fix: drop apps that quit, and reattach apps whose actor gave up

src/actor/app.rs

@@ -6,6 +6,7 @@
 use std::cell::RefCell;
 use std::fmt::Debug;
 use std::num::NonZeroU32;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, LazyLock, Mutex};
 use std::thread;
 use std::time::{Duration, Instant};
@@ -301,6 +302,8 @@ pub struct AppThreadHandle {
     requests_tx: actor::Sender<Request>,
     interactive_frames: InteractiveFrameQueue,
     frame_authority: FrameAuthority,
+    /// Set once the actor has attached to its app, shared by every clone.
+    attached: Arc<AtomicBool>,
 }
 
 /// The topology accepted when this producer was created. Clones held by an old
@@ -461,6 +464,7 @@ impl AppThreadHandle {
             requests_tx,
             interactive_frames: Default::default(),
             frame_authority: Default::default(),
+            attached: Default::default(),
         }
     }
 
@@ -471,6 +475,7 @@ impl AppThreadHandle {
                 requests_tx,
                 interactive_frames: Default::default(),
                 frame_authority: Default::default(),
+                attached: Default::default(),
             },
             rx,
         )
@@ -482,6 +487,11 @@ impl AppThreadHandle {
         self.requests_tx.same_channel(&other.requests_tx)
     }
 
+    /// Whether the actor got through `init`: watching its app and holding its windows.
+    pub(crate) fn is_attached(&self) -> bool { self.attached.load(Ordering::Relaxed) }
+
+    pub(crate) fn mark_attached(&self) { self.attached.store(true, Ordering::Relaxed) }
+
     pub(crate) fn set_topology_authority(
         &mut self,
         guard: &crate::actor::spaces::TopologyGuard,
@@ -1092,6 +1102,7 @@ impl State {
         if !self.init(handle.clone(), info) {
             return;
         }
+        handle.mark_attached();
 
         let this = RefCell::new(self);
         // The raises channel is owned by State, so joining both tasks would keep

src/actor/process.rs

@@ -88,7 +88,15 @@ impl ProcessActor {
 
             let pid = match unsafe { pid_for_psn(&psn) } {
                 Some(pid) => pid,
-                None => return NO_ERR,
+                None => {
+                    // A terminated process's PSN no longer resolves to a pid by
+                    // the time the event arrives; look for the apps that ended.
+                    if ev.kind == K_EVENT_APP_TERMINATED {
+                        debug!("Carbon: App terminated (pid unknown)");
+                        wm_sender.send(WmEvent::AppsMayHaveTerminated);
+                    }
+                    return NO_ERR;
+                }
             };
 
             match ev.kind {