Use ThreadExecutor instead of calloop executor

I thought the calloop executor had been fixed, but it still seems to
have issues that were preventing capture of continuous frames from
working consistently.

Fixes https://github.com/pop-os/cosmic-workspaces-epoch/issues/160.

Cargo.lock

@@ -1265,6 +1265,7 @@ dependencies = [
  "freedesktop-desktop-entry",
  "freedesktop-icons",
  "futures-channel",
+ "futures-executor",
  "gbm",
  "i18n-embed",
  "i18n-embed-fl",

Cargo.toml

@@ -29,6 +29,7 @@ rust-embed = "8.1.0"
 rustix = { version = "0.38.30", features  = ["fs"] }
 calloop-wayland-source = "0.4.0"
 aliasable = "0.1.3"
+futures-executor = { version = "0.3.31", features = ["thread-pool"] }
 
 [dependencies.i18n-embed]
 version = "0.15.3"

src/backend/wayland/mod.rs

@@ -59,7 +59,7 @@ pub struct AppData {
     captures: RefCell<HashMap<CaptureSource, Arc<Capture>>>,
     dmabuf_feedback: Option<DmabufFeedback>,
     gbm: Option<(PathBuf, gbm::Device<fs::File>)>,
-    scheduler: calloop::futures::Scheduler<()>,
+    thread_pool: futures_executor::ThreadPool,
 }
 
 impl AppData {
@@ -227,7 +227,12 @@ fn start(conn: Connection) -> mpsc::Receiver<Event> {
     }
 
     thread::spawn(move || {
-        let (executor, scheduler) = calloop::futures::executor().unwrap();
+        // TODO: The `calloop` executor doesn't seem to be working properly, so
+        // spawn an executor using one additional thread.
+        let thread_pool = futures_executor::ThreadPool::builder()
+            .pool_size(1)
+            .create()
+            .unwrap();
 
         let registry_state = RegistryState::new(&globals);
         let mut app_data = AppData {
@@ -245,7 +250,7 @@ fn start(conn: Connection) -> mpsc::Receiver<Event> {
             captures: RefCell::new(HashMap::new()),
             dmabuf_feedback: None,
             gbm: None,
-            scheduler,
+            thread_pool,
         };
 
         let (cmd_sender, cmd_channel) = calloop::channel::channel();
@@ -263,10 +268,6 @@ fn start(conn: Connection) -> mpsc::Receiver<Event> {
                 }
             })
             .unwrap();
-        event_loop
-            .handle()
-            .insert_source(executor, |(), _, _| {})
-            .unwrap();
 
         loop {
             event_loop.dispatch(None, &mut app_data).unwrap();

src/backend/wayland/screencopy.rs

@@ -159,19 +159,17 @@ impl ScreencopyHandler for AppData {
         let conn = conn.clone();
         let release = session.release.take();
         let qh = qh.clone();
-        self.scheduler
-            .schedule(async move {
-                if let Some(release) = release {
-                    // Wait for buffer to be released by server
-                    release.await;
-                }
-                let mut session = capture_clone.session.lock().unwrap();
-                let Some(session) = session.as_mut() else {
-                    return;
-                };
-                session.attach_buffer_and_commit(&capture_clone, &conn, &qh);
-            })
-            .unwrap();
+        self.thread_pool.spawn_ok(async move {
+            if let Some(release) = release {
+                // Wait for buffer to be released by server
+                release.await;
+            }
+            let mut session = capture_clone.session.lock().unwrap();
+            let Some(session) = session.as_mut() else {
+                return;
+            };
+            session.attach_buffer_and_commit(&capture_clone, &conn, &qh);
+        });
 
         let front = session.buffers.as_mut().unwrap().first_mut().unwrap();
         let (buffer, release) = SubsurfaceBuffer::new(front.backing.clone());