ndk,ndk-glue: Do not pass Looper ident as userdata pointer (#112)

* ndk,ndk-glue: Do not pass Looper ident as userdata pointer

The value of `0` or `1` is not a valid pointer to a userdata structure.
Not that it has to be, but with the nasty consequence that winit Android
code was accidentally reinterpreting this pointer as integer to extract
the identifier from, instead of using the appropriate `ident` field
directly. After that is addressed in winit we can set the pointer back
to 0 cleanly (and prepare for a potential pointer to some user data that
may be passed in the future).

Also add some constants to document these "special" identifiers.

* ndk,ndk-glue: Bump version to 0.3.0

ndk-glue/CHANGELOG.md

@@ -1,5 +1,12 @@
 # Unreleased
 
+# 0.3.0 (2021-01-30)
+
+- **Breaking** Looper `ident` not passed in `data` pointer anymore.
+  If you are relying on `Poll::Event::data` to tell event fd and
+  input queue apart, please use `Poll::Event::ident` and the new
+  constants introduced in `ndk-glue`!
+
 # 0.2.1 (2020-10-15)
 
 - Fix documentation build on docs.rs

ndk-glue/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ndk-glue"
-version = "0.2.1"
+version = "0.3.0"
 authors = ["The Rust Windowing contributors"]
 edition = "2018"
 description = "Startup code for android binaries"
@@ -12,7 +12,7 @@ homepage = "https://github.com/rust-windowing/android-ndk-rs"
 repository = "https://github.com/rust-windowing/android-ndk-rs"
 
 [dependencies]
-ndk = { path = "../ndk", version = "0.2.1" }
+ndk = { path = "../ndk", version = "0.3.0" }
 ndk-sys = { path = "../ndk-sys", version = "0.2.1" }
 ndk-macro = { path = "../ndk-macro", version = "0.2.0" }
 lazy_static = "1.4.0"

ndk-glue/src/lib.rs

@@ -16,6 +16,18 @@ use std::thread;
 
 pub use ndk_macro::main;
 
+/// `ndk-glue` macros register the reading end of an event pipe with the
+/// main [`ThreadLooper`] under this `ident`.
+/// When returned from [`ThreadLooper::poll_*`](ThreadLooper::poll_once)
+/// an event can be retrieved from [`poll_events()`].
+pub const NDK_GLUE_LOOPER_EVENT_PIPE_IDENT: i32 = 0;
+
+/// The [`InputQueue`] received from Android is registered with the main
+/// [`ThreadLooper`] under this `ident`.
+/// When returned from [`ThreadLooper::poll_*`](ThreadLooper::poll_once)
+/// an event can be retrieved from [`input_queue()`].
+pub const NDK_GLUE_LOOPER_INPUT_QUEUE_IDENT: i32 = 1;
+
 pub fn android_log(level: Level, tag: &CStr, msg: &CStr) {
     let prio = match level {
         Level::Error => ndk_sys::android_LogPriority_ANDROID_LOG_ERROR,
@@ -164,7 +176,12 @@ pub unsafe fn init(
         let looper = ThreadLooper::prepare();
         let foreign = looper.into_foreign();
         foreign
-            .add_fd(PIPE[0], 0, ALOOPER_EVENT_INPUT as _, 0 as _)
+            .add_fd(
+                PIPE[0],
+                NDK_GLUE_LOOPER_EVENT_PIPE_IDENT,
+                ALOOPER_EVENT_INPUT as _,
+                std::ptr::null_mut(),
+            )
             .unwrap();
         LOOPER = Some(foreign);
         main()
@@ -253,7 +270,7 @@ unsafe extern "C" fn on_input_queue_created(
 ) {
     let input_queue = InputQueue::from_ptr(NonNull::new(queue).unwrap());
     let looper = LOOPER.as_ref().unwrap();
-    input_queue.attach_looper(looper, 1);
+    input_queue.attach_looper(looper, NDK_GLUE_LOOPER_INPUT_QUEUE_IDENT);
     *INPUT_QUEUE.write().unwrap() = Some(input_queue);
     wake(activity, Event::InputQueueCreated);
 }

ndk/CHANGELOG.md

@@ -1,5 +1,14 @@
 # Unreleased
 
+# 0.3.0 (2021-01-30)
+
+- **Breaking** Looper `ident` not passed in `data` pointer anymore.
+  `attach_looper` now only sets the `ident` field when attaching an
+  `InputQueue` to a `ForeignLooper`.
+  If you are relying on `Poll::Event::data` to tell event fd and
+  input queue apart, please use `Poll::Event::ident` and the new
+  constants introduced in `ndk-glue`!
+
 # 0.2.1 (2020-10-15)
 
 - Fix documentation build on docs.rs

ndk/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ndk"
-version = "0.2.1"
+version = "0.3.0"
 authors = ["The Rust Windowing contributors"]
 edition = "2018"
 description = "Safe Rust bindings to the Android NDK"

ndk/src/input_queue.rs

@@ -71,14 +71,14 @@ impl InputQueue {
         }
     }
 
-    pub fn attach_looper(&self, looper: &ForeignLooper, id: u32) {
+    pub fn attach_looper(&self, looper: &ForeignLooper, id: i32) {
         unsafe {
             ffi::AInputQueue_attachLooper(
                 self.ptr.as_ptr(),
                 looper.ptr().as_ptr(),
-                id as _,
+                id,
                 None,
-                id as _,
+                std::ptr::null_mut(),
             );
         }
     }