feat: handle global removals, recalc output scale (#367)

All `GlobalRemove` events sent from the server are now handled by
recording them in a new clientside `vec` and passing the identifier
returned by `create_global` (now stored by a map in the state) to
`disable_global`. `handle_globals` (the top-level function) and
`handle_new_globals` (the `InnerServerState` member function) have
swapped names to better represent their new purposes.

This enables action to be taken when globals are removed. In this case,
the desired action is to forward output removal, so that the scaling
calculation does not account for disconnected monitors in its logic.

Resolves #351.

src/server/clientside.rs

@@ -1,6 +1,6 @@
 use super::decoration::DecorationMarker;
 
-use super::ObjectEvent;
+use super::{GlobalName, ObjectEvent};
 use hecs::{Entity, World};
 use smithay_client_toolkit::{
     activation::{ActivationHandler, RequestData, RequestDataExt},
@@ -115,6 +115,7 @@ pub(super) struct MyWorld {
     pub world: World,
     pub global_list: GlobalList,
     pub new_globals: Vec<Global>,
+    pub removed_globals: Vec<GlobalName>,
     events: Vec<(Entity, ObjectEvent)>,
     queued_events: Vec<mpsc::Receiver<(Entity, ObjectEvent)>>,
     pub clipboard: SelectionEvents<SelectionOffer>,
@@ -128,6 +129,7 @@ impl MyWorld {
             world: World::new(),
             global_list,
             new_globals: Vec::new(),
+            removed_globals: Vec::new(),
             events: Vec::new(),
             queued_events: Vec::new(),
             clipboard: Default::default(),
@@ -204,18 +206,23 @@ impl Dispatch<WlRegistry, GlobalListContents> for MyWorld {
         _: &wayland_client::Connection,
         _: &wayland_client::QueueHandle<Self>,
     ) {
-        if let Event::<WlRegistry>::Global {
-            name,
-            interface,
-            version,
-        } = event
-        {
-            state.new_globals.push(Global {
+        match event {
+            Event::<WlRegistry>::Global {
                 name,
                 interface,
                 version,
-            });
-        };
+            } => {
+                state.new_globals.push(Global {
+                    name,
+                    interface,
+                    version,
+                });
+            }
+            Event::<WlRegistry>::GlobalRemove { name } => {
+                state.removed_globals.push(GlobalName(name));
+            }
+            _ => {}
+        }
     }
 }
 

src/server/dispatch.rs

@@ -1479,6 +1479,7 @@ impl<S: X11Selection> GlobalDispatch<WlOutput, Global> for InnerServerState<S> {
                 client,
                 event::OutputScaleFactor::Output(1),
                 event::OutputDimensions::default(),
+                GlobalName(data.name),
             ),
         );
         state.updated_outputs.push(entity);

src/server/mod.rs

@@ -65,6 +65,7 @@ use wayland_protocols::{
 use wayland_server::protocol::wl_seat::WlSeat;
 use wayland_server::{
     Client, DisplayHandle, Resource, WEnum,
+    backend::GlobalId,
     protocol::{
         wl_callback::WlCallback, wl_compositor::WlCompositor, wl_output::WlOutput, wl_shm::WlShm,
         wl_surface::WlSurface,
@@ -342,7 +343,8 @@ enum ObjectEvent {
 }
 }
 
-fn handle_globals<'a, S: X11Selection + 'static>(
+fn handle_new_globals<'a, S: X11Selection + 'static>(
+    globals_map: &mut HashMap<GlobalName, (Global, GlobalId)>,
     dh: &DisplayHandle,
     globals: impl IntoIterator<Item = &'a Global>,
 ) {
@@ -353,7 +355,8 @@ fn handle_globals<'a, S: X11Selection + 'static>(
                     $(
                         ref x if x == <$global>::interface().name => {
                             let version = u32::min(global.version, <$global>::interface().version);
-                            dh.create_global::<InnerServerState<S>, $global, Global>(version, global.clone());
+                            let global_id = dh.create_global::<InnerServerState<S>, $global, Global>(version, global.clone());
+                            globals_map.insert(GlobalName(global.name), (global.clone(), global_id));
                         }
                     )+
                     _ => {}
@@ -377,6 +380,9 @@ fn handle_globals<'a, S: X11Selection + 'static>(
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub(super) struct GlobalName(pub u32);
+
 struct FocusData {
     window: x::Window,
     output_name: Option<String>,
@@ -446,6 +452,7 @@ pub struct InnerServerState<S: X11Selection> {
     world: MyWorld,
     queue: EventQueue<MyWorld>,
     qh: QueueHandle<MyWorld>,
+    globals_map: HashMap<GlobalName, (Global, GlobalId)>,
     client: Client,
     to_focus: Option<FocusData>,
     unfocus: bool,
@@ -532,9 +539,10 @@ impl<S: X11Selection> ServerState<NoConnection<S>> {
 
         dh.create_global::<InnerServerState<S>, XwaylandShellV1, _>(1, ());
 
+        let mut globals_map = HashMap::new();
         global_list
             .contents()
-            .with_list(|globals| handle_globals::<S>(&dh, globals));
+            .with_list(|globals| handle_new_globals::<S>(&mut globals_map, &dh, globals));
 
         let world = MyWorld::new(global_list);
         let client = dh.insert_client(client, std::sync::Arc::new(())).unwrap();
@@ -545,6 +553,7 @@ impl<S: X11Selection> ServerState<NoConnection<S>> {
             client,
             queue,
             qh,
+            globals_map,
             dh,
             to_focus: None,
             unfocus: false,
@@ -613,7 +622,7 @@ impl<C: XConnection> ServerState<C> {
     }
 
     pub fn handle_clientside_events(&mut self) {
-        self.handle_new_globals();
+        self.handle_globals();
 
         for (target, event) in self.world.read_events() {
             if !self.world.contains(target) {
@@ -659,8 +668,10 @@ impl<C: XConnection> ServerState<C> {
         }
 
         if !self.updated_outputs.is_empty() {
-            for output in self.updated_outputs.iter() {
-                let output_scale = self.world.get::<&OutputScaleFactor>(*output).unwrap();
+            for output in std::mem::take(&mut self.updated_outputs).iter() {
+                let Ok(output_scale) = self.world.get::<&OutputScaleFactor>(*output) else {
+                    continue;
+                };
                 if matches!(*output_scale, OutputScaleFactor::Output(..)) {
                     let mut surface_query = self
                         .world
@@ -684,7 +695,6 @@ impl<C: XConnection> ServerState<C> {
                     }
                 }
             }
-            self.updated_outputs.clear();
 
             let mut mixed_scale = false;
             let mut scale;
@@ -780,9 +790,33 @@ impl<S: X11Selection + 'static> InnerServerState<S> {
         self.queue.as_fd()
     }
 
-    fn handle_new_globals(&mut self) {
+    fn handle_globals(&mut self) {
         let globals = std::mem::take(&mut self.world.new_globals);
-        handle_globals::<S>(&self.dh, globals.iter());
+        handle_new_globals::<S>(&mut self.globals_map, &self.dh, &globals);
+
+        let globals = std::mem::take(&mut self.world.removed_globals);
+        if globals.is_empty() {
+            return;
+        }
+        let query = self
+            .world
+            .query_mut::<(&WlOutput, &GlobalName)>()
+            .into_iter()
+            .map(|(e, (_, name))| (e, *name))
+            .collect::<Vec<_>>();
+        for global in globals {
+            let (global_struct, global_id) = self.globals_map.remove(&global).unwrap();
+            self.dh.disable_global::<InnerServerState<S>>(global_id);
+            if global_struct.interface == <WlOutput>::interface().name {
+                for (entity, name) in query.iter() {
+                    if *name == global {
+                        self.updated_outputs.push(*entity);
+                        self.world.despawn(*entity).unwrap();
+                        break;
+                    }
+                }
+            }
+        }
     }
 
     pub fn new_window(

src/server/tests.rs

@@ -530,7 +530,19 @@ impl<C: XConnection> TestFixture<C> {
         );
         self.run();
         self.run();
-        (output, self.testwl.last_created_output())
+        (output, self.testwl.finalize_output())
+    }
+
+    fn remove_output(&mut self, output_s: wayland_server::protocol::wl_output::WlOutput) {
+        self.testwl.remove_output(output_s);
+        self.run();
+        self.run();
+        let mut events = std::mem::take(&mut *self.registry.data.events.lock().unwrap());
+        assert_eq!(events.len(), 1);
+        let event = events.pop().unwrap();
+        let Ev::<WlRegistry>::GlobalRemove { .. } = event else {
+            panic!("Unexpected event: {event:?}");
+        };
     }
 }
 
@@ -2725,6 +2737,52 @@ fn scaled_pointer_lock_position_hint() {
     );
 }
 
+#[test]
+fn disconnected_output_rescaling() {
+    let mut f = TestFixture::new_pre_connect(|testwl| {
+        testwl.enable_fractional_scale();
+    });
+    let comp = f.compositor();
+    let (_, output_main) = f.new_output(0, 0);
+    let (_, output_ext) = f.new_output(1000, 0);
+
+    let window = Window::new(1);
+    let (_, id) = f.create_toplevel(&comp, window);
+
+    let surface_data = f.testwl.get_surface_data(id).expect("No surface data");
+    let fractional = surface_data
+        .fractional
+        .as_ref()
+        .expect("No fractional scale for surface");
+    fractional.preferred_scale(240); // 2.0 scale
+    f.testwl.move_surface_to_output(id, &output_main);
+    f.run();
+
+    let surface_data = f.testwl.get_surface_data(id).expect("No surface data");
+    let fractional = surface_data
+        .fractional
+        .as_ref()
+        .expect("No fractional scale for surface");
+    fractional.preferred_scale(180); // 1.5 scale
+    f.testwl.move_surface_to_output(id, &output_ext);
+    f.run();
+    // Multiple monitors with different scaling will select the lowest scale across monitors
+    assert_eq!(f.satellite.inner.new_scale, Some(1.5));
+
+    f.remove_output(output_ext);
+    f.testwl.move_surface_to_output(id, &output_main);
+    let surface_data = f.testwl.get_surface_data(id).expect("No surface data");
+    let fractional = surface_data
+        .fractional
+        .as_ref()
+        .expect("No fractional scale for surface");
+    fractional.preferred_scale(240); // 2.0 scale
+    f.run();
+    f.run();
+    // Afteer the output is disconnected, only the 2x scale output remains, so use that scale
+    assert_eq!(f.satellite.inner.new_scale, Some(2.0));
+}
+
 #[test]
 fn client_side_decorations() {
     let (mut f, compositor) = TestFixture::new_with_compositor();

tests/integration.rs

@@ -319,7 +319,7 @@ impl Fixture {
     fn create_output(&mut self, x: i32, y: i32) -> wayland_server::protocol::wl_output::WlOutput {
         self.testwl.new_output(x, y);
         self.wait_and_dispatch();
-        self.testwl.last_created_output()
+        self.testwl.finalize_output()
     }
 }
 
@@ -2233,7 +2233,7 @@ fn xsettings_fractional_scale() {
     let mut connection = Connection::new(&f.display);
     f.testwl.enable_xdg_output_manager();
 
-    let output = f.testwl.last_created_output();
+    let output = f.testwl.finalize_output();
 
     let window = connection.new_window(connection.root, 0, 0, 20, 20, false);
     let surface = f.map_as_toplevel(&mut connection, window);

testwl/src/lib.rs

@@ -233,6 +233,7 @@ struct DataSourceData {
 struct Output {
     name: String,
     xdg: Option<ZxdgOutputV1>,
+    global_id: Option<GlobalId>,
 }
 
 struct KeyboardState {
@@ -266,6 +267,8 @@ struct State {
     last_surface_id: Option<SurfaceId>,
     created_surfaces: Vec<SurfaceId>,
     last_output: Option<WlOutput>,
+    last_output_global: Option<GlobalId>,
+    output_counter: u32,
     callbacks: Vec<WlCallback>,
     seat: Option<WlSeat>,
     pointer: Option<PointerState>,
@@ -296,6 +299,8 @@ impl Default for State {
             begin: Instant::now(),
             last_surface_id: None,
             last_output: None,
+            last_output_global: None,
+            output_counter: 0,
             callbacks: Vec::new(),
             seat: None,
             pointer: None,
@@ -572,13 +577,15 @@ impl Server {
         &self.state.created_surfaces
     }
 
+    /// Finish the initialization of an output created by `new_output`.
+    /// This function must be called after the globals have been dispatched in order to use the
+    /// output on the server side created by `new_output` (this function's return value).
     #[track_caller]
-    pub fn last_created_output(&self) -> WlOutput {
-        self.state
-            .last_output
-            .as_ref()
-            .expect("No outputs created!")
-            .clone()
+    pub fn finalize_output(&mut self) -> WlOutput {
+        let output_s = self.state.last_output.take().expect("No new outputs");
+        let output_data = self.state.outputs.get_mut(&output_s).unwrap();
+        output_data.global_id = self.state.last_output_global.take();
+        output_s
     }
 
     pub fn get_object<T: Resource + 'static>(
@@ -845,7 +852,8 @@ impl Server {
     }
 
     pub fn new_output(&mut self, x: i32, y: i32) {
-        self.dh.create_global::<State, WlOutput, _>(4, (x, y));
+        self.state.last_output_global =
+            Some(self.dh.create_global::<State, WlOutput, _>(4, (x, y)));
         self.display.flush_clients().unwrap();
     }
 
@@ -877,6 +885,12 @@ impl Server {
         self.display.flush_clients().unwrap();
     }
 
+    pub fn remove_output(&mut self, output: WlOutput) {
+        let output = self.state.outputs.remove(&output).unwrap();
+        self.dh.remove_global::<State>(output.global_id.unwrap());
+        self.display.flush_clients().unwrap();
+    }
+
     pub fn enable_xdg_output_manager(&mut self) {
         self.dh
             .create_global::<State, ZxdgOutputManagerV1, _>(3, ());
@@ -1126,13 +1140,19 @@ impl GlobalDispatch<WlOutput, (i32, i32)> for State {
             "fake monitor".to_string(),
             wl_output::Transform::Normal,
         );
-        let name = format!("WL-{}", state.outputs.len() + 1);
+        state.output_counter += 1;
+        let name = format!("WL-{}", state.output_counter);
         output.name(name.clone());
         output.mode(wl_output::Mode::Current, 1000, 1000, 0);
         output.done();
-        state
-            .outputs
-            .insert(output.clone(), Output { name, xdg: None });
+        state.outputs.insert(
+            output.clone(),
+            Output {
+                name,
+                xdg: None,
+                global_id: None,
+            },
+        );
         state.last_output = Some(output);
     }
 }