wayland: attempt to handle seat changes that impact the keyboard

A couple of times today while debugging things on wayland, I lost
keyboard input to wezterm.

I don't know if that is strictly a wezterm bug, or just a general
wayland bug (not long after, the whole mutter session hung, and
somehow wedged all processes with my uid).

So, this is a quick stab in that direction.

window/src/os/wayland/connection.rs

@@ -16,6 +16,7 @@ use std::time::{Duration, Instant};
 use toolkit::environment::Environment;
 use toolkit::reexports::calloop::{EventLoop, EventSource, Interest, Mode, Poll, Readiness, Token};
 use toolkit::reexports::client::Display;
+use toolkit::seat::SeatListener;
 use toolkit::WaylandSource;
 
 toolkit::default_environment!(MyEnvironment, desktop);
@@ -37,6 +38,7 @@ pub struct WaylandConnection {
     pub(crate) gl_connection: RefCell<Option<Rc<crate::egl::GlConnection>>>,
     pub(crate) pointer: PointerDispatcher,
     pub(crate) keyboard: KeyboardDispatcher,
+    seat_listener: SeatListener,
     pub(crate) environment: RefCell<Environment<MyEnvironment>>,
     event_q: RefCell<EventLoop<()>>,
     pub(crate) display: RefCell<Display>,
@@ -52,14 +54,17 @@ impl WaylandConnection {
         let mut pointer = None;
 
         for seat in environment.get_all_seats() {
-            if let Some((has_kbd, has_ptr)) = toolkit::seat::with_seat_data(&seat, |seat_data| {
+            if let Some((has_kbd, has_ptr, name)) =
+                toolkit::seat::with_seat_data(&seat, |seat_data| {
                     (
                         seat_data.has_keyboard && !seat_data.defunct,
                         seat_data.has_pointer && !seat_data.defunct,
+                        seat_data.name.clone(),
                     )
-            }) {
+                })
+            {
                 if has_kbd {
-                    keyboard.register(event_loop.handle(), &seat)?;
+                    keyboard.register(event_loop.handle(), &seat, &name)?;
                 }
                 if has_ptr {
                     pointer.replace(PointerDispatcher::register(
@@ -72,6 +77,36 @@ impl WaylandConnection {
             }
         }
 
+        let seat_listener;
+        {
+            let loop_handle = event_loop.handle();
+            let keyboard = keyboard.clone();
+            seat_listener = environment.listen_for_seats(move |seat, seat_data, _| {
+                if seat_data.has_keyboard {
+                    if seat_data.defunct {
+                        keyboard.deregister(loop_handle.clone(), &seat_data.name);
+                    } else {
+                        if let Err(err) =
+                            keyboard.register(loop_handle.clone(), &seat, &seat_data.name)
+                        {
+                            log::error!("{:#}", err);
+                        }
+                    }
+                }
+                if seat_data.has_pointer {
+                    // TODO: ideally do something similar to the keyboard state,
+                    // but the pointer state has a lot of other stuff floating
+                    // around it so it's not so clear cut right now.
+                    log::error!(
+                        "seat {} changed; it has a pointer that is
+                        defunct={} and we don't know what to do about it",
+                        seat_data.name,
+                        seat_data.defunct
+                    );
+                }
+            });
+        }
+
         WaylandSource::new(event_q)
             .quick_insert(event_loop.handle())
             .map_err(|e| anyhow!("failed to setup WaylandSource: {:?}", e))?;
@@ -86,6 +121,7 @@ impl WaylandConnection {
             windows: RefCell::new(HashMap::new()),
             keyboard,
             pointer: pointer.unwrap(),
+            seat_listener,
             gl_connection: RefCell::new(None),
         })
     }

window/src/os/wayland/keyboard.rs

@@ -3,10 +3,11 @@ use anyhow::anyhow;
 use smithay_client_toolkit as toolkit;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
-use toolkit::reexports::calloop::LoopHandle;
+use toolkit::reexports::calloop::{LoopHandle, Source};
 use toolkit::seat::keyboard::{
-    map_keyboard_repeat, Event as KbEvent, KeyState, ModifiersState, RepeatKind,
+    map_keyboard_repeat, Event as KbEvent, KeyState, ModifiersState, RepeatKind, RepeatSource,
 };
+use wayland_client::protocol::wl_keyboard::WlKeyboard;
 use wayland_client::protocol::wl_seat::WlSeat;
 use wayland_client::protocol::wl_surface::WlSurface;
 use wayland_client::Attached;
@@ -16,6 +17,7 @@ use wezterm_input_types::*;
 struct Inner {
     active_surface_id: u32,
     surface_to_window_id: HashMap<u32, usize>,
+    by_name: HashMap<String, (WlKeyboard, Source<RepeatSource>)>,
 }
 
 impl Inner {
@@ -64,9 +66,10 @@ impl KeyboardDispatcher {
         &self,
         loop_handle: LoopHandle<()>,
         seat: &Attached<WlSeat>,
+        name: &str,
     ) -> anyhow::Result<()> {
         let inner = Arc::clone(&self.inner);
-        let (_kbd, _source) = map_keyboard_repeat(
+        let pair = map_keyboard_repeat(
             loop_handle,
             &seat,
             None,
@@ -90,9 +93,22 @@ impl KeyboardDispatcher {
         )
         .map_err(|e| anyhow!("Failed to configure keyboard callback: {:?}", e))?;
 
+        self.inner
+            .lock()
+            .unwrap()
+            .by_name
+            .insert(name.to_string(), pair);
+
         Ok(())
     }
 
+    pub fn deregister(&self, loop_handle: LoopHandle<()>, name: &str) {
+        if let Some((kbd, source)) = self.inner.lock().unwrap().by_name.remove(name) {
+            kbd.release();
+            loop_handle.remove(source);
+        }
+    }
+
     pub fn add_window(&self, window_id: usize, surface: &WlSurface) {
         let mut inner = self.inner.lock().unwrap();
         inner