android: capture current keyboard height

expose a new virtual_keyboard_height function under notedeck::platform::android

which gets the current height of the virtual keyboard. We can use this
to tranlate the view out of the way

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck/Cargo.toml

@@ -6,6 +6,7 @@ description = "The APIs and data structures used by notedeck apps"
 
 [dependencies]
 nostrdb = { workspace = true }
+jni = { workspace = true }
 url = { workspace = true }
 strum = { workspace = true }
 strum_macros = { workspace = true }
@@ -35,5 +36,8 @@ tempfile = { workspace = true }
 [target.'cfg(target_os = "macos")'.dependencies]
 security-framework = { workspace = true }
 
+[target.'cfg(target_os = "android")'.dependencies]
+jni = { workspace = true }
+
 [features]
 profiling = ["puffin", "puffin_egui"]

crates/notedeck/src/lib.rs

@@ -11,6 +11,7 @@ mod muted;
 pub mod note;
 mod notecache;
 mod persist;
+pub mod platform;
 pub mod relay_debug;
 pub mod relayspec;
 mod result;

crates/notedeck/src/platform/android.rs

@@ -0,0 +1,26 @@
+use std::sync::atomic::{AtomicI32, Ordering};
+use tracing::debug;
+
+// Thread-safe static global
+static KEYBOARD_HEIGHT: AtomicI32 = AtomicI32::new(0);
+
+/// This function is called by our main notedeck android activity when the
+/// keyboard height changes. You can use [`virtual_keyboard_height`] to access
+/// this
+#[no_mangle]
+pub extern "C" fn Java_com_damus_notedeck_KeyboardHeightHelper_nativeKeyboardHeightChanged(
+    _env: jni::JNIEnv,
+    _class: jni::objects::JClass,
+    height: jni::sys::jint,
+) {
+    debug!("updating virtual keyboard height {}", height);
+
+    // Convert and store atomically
+    KEYBOARD_HEIGHT.store(height as i32, Ordering::SeqCst);
+}
+
+/// Gets the current Android virtual keyboard height. Useful for transforming
+/// the view
+pub fn virtual_keyboard_height() -> i32 {
+    KEYBOARD_HEIGHT.load(Ordering::SeqCst)
+}

crates/notedeck/src/platform/mod.rs

@@ -0,0 +1,2 @@
+#[cfg(target_os = "android")]
+pub mod android;