Restart PipeWire on errors

This lets you restart pipewire and then get a screencast successfully.

src/niri.rs

@@ -1,4 +1,4 @@
-use std::cell::{Cell, LazyCell, OnceCell, RefCell};
+use std::cell::{Cell, OnceCell, RefCell};
 use std::collections::{HashMap, HashSet};
 use std::ffi::OsString;
 use std::path::PathBuf;
@@ -345,7 +345,9 @@ pub struct Niri {
 
     // Casts are dropped before PipeWire to prevent a double-free (yay).
     pub casts: Vec<Cast>,
-    pub pipewire: LazyCell<Option<PipeWire>, Box<dyn FnOnce() -> Option<PipeWire>>>,
+    pub pipewire: Option<PipeWire>,
+    #[cfg(feature = "xdp-gnome-screencast")]
+    pub pw_to_niri: calloop::channel::Sender<PwToNiri>,
 
     // Screencast output for each mapped window.
     #[cfg(feature = "xdp-gnome-screencast")]
@@ -1504,6 +1506,16 @@ impl State {
                     });
                 }
             },
+            PwToNiri::FatalError => {
+                warn!("stopping PipeWire due to fatal error");
+                if let Some(pw) = self.niri.pipewire.take() {
+                    let ids: Vec<_> = self.niri.casts.iter().map(|cast| cast.session_id).collect();
+                    for id in ids {
+                        self.niri.stop_cast(id);
+                    }
+                    self.niri.event_loop.remove(pw.token);
+                }
+            }
         }
     }
 
@@ -1533,10 +1545,19 @@ impl State {
                     }
                 };
 
-                let Some(pw) = &*self.niri.pipewire else {
-                    warn!("error starting screencast: PipeWire failed to initialize");
-                    self.niri.stop_cast(session_id);
-                    return;
+                let pw = if let Some(pw) = &self.niri.pipewire {
+                    pw
+                } else {
+                    match PipeWire::new(&self.niri.event_loop, self.niri.pw_to_niri.clone()) {
+                        Ok(pipewire) => self.niri.pipewire.insert(pipewire),
+                        Err(err) => {
+                            warn!(
+                                "error starting screencast: PipeWire failed to initialize: {err:?}"
+                            );
+                            self.niri.stop_cast(session_id);
+                            return;
+                        }
+                    }
                 };
 
                 let (target, size, refresh, alpha) = match target {
@@ -1911,14 +1932,17 @@ impl Niri {
             }
         };
 
-        let loop_handle = event_loop.clone();
-        let pipewire = LazyCell::new(Box::new(move || match PipeWire::new(&loop_handle) {
-            Ok(pipewire) => Some(pipewire),
-            Err(err) => {
-                warn!("error connecting to PipeWire, screencasting will not work: {err:?}");
-                None
-            }
-        }) as _);
+        #[cfg(feature = "xdp-gnome-screencast")]
+        let pw_to_niri = {
+            let (pw_to_niri, from_pipewire) = calloop::channel::channel();
+            event_loop
+                .insert_source(from_pipewire, move |event, _, state| match event {
+                    calloop::channel::Event::Msg(msg) => state.on_pw_msg(msg),
+                    calloop::channel::Event::Closed => (),
+                })
+                .unwrap();
+            pw_to_niri
+        };
 
         let display_source = Generic::new(display, Interest::READ, Mode::Level);
         event_loop
@@ -2061,8 +2085,10 @@ impl Niri {
             ipc_server,
             ipc_outputs_changed: false,
 
-            pipewire,
+            pipewire: None,
             casts: vec![],
+            #[cfg(feature = "xdp-gnome-screencast")]
+            pw_to_niri,
 
             #[cfg(feature = "xdp-gnome-screencast")]
             mapped_cast_output: HashMap::new(),

src/pw_utils.rs

@@ -11,7 +11,7 @@ use anyhow::Context as _;
 use calloop::timer::{TimeoutAction, Timer};
 use calloop::RegistrationToken;
 use pipewire::context::Context;
-use pipewire::core::Core;
+use pipewire::core::{Core, PW_ID_CORE};
 use pipewire::main_loop::MainLoop;
 use pipewire::properties::Properties;
 use pipewire::spa::buffer::DataType;
@@ -54,12 +54,14 @@ const CAST_DELAY_ALLOWANCE: Duration = Duration::from_micros(100);
 pub struct PipeWire {
     _context: Context,
     pub core: Core,
+    pub token: RegistrationToken,
     to_niri: calloop::channel::Sender<PwToNiri>,
 }
 
 pub enum PwToNiri {
     StopCast { session_id: usize },
     Redraw(CastTarget),
+    FatalError,
 }
 
 pub struct Cast {
@@ -134,15 +136,26 @@ macro_rules! make_params {
 }
 
 impl PipeWire {
-    pub fn new(event_loop: &LoopHandle<'static, State>) -> anyhow::Result<Self> {
+    pub fn new(
+        event_loop: &LoopHandle<'static, State>,
+        to_niri: calloop::channel::Sender<PwToNiri>,
+    ) -> anyhow::Result<Self> {
         let main_loop = MainLoop::new(None).context("error creating MainLoop")?;
         let context = Context::new(&main_loop).context("error creating Context")?;
         let core = context.connect(None).context("error creating Core")?;
 
+        let to_niri_ = to_niri.clone();
         let listener = core
             .add_listener_local()
-            .error(|id, seq, res, message| {
+            .error(move |id, seq, res, message| {
                 warn!(id, seq, res, message, "pw error");
+
+                // Reset PipeWire on connection errors.
+                if id == PW_ID_CORE && res == -32 {
+                    if let Err(err) = to_niri_.send(PwToNiri::FatalError) {
+                        warn!("error sending FatalError to niri: {err:?}");
+                    }
+                }
             })
             .register();
         mem::forget(listener);
@@ -154,7 +167,7 @@ impl PipeWire {
             }
         }
         let generic = Generic::new(AsFdWrapper(main_loop), Interest::READ, Mode::Level);
-        event_loop
+        let token = event_loop
             .insert_source(generic, move |_, wrapper, _| {
                 let _span = tracy_client::span!("pipewire iteration");
                 wrapper.0.loop_().iterate(Duration::ZERO);
@@ -162,17 +175,10 @@ impl PipeWire {
             })
             .unwrap();
 
-        let (to_niri, from_pipewire) = calloop::channel::channel();
-        event_loop
-            .insert_source(from_pipewire, move |event, _, state| match event {
-                calloop::channel::Event::Msg(msg) => state.on_pw_msg(msg),
-                calloop::channel::Event::Closed => (),
-            })
-            .unwrap();
-
         Ok(Self {
             _context: context,
             core,
+            token,
             to_niri,
         })
     }