Add trivial Mutter ServiceChannel impl

Makes xdp-gnome work.

src/dbus/mod.rs

@@ -0,0 +1 @@
+pub mod mutter_service_channel;

src/dbus/mutter_service_channel.rs

@@ -0,0 +1,38 @@
+use std::os::fd::{FromRawFd, IntoRawFd};
+use std::os::unix::net::UnixStream;
+use std::sync::Arc;
+
+use smithay::reexports::wayland_server::DisplayHandle;
+use zbus::dbus_interface;
+
+use crate::niri::ClientState;
+
+pub struct ServiceChannel {
+    display: DisplayHandle,
+}
+
+#[dbus_interface(name = "org.gnome.Mutter.ServiceChannel")]
+impl ServiceChannel {
+    async fn open_wayland_service_connection(
+        &mut self,
+        service_client_type: u32,
+    ) -> zbus::fdo::Result<zbus::zvariant::OwnedFd> {
+        if service_client_type != 1 {
+            return Err(zbus::fdo::Error::InvalidArgs(
+                "Invalid service client type".to_owned(),
+            ));
+        }
+
+        let (sock1, sock2) = UnixStream::pair().unwrap();
+        self.display
+            .insert_client(sock2, Arc::new(ClientState::default()))
+            .unwrap();
+        Ok(unsafe { zbus::zvariant::OwnedFd::from_raw_fd(sock1.into_raw_fd()) })
+    }
+}
+
+impl ServiceChannel {
+    pub fn new(display: DisplayHandle) -> Self {
+        Self { display }
+    }
+}

src/main.rs

@@ -5,6 +5,7 @@ mod handlers;
 
 mod animation;
 mod backend;
+mod dbus;
 mod frame_clock;
 mod input;
 mod layout;

src/niri.rs

@@ -44,6 +44,7 @@ use smithay::wayland::socket::ListeningSocketSource;
 use smithay::wayland::tablet_manager::TabletManagerState;
 
 use crate::backend::Backend;
+use crate::dbus::mutter_service_channel::ServiceChannel;
 use crate::frame_clock::FrameClock;
 use crate::layout::{MonitorRenderElement, MonitorSet};
 use crate::utils::{center, get_monotonic_time, load_default_cursor};
@@ -85,6 +86,8 @@ pub struct Niri {
     pub pointer_buffer: Option<(TextureBuffer<GlesTexture>, Point<i32, Physical>)>,
     pub cursor_image: CursorImageStatus,
     pub dnd_icon: Option<WlSurface>,
+
+    pub zbus_conn: Option<zbus::blocking::Connection>,
 }
 
 pub struct OutputState {
@@ -151,6 +154,7 @@ impl Niri {
             socket_name.to_string_lossy()
         );
 
+        let mut zbus_conn = None;
         if std::env::var_os("NOTIFY_SOCKET").is_some() {
             // We're starting as a systemd service. Export our variables and tell systemd we're
             // ready.
@@ -166,6 +170,20 @@ impl Niri {
                 warn!("error spawning shell to import environment into systemd: {err:?}");
             }
 
+            // Set up zbus, make sure it happens before anything might want it.
+            let conn = zbus::blocking::ConnectionBuilder::session()
+                .unwrap()
+                .name("org.gnome.Mutter.ServiceChannel")
+                .unwrap()
+                .serve_at(
+                    "/org/gnome/Mutter/ServiceChannel",
+                    ServiceChannel::new(display_handle.clone()),
+                )
+                .unwrap()
+                .build()
+                .unwrap();
+            zbus_conn = Some(conn);
+
             // Notify systemd we're ready.
             if let Err(err) = sd_notify::notify(false, &[NotifyState::Ready]) {
                 warn!("error notifying systemd: {err:?}");
@@ -210,6 +228,8 @@ impl Niri {
             pointer_buffer: None,
             cursor_image: CursorImageStatus::Default,
             dnd_icon: None,
+
+            zbus_conn,
         }
     }