ndk: Implement HasRawWindowHandle directly on NativeWindow

Crates wrapping the NDK (winit and others), and `NativeWindow` in
particular have to implement `HasRawWindowHandle` on their own wrapper
types, yet the `ndk` should also implement this trait on the
`NativeWindow` type directly for them to reuse.  Or more importantly,
when the "raw" `ndk` crate is used directly.

ndk/Cargo.toml

@@ -35,6 +35,7 @@ test = ["ffi/test", "jni", "jni-glue", "all"]
 bitflags = "1.2.1"
 jni-sys = "0.3.0"
 num_enum = "0.5.1"
+raw-window-handle = "0.4"
 thiserror = "1.0.23"
 
 [dependencies.jni]

ndk/src/native_window.rs

@@ -1,5 +1,6 @@
 //! Bindings for [`ffi::ANativeWindow`]
-use std::ptr::NonNull;
+use raw_window_handle::{AndroidNdkHandle, HasRawWindowHandle, RawWindowHandle};
+use std::{ffi::c_void, ptr::NonNull};
 
 #[derive(Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
 pub struct NativeWindow {
@@ -24,6 +25,14 @@ impl Clone for NativeWindow {
     }
 }
 
+unsafe impl HasRawWindowHandle for NativeWindow {
+    fn raw_window_handle(&self) -> RawWindowHandle {
+        let mut handle = AndroidNdkHandle::empty();
+        handle.a_native_window = self.ptr.as_ptr() as *mut c_void;
+        RawWindowHandle::AndroidNdk(handle)
+    }
+}
+
 impl NativeWindow {
     /// Assumes ownership of `ptr`
     ///