ndk/bitmap: Provide detailed implementation for AndroidBitmapInfoFlags

As per the TODO, wrap this flags type with some helpers that fish out
the two bit-representations for the `IS_HARDWARE` flag and `ALPHA`
value.

Also add missing documentation and aliases across the `bitmap` module.

ndk/CHANGELOG.md

@@ -24,6 +24,7 @@
 - looper: Add `remove_fd()` to unregister events/callbacks for a file descriptor. (#416)
 - **Breaking:** Use `BorrowedFd` and `OwnedFd` to clarify possible ownership transitions. (#417)
 - **Breaking:** Upgrade to [`ndk-sys 0.5.0`](../ndk-sys/CHANGELOG.md#050-beta0-2023-08-15). (#420)
+- **Breaking:** bitmap: Provide detailed implementation for `AndroidBitmapInfoFlags`. (#424)
 
 # 0.7.0 (2022-07-24)
 

ndk/src/bitmap.rs

@@ -14,11 +14,14 @@ use std::mem::MaybeUninit;
 use crate::hardware_buffer::HardwareBufferRef;
 
 #[repr(i32)]
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum BitmapError {
     Unknown,
+    #[doc(alias = "ANDROID_BITMAP_RESULT_ALLOCATION_FAILED")]
     AllocationFailed = ffi::ANDROID_BITMAP_RESULT_ALLOCATION_FAILED,
+    #[doc(alias = "ANDROID_BITMAP_RESULT_BAD_PARAMETER")]
     BadParameter = ffi::ANDROID_BITMAP_RESULT_BAD_PARAMETER,
+    #[doc(alias = "ANDROID_BITMAP_RESULT_JNI_EXCEPTION")]
     JniException = ffi::ANDROID_BITMAP_RESULT_JNI_EXCEPTION,
 }
 
@@ -43,16 +46,23 @@ fn construct<T>(with_ptr: impl FnOnce(*mut T) -> i32) -> BitmapResult<T> {
 }
 
 #[repr(u32)]
-#[derive(Copy, Clone, Debug, PartialEq, Eq, IntoPrimitive, TryFromPrimitive)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, IntoPrimitive, TryFromPrimitive)]
 #[allow(non_camel_case_types)]
 pub enum BitmapFormat {
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_NONE")]
     NONE = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_NONE.0,
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_RGBA_8888")]
     RGBA_8888 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_RGBA_8888.0,
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_RGB_565")]
     RGB_565 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_RGB_565.0,
     #[deprecated = "Deprecated in API level 13. Because of the poor quality of this configuration, it is advised to use ARGB_8888 instead."]
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_RGBA_4444")]
     RGBA_4444 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_RGBA_4444.0,
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_A_8")]
     A_8 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_A_8.0,
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_RGBA_F16")]
     RGBA_F16 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_RGBA_F16.0,
+    #[doc(alias = "ANDROID_BITMAP_FORMAT_RGBA_1010102")]
     RGBA_1010102 = ffi::AndroidBitmapFormat::ANDROID_BITMAP_FORMAT_RGBA_1010102.0,
 }
 
@@ -77,26 +87,42 @@ impl AndroidBitmap {
         Self { env, inner: bitmap }
     }
 
+    /// Fills out and returns the [`AndroidBitmapInfo`] struct for the given Java bitmap object.
+    #[doc(alias = "AndroidBitmap_getInfo")]
     pub fn get_info(&self) -> BitmapResult<AndroidBitmapInfo> {
         let inner =
             construct(|res| unsafe { ffi::AndroidBitmap_getInfo(self.env, self.inner, res) })?;
 
         Ok(AndroidBitmapInfo { inner })
     }
 
+    /// Attempt to lock the pixel address.
+    ///
+    /// Locking will ensure that the memory for the pixels will not move until the
+    /// [`AndroidBitmap::unlock_pixels()`] call, and ensure that, if the pixels had been previously
+    /// purged, they will have been restored.
+    ///
+    /// If this call succeeds, it must be balanced by a call to [`AndroidBitmap::unlock_pixels()`],
+    /// after which time the address of the pixels should no longer be used.
+    #[doc(alias = "AndroidBitmap_lockPixels")]
     pub fn lock_pixels(&self) -> BitmapResult<*mut std::os::raw::c_void> {
         construct(|res| unsafe { ffi::AndroidBitmap_lockPixels(self.env, self.inner, res) })
     }
 
+    /// Call this to balance a successful call to [`AndroidBitmap::lock_pixels()`].
+    #[doc(alias = "AndroidBitmap_unlockPixels")]
     pub fn unlock_pixels(&self) -> BitmapResult<()> {
         let status = unsafe { ffi::AndroidBitmap_unlockPixels(self.env, self.inner) };
         BitmapError::from_status(status)
     }
 
-    /// Retrieve the native object associated with a `HARDWARE` [`AndroidBitmap`].
+    /// Retrieve the native object associated with an [`ffi::ANDROID_BITMAP_FLAGS_IS_HARDWARE`]
+    /// [`AndroidBitmap`] (requires [`AndroidBitmapInfoFlags::is_hardware()`] on
+    /// [`AndroidBitmapInfo::flags()`] to return [`true`]).
     ///
     /// Client must not modify it while an [`AndroidBitmap`] is wrapping it.
     #[cfg(feature = "api-level-30")]
+    #[doc(alias = "AndroidBitmap_getHardwareBuffer")]
     pub fn get_hardware_buffer(&self) -> BitmapResult<HardwareBufferRef> {
         unsafe {
             let result =
@@ -111,27 +137,102 @@ impl AndroidBitmap {
     }
 }
 
+/// Possible values for [`ffi::ANDROID_BITMAP_FLAGS_ALPHA_MASK`] within [`AndroidBitmapInfoFlags`]
+#[cfg(feature = "api-level-30")]
+#[derive(Clone, Copy, Debug)]
+pub enum AndroidBitmapInfoFlagsAlpha {
+    /// Pixel components are premultiplied by alpha.
+    #[doc(alias = "ANDROID_BITMAP_FLAGS_ALPHA_PREMUL")]
+    Premultiplied,
+    /// Pixels are opaque.
+    #[doc(alias = "ANDROID_BITMAP_FLAGS_ALPHA_OPAQUE")]
+    Opaque,
+    /// Pixel components are independent of alpha.
+    #[doc(alias = "ANDROID_BITMAP_FLAGS_ALPHA_UNPREMUL")]
+    Unpremultiplied,
+}
+
+/// Bitfield containing information about the bitmap.
+#[cfg(feature = "api-level-30")]
+#[derive(Clone, Copy, Hash, PartialEq, Eq)]
+#[repr(transparent)]
+pub struct AndroidBitmapInfoFlags(u32);
+
+#[cfg(feature = "api-level-30")]
+impl std::fmt::Debug for AndroidBitmapInfoFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "AndroidBitmapInfoFlags({:#x}, alpha: {:?}, is_hardware: {})",
+            self.0,
+            self.alpha(),
+            self.is_hardware()
+        )
+    }
+}
+
+#[cfg(feature = "api-level-30")]
+impl AndroidBitmapInfoFlags {
+    /// Returns the alpha value contained in the [`ffi::ANDROID_BITMAP_FLAGS_ALPHA_MASK`] bit range
+    #[doc(alias = "ANDROID_BITMAP_FLAGS_ALPHA_MASK")]
+    pub fn alpha(self) -> AndroidBitmapInfoFlagsAlpha {
+        // Note that ffi::ANDROID_BITMAP_FLAGS_ALPHA_SHIFT is 0 and hence irrelevant.
+        match self.0 & ffi::ANDROID_BITMAP_FLAGS_ALPHA_MASK {
+            ffi::ANDROID_BITMAP_FLAGS_ALPHA_PREMUL => AndroidBitmapInfoFlagsAlpha::Premultiplied,
+            ffi::ANDROID_BITMAP_FLAGS_ALPHA_OPAQUE => AndroidBitmapInfoFlagsAlpha::Opaque,
+            ffi::ANDROID_BITMAP_FLAGS_ALPHA_UNPREMUL => {
+                AndroidBitmapInfoFlagsAlpha::Unpremultiplied
+            }
+            3 => todo!("ALPHA_MASK value 3"),
+            _ => unreachable!(),
+        }
+    }
+
+    /// Returns [`true`] when [`ffi::ANDROID_BITMAP_FLAGS_IS_HARDWARE`] is set, meaning this
+    /// [`AndroidBitmap`] uses "HARDWARE Config" and its [`HardwareBufferRef`] can be retrieved via
+    /// [`AndroidBitmap::get_hardware_buffer()`].
+    #[doc(alias = "ANDROID_BITMAP_FLAGS_IS_HARDWARE")]
+    pub fn is_hardware(self) -> bool {
+        // This constant is defined in a separate anonymous enum which bindgen treats as i32.
+        (self.0 & ffi::ANDROID_BITMAP_FLAGS_IS_HARDWARE as u32) != 0
+    }
+}
+
 /// A native [`AndroidBitmapInfo`]
 ///
 /// [`AndroidBitmapInfo`]: https://developer.android.com/ndk/reference/struct/android-bitmap-info#struct_android_bitmap_info
-#[derive(Copy, Clone, Debug)]
+#[derive(Clone, Copy)]
 pub struct AndroidBitmapInfo {
     inner: ffi::AndroidBitmapInfo,
 }
 
-// TODO: flesh out when API 30 is released
-#[cfg(feature = "api-level-30")]
-pub type AndroidBitmapInfoFlags = u32;
+impl std::fmt::Debug for AndroidBitmapInfo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut f = f.debug_struct("AndroidBitmapInfo");
+        f.field("width", &self.width())
+            .field("height", &self.height())
+            .field("stride", &self.stride())
+            .field("format", &self.try_format());
+
+        #[cfg(feature = "api-level-30")]
+        f.field("flags", &self.flags());
+
+        f.finish()
+    }
+}
 
 impl AndroidBitmapInfo {
+    /// The bitmap width in pixels.
     pub fn width(&self) -> u32 {
         self.inner.width
     }
 
+    /// The bitmap height in pixels.
     pub fn height(&self) -> u32 {
         self.inner.height
     }
 
+    /// The number of byte per row.
     pub fn stride(&self) -> u32 {
         self.inner.stride
     }
@@ -155,8 +256,9 @@ impl AndroidBitmapInfo {
         format.try_into()
     }
 
+    /// Bitfield containing information about the bitmap.
     #[cfg(feature = "api-level-30")]
     pub fn flags(&self) -> AndroidBitmapInfoFlags {
-        self.inner.flags
+        AndroidBitmapInfoFlags(self.inner.flags)
     }
 }