feat: Android adapter

.github/workflows/ci.yml

@@ -22,6 +22,11 @@ jobs:
       - name: cargo fmt
         run: cargo fmt --all -- --check
 
+      - name: check Java formatting
+        uses: axel-op/googlejavaformat-action@v4
+        with:
+          args: "--aosp --set-exit-if-changed"
+
   cargo-deny:
     runs-on: ubuntu-22.04
     steps:
@@ -81,3 +86,18 @@ jobs:
       - name: cargo test -p accesskit_windows
         if: matrix.os == 'windows-2019'
         run: cargo test -p accesskit_windows
+
+  check-android-dex:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v3
+        with:
+          distribution: 'temurin'
+          java-version: '17'
+      - uses: android-actions/setup-android@v2
+      - run: sdkmanager "platforms;android-30"
+      - run: sdkmanager "build-tools;33.0.2"
+      - run: cp platforms/android/classes.dex platforms/android/classes.dex.orig
+      - run: ./platforms/android/build-dex.sh
+      - run: cmp platforms/android/classes.dex.orig platforms/android/classes.dex

Cargo.toml

@@ -3,6 +3,7 @@ resolver = "2"
 members = [
     "common",
     "consumer",
+    "platforms/android",
     "platforms/atspi-common",
     "platforms/macos",
     "platforms/unix",

README.md

@@ -36,6 +36,7 @@ The current released platform adapters are all at rough feature parity. They don
 
 The following platform adapters are currently available:
 
+* [Android adapter](https://crates.io/crates/accesskit_android): This adapter implements the Java-based Android accessibility API.
 * [macOS adapter](https://crates.io/crates/accesskit_macos): This adapter implements the NSAccessibility protocols in the AppKit framework.
 * [Unix adapter](https://crates.io/crates/accesskit_unix): This adapter implements the AT-SPI D-Bus interfaces, using [zbus](https://github.com/dbus2/zbus), a pure-Rust implementation of D-Bus.
 * [Windows adapter](https://crates.io/crates/accesskit_windows): This adapter implements UI Automation, the current Windows accessibility API.

common/README.md

@@ -7,6 +7,7 @@ To use AccessKit in your application or toolkit, you will also need a platform a
 * [accesskit_windows](https://crates.io/crates/accesskit_windows): exposes an AccessKit tree on Windows using the UI Automation API
 * [accesskit_macos](https://crates.io/crates/accesskit_macos): exposes an AccessKit tree on MacOS through the Cocoa `NSAccessibility` protocol
 * [accesskit_unix](https://crates.io/crates/accesskit_unix): exposes an AccessKit tree on Linux and Unix systems through the AT-SPI protocol
+* [accesskit_android](https://crates.io/crates/accesskit_android): exposes an AccessKit tree on Android through the Java-based Android accessibility API
 * [accesskit_winit](https://crates.io/crates/accesskit_winit): wraps other platform adapters for use with the [winit](https://crates.io/crates/winit) windowing library
 
 Some platform adapters include simple examples.

common/src/lib.rs

@@ -1382,6 +1382,20 @@ impl From<Node> for FrozenNode {
     }
 }
 
+impl From<&FrozenNode> for Node {
+    fn from(node: &FrozenNode) -> Self {
+        Self {
+            role: node.role,
+            actions: node.actions,
+            flags: node.flags,
+            properties: Properties {
+                indices: node.properties.indices,
+                values: node.properties.values.to_vec(),
+            },
+        }
+    }
+}
+
 impl FrozenNode {
     #[inline]
     pub fn role(&self) -> Role {

consumer/src/node.rs

@@ -43,7 +43,7 @@ pub struct Node<'a> {
 }
 
 impl<'a> Node<'a> {
-    pub(crate) fn data(&self) -> &NodeData {
+    pub fn data(&self) -> &NodeData {
         &self.state.data
     }
 
@@ -446,9 +446,7 @@ impl<'a> Node<'a> {
             && self.is_selected().is_none()
     }
 
-    // The future of the `Action` enum is undecided, so keep the following
-    // function private for now.
-    fn supports_action(&self, action: Action) -> bool {
+    pub fn supports_action(&self, action: Action) -> bool {
         self.data().supports_action(action)
     }
 

consumer/src/text.rs

@@ -192,6 +192,10 @@ pub struct Position<'a> {
 }
 
 impl<'a> Position<'a> {
+    pub fn to_raw(self) -> WeakPosition {
+        self.inner.downgrade()
+    }
+
     pub fn inner_node(&self) -> &Node {
         &self.inner.node
     }
@@ -223,6 +227,14 @@ impl<'a> Position<'a> {
         self.is_document_end() || self.inner.is_paragraph_end()
     }
 
+    pub fn is_paragraph_separator(&self) -> bool {
+        if self.is_document_end() {
+            return false;
+        }
+        let next = self.forward_to_character_end();
+        !next.is_document_end() && next.is_paragraph_end()
+    }
+
     pub fn is_page_start(&self) -> bool {
         self.is_document_start()
     }
@@ -292,6 +304,20 @@ impl<'a> Position<'a> {
         lines_before_current
     }
 
+    pub fn biased_to_start(&self) -> Self {
+        Self {
+            root_node: self.root_node,
+            inner: self.inner.biased_to_start(&self.root_node),
+        }
+    }
+
+    pub fn biased_to_end(&self) -> Self {
+        Self {
+            root_node: self.root_node,
+            inner: self.inner.biased_to_end(&self.root_node),
+        }
+    }
+
     pub fn forward_to_character_start(&self) -> Self {
         let pos = self.inner.biased_to_start(&self.root_node);
         Self {
@@ -905,6 +931,16 @@ impl<'a> Node<'a> {
         })
     }
 
+    pub fn text_selection_anchor(&self) -> Option<Position> {
+        self.data().text_selection().map(|selection| {
+            let anchor = InnerPosition::clamped_upgrade(self.tree_state, selection.anchor).unwrap();
+            Position {
+                root_node: *self,
+                inner: anchor,
+            }
+        })
+    }
+
     pub fn text_selection_focus(&self) -> Option<Position> {
         self.data().text_selection().map(|selection| {
             let focus = InnerPosition::clamped_upgrade(self.tree_state, selection.focus).unwrap();

consumer/src/tree.rs

@@ -205,6 +205,14 @@ impl State {
         self.is_host_focused
     }
 
+    pub fn focus_id_in_tree(&self) -> NodeId {
+        self.focus
+    }
+
+    pub fn focus_in_tree(&self) -> Node<'_> {
+        self.node_by_id(self.focus_id_in_tree()).unwrap()
+    }
+
     pub fn focus_id(&self) -> Option<NodeId> {
         self.is_host_focused.then_some(self.focus)
     }

platforms/android/.gitignore

@@ -0,0 +1 @@
+*.class

platforms/android/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "accesskit_android"
+version = "0.1.0"
+authors.workspace = true
+license.workspace = true
+description = "AccessKit UI accessibility infrastructure: Android adapter"
+categories.workspace = true
+keywords = ["gui", "ui", "accessibility"]
+repository.workspace = true
+readme = "README.md"
+edition.workspace = true
+rust-version.workspace = true
+
+[features]
+embedded-dex = []
+
+[dependencies]
+accesskit = { version = "0.17.1", path = "../../common" }
+accesskit_consumer = { version = "0.26.0", path = "../../consumer" }
+jni = "0.21.1"
+log = "0.4.17"
+once_cell = "1.17.1"
+paste = "1.0.12"

platforms/android/README.md

@@ -0,0 +1,10 @@
+# AccessKit Android adapter
+
+This is the Android adapter for [AccessKit](https://accesskit.dev/).
+
+This adapter is implemented in two layers:
+
+* The `Adapter` struct is the core low-level adapter. It provides maximum flexibility in the application threading model, the interface between Java and native code, and the implementation of action callbacks, at the expense of requiring its caller to provide glue code.
+* The `InjectingAdapter` struct injects accessibility into an arbitrary Android view without requiring the view class to be modified, at the expense of depending on a specific Java class and providing less flexibility in the aspects listed above.
+
+The most convenient way to use `InjectingAdapter` is to embed a precompiled `.dex` file containing the associated Java class and its inner classes into the native code. This approach requires the `embedded-dex` Cargo feature.

platforms/android/build-dex.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+set -e -u -o pipefail
+cd `dirname $0`
+ANDROID_JAR=$ANDROID_HOME/platforms/android-30/android.jar
+find java -name '*.class' -delete
+javac --source 8 --target 8 --boot-class-path $ANDROID_JAR -Xlint:deprecation `find java -name '*.java'`
+$ANDROID_HOME/build-tools/33.0.2/d8 --classpath $ANDROID_JAR --output . `find java -name '*.class'`