ndk-glue: Finish native activity after returning from main()

When an application returns its control flow back from `main()` it is
generally assumed to be done polling on the looper and wishes to
terminate.  Android is made aware of this by calling
`ANativeActivity_finish`, otherwise it'll continue sending input events
and eventually ANR as the app didn't consume them anymore.

ndk-glue/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Reexport `android_logger` and `log` from the crate root for `ndk-macro` to use.
 - Use new `FdEvents` `bitflags` for looper file descriptor events.
+- **Breaking** `NativeActivity` is now dropped (calling `ANativeActivity_finish()`
+  under the hood) after returning from `fn main()`.
 
 # 0.3.0 (2021-01-30)
 

ndk-glue/src/lib.rs

@@ -198,7 +198,11 @@ pub unsafe fn init(
             signal_looper_ready.notify_one();
         }
 
-        main()
+        main();
+
+        NATIVE_ACTIVITY
+            .take()
+            .expect("Native activity should not have been taken before main() returns!")
     });
 
     // Don't return from this function (`ANativeActivity_onCreate`) until the thread

ndk/CHANGELOG.md

@@ -1,6 +1,8 @@
 # Unreleased
 
 - **Breaking** Model looper file descriptor events integer as `bitflags`.
+- **Breaking** `NativeActivity` now calls `ANativeActivity_finish()` on
+  drop instead of relying on `NativeActivity::finish()` to be called.
 
 # 0.3.0 (2021-01-30)
 

ndk/src/native_activity.rs

@@ -130,11 +130,6 @@ impl NativeActivity {
 /// The relevant NDK docs can be found
 /// [here.](https://developer.android.com/ndk/reference/group/native-activity)
 impl NativeActivity {
-    /// Sends a destroy event to the activity and stops it.
-    pub fn finish(&self) {
-        unsafe { ffi::ANativeActivity_finish(self.ptr.as_ptr()) }
-    }
-
     /// Shows the IME (the on-screen keyboard).
     ///
     /// If `force` is true, the `SHOW_FORCED` flag is used; otherwise, the `SHOW_IMPLICIT` flag is
@@ -176,6 +171,13 @@ impl NativeActivity {
     }*/
 }
 
+impl Drop for NativeActivity {
+    /// Sends a destroy event to the activity and stops it.
+    fn drop(&mut self) {
+        unsafe { ffi::ANativeActivity_finish(self.ptr.as_ptr()) }
+    }
+}
+
 /*#[derive(Debug, Clone, Copy, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]
 #[repr(u32)]
 pub enum WindowFormat {