xwayland: rework as an EventSource

Reorganize the XWayland abstraction into a calloop EventLoop.

Fixes #245
Fixes #203

anvil/src/state.rs

@@ -23,11 +23,9 @@ use smithay::{
 #[cfg(feature = "egl")]
 use smithay::backend::egl::display::EGLBufferReader;
 #[cfg(feature = "xwayland")]
-use smithay::xwayland::XWayland;
+use smithay::xwayland::{XWayland, XWaylandEvent};
 
 use crate::shell::init_shell;
-#[cfg(feature = "xwayland")]
-use crate::xwayland::XWm;
 
 pub struct AnvilState<BackendData> {
     pub backend_data: BackendData,
@@ -48,9 +46,8 @@ pub struct AnvilState<BackendData> {
     pub start_time: std::time::Instant,
     #[cfg(feature = "egl")]
     pub egl_reader: Option<EGLBufferReader>,
-    // things we must keep alive
     #[cfg(feature = "xwayland")]
-    _xwayland: XWayland<XWm<BackendData>>,
+    pub xwayland: XWayland<AnvilState<BackendData>>,
 }
 
 impl<BackendData: Backend + 'static> AnvilState<BackendData> {
@@ -141,14 +138,19 @@ impl<BackendData: Backend + 'static> AnvilState<BackendData> {
             .expect("Failed to initialize the keyboard");
 
         #[cfg(feature = "xwayland")]
-        let _xwayland = {
+        let xwayland = {
-            let xwm = XWm::new(
+            let (xwayland, channel) = XWayland::new(handle.clone(), display.clone(), log.clone());
-                handle.clone(),
+            let ret = handle.insert_source(channel, |event, _, anvil_state| match event {
-                shell_handles.token,
+                XWaylandEvent::Ready { connection, client } => anvil_state.xwayland_ready(connection, client),
-                shell_handles.window_map.clone(),
+                XWaylandEvent::Exited => anvil_state.xwayland_exited(),
-                log.clone(),
+            });
+            if let Err(e) = ret {
+                error!(
+                    log,
+                    "Failed to insert the XWaylandSource into the event loop: {}", e
                 );
-            XWayland::init(xwm, handle.clone(), display.clone(), &mut (), log.clone()).unwrap()
+            }
+            xwayland
         };
 
         AnvilState {
@@ -170,7 +172,7 @@ impl<BackendData: Backend + 'static> AnvilState<BackendData> {
             egl_reader,
             start_time: std::time::Instant::now(),
             #[cfg(feature = "xwayland")]
-            _xwayland,
+            xwayland,
         }
     }
 }

anvil/src/udev.rs

@@ -219,6 +219,12 @@ pub fn run_udev(
         .map_err(|e| -> IoError { e.into() })
         .unwrap();
 
+    /*
+     * Start XWayland if supported
+     */
+    #[cfg(feature = "xwayland")]
+    state.start_xwayland();
+
     /*
      * And run our loop
      */

anvil/src/winit.rs

@@ -98,6 +98,9 @@ pub fn run_winit(
     let start_time = std::time::Instant::now();
     let mut cursor_visible = true;
 
+    #[cfg(feature = "xwayland")]
+    state.start_xwayland();
+
     info!(log, "Initialization completed, starting the main loop.");
 
     while state.running.load(Ordering::SeqCst) {

anvil/src/xwayland/mod.rs

@@ -1,12 +1,8 @@
 use std::{cell::RefCell, collections::HashMap, convert::TryFrom, os::unix::net::UnixStream, rc::Rc};
 
 use smithay::{
-    reexports::{
+    reexports::wayland_server::{protocol::wl_surface::WlSurface, Client},
-        calloop::LoopHandle,
-        wayland_server::{protocol::wl_surface::WlSurface, Client},
-    },
     wayland::compositor::CompositorToken,
-    xwayland::XWindowManager,
 };
 
 use x11rb::{
@@ -33,35 +29,16 @@ use x11rb_event_source::X11Source;
 
 mod x11rb_event_source;
 
-/// Implementation of [`smithay::xwayland::XWindowManager`] that is used for starting XWayland.
+impl<BackendData: 'static> AnvilState<BackendData> {
-/// After XWayland was started, the actual state is kept in `X11State`.
+    pub fn start_xwayland(&mut self) {
-pub struct XWm<Backend> {
+        if let Err(e) = self.xwayland.start() {
-    handle: LoopHandle<'static, AnvilState<Backend>>,
+            error!(self.log, "Failed to start XWayland: {}", e);
-    token: CompositorToken<Roles>,
-    window_map: Rc<RefCell<MyWindowMap>>,
-    log: slog::Logger,
-}
-
-impl<Backend> XWm<Backend> {
-    pub fn new(
-        handle: LoopHandle<'static, AnvilState<Backend>>,
-        token: CompositorToken<Roles>,
-        window_map: Rc<RefCell<MyWindowMap>>,
-        log: slog::Logger,
-    ) -> Self {
-        Self {
-            handle,
-            token,
-            window_map,
-            log,
         }
     }
-}
 
-impl<Backend> XWindowManager for XWm<Backend> {
+    pub fn xwayland_ready(&mut self, connection: UnixStream, client: Client) {
-    fn xwayland_ready(&mut self, connection: UnixStream, client: Client) {
         let (wm, source) =
-            X11State::start_wm(connection, self.token, self.window_map.clone(), self.log.clone()).unwrap();
+            X11State::start_wm(connection, self.ctoken, self.window_map.clone(), self.log.clone()).unwrap();
         let wm = Rc::new(RefCell::new(wm));
         client.data_map().insert_if_missing(|| Rc::clone(&wm));
         self.handle
@@ -75,7 +52,9 @@ impl<Backend> XWindowManager for XWm<Backend> {
             .unwrap();
     }
 
-    fn xwayland_exited(&mut self) {}
+    pub fn xwayland_exited(&mut self) {
+        error!(self.log, "Xwayland crashed");
+    }
 }
 
 x11rb::atom_manager! {

src/xwayland/mod.rs

@@ -6,14 +6,13 @@
 //! The starting point is the [`XWayland`](struct.XWayland.html) struct, which represents the
 //! running `XWayland` instance. Dropping it will shutdown XWayland.
 //!
-//! You need to provide an implementation of the `XWindowManager` trait which gives you
+//! You need to provide an implementation of a X11 Window Manager for XWayland to
-//! access to the X11 WM connection and the `Client` associated with XWayland. You'll need
+//! function properly. You'll need to treat XWayland (and all its X11 apps) as one
-//! to treat XWayland (and all its X11 apps) as one special client, and play the role of
+//! special client, and play the role of an X11 Window Manager.
-//! an X11 Window Manager.
 //!
 //! Smithay does not provide any helper for doing that yet, but it is planned.
 
 mod x11_sockets;
 mod xserver;
 
-pub use self::xserver::{XWayland, XWindowManager};
+pub use self::xserver::{XWayland, XWaylandEvent};

src/xwayland/x11_sockets.rs

@@ -6,7 +6,7 @@ use std::{
 use nix::{errno::Errno, sys::socket, Error as NixError, Result as NixResult};
 
 /// Find a free X11 display slot and setup
-pub(crate) fn prepare_x11_sockets(log: ::slog::Logger) -> Result<(X11Lock, [UnixStream; 2]), ()> {
+pub(crate) fn prepare_x11_sockets(log: ::slog::Logger) -> Result<(X11Lock, [UnixStream; 2]), std::io::Error> {
     for d in 0..33 {
         // if fails, try the next one
         if let Ok(lock) = X11Lock::grab(d, log.clone()) {
@@ -18,7 +18,10 @@ pub(crate) fn prepare_x11_sockets(log: ::slog::Logger) -> Result<(X11Lock, [Unix
     }
     // If we reach here, all values from 0 to 32 failed
     // we need to stop trying at some point
-    Err(())
+    Err(std::io::Error::new(
+        std::io::ErrorKind::AddrInUse,
+        "Could not find a free socket for the XServer.",
+    ))
 }
 
 pub(crate) struct X11Lock {

src/xwayland/xserver.rs

@@ -54,6 +54,7 @@ use std::{
 };
 
 use calloop::{
+    channel::{sync_channel, Channel, SyncSender},
     generic::{Fd, Generic},
     Interest, LoopHandle, Mode, RegistrationToken,
 };
@@ -65,69 +66,75 @@ use wayland_server::{Client, Display, Filter};
 use super::x11_sockets::{prepare_x11_sockets, X11Lock};
 
 /// The XWayland handle
-pub struct XWayland<WM: XWindowManager> {
+pub struct XWayland<Data> {
-    inner: Rc<RefCell<Inner<WM>>>,
+    inner: Rc<RefCell<Inner<Data>>>,
 }
 
-/// Trait to be implemented by you WM for XWayland
+/// Events generated by the XWayland manager
 ///
-/// This is a very low-level trait, only notifying you
+/// This is a very low-level interface, only notifying you when the connection
-/// when the connection with XWayland is up, or when
+/// with XWayland is up, or when it terminates.
-/// it terminates.
 ///
-/// You WM must be able handle the XWayland server connecting
+/// Your WM code must be able handle the XWayland server connecting then
-/// then disconnecting several time in a row, but only a single
+/// disconnecting several time in a row, but only a single connection will
-/// connection will be active at any given time.
+/// be active at any given time.
-pub trait XWindowManager {
+pub enum XWaylandEvent {
     /// The XWayland server is ready
-    ///
+    Ready {
-    /// Your privileged connection to it is this `UnixStream`
+        /// Privileged X11 connection to XWayland
-    fn xwayland_ready(&mut self, connection: UnixStream, client: Client);
+        connection: UnixStream,
-    /// The XWayland server has exited
+        /// Wayland client representing XWayland
-    fn xwayland_exited(&mut self);
+        client: Client,
+    },
+    /// The XWayland server exited
+    Exited,
 }
 
-impl<WM: XWindowManager + 'static> XWayland<WM> {
+impl<Data: Any + 'static> XWayland<Data> {
-    /// Start the XWayland server
+    /// Create a new XWayland manager
-    pub fn init<L, T: Any, Data: 'static>(
+    pub fn new<L>(
-        wm: WM,
         handle: LoopHandle<'static, Data>,
         display: Rc<RefCell<Display>>,
-        data: &mut T,
         logger: L,
-    ) -> Result<XWayland<WM>, ()>
+    ) -> (XWayland<Data>, XWaylandSource)
     where
         L: Into<Option<::slog::Logger>>,
     {
         let log = crate::slog_or_fallback(logger);
+        // We don't expect to ever have more than 2 messages in flight, if XWayland got ready and then died right away
+        let (sender, channel) = sync_channel(2);
         let inner = Rc::new(RefCell::new(Inner {
-            wm,
+            handle,
-            kill_source: {
-                let handle = handle.clone();
-                Box::new(move |source| handle.kill(source))
-            },
-            source_maker: Box::new(move |inner, fd| {
-                handle
-                    .insert_source(
-                        Generic::new(Fd(fd), Interest::READ, Mode::Level),
-                        move |evt, _, _| {
-                            debug_assert!(evt.readable);
-                            xwayland_ready(&inner);
-                            Ok(())
-                        },
-                    )
-                    .map_err(|_| ())
-            }),
             wayland_display: display,
             instance: None,
+            sender,
             log: log.new(o!("smithay_module" => "XWayland")),
         }));
-        launch(&inner, data)?;
+        (XWayland { inner }, XWaylandSource { channel })
-        Ok(XWayland { inner })
+    }
+
+    /// 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(&self) -> std::io::Result<()> {
+        launch(&self.inner)
+    }
+
+    /// 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.borrow_mut().shutdown();
     }
 }
 
-impl<WM: XWindowManager> Drop for XWayland<WM> {
+impl<Data> Drop for XWayland<Data> {
     fn drop(&mut self) {
         self.inner.borrow_mut().shutdown();
     }
@@ -135,32 +142,25 @@ impl<WM: XWindowManager> Drop for XWayland<WM> {
 
 struct XWaylandInstance {
     display_lock: X11Lock,
-    wayland_client: Client,
+    wayland_client: Option<Client>,
     startup_handler: Option<RegistrationToken>,
     wm_fd: Option<UnixStream>,
-    started_at: ::std::time::Instant,
     child_stdout: Option<ChildStdout>,
 }
 
-type SourceMaker<WM> = dyn FnMut(Rc<RefCell<Inner<WM>>>, RawFd) -> Result<RegistrationToken, ()>;
-
 // Inner implementation of the XWayland manager
-struct Inner<WM: XWindowManager> {
+struct Inner<Data> {
-    wm: WM,
+    sender: SyncSender<XWaylandEvent>,
-    source_maker: Box<SourceMaker<WM>>,
+    handle: LoopHandle<'static, Data>,
     wayland_display: Rc<RefCell<Display>>,
     instance: Option<XWaylandInstance>,
-    kill_source: Box<dyn Fn(RegistrationToken)>,
     log: ::slog::Logger,
 }
 
 // Launch an XWayland server
 //
 // Does nothing if there is already a launched instance
-fn launch<WM: XWindowManager + 'static, T: Any>(
+fn launch<Data: Any>(inner: &Rc<RefCell<Inner<Data>>>) -> std::io::Result<()> {
-    inner: &Rc<RefCell<Inner<WM>>>,
-    data: &mut T,
-) -> Result<(), ()> {
     let mut guard = inner.borrow_mut();
     if guard.instance.is_some() {
         return Ok(());
@@ -168,16 +168,20 @@ fn launch<WM: XWindowManager + 'static, T: Any>(
 
     info!(guard.log, "Starting XWayland");
 
-    let (x_wm_x11, x_wm_me) = UnixStream::pair().map_err(|_| ())?;
+    let (x_wm_x11, x_wm_me) = UnixStream::pair()?;
-    let (wl_x11, wl_me) = UnixStream::pair().map_err(|_| ())?;
+    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
 
-    // record launch time
+    // Setup the associated wayland client to be created in an idle callback, so that we don't need
-    let creation_time = ::std::time::Instant::now();
+    // to access the dispatch_data *right now*
-
+    let idle_inner = inner.clone();
+    guard.handle.insert_idle(move |data| {
+        let mut guard = idle_inner.borrow_mut();
+        let guard = &mut *guard;
+        if let Some(ref mut instance) = guard.instance {
             // create the wayland client for XWayland
             let client = unsafe {
                 guard
@@ -185,47 +189,98 @@ fn launch<WM: XWindowManager + 'static, T: Any>(
                     .borrow_mut()
                     .create_client(wl_me.into_raw_fd(), data)
             };
-    client.data_map().insert_if_missing(|| inner.clone());
+            client.data_map().insert_if_missing(|| idle_inner.clone());
-    client.add_destructor(Filter::new(|e: Arc<_>, _, mut data| {
+            client.add_destructor(Filter::new(|e: Arc<_>, _, _| client_destroy::<Data>(&e)));
-        client_destroy::<WM, T>(&e, data.get().unwrap())
+
-    }));
+            instance.wayland_client = Some(client.clone());
+        }
+    });
 
     // 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(());
+            return Err(e);
         }
     };
 
-    let startup_handler = (&mut *guard.source_maker)(inner.clone(), child_stdout.as_raw_fd())?;
+    let inner = inner.clone();
+    let startup_handler = guard.handle.insert_source(
+        Generic::new(Fd(child_stdout.as_raw_fd()), Interest::READ, Mode::Level),
+        move |_, _, _| {
+            // the closure must be called exactly one time, this cannot panic
+            xwayland_ready(&inner);
+            Ok(())
+        },
+    )?;
 
     guard.instance = Some(XWaylandInstance {
         display_lock: lock,
-        wayland_client: client,
         startup_handler: Some(startup_handler),
+        wayland_client: None,
         wm_fd: Some(x_wm_me),
-        started_at: creation_time,
         child_stdout: Some(child_stdout),
     });
 
     Ok(())
 }
 
-impl<WM: XWindowManager> Inner<WM> {
+pub struct XWaylandSource {
+    channel: Channel<XWaylandEvent>,
+}
+
+impl calloop::EventSource for XWaylandSource {
+    type Event = XWaylandEvent;
+    type Metadata = ();
+    type Ret = ();
+
+    fn process_events<F>(
+        &mut self,
+        readiness: calloop::Readiness,
+        token: calloop::Token,
+        mut callback: F,
+    ) -> std::io::Result<()>
+    where
+        F: FnMut(Self::Event, &mut Self::Metadata) -> Self::Ret,
+    {
+        self.channel
+            .process_events(readiness, token, |event, &mut ()| match event {
+                calloop::channel::Event::Msg(msg) => callback(msg, &mut ()),
+                calloop::channel::Event::Closed => {}
+            })
+    }
+
+    fn register(&mut self, poll: &mut calloop::Poll, token: calloop::Token) -> std::io::Result<()> {
+        self.channel.register(poll, token)
+    }
+
+    fn reregister(&mut self, poll: &mut calloop::Poll, token: calloop::Token) -> std::io::Result<()> {
+        self.channel.reregister(poll, token)
+    }
+
+    fn unregister(&mut self, poll: &mut calloop::Poll) -> std::io::Result<()> {
+        self.channel.unregister(poll)
+    }
+}
+
+impl<Data> Inner<Data> {
     // Shutdown the XWayland server and cleanup everything
     fn shutdown(&mut self) {
         // don't do anything if not running
         if let Some(mut instance) = self.instance.take() {
             info!(self.log, "Shutting down XWayland.");
-            self.wm.xwayland_exited();
             // kill the client
-            instance.wayland_client.kill();
+            if let Some(client) = instance.wayland_client {
+                client.kill();
+            }
             // remove the event source
             if let Some(s) = instance.startup_handler.take() {
-                (self.kill_source)(s);
+                self.handle.kill(s);
             }
+            // 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
@@ -238,32 +293,17 @@ impl<WM: XWindowManager> Inner<WM> {
     }
 }
 
-fn client_destroy<WM: XWindowManager + 'static, T: Any>(map: &::wayland_server::UserDataMap, data: &mut T) {
+fn client_destroy<Data: 'static>(map: &::wayland_server::UserDataMap) {
-    let inner = map.get::<Rc<RefCell<Inner<WM>>>>().unwrap();
+    let inner = map.get::<Rc<RefCell<Inner<Data>>>>().unwrap();
-
-    // shutdown the server
-    let started_at = inner.borrow().instance.as_ref().map(|i| i.started_at);
     inner.borrow_mut().shutdown();
-
-    // restart it, unless we really just started it, if it crashes right
-    // at startup there is no point
-    if started_at.map(|t| t.elapsed().as_secs()).unwrap_or(10) > 5 {
-        warn!(inner.borrow().log, "XWayland crashed, restarting.");
-        let _ = launch(&inner, data);
-    } else {
-        warn!(
-            inner.borrow().log,
-            "XWayland crashed less than 5 seconds after its startup, not restarting."
-        );
-    }
 }
 
-fn xwayland_ready<WM: XWindowManager>(inner: &Rc<RefCell<Inner<WM>>>) {
+fn xwayland_ready<Data: 'static>(inner: &Rc<RefCell<Inner<Data>>>) {
+    // Lots of re-borrowing to please the borrow-checker
     let mut guard = inner.borrow_mut();
-    let inner = &mut *guard;
+    let guard = &mut *guard;
     // instance should never be None at this point
-    let instance = inner.instance.as_mut().unwrap();
+    let instance = guard.instance.as_mut().unwrap();
-    let wm = &mut inner.wm;
     // neither the child_stdout
     let child_stdout = instance.child_stdout.as_mut().unwrap();
 
@@ -272,7 +312,7 @@ fn xwayland_ready<WM: XWindowManager>(inner: &Rc<RefCell<Inner<WM>>>) {
     let success = match child_stdout.read(&mut buffer) {
         Ok(len) => len > 0 && buffer[0] == b'S',
         Err(e) => {
-            error!(inner.log, "Checking launch status failed"; "err" => format!("{:?}", e));
+            error!(guard.log, "Checking launch status failed"; "err" => format!("{:?}", e));
             false
         }
     };
@@ -282,21 +322,22 @@ fn xwayland_ready<WM: XWindowManager>(inner: &Rc<RefCell<Inner<WM>>>) {
         ::std::env::set_var("DISPLAY", format!(":{}", instance.display_lock.display()));
 
         // signal the WM
-        info!(inner.log, "XWayland is ready, signaling the WM.");
+        info!(guard.log, "XWayland is ready, signaling the WM.");
-        wm.xwayland_ready(
+        // send error occurs if the user dropped the channel... We cannot do much except ignore.
-            instance.wm_fd.take().unwrap(), // This is a bug if None
+        let _ = guard.sender.send(XWaylandEvent::Ready {
-            instance.wayland_client.clone(),
+            connection: instance.wm_fd.take().unwrap(), // This is a bug if None
-        );
+            client: instance.wayland_client.clone().unwrap(),
+        });
     } else {
         error!(
-            inner.log,
+            guard.log,
             "XWayland crashed at startup, will not try to restart it."
         );
     }
 
     // in all cases, cleanup
     if let Some(s) = instance.startup_handler.take() {
-        (inner.kill_source)(s);
+        guard.handle.kill(s);
     }
 }