown();
    }
            .borrow_mut()
            .create_client(wl_me.into_raw_fd())
    };
    client.set_user_data(Rc::into_raw(inner.clone()) as *const () as *mut ());
    client.set_destructor(client_destroy::<WM>);

    // setup the SIGUSR1 handler
    let my_inner = inner.clone();
    let sigusr1_handler = guard
        .token
        .add_signal_event_source(signal::Signal::SIGUSR1, move |_, ()| {
            xwayland_ready(&my_inner)
        })
        .map_err(|_| ())?;

    // all is ready, we can do the fork dance
    let child_pid = match fork() {
    wayland_client: Client,
    wayland_client_fd: RawFd,
    wm_fd: Option<UnixStream>,
    child_stdout: ChildStdout,
}

// Inner implementation of the XWayland manager
#[derive(Debug)]
struct Inner {
    sender: SyncSender<XWaylandEvent>,
    instance: Option<XWaylandInstance>,
    dh: DisplayHandle,
    log: ::slog::Logger,
}

struct XWaylandClientData {
    inner: Arc<Mutex<Inner>>,
}

impl ClientData for XWaylandClientData {
    fn initialized(&self, _client_id: ClientId) {}
    fn disconnected(&self, _client_id: ClientId, _reason: DisconnectReason) {
        // If we are unable to take a lock we are most likely called during
        // a shutdown. This will definitely be the case when the compositor exits
        // and the XWayland instance is dropped.
        if let Ok(mut guard) = self.inner.try_lock() {
            guard.shutdown();
        }
    }
}

// Launch an XWayland server
//
// Does nothing if there is already a launched instance
fn launch<D>(
    inner: &Arc<Mutex<Inner>>,
    loop_handle: LoopHandle<'_, D>,
    mut dh: DisplayHandle,
) -> io::Result<()> {
    let mut guard = inner.lock().unwrap();
    if guard.instance.is_some() {
        return Ok(());
    }

    info!(guard.log, "Starting XWayland");

    let (x_wm_x11, x_wm_me) = UnixStream::pair()?;
    let (wl_x11, wl_me) = UnixStream::pair()?;

    let (lock, x_fds) = prepare_x11_sockets(guard.log.clone())?;

    // we have now created all the required sockets

    // all is ready, we can do the fork dance
    let child_stdout = match spawn_xwayland(lock.display(), wl_x11, x_wm_x11, &x_fds) {
        Ok(child_stdout) => child_stdout,
        Err(e) => {
            error!(guard.log, "XWayland failed to spawn"; "err" => format!("{:?}", e));
            return Err(e);
        }
    };

    let loop_inner = inner.clone();
    loop_handle
        .insert_source(
            Generic::<_, io::Error>::new(child_stdout.as_raw_fd(), Interest::READ, Mode::Level),
            move |_, _, _| {
                // the closure must be called exactly one time, this cannot panic
                xwayland_ready(&loop_inner);
                Ok(calloop::PostAction::Remove)
            },
        )
        .map_err(|err| io::Error::new(io::ErrorKind::Other, err))?;

    let client_fd = wl_me.as_raw_fd();
    let client = dh.insert_client(wl_me, Arc::new(XWaylandClientData { inner: inner.clone() }))?;
    guard.instance = Some(XWaylandInstance {
        display_lock: lock,
        wayland_client: client,
        wayland_client_fd: client_fd,
        wm_fd: Some(x_wm_me),
        child_stdout,
    });

    Ok(())
    }
}

fn client_destroy<WM: XWindowManager + 'static>(data: *mut ()) {
    let inner = unsafe { Rc::from_raw(data as *const () as *const RefCell<Inner<WM>>) };

    // shutdown the server
    let started_at = inner.borrow().instance.as_ref().map(|i| i.started_at);
#[must_use]
pub struct XWaylandSource {
    channel: Channel<XWaylandEvent>,
}

impl calloop::EventSource for XWaylandSource {
    type Event = XWaylandEvent;
    type Metadata = ();
    type Ret = ();
    type Error = io::Error;

    fn process_events<F>(
        &mut self,
        readiness: calloop::Readiness,
        token: calloop::Token,
        mut callback: F,
    ) -> io::Result<calloop::PostAction>
    where
        F: FnMut(Self::Event, &mut Self::Metadata) -> Self::Ret,
    {
        self.channel
            .process_events(readiness, token, |event, &mut ()| match event {
                channel::Event::Msg(msg) => callback(msg, &mut ()),
                channel::Event::Closed => {}
            })
            .map_err(|err| io::Error::new(io::ErrorKind::BrokenPipe, err))
    }

    fn register(
        &mut self,
        poll: &mut calloop::Poll,
        factory: &mut calloop::TokenFactory,
    ) -> calloop::Result<()> {
        self.channel.register(poll, factory)
    }

    fn reregister(
        &mut self,
        poll: &mut calloop::Poll,
        factory: &mut calloop::TokenFactory,
    ) -> calloop::Result<()> {
        self.channel.reregister(poll, factory)
    }

    fn unregister(&mut self, poll: &mut calloop::Poll) -> calloop::Result<()> {
        self.channel.unregister(poll)
    }
}

impl Inner {
    // Shutdown the XWayland server and cleanup everything
    fn shutdown(&mut self) {
        // don't do anything if not running
        if let Some(instance) = self.instance.take() {
            info!(self.log, "Shutting down XWayland.");
            self.dh
                .backend_handle()
                .kill_client(instance.wayland_client.id(), DisconnectReason::ConnectionClosed);

            // send error occurs if the user dropped the channel... We cannot do much except ignore.
            let _ = self.sender.send(XWaylandEvent::Exited);

            // All connections and lockfiles are cleaned by their destructors

            // Remove DISPLAY from the env
            ::std::env::remove_var("DISPLAY");
            // We do like wlroots:
            // > We do not kill the XWayland process, it dies to broken pipe
            // > after we close our side of the wm/wl fds. This is more reliable
            // > than trying to kill something that might no longer be XWayland.
        }
    }
}

fn xwayland_ready(inner: &Arc<Mutex<Inner>>) {
    // Lots of re-borrowing to please the borrow-checker
    let mut guard = inner.lock().unwrap();
    let guard = &mut *guard;
    info!(guard.log, "XWayland ready");
    // instance should never be None at this point
    let instance = guard.instance.as_mut().unwrap();
    // neither the child_stdout
    let child_stdout = &mut instance.child_stdout;

    // This reads the one byte that is written when sh receives SIGUSR1
    let mut buffer = [0];
    let success = match child_stdout.read(&mut buffer) {
        Ok(len) => len > 0 && buffer[0] == b'S',
        Err(e) => {
            error!(guard.log, "Checking launch status failed"; "err" => format!("{:?}", e));
            false
        }
    };

    if success {
        // setup the environment
        ::std::env::set_var("DISPLAY", format!(":{}", instance.display_lock.display()));

        // signal the WM
        info!(
            guard.log,
            "XWayland is ready on DISPLAY \":{}\", signaling the WM.",
            instance.display_lock.display()
        );
        // send error occurs if the user dropped the channel... We cannot do much except ignore.
        let _ = guard.sender.send(XWaylandEvent::Ready {
            connection: instance.wm_fd.take().unwrap(), // This is a bug if None
            client: instance.wayland_client.clone(),
            client_fd: instance.wayland_client_fd,
            display: instance.display_lock.display(),
        });
    } else {
        error!(
            guard.log,
            "XWayland crashed at startup, will not try to restart it."
        );
    }
}

/// Spawn XWayland with given sockets on given display
///
/// Returns a pipe that outputs 'S' upon successful launch.
fn spawn_xwayland(
    display: u32,
    wayland_socket: UnixStream,
    wm_socket: UnixStream,
    listen_sockets: &[UnixStream],
) -> io::Result<ChildStdout> {
    let mut command = Command::new("sh");

    // We use output stream to communicate because FD is easier to handle than exit code.
    command.stdout(Stdio::piped());

    let mut xwayland_args = format!(":{} -rootless -terminate -wm {}", display, wm_socket.as_raw_fd());
    for socket in listen_sockets {
        // Will only fail to write on OOM, so this panic is fine.
        write!(xwayland_args, " -listenfd {}", socket.as_raw_fd()).unwrap();
    }
    // This command let sh to:
    // * Set up signal handler for USR1
    // * Launch Xwayland with USR1 ignored so Xwayland will signal us when it is ready (also redirect
    //   Xwayland's STDOUT to STDERR so its output, if any, won't distract us)
    // * Print "S" and exit if USR1 is received
    command.arg("-c").arg(format!(
        "trap 'echo S' USR1; (trap '' USR1; exec Xwayland {}) 1>&2 & wait",
        xwayland_args
    ));

    // Setup the environment: clear everything except PATH and XDG_RUNTIME_DIR
    command.env_clear();
    for (key, value) in env::vars_os() {
        if key.to_str() == Some("PATH") || key.to_str() == Some("XDG_RUNTIME_DIR") {
            command.env(key, value);
            continue;
        }
    }
    command.env("WAYLAND_SOCKET", format!("{}", wayland_socket.as_raw_fd()));

    unsafe {
        let wayland_socket_fd = wayland_socket.as_raw_fd();
        let wm_socket_fd = wm_socket.as_raw_fd();
        let socket_fds: Vec<_> = listen_sockets.iter().map(|socket| socket.as_raw_fd()).collect();
        command.pre_exec(move || {
            // unset the CLOEXEC flag from the sockets we need to pass
            // to xwayland
            unset_cloexec(wayland_socket_fd)?;
            unset_cloexec(wm_socket_fd)?;
            for &socket in socket_fds.iter() {
                unset_cloexec(socket)?;
            }
            Ok(())
        });
    }

    let mut child = command.spawn()?;
    Ok(child.stdout.take().expect("stdout should be piped"))
}

/// Remove the `O_CLOEXEC` flag from this `Fd`
///
/// This means that the `Fd` will *not* be automatically
/// closed when we `exec()` into XWayland
fn unset_cloexec(fd: RawFd) -> io::Result<()> {
    use nix::fcntl::{fcntl, FcntlArg, FdFlag};
    fcntl(fd, FcntlArg::F_SETFD(FdFlag::empty()))?;
    Ok(())
}

<MSG> Merge pull request #101 from Smithay/wayland-021

Update to wayland-rs 0.21
<DFF> @@ -25,21 +25,22 @@
  *
  */
 use std::cell::RefCell;
-use std::rc::Rc;
 use std::env;
 use std::ffi::CString;
 use std::os::unix::io::{AsRawFd, IntoRawFd};
 use std::os::unix::net::UnixStream;
+use std::rc::Rc;
 
-use nix::{Error as NixError, Result as NixResult};
 use nix::errno::Errno;
-use nix::unistd::{fork, ForkResult, Pid};
 use nix::sys::signal;
+use nix::unistd::{fork, ForkResult, Pid};
+use nix::{Error as NixError, Result as NixResult};
 
-use wayland_server::{Client, Display, LoopToken};
-use wayland_server::sources::{SignalEvent, Source};
+use wayland_server::calloop::signals::{Signal, Signals};
+use wayland_server::calloop::{LoopHandle, Source};
+use wayland_server::{Client, Display};
 
-use super::x11_sockets::{X11Lock, prepare_x11_sockets};
+use super::x11_sockets::{prepare_x11_sockets, X11Lock};
 
 /// The XWayland handle
 pub struct XWayland<WM: XWindowManager> {
@@ -66,9 +67,9 @@ pub trait XWindowManager {
 
 impl<WM: XWindowManager + 'static> XWayland<WM> {
     /// Start the XWayland server
-    pub fn init<L>(
+    pub fn init<L, Data: 'static>(
         wm: WM,
-        token: LoopToken,
+        handle: LoopHandle<Data>,
         display: Rc<RefCell<Display>>,
         logger: L,
     ) -> Result<XWayland<WM>, ()>
@@ -78,7 +79,16 @@ impl<WM: XWindowManager + 'static> XWayland<WM> {
         let log = ::slog_or_stdlog(logger);
         let inner = Rc::new(RefCell::new(Inner {
             wm,
-            token,
+            source_maker: Box::new(move |inner| {
+                handle
+                    .insert_source(
+                        Signals::new(&[Signal::SIGUSR1]).map_err(|_| ())?,
+                        move |evt, _| {
+                            debug_assert!(evt.signal() == Signal::SIGUSR1);
+                            xwayland_ready(&inner);
+                        },
+                    ).map_err(|_| ())
+            }),
             wayland_display: display,
             instance: None,
             log: log.new(o!("smithay_module" => "XWayland")),
@@ -97,7 +107,7 @@ impl<WM: XWindowManager> Drop for XWayland<WM> {
 struct XWaylandInstance {
     display_lock: X11Lock,
     wayland_client: Client,
-    sigusr1_handler: Option<Source<SignalEvent>>,
+    sigusr1_handler: Option<Source<Signals>>,
     wm_fd: Option<UnixStream>,
     started_at: ::std::time::Instant,
     child_pid: Option<Pid>,
@@ -106,7 +116,7 @@ struct XWaylandInstance {
 // Inner implementation of the XWayland manager
 struct Inner<WM: XWindowManager> {
     wm: WM,
-    token: LoopToken,
+    source_maker: Box<FnMut(Rc<RefCell<Inner<WM>>>) -> Result<Source<Signals>, ()>>,
     wayland_display: Rc<RefCell<Display>>,
     instance: Option<XWaylandInstance>,
     log: ::slog::Logger,
@@ -140,17 +150,11 @@ fn launch<WM: XWindowManager + 'static>(inner: &Rc<RefCell<Inner<WM>>>) -> Resul
             .borrow_mut()
             .create_client(wl_me.into_raw_fd())
     };
-    client.set_user_data(Rc::into_raw(inner.clone()) as *const () as *mut ());
-    client.set_destructor(client_destroy::<WM>);
+    client.data_map().insert_if_missing(|| inner.clone());
+    client.add_destructor(client_destroy::<WM>);
 
     // setup the SIGUSR1 handler
-    let my_inner = inner.clone();
-    let sigusr1_handler = guard
-        .token
-        .add_signal_event_source(signal::Signal::SIGUSR1, move |_, ()| {
-            xwayland_ready(&my_inner)
-        })
-        .map_err(|_| ())?;
+    let sigusr1_handler = (&mut *guard.source_maker)(inner.clone())?;
 
     // all is ready, we can do the fork dance
     let child_pid = match fork() {
@@ -242,8 +246,8 @@ impl<WM: XWindowManager> Inner<WM> {
     }
 }
 
-fn client_destroy<WM: XWindowManager + 'static>(data: *mut ()) {
-    let inner = unsafe { Rc::from_raw(data as *const () as *const RefCell<Inner<WM>>) };
+fn client_destroy<WM: XWindowManager + 'static>(map: &::wayland_server::UserDataMap) {
+    let inner = map.get::<Rc<RefCell<Inner<WM>>>>().unwrap();
 
     // shutdown the server
     let started_at = inner.borrow().instance.as_ref().map(|i| i.started_at);

Merge pull request #101 from Smithay/wayland-021