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ndk/native_window: Add bindings to convert to and from Java Surface representation #272

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May 14, 2022
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ndk/native_window: Add bindings to convert to and from Java Surface representation #272

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27 changes: 25 additions & 2 deletions ndk/src/native_window.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
//! Bindings for [`ffi::ANativeWindow`]

use jni_sys::{jobject, JNIEnv};
use std::ptr::NonNull;

#[derive(Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
Expand Down Expand Up @@ -45,14 +47,35 @@ impl NativeWindow {
pub fn ptr(&self) -> NonNull<ffi::ANativeWindow> {
self.ptr
}
}

impl NativeWindow {
pub fn height(&self) -> i32 {
unsafe { ffi::ANativeWindow_getHeight(self.ptr.as_ptr()) }
}

pub fn width(&self) -> i32 {
unsafe { ffi::ANativeWindow_getWidth(self.ptr.as_ptr()) }
}

/// Return the [`NativeWindow`] associated with a JNI [`android.view.Surface`] pointer.
///
/// # Safety
/// By calling this function, you assert that `env` is a valid pointer to a [`JNIEnv`] and
/// `surface` is a valid pointer to an [`android.view.Surface`].
///
/// [`android.view.Surface`]: https://developer.android.com/reference/android/view/Surface
pub unsafe fn from_surface(env: *mut JNIEnv, surface: jobject) -> Option<Self> {
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Do we somehow need to release this surface? (ANativeWindow_release)

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Nope! You'll get a NativeWindow here which already implements acquire/release semantics in clone() and drop(), respectively.

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I don't know if you need to retain the life of the surface JNI object (in Java land), though - https://developer.android.com/ndk/reference/group/native-activity#anativewindow_fromsurface doesn't specify 😞

All I know is that to_surface gives you a Java Surface which internally keeps the NativeWindow alive, so you don't need to do that at least.

let ptr = ffi::ANativeWindow_fromSurface(env, surface);
Some(Self::from_ptr(NonNull::new(ptr)?))
}

/// Return a JNI [`android.view.Surface`] pointer derived from this [`NativeWindow`].
///
/// # Safety
/// By calling this function, you assert that `env` is a valid pointer to a [`JNIEnv`].
///
/// [`android.view.Surface`]: https://developer.android.com/reference/android/view/Surface
#[cfg(feature = "api-level-26")]
pub unsafe fn to_surface(&self, env: *mut JNIEnv) -> jobject {
ffi::ANativeWindow_toSurface(env, self.ptr().as_ptr())
}
}