Add initial layer-shell implementation

Those surfaces never receive mouse focus and always keyboard focus,
which may not be always good, but it'll do for now.

3 files changed, 104 insertions, 0 deletions

diff --git a/src/handlers/compositor.rs b/src/handlers/compositor.rs
index 8b0f032b..2feba445 100644
--- a/src/handlers/compositor.rs
+++ b/src/handlers/compositor.rs
@@ -112,6 +112,9 @@ impl CompositorHandler for Niri {
                 }
             }
         }
+
+        // This might be a layer-shell surface.
+        self.layer_shell_handle_commit(surface);
     }
 }
 
diff --git a/src/handlers/layer_shell.rs b/src/handlers/layer_shell.rs
new file mode 100644
index 00000000..236ae7ab
--- /dev/null
+++ b/src/handlers/layer_shell.rs
@@ -0,0 +1,100 @@
+use smithay::delegate_layer_shell;
+use smithay::desktop::{layer_map_for_output, LayerSurface, WindowSurfaceType};
+use smithay::output::Output;
+use smithay::reexports::wayland_server::protocol::wl_output::WlOutput;
+use smithay::reexports::wayland_server::protocol::wl_surface::WlSurface;
+use smithay::wayland::compositor::with_states;
+use smithay::wayland::shell::wlr_layer::{
+    Layer, LayerSurface as WlrLayerSurface, LayerSurfaceData, WlrLayerShellHandler,
+    WlrLayerShellState,
+};
+
+use crate::niri::Niri;
+
+impl WlrLayerShellHandler for Niri {
+    fn shell_state(&mut self) -> &mut WlrLayerShellState {
+        &mut self.layer_shell_state
+    }
+
+    fn new_layer_surface(
+        &mut self,
+        surface: WlrLayerSurface,
+        wl_output: Option<WlOutput>,
+        _layer: Layer,
+        namespace: String,
+    ) {
+        let output = wl_output
+            .as_ref()
+            .and_then(Output::from_resource)
+            .or_else(|| self.monitor_set.active_output().cloned())
+            .unwrap();
+        let mut map = layer_map_for_output(&output);
+        map.map_layer(&LayerSurface::new(surface, namespace))
+            .unwrap();
+    }
+
+    fn layer_destroyed(&mut self, surface: WlrLayerSurface) {
+        let output = if let Some((output, mut map, layer)) =
+            self.monitor_set.outputs().find_map(|o| {
+                let map = layer_map_for_output(o);
+                let layer = map
+                    .layers()
+                    .find(|&layer| layer.layer_surface() == &surface)
+                    .cloned();
+                layer.map(|layer| (o.clone(), map, layer))
+            }) {
+            map.unmap_layer(&layer);
+            Some(output)
+        } else {
+            None
+        };
+        if let Some(output) = output {
+            self.queue_redraw(output);
+        }
+    }
+}
+delegate_layer_shell!(Niri);
+
+impl Niri {
+    pub fn layer_shell_handle_commit(&mut self, surface: &WlSurface) {
+        let Some(output) = self
+            .monitor_set
+            .outputs()
+            .find(|o| {
+                let map = layer_map_for_output(o);
+                map.layer_for_surface(surface, WindowSurfaceType::TOPLEVEL)
+                    .is_some()
+            })
+            .cloned()
+        else {
+            return;
+        };
+
+        let initial_configure_sent = with_states(surface, |states| {
+            states
+                .data_map
+                .get::<LayerSurfaceData>()
+                .unwrap()
+                .lock()
+                .unwrap()
+                .initial_configure_sent
+        });
+
+        let mut map = layer_map_for_output(&output);
+
+        // arrange the layers before sending the initial configure
+        // to respect any size the client may have sent
+        map.arrange();
+        // send the initial configure if relevant
+        if !initial_configure_sent {
+            let layer = map
+                .layer_for_surface(surface, WindowSurfaceType::TOPLEVEL)
+                .unwrap();
+
+            layer.layer_surface().send_configure();
+        }
+        drop(map);
+
+        self.queue_redraw(output);
+    }
+}
diff --git a/src/handlers/mod.rs b/src/handlers/mod.rs
index ab2a1596..4ad355ca 100644
--- a/src/handlers/mod.rs
+++ b/src/handlers/mod.rs
@@ -1,4 +1,5 @@
 mod compositor;
+mod layer_shell;
 mod xdg_shell;
 
 //