feat(macos): Expose the adapter's activation state

adapters/macos/src/adapter.rs

@@ -23,6 +23,19 @@ use std::{ffi::c_void, ptr::null_mut, rc::Rc};
 
 const PLACEHOLDER_ROOT_ID: NodeId = NodeId(0);
 
+/// See [`Adapter::activation_state`].
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ActivationState {
+    /// No assistive technology has activated the adapter yet.
+    Inactive,
+    /// Activated while [`ActivationHandler::request_initial_tree`] returned
+    /// `None`; the next update passed to [`Adapter::update_if_active`] must
+    /// contain a full tree.
+    Placeholder,
+    /// The tree is live.
+    Active,
+}
+
 enum State {
     Inactive {
         view: WeakId<NSView>,
@@ -144,6 +157,17 @@ impl Adapter {
         }
     }
 
+    /// The adapter's current activation state. This lets a host whose
+    /// [`ActivationHandler::request_initial_tree`] returns `None` know when
+    /// the full tree is due without tracking activation itself.
+    pub fn activation_state(&self) -> ActivationState {
+        match &self.state {
+            State::Inactive { .. } => ActivationState::Inactive,
+            State::Placeholder { .. } => ActivationState::Placeholder,
+            State::Active(_) => ActivationState::Active,
+        }
+    }
+
     /// Update the tree state based on whether the window is focused.
     ///
     /// If a [`QueuedEvents`] instance is returned, the caller must call

adapters/macos/src/lib.rs

@@ -11,7 +11,7 @@ mod node;
 mod util;
 
 mod adapter;
-pub use adapter::Adapter;
+pub use adapter::{ActivationState, Adapter};
 
 mod event;
 pub use event::QueuedEvents;

adapters/macos/src/subclass.rs

@@ -22,7 +22,7 @@ use objc2_app_kit::{NSView, NSWindow};
 use objc2_foundation::{NSArray, NSObject, NSPoint};
 use std::{cell::RefCell, ffi::c_void, sync::Mutex};
 
-use crate::{Adapter, event::QueuedEvents};
+use crate::{ActivationState, Adapter, event::QueuedEvents};
 
 static SUBCLASSES: Mutex<Vec<(&'static AnyClass, &'static AnyClass)>> = Mutex::new(Vec::new());
 
@@ -254,6 +254,12 @@ impl SubclassingAdapter {
         let mut state = self.associated.ivars().state.borrow_mut();
         state.adapter.update_view_focus_state(is_focused)
     }
+
+    /// See [`Adapter::activation_state`].
+    pub fn activation_state(&self) -> ActivationState {
+        let state = self.associated.ivars().state.borrow();
+        state.adapter.activation_state()
+    }
 }
 
 impl Drop for SubclassingAdapter {