Switch from android_glue to ndk-glue

Additionally remove the Android lifecycle handling code, as winit no longer provides the required callback meaning it does not compile. This fixes compilation on Android. However, there is a caveat: Glutin is no longer able to automatically destroy and create the Surface in response to Android lifecycle events. The application must therefore ensure they only create a Context following a winit Event::Resumed, and they destroy the context when receiving an Event::Suspended.
rust-windowing · May 30, 2022 · 008e5c2 · 008e5c2
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,8 +2,11 @@
 
 - Fix crash when creating OpenGLES context without explicit version.
 - Add `buffer_age` method on `WindowedContext`.
-- On Android, switched from `StaticStructGenerator` to `StructGenerator`, fixing some compilation errors.
 - Return an `Err` instead of panicking when surfaceless GLX context creation fails on Linux.
+- Fix compilation on Android:
+  - Switch from `StaticStructGenerator` to `StructGenerator` to dynamically load symbols.
+  - Replace `android_glue` dependency with `ndk-glue`, and remove broken lifecycle event handling.
+  - Glutin can now be used on Android, however, the application must ensure it only creates the Context following a winit `Event::Resumed` event, and destroys the context in response to a `Event::Suspended` event.
 
 # Version 0.28.0 (2021-12-02)
 

diff --git a/README.md b/README.md
@@ -50,7 +50,7 @@ Glutin is only officially supported on the latest stable version of the Rust com
 
 To compile the examples for android, you have to use the `cargo apk` utility.
 
-See [the `android-rs-glue` repository](https://github.com/rust-windowing/android-rs-glue) for instructions.
+See [`cargo-apk` in the `android-ndk-rs` repository](https://github.com/rust-windowing/android-ndk-rs/cargo-apk) for instructions.
 
 ### Emscripten with asmjs
 

diff --git a/glutin/Cargo.toml b/glutin/Cargo.toml
@@ -25,9 +25,9 @@ lazy_static = "1.3"
 winit = { version = "0.26", default-features = false }
 
 [target.'cfg(target_os = "android")'.dependencies]
-android_glue = "0.2"
 glutin_egl_sys = { version = "0.1.5", path = "../glutin_egl_sys" }
 libloading = "0.7"
+ndk-glue = "0.5" # Keep in sync with winit
 parking_lot = "0.11"
 
 [target.'cfg(target_os = "emscripten")'.dependencies]

diff --git a/glutin/src/api/android/mod.rs b/glutin/src/api/android/mod.rs
@@ -4,7 +4,6 @@ use crate::api::egl::{Context as EglContext, NativeDisplay, SurfaceType as EglSu
 use crate::CreationError::{self, OsError};
 use crate::{Api, ContextError, GlAttributes, PixelFormat, PixelFormatRequirements, Rect};
 
-use crate::platform::android::EventLoopExtAndroid;
 use glutin_egl_sys as ffi;
 use parking_lot::Mutex;
 use winit;
@@ -23,30 +22,6 @@ struct AndroidContext {
 #[derive(Debug)]
 pub struct Context(Arc<AndroidContext>);
 
-#[derive(Debug)]
-struct AndroidSyncEventHandler(Arc<AndroidContext>);
-
-impl android_glue::SyncEventHandler for AndroidSyncEventHandler {
-    fn handle(&mut self, event: &android_glue::Event) {
-        match *event {
-            // 'on_surface_destroyed' Android event can arrive with some delay
-            // because multithreading communication. Because of
-            // that, swap_buffers can be called before processing
-            // 'on_surface_destroyed' event, with the native window
-            // surface already destroyed. EGL generates a BAD_SURFACE error in
-            // this situation. Set stop to true to prevent
-            // swap_buffer call race conditions.
-            android_glue::Event::TermWindow => {
-                let mut stopped = self.0.stopped.as_ref().unwrap().lock();
-                *stopped = true;
-            }
-            _ => {
-                return;
-            }
-        };
-    }
-}
-
 impl Context {
     #[inline]
     pub fn new_windowed<T>(
@@ -57,41 +32,19 @@ impl Context {
     ) -> Result<(winit::window::Window, Self), CreationError> {
         let win = wb.build(el)?;
         let gl_attr = gl_attr.clone().map_sharing(|c| &c.0.egl_context);
-        let nwin = unsafe { android_glue::get_native_window() };
-        if nwin.is_null() {
-            return Err(OsError("Android's native window is null".to_string()));
-        }
+        let nwin = ndk_glue::native_window();
+        let nwin =
+            nwin.as_ref().ok_or_else(|| OsError("Android's native window is null".to_string()))?;
         let native_display = NativeDisplay::Android;
         let egl_context =
             EglContext::new(pf_reqs, &gl_attr, native_display, EglSurfaceType::Window, |c, _| {
                 Ok(c[0])
             })
-            .and_then(|p| p.finish(nwin as *const _))?;
+            .and_then(|p| p.finish(nwin.ptr().as_ptr() as *const _))?;
         let ctx = Arc::new(AndroidContext { egl_context, stopped: Some(Mutex::new(false)) });
 
-        let handler = Box::new(AndroidSyncEventHandler(ctx.clone()));
-        android_glue::add_sync_event_handler(handler);
         let context = Context(ctx.clone());
 
-        el.set_suspend_callback(Some(Box::new(move |suspended| {
-            let mut stopped = ctx.stopped.as_ref().unwrap().lock();
-            *stopped = suspended;
-            if suspended {
-                // Android has stopped the activity or sent it to background.
-                // Release the EGL surface and stop the animation loop.
-                unsafe {
-                    ctx.egl_context.on_surface_destroyed();
-                }
-            } else {
-                // Android has started the activity or sent it to foreground.
-                // Restore the EGL surface and animation loop.
-                unsafe {
-                    let nwin = android_glue::get_native_window();
-                    ctx.egl_context.on_surface_created(nwin as *const _);
-                }
-            }
-        })));
-
         Ok((win, context))
     }
 

diff --git a/glutin/src/api/egl/mod.rs b/glutin/src/api/egl/mod.rs
@@ -161,8 +161,6 @@ pub struct Context {
     surface: Option<Mutex<ffi::egl::types::EGLSurface>>,
     api: Api,
     pixel_format: PixelFormat,
-    #[cfg(target_os = "android")]
-    config_id: ffi::egl::types::EGLConfig,
 }
 
 fn get_egl_version(
@@ -511,52 +509,6 @@ impl Context {
         self.display
     }
 
-    // Handle Android Life Cycle.
-    // Android has started the activity or sent it to foreground.
-    // Create a new surface and attach it to the recreated ANativeWindow.
-    // Restore the EGLContext.
-    #[cfg(target_os = "android")]
-    pub unsafe fn on_surface_created(&self, nwin: ffi::EGLNativeWindowType) {
-        let egl = EGL.as_ref().unwrap();
-        let mut surface = self.surface.as_ref().unwrap().lock();
-        if *surface != ffi::egl::NO_SURFACE {
-            return;
-        }
-        *surface = egl.CreateWindowSurface(self.display, self.config_id, nwin, std::ptr::null());
-        if surface.is_null() {
-            panic!("on_surface_created: eglCreateWindowSurface failed with 0x{:x}", egl.GetError())
-        }
-        let ret = egl.MakeCurrent(self.display, *surface, *surface, self.context);
-        if ret == 0 {
-            panic!("on_surface_created: eglMakeCurrent failed with 0x{:x}", egl.GetError())
-        }
-    }
-
-    // Handle Android Life Cycle.
-    // Android has stopped the activity or sent it to background.
-    // Release the surface attached to the destroyed ANativeWindow.
-    // The EGLContext is not destroyed so it can be restored later.
-    #[cfg(target_os = "android")]
-    pub unsafe fn on_surface_destroyed(&self) {
-        let egl = EGL.as_ref().unwrap();
-        let mut surface = self.surface.as_ref().unwrap().lock();
-        if *surface == ffi::egl::NO_SURFACE {
-            return;
-        }
-        let ret = egl.MakeCurrent(
-            self.display,
-            ffi::egl::NO_SURFACE,
-            ffi::egl::NO_SURFACE,
-            ffi::egl::NO_CONTEXT,
-        );
-        if ret == 0 {
-            panic!("on_surface_destroyed: eglMakeCurrent failed with 0x{:x}", egl.GetError())
-        }
-
-        egl.DestroySurface(self.display, *surface);
-        *surface = ffi::egl::NO_SURFACE;
-    }
-
     #[inline]
     pub fn get_proc_address(&self, addr: &str) -> *const core::ffi::c_void {
         let egl = EGL.as_ref().unwrap();
@@ -991,8 +943,6 @@ impl<'a> ContextPrototype<'a> {
             surface: surface.map(|s| Mutex::new(s)),
             api: self.api,
             pixel_format: self.pixel_format,
-            #[cfg(target_os = "android")]
-            config_id: self.config_id,
         })
     }
 }