feat(platforms/macos): Basic macOS platform adapter (#158)

The major missing feature at this point is text editing support.

Co-authored-by: Mads Marquart <mads@marquart.dk>

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
     "common",
     "consumer",
+    "platforms/macos",
     "platforms/windows",
     "platforms/winit",
 ]

consumer/src/node.rs

@@ -12,7 +12,7 @@ use std::{iter::FusedIterator, ops::Deref, sync::Arc};
 
 use accesskit::kurbo::{Affine, Point, Rect};
 use accesskit::{
-    CheckedState, DefaultActionVerb, Live, Node as NodeData, NodeId, Role, TextSelection,
+    Action, CheckedState, DefaultActionVerb, Live, Node as NodeData, NodeId, Role, TextSelection,
 };
 
 use crate::iterators::{
@@ -275,6 +275,10 @@ impl<'a> Node<'a> {
         parent_transform * self.direct_transform()
     }
 
+    pub fn has_bounds(&self) -> bool {
+        self.data().bounds.is_some()
+    }
+
     /// Returns the node's transformed bounding box relative to the tree's
     /// container (e.g. window).
     pub fn bounding_box(&self) -> Option<Rect> {
@@ -464,6 +468,20 @@ impl NodeState {
             && !self.supports_toggle()
             && !self.supports_expand_collapse()
     }
+
+    // The future of the `Action` enum is undecided, so keep the following
+    // function private for now.
+    fn supports_action(&self, action: Action) -> bool {
+        self.data().actions.contains(action)
+    }
+
+    pub fn supports_increment(&self) -> bool {
+        self.supports_action(Action::Increment)
+    }
+
+    pub fn supports_decrement(&self) -> bool {
+        self.supports_action(Action::Decrement)
+    }
 }
 
 impl<'a> Node<'a> {

consumer/src/tree.rs

@@ -397,6 +397,22 @@ impl Tree {
             data: Some(ActionData::SetTextSelection(selection)),
         })
     }
+
+    pub fn increment(&self, target: NodeId) {
+        self.action_handler.do_action(ActionRequest {
+            action: Action::Increment,
+            target,
+            data: None,
+        })
+    }
+
+    pub fn decrement(&self, target: NodeId) {
+        self.action_handler.do_action(ActionRequest {
+            action: Action::Decrement,
+            target,
+            data: None,
+        })
+    }
 }
 
 #[cfg(test)]

platforms/macos/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "accesskit_macos"
+version = "0.0.0"
+authors = ["Matt Campbell <mattcampbell@pobox.com>"]
+license = "MIT/Apache-2.0"
+description = "AccessKit UI accessibility infrastructure: macOS adapter"
+categories = ["gui"]
+keywords = ["gui", "ui", "accessibility"]
+repository = "https://github.com/AccessKit/accesskit"
+readme = "README.md"
+edition = "2021"
+
+[dependencies]
+accesskit = { version = "0.8.0", path = "../../common" }
+accesskit_consumer = { version = "0.8.0", path = "../../consumer" }
+objc2 = "0.3.0-beta.3"
+once_cell = "1.13.0"
+parking_lot = "0.12.1"

platforms/macos/README.md

@@ -0,0 +1,3 @@
+# AccessKit macOS adapter
+
+This is the macOS adapter for [AccessKit](https://accesskit.dev/). It exposes an AccessKit accessibility tree through the Cocoa `NSAccessibility` protocol.

platforms/macos/src/adapter.rs

@@ -0,0 +1,127 @@
+// Copyright 2022 The AccessKit Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (found in
+// the LICENSE-APACHE file) or the MIT license (found in
+// the LICENSE-MIT file), at your option.
+
+use accesskit::{kurbo::Point, ActionHandler, TreeUpdate};
+use accesskit_consumer::{FilterResult, Tree};
+use objc2::{
+    foundation::{MainThreadMarker, NSArray, NSObject, NSPoint},
+    rc::{Id, Shared, WeakId},
+};
+use once_cell::unsync::Lazy;
+use std::{ffi::c_void, ptr::null_mut, rc::Rc};
+
+use crate::{appkit::NSView, context::Context, event::QueuedEvents, node::filter};
+
+pub struct Adapter {
+    context: Lazy<Rc<Context>, Box<dyn FnOnce() -> Rc<Context>>>,
+}
+
+impl Adapter {
+    /// Create a new macOS adapter. This function must be called on
+    /// the main thread.
+    ///
+    /// # Safety
+    ///
+    /// `view` must be a valid, unreleased pointer to an `NSView`.
+    pub unsafe fn new(
+        view: *mut c_void,
+        source: Box<dyn FnOnce() -> TreeUpdate>,
+        action_handler: Box<dyn ActionHandler>,
+    ) -> Self {
+        let view = unsafe { Id::retain(view as *mut NSView) }.unwrap();
+        let view = WeakId::new(&view);
+        let mtm = MainThreadMarker::new().unwrap();
+        Self {
+            context: Lazy::new(Box::new(move || {
+                let tree = Tree::new(source(), action_handler);
+                Context::new(view, tree, mtm)
+            })),
+        }
+    }
+
+    /// Initialize the tree if it hasn't been initialized already, then apply
+    /// the provided update.
+    ///
+    /// The caller must call [`QueuedEvents::raise`] on the return value.
+    ///
+    /// This method may be safely called on any thread, but refer to
+    /// [`QueuedEvents::raise`] for restrictions on the context in which
+    /// it should be called.
+    pub fn update(&self, update: TreeUpdate) -> QueuedEvents {
+        let context = Lazy::force(&self.context);
+        context.update(update)
+    }
+
+    /// If and only if the tree has been initialized, call the provided function
+    /// and apply the resulting update.
+    ///
+    /// If a [`QueuedEvents`] instance is returned, the caller must call
+    /// [`QueuedEvents::raise`] on it.
+    ///
+    /// This method may be safely called on any thread, but refer to
+    /// [`QueuedEvents::raise`] for restrictions on the context in which
+    /// it should be called.
+    pub fn update_if_active(&self, updater: impl FnOnce() -> TreeUpdate) -> Option<QueuedEvents> {
+        Lazy::get(&self.context).map(|context| context.update(updater()))
+    }
+
+    pub fn view_children(&self) -> *mut NSArray<NSObject> {
+        let context = Lazy::force(&self.context);
+        let state = context.tree.read();
+        let node = state.root();
+        let platform_nodes = if filter(&node) == FilterResult::Include {
+            vec![Id::into_super(Id::into_super(
+                context.get_or_create_platform_node(node.id()),
+            ))]
+        } else {
+            node.filtered_children(filter)
+                .map(|node| {
+                    Id::into_super(Id::into_super(
+                        context.get_or_create_platform_node(node.id()),
+                    ))
+                })
+                .collect::<Vec<Id<NSObject, Shared>>>()
+        };
+        let array = NSArray::from_vec(platform_nodes);
+        Id::autorelease_return(array)
+    }
+
+    pub fn focus(&self) -> *mut NSObject {
+        let context = Lazy::force(&self.context);
+        let state = context.tree.read();
+        if let Some(node) = state.focus() {
+            if filter(&node) == FilterResult::Include {
+                return Id::autorelease_return(context.get_or_create_platform_node(node.id()))
+                    as *mut _;
+            }
+        }
+        null_mut()
+    }
+
+    pub fn hit_test(&self, point: NSPoint) -> *mut NSObject {
+        let context = Lazy::force(&self.context);
+        let view = match context.view.load() {
+            Some(view) => view,
+            None => {
+                return null_mut();
+            }
+        };
+
+        let window = view.window().unwrap();
+        let point = window.convert_point_from_screen(point);
+        let point = view.convert_point_from_view(point, None);
+        let view_bounds = view.bounds();
+        let point = Point::new(point.x, view_bounds.size.height - point.y);
+
+        let state = context.tree.read();
+        let root = state.root();
+        let point = root.transform().inverse() * point;
+        if let Some(node) = root.node_at_point(point, &filter) {
+            return Id::autorelease_return(context.get_or_create_platform_node(node.id()))
+                as *mut _;
+        }
+        null_mut()
+    }
+}

platforms/macos/src/appkit/accessibility_constants.rs

@@ -0,0 +1,47 @@
+// Copyright 2022 The AccessKit Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (found in
+// the LICENSE-APACHE file) or the MIT license (found in
+// the LICENSE-MIT file), at your option.
+
+use objc2::foundation::NSString;
+
+#[link(name = "AppKit", kind = "framework")]
+extern "C" {
+    // Notifications
+    pub(crate) static NSAccessibilityUIElementDestroyedNotification: &'static NSString;
+    pub(crate) static NSAccessibilityFocusedUIElementChangedNotification: &'static NSString;
+    pub(crate) static NSAccessibilityTitleChangedNotification: &'static NSString;
+    pub(crate) static NSAccessibilityValueChangedNotification: &'static NSString;
+
+    // Roles
+    pub(crate) static NSAccessibilityButtonRole: &'static NSString;
+    pub(crate) static NSAccessibilityCheckBoxRole: &'static NSString;
+    pub(crate) static NSAccessibilityCellRole: &'static NSString;
+    pub(crate) static NSAccessibilityColorWellRole: &'static NSString;
+    pub(crate) static NSAccessibilityColumnRole: &'static NSString;
+    pub(crate) static NSAccessibilityComboBoxRole: &'static NSString;
+    pub(crate) static NSAccessibilityGroupRole: &'static NSString;
+    pub(crate) static NSAccessibilityImageRole: &'static NSString;
+    pub(crate) static NSAccessibilityIncrementorRole: &'static NSString;
+    pub(crate) static NSAccessibilityLevelIndicatorRole: &'static NSString;
+    pub(crate) static NSAccessibilityLinkRole: &'static NSString;
+    pub(crate) static NSAccessibilityListRole: &'static NSString;
+    pub(crate) static NSAccessibilityMenuRole: &'static NSString;
+    pub(crate) static NSAccessibilityMenuBarRole: &'static NSString;
+    pub(crate) static NSAccessibilityMenuItemRole: &'static NSString;
+    pub(crate) static NSAccessibilityOutlineRole: &'static NSString;
+    pub(crate) static NSAccessibilityPopUpButtonRole: &'static NSString;
+    pub(crate) static NSAccessibilityProgressIndicatorRole: &'static NSString;
+    pub(crate) static NSAccessibilityRadioButtonRole: &'static NSString;
+    pub(crate) static NSAccessibilityRadioGroupRole: &'static NSString;
+    pub(crate) static NSAccessibilityRowRole: &'static NSString;
+    pub(crate) static NSAccessibilityScrollBarRole: &'static NSString;
+    pub(crate) static NSAccessibilitySliderRole: &'static NSString;
+    pub(crate) static NSAccessibilitySplitterRole: &'static NSString;
+    pub(crate) static NSAccessibilityStaticTextRole: &'static NSString;
+    pub(crate) static NSAccessibilityTabGroupRole: &'static NSString;
+    pub(crate) static NSAccessibilityTableRole: &'static NSString;
+    pub(crate) static NSAccessibilityTextFieldRole: &'static NSString;
+    pub(crate) static NSAccessibilityToolbarRole: &'static NSString;
+    pub(crate) static NSAccessibilityUnknownRole: &'static NSString;
+}

platforms/macos/src/appkit/accessibility_element.rs

@@ -0,0 +1,15 @@
+// Copyright 2022 The AccessKit Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (found in
+// the LICENSE-APACHE file) or the MIT license (found in
+// the LICENSE-MIT file), at your option.
+
+use objc2::{extern_class, foundation::NSObject, ClassType};
+
+extern_class!(
+    #[derive(Debug)]
+    pub struct NSAccessibilityElement;
+
+    unsafe impl ClassType for NSAccessibilityElement {
+        type Super = NSObject;
+    }
+);

platforms/macos/src/appkit/accessibility_functions.rs

@@ -0,0 +1,11 @@
+// Copyright 2022 The AccessKit Authors. All rights reserved.
+// Licensed under the Apache License, Version 2.0 (found in
+// the LICENSE-APACHE file) or the MIT license (found in
+// the LICENSE-MIT file), at your option.
+
+use objc2::foundation::{NSObject, NSString};
+
+#[link(name = "AppKit", kind = "framework")]
+extern "C" {
+    pub(crate) fn NSAccessibilityPostNotification(element: &NSObject, notification: &NSString);
+}