feat(android): add zoom slider

fix(android): gray screen bug

apps/tauri/src-tauri/src/accessibility_backend.rs

@@ -0,0 +1,135 @@
+#[cfg(not(target_os = "android"))]
+const DEFAULT_INITIAL_SCALE: i32 = 290;
+const MIN_INITIAL_SCALE: i32 = 210;
+const MAX_INITIAL_SCALE: i32 = 500;
+
+#[tauri::command]
+pub fn accessibility_get_initial_scale() -> Result<i32, String> {
+    android_get_initial_scale()
+}
+
+#[tauri::command]
+pub fn accessibility_set_initial_scale(initial_scale: i32) -> Result<(), String> {
+    if !(MIN_INITIAL_SCALE..=MAX_INITIAL_SCALE).contains(&initial_scale) {
+        return Err(format!(
+            "Initial scale must be between {MIN_INITIAL_SCALE} and {MAX_INITIAL_SCALE}"
+        ));
+    }
+
+    android_set_initial_scale(initial_scale)
+}
+
+#[cfg(not(target_os = "android"))]
+fn android_get_initial_scale() -> Result<i32, String> {
+    Ok(DEFAULT_INITIAL_SCALE)
+}
+
+#[cfg(not(target_os = "android"))]
+fn android_set_initial_scale(_: i32) -> Result<(), String> {
+    Ok(())
+}
+
+#[cfg(target_os = "android")]
+mod android {
+    use std::sync::OnceLock;
+
+    use jni::{
+        jni_sig, jni_str,
+        objects::{Global, JClass, JObject, JValue},
+        Env, EnvUnowned, JavaVM,
+    };
+
+    struct Host {
+        vm: JavaVM,
+        context: Global<JObject<'static>>,
+        bridge: Global<JObject<'static>>,
+    }
+
+    static HOST: OnceLock<Host> = OnceLock::new();
+
+    fn attach(env: &mut Env, context: JObject) -> Result<(), String> {
+        if HOST.get().is_some() {
+            return Ok(());
+        }
+
+        let class = env
+            .find_class(jni_str!("net/tensamin/client/NativeAccessibilityBridge"))
+            .map_err(|error| error.to_string())?;
+        let bridge = env
+            .get_static_field(
+                class,
+                jni_str!("INSTANCE"),
+                jni_sig!("Lnet/tensamin/client/NativeAccessibilityBridge;"),
+            )
+            .and_then(|value| value.l())
+            .map_err(|error| error.to_string())?;
+
+        HOST.set(Host {
+            vm: env.get_java_vm().map_err(|error| error.to_string())?,
+            context: env
+                .new_global_ref(context)
+                .map_err(|error| error.to_string())?,
+            bridge: env
+                .new_global_ref(bridge)
+                .map_err(|error| error.to_string())?,
+        })
+        .map_err(|_| "Android accessibility host is already attached".to_string())
+    }
+
+    fn with_env<T>(call: impl FnOnce(&mut Env, &Host) -> Result<T, String>) -> Result<T, String> {
+        let host = HOST
+            .get()
+            .ok_or("Android accessibility host is not attached")?;
+        host.vm
+            .attach_current_thread(|env| Ok::<_, jni::errors::Error>(call(env, host)))
+            .map_err(|error| error.to_string())?
+    }
+
+    pub fn get_initial_scale() -> Result<i32, String> {
+        with_env(|env, host| {
+            env.call_method(
+                host.bridge.as_obj(),
+                jni_str!("getInitialScale"),
+                jni_sig!("(Landroid/content/Context;)I"),
+                &[JValue::Object(host.context.as_obj())],
+            )
+            .and_then(|value| value.i())
+            .map_err(|error| error.to_string())
+        })
+    }
+
+    pub fn set_initial_scale(initial_scale: i32) -> Result<(), String> {
+        with_env(|env, host| {
+            env.call_method(
+                host.bridge.as_obj(),
+                jni_str!("setInitialScale"),
+                jni_sig!("(Landroid/content/Context;I)V"),
+                &[
+                    JValue::Object(host.context.as_obj()),
+                    JValue::Int(initial_scale),
+                ],
+            )
+            .map_err(|error| error.to_string())?;
+            Ok(())
+        })
+    }
+
+    #[no_mangle]
+    pub extern "system" fn Java_net_tensamin_client_NativeAccessibilityBridge_nativeAttach<
+        'caller,
+    >(
+        mut env: EnvUnowned<'caller>,
+        _class: JClass,
+        context: JObject<'caller>,
+    ) {
+        let _ = env.with_env(|env| {
+            let _ = attach(env, context);
+            Ok::<_, jni::errors::Error>(())
+        });
+    }
+}
+
+#[cfg(target_os = "android")]
+use android::{
+    get_initial_scale as android_get_initial_scale, set_initial_scale as android_set_initial_scale,
+};