Wayland: Fix panic when calling set_cursor_grab from a different thread than evlp's one. (#1206)

This commit also start following X11 behavior on cursor icon update when
cursor is invisible.

Fixes regression introdced in 5ced36e319

src/platform_impl/linux/wayland/event_loop.rs

@@ -132,10 +132,11 @@ impl CursorManager {
     }
 
     pub fn set_cursor_icon(&mut self, cursor: CursorIcon) {
-        if self.cursor_visible && cursor != self.current_cursor {
+        if cursor != self.current_cursor {
             self.current_cursor = cursor;
-
-            self.set_cursor_icon_impl(cursor);
+            if self.cursor_visible {
+                self.set_cursor_icon_impl(cursor);
+            }
         }
     }
 
@@ -191,7 +192,11 @@ impl CursorManager {
         }
     }
 
-    pub fn grab_pointer(&mut self, surface: Option<&WlSurface>) {
+    // This function can only be called from a thread on which `pointer_constraints_proxy` event
+    // queue is located, so calling it directly from a Window doesn't work well, in case
+    // you've sent your window to another thread, so we need to pass cursor grab updates to
+    // the event loop and call this function from there.
+    fn grab_pointer(&mut self, surface: Option<&WlSurface>) {
         for locked_pointer in self.locked_pointers.drain(..) {
             locked_pointer.destroy();
         }
@@ -230,6 +235,8 @@ pub struct EventLoop<T: 'static> {
     // Our sink, shared with some handlers, buffering the events
     sink: Arc<Mutex<WindowEventsSink<T>>>,
     pending_user_events: Rc<RefCell<VecDeque<T>>>,
+    // The cursor manager
+    cursor_manager: Arc<Mutex<CursorManager>>,
     // Utility for grabbing the cursor and changing visibility
     _user_source: ::calloop::Source<::calloop::channel::Channel<T>>,
     user_sender: ::calloop::channel::Sender<T>,
@@ -416,6 +423,7 @@ impl<T: 'static> EventLoop<T> {
             outputs: env.outputs.clone(),
             _user_source: user_source,
             user_sender,
+            cursor_manager,
             _kbd_source: kbd_source,
             window_target: RootELW {
                 p: crate::platform_impl::EventLoopWindowTarget::Wayland(EventLoopWindowTarget {
@@ -654,7 +662,16 @@ impl<T> EventLoop<T> {
         }
         // process pending resize/refresh
         window_target.store.lock().unwrap().for_each(
-            |newsize, size, new_dpi, refresh, frame_refresh, closed, wid, frame| {
+            |newsize,
+             size,
+             new_dpi,
+             refresh,
+             frame_refresh,
+             closed,
+             grab_cursor,
+             surface,
+             wid,
+             frame| {
                 if let Some(frame) = frame {
                     if let Some((w, h)) = newsize {
                         frame.resize(w, h);
@@ -684,6 +701,11 @@ impl<T> EventLoop<T> {
                 if closed {
                     sink.send_window_event(crate::event::WindowEvent::CloseRequested, wid);
                 }
+
+                if let Some(grab_cursor) = grab_cursor {
+                    let surface = if grab_cursor { Some(surface) } else { None };
+                    self.cursor_manager.lock().unwrap().grab_pointer(surface);
+                }
             },
         )
     }

src/platform_impl/linux/wayland/window.rs

@@ -40,6 +40,7 @@ pub struct Window {
     need_frame_refresh: Arc<Mutex<bool>>,
     need_refresh: Arc<Mutex<bool>>,
     fullscreen: Arc<Mutex<bool>>,
+    cursor_grab_changed: Arc<Mutex<Option<bool>>>, // Update grab state
 }
 
 impl Window {
@@ -143,6 +144,7 @@ impl Window {
         let need_frame_refresh = Arc::new(Mutex::new(true));
         let frame = Arc::new(Mutex::new(frame));
         let need_refresh = Arc::new(Mutex::new(true));
+        let cursor_grab_changed = Arc::new(Mutex::new(None));
 
         evlp.store.lock().unwrap().windows.push(InternalWindow {
             closed: false,
@@ -150,6 +152,7 @@ impl Window {
             size: size.clone(),
             need_refresh: need_refresh.clone(),
             fullscreen: fullscreen.clone(),
+            cursor_grab_changed: cursor_grab_changed.clone(),
             need_frame_refresh: need_frame_refresh.clone(),
             surface: surface.clone(),
             kill_switch: kill_switch.clone(),
@@ -170,6 +173,7 @@ impl Window {
             need_refresh,
             cursor_manager,
             fullscreen,
+            cursor_grab_changed,
         })
     }
 
@@ -309,12 +313,7 @@ impl Window {
 
     #[inline]
     pub fn set_cursor_grab(&self, grab: bool) -> Result<(), ExternalError> {
-        let mut cursor_manager = self.cursor_manager.lock().unwrap();
-        if grab {
-            cursor_manager.grab_pointer(Some(&self.surface));
-        } else {
-            cursor_manager.grab_pointer(None);
-        }
+        *self.cursor_grab_changed.lock().unwrap() = Some(grab);
         Ok(())
     }
 
@@ -374,6 +373,7 @@ struct InternalWindow {
     need_refresh: Arc<Mutex<bool>>,
     fullscreen: Arc<Mutex<bool>>,
     need_frame_refresh: Arc<Mutex<bool>>,
+    cursor_grab_changed: Arc<Mutex<Option<bool>>>,
     closed: bool,
     kill_switch: Arc<Mutex<bool>>,
     frame: Weak<Mutex<SWindow<ConceptFrame>>>,
@@ -441,6 +441,8 @@ impl WindowStore {
             bool,
             bool,
             bool,
+            Option<bool>,
+            &wl_surface::WlSurface,
             WindowId,
             Option<&mut SWindow<ConceptFrame>>,
         ),
@@ -455,6 +457,8 @@ impl WindowStore {
                 replace(&mut *window.need_refresh.lock().unwrap(), false),
                 replace(&mut *window.need_frame_refresh.lock().unwrap(), false),
                 window.closed,
+                window.cursor_grab_changed.lock().unwrap().take(),
+                &window.surface,
                 make_wid(&window.surface),
                 opt_mutex_lock.as_mut().map(|m| &mut **m),
             );