Function audio_render_callback

native/macos/src/lib.rs:223–244

(
    _in_ref_con: *mut std::ffi::c_void,
    _io_action_flags: *mut u32,
    _in_time_stamp: *const std::ffi::c_void,
    _in_bus_number: u32,
    in_number_frames: u32,
    io_data: *mut AudioBuffer

unsafe impl Sync for AudioUnitInstance {}

unsafe extern "C" fn audio_render_callback(
    _in_ref_con: *mut std::ffi::c_void,
    _io_action_flags: *mut u32,
    _in_time_stamp: *const std::ffi::c_void,
    _in_bus_number: u32,
    in_number_frames: u32,
    io_data: *mut AudioBufferList,
) -> OSStatus {
    let buffer_list = &mut *io_data;
    let buffer = &mut buffer_list.buffers[0];
    let num_samples = in_number_frames as usize * 2; // stereo
    let output = std::slice::from_raw_parts_mut(
        buffer.data as *mut f32,
        num_samples,
    );

    ENGINE.get_mut().map(|eng| {
        eng.audio.mix_output(output);
    });

    0 // noErr
}

// ============================================================
// FFI entry points