ndk-glue: Replace ancient lazy_static crate with once_cell (#285)

Piggybacking on the [motivation in winit]: `lazy_static!` is a macro
whereas `once_cell` achieves the same using generics.  Its
implementation has also been [proposed for inclusion in `std`], making
it easier for us to switch to a standardized version if/when that
happens.  The author of that winit PR is making this change to many more
crates, slowly turning the scales in favour of `once_cell` in our
dependency tree too.

Furthermore `lazy_static` hasn't published any updates for 3 years, and
the new syntax is closer for dropping this wrapping completely when the
necessary constructors become `const` (i.e. switching to `parking_lot`
will give us a [`const fn new()` on `RwLock`]) or this feature lands in stable
`std`.

[motivation in winit]: rust-windowing/winit#2313
[proposed for inclusion in `std`]: rust-lang/rust#74465
[`const fn new()` on `RwLock`]: https://docs.rs/lock_api/latest/lock_api/struct.RwLock.html#method.new

ndk-glue/Cargo.toml

@@ -16,7 +16,7 @@ ndk = { path = "../ndk", version = "0.6.0" }
 ndk-context = { path = "../ndk-context", version = "0.1.1" }
 ndk-macro = { path = "../ndk-macro", version = "0.3.0" }
 ndk-sys = { path = "../ndk-sys", version = "0.3.0" }
-lazy_static = "1.4.0"
+once_cell = "1"
 libc = "0.2.84"
 log = "0.4.14"
 android_logger = { version = "0.10.1", optional = true }

ndk-glue/src/lib.rs

@@ -1,10 +1,10 @@
-use lazy_static::lazy_static;
 use log::Level;
 use ndk::input_queue::InputQueue;
 use ndk::looper::{FdEvent, ForeignLooper, ThreadLooper};
 use ndk::native_activity::NativeActivity;
 use ndk::native_window::NativeWindow;
 use ndk_sys::{AInputQueue, ANativeActivity, ANativeWindow, ARect};
+use once_cell::sync::Lazy;
 use std::ffi::{CStr, CString};
 use std::fs::File;
 use std::io::{BufRead, BufReader};
@@ -46,12 +46,10 @@ pub fn android_log(level: Level, tag: &CStr, msg: &CStr) {
     }
 }
 
-lazy_static! {
-    static ref NATIVE_WINDOW: RwLock<Option<NativeWindow>> = Default::default();
-    static ref INPUT_QUEUE: RwLock<Option<InputQueue>> = Default::default();
-    static ref CONTENT_RECT: RwLock<Rect> = Default::default();
-    static ref LOOPER: Mutex<Option<ForeignLooper>> = Default::default();
-}
+static NATIVE_WINDOW: Lazy<RwLock<Option<NativeWindow>>> = Lazy::new(Default::default);
+static INPUT_QUEUE: Lazy<RwLock<Option<InputQueue>>> = Lazy::new(Default::default);
+static CONTENT_RECT: Lazy<RwLock<Rect>> = Lazy::new(Default::default);
+static LOOPER: Lazy<Mutex<Option<ForeignLooper>>> = Lazy::new(Default::default);
 
 static mut NATIVE_ACTIVITY: Option<NativeActivity> = None;
 
@@ -72,13 +70,11 @@ pub fn content_rect() -> Rect {
     CONTENT_RECT.read().unwrap().clone()
 }
 
-lazy_static! {
-    static ref PIPE: [RawFd; 2] = {
-        let mut pipe: [RawFd; 2] = Default::default();
-        unsafe { libc::pipe(pipe.as_mut_ptr()) };
-        pipe
-    };
-}
+static PIPE: Lazy<[RawFd; 2]> = Lazy::new(|| {
+    let mut pipe: [RawFd; 2] = Default::default();
+    unsafe { libc::pipe(pipe.as_mut_ptr()) };
+    pipe
+});
 
 pub fn poll_events() -> Option<Event> {
     unsafe {