objc2-audio-toolbox 0.3.2

//! This file has been automatically generated by `objc2`'s `header-translator`.
//! DO NOT EDIT
use core::ffi::*;
use core::ptr::NonNull;
use objc2::__framework_prelude::*;
#[cfg(feature = "objc2-core-audio-types")]
use objc2_core_audio_types::*;
#[cfg(feature = "objc2-core-midi")]
use objc2_core_midi::*;
use objc2_foundation::*;

use crate::*;

/// [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudioobjectid?language=objc)
pub type AUAudioObjectID = u32;

/// A result code returned from an audio unit's render function.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounitstatus?language=objc)
pub type AUAudioUnitStatus = OSStatus;

/// [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aueventsampletimeimmediate?language=objc)
#[cfg(feature = "AudioUnitProperties")]
pub const AUEventSampleTimeImmediate: AUEventSampleTime = -4294967296;

/// A number of audio sample frames.
///
/// This is `uint32_t` for impedence-matching with the pervasive use of `UInt32` in AudioToolbox
/// and C AudioUnit API's, as well as `AVAudioFrameCount`.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudioframecount?language=objc)
pub type AUAudioFrameCount = u32;

/// A number of audio channels.
///
/// This is `uint32_t` for impedence-matching with the pervasive use of `UInt32` in AudioToolbox
/// and C AudioUnit API's, as well as `AVAudioChannelCount`.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiochannelcount?language=objc)
pub type AUAudioChannelCount = u32;

/// Describes whether a bus array is for input or output.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounitbustype?language=objc)
// NS_ENUM
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct AUAudioUnitBusType(pub NSInteger);
impl AUAudioUnitBusType {
    #[doc(alias = "AUAudioUnitBusTypeInput")]
    pub const Input: Self = Self(1);
    #[doc(alias = "AUAudioUnitBusTypeOutput")]
    pub const Output: Self = Self(2);
}

unsafe impl Encode for AUAudioUnitBusType {
    const ENCODING: Encoding = NSInteger::ENCODING;
}

unsafe impl RefEncode for AUAudioUnitBusType {
    const ENCODING_REF: Encoding = Encoding::Pointer(&Self::ENCODING);
}

/// Block to supply audio input to AURenderBlock.
///
/// Parameter `actionFlags`: Pointer to action flags.
///
/// Parameter `timestamp`: The HAL time at which the input data will be rendered. If there is a sample rate conversion
/// or time compression/expansion downstream, the sample time will not be valid.
///
/// Parameter `frameCount`: The number of sample frames of input requested.
///
/// Parameter `inputBusNumber`: The index of the input bus being pulled.
///
/// Parameter `inputData`: The input audio data.
///
/// The caller must supply valid buffers in inputData's mBuffers' mData and mDataByteSize.
/// mDataByteSize must be consistent with frameCount. This block may provide input in those
/// specified buffers, or it may replace the mData pointers with pointers to memory which it
/// owns and guarantees will remain valid until the next render cycle.
///
/// Returns: An AUAudioUnitStatus result code. If an error is returned, the input data should be assumed
/// to be invalid.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aurenderpullinputblock?language=objc)
#[cfg(all(
    feature = "AUComponent",
    feature = "block2",
    feature = "objc2-core-audio-types"
))]
pub type AURenderPullInputBlock = *mut block2::DynBlock<
    dyn Fn(
        NonNull<AudioUnitRenderActionFlags>,
        NonNull<AudioTimeStamp>,
        AUAudioFrameCount,
        NSInteger,
        NonNull<AudioBufferList>,
    ) -> AUAudioUnitStatus,
>;

/// Block to render the audio unit.
///
/// All realtime operations are implemented using blocks to avoid ObjC method dispatching and
/// the possibility of blocking.
///
/// Parameter `actionFlags`: Pointer to action flags.
///
/// Parameter `timestamp`: The HAL time at which the output data will be rendered. If there is a sample rate conversion
/// or time compression/expansion downstream, the sample time will not have a defined
/// correlation with the AudioDevice sample time.
///
/// Parameter `frameCount`: The number of sample frames to render.
///
/// Parameter `outputBusNumber`: The index of the output bus to render.
///
/// Parameter `outputData`: The output bus's render buffers and flags.
///
/// The buffer pointers (outputData->mBuffers[x].mData) may be null on entry, in which case the
/// block will render into memory it owns and modify the mData pointers to point to that memory.
/// The block is responsible for preserving the validity of that memory until it is next called
/// to render, or deallocateRenderResources is called.
///
/// If, on entry, the mData pointers are non-null, the block will render into those buffers.
///
/// Parameter `pullInputBlock`: A block which the AU will call in order to pull for input data. May be nil for instrument
/// and generator audio units (which do not have input busses).
///
/// Returns: An `AUAudioUnitStatus` result code. If an error is returned, the output data should be assumed
/// to be invalid.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aurenderblock?language=objc)
#[cfg(all(
    feature = "AUComponent",
    feature = "block2",
    feature = "objc2-core-audio-types"
))]
pub type AURenderBlock = *mut block2::DynBlock<
    dyn Fn(
        NonNull<AudioUnitRenderActionFlags>,
        NonNull<AudioTimeStamp>,
        AUAudioFrameCount,
        NSInteger,
        NonNull<AudioBufferList>,
        AURenderPullInputBlock,
    ) -> AUAudioUnitStatus,
>;

/// Block called when an audio unit renders.
///
/// This block is called by the base class's AURenderBlock before and after each render cycle.
/// The observer can distinguish between before and after using the PreRender and PostRender
/// flags.
///
/// The parameters are identical to those of AURenderBlock.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aurenderobserver?language=objc)
#[cfg(all(
    feature = "AUComponent",
    feature = "block2",
    feature = "objc2-core-audio-types"
))]
pub type AURenderObserver = *mut block2::DynBlock<
    dyn Fn(AudioUnitRenderActionFlags, NonNull<AudioTimeStamp>, AUAudioFrameCount, NSInteger),
>;

/// Block to schedule parameter changes.
///
/// Not all parameters are rampable; check the parameter's flags.
/// Note: If the parameter is not rampable, a rampDuration of zero will result in an immediate change to
/// the target value, however, if rampDuration is non-zero, the parameter will not change.
///
///
/// Parameter `eventSampleTime`: The sample time (timestamp->mSampleTime) at which the parameter is to begin changing. When
/// scheduling parameters during the render cycle (e.g. via a render observer) this time can be
/// AUEventSampleTimeImmediate plus an optional buffer offset, in which case the event is
/// scheduled at that position in the current render cycle.
///
/// Parameter `rampDurationSampleFrames`: The number of sample frames over which the parameter's value is to ramp, or 0 if the
/// parameter change should take effect immediately.
///
/// Parameter `parameterAddress`: The parameter's address.
///
/// Parameter `value`: The parameter's new value if the ramp duration is 0; otherwise, the value at the end
/// of the scheduled ramp.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auscheduleparameterblock?language=objc)
#[cfg(all(
    feature = "AUParameters",
    feature = "AudioUnitProperties",
    feature = "block2"
))]
pub type AUScheduleParameterBlock = *mut block2::DynBlock<
    dyn Fn(AUEventSampleTime, AUAudioFrameCount, AUParameterAddress, AUValue),
>;

/// Block to schedule MIDI events.
///
/// Parameter `eventSampleTime`: The sample time (timestamp->mSampleTime) at which the MIDI event is to occur. When
/// scheduling events during the render cycle (e.g. via a render observer) this time can be
/// AUEventSampleTimeImmediate plus an optional buffer offset, in which case the event is
/// scheduled at that position in the current render cycle.
///
/// Parameter `cable`: The virtual cable number.
///
/// Parameter `length`: The number of bytes of MIDI data in the provided event(s).
///
/// Parameter `midiBytes`: One or more valid MIDI 1.0 events, except sysex which must always be sent as the only event
/// in the chunk. Also, running status is not allowed.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auschedulemidieventblock?language=objc)
#[cfg(all(feature = "AudioUnitProperties", feature = "block2"))]
pub type AUScheduleMIDIEventBlock =
    *mut block2::DynBlock<dyn Fn(AUEventSampleTime, u8, NSInteger, NonNull<u8>)>;

/// Block to provide MIDI output events to the host.
///
/// Parameter `eventSampleTime`: The timestamp associated with the MIDI data in this chunk.
///
/// Parameter `cable`: The virtual cable number associated with this MIDI data.
///
/// Parameter `length`: The number of bytes of MIDI data in the provided event(s).
///
/// Parameter `midiBytes`: One or more valid MIDI 1.0 events, except sysex which must always be sent as the only event
/// in the chunk.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aumidioutputeventblock?language=objc)
#[cfg(all(feature = "AudioUnitProperties", feature = "block2"))]
pub type AUMIDIOutputEventBlock =
    *mut block2::DynBlock<dyn Fn(AUEventSampleTime, u8, NSInteger, NonNull<u8>) -> OSStatus>;

/// Block by which hosts provide musical tempo, time signature, and beat position.
///
/// Parameter `currentTempo`: The current tempo in beats per minute.
///
/// Parameter `timeSignatureNumerator`: The numerator of the current time signature.
///
/// Parameter `timeSignatureDenominator`: The denominator of the current time signature.
///
/// Parameter `currentBeatPosition`: The precise beat position of the beginning of the current buffer being rendered.
///
/// Parameter `sampleOffsetToNextBeat`: The number of samples between the beginning of the buffer being rendered and the next beat
/// (can be 0).
///
/// Parameter `currentMeasureDownbeatPosition`: The beat position corresponding to the beginning of the current measure.
///
/// Returns: YES for success.
///
/// If the host app provides this block to an AUAudioUnit (as its musicalContextBlock), then
/// the block may be called at the beginning of each render cycle to obtain information about
/// the current render cycle's musical context.
///
/// Any of the provided parameters may be null to indicate that the audio unit is not interested
/// in that particular piece of information.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auhostmusicalcontextblock?language=objc)
#[cfg(feature = "block2")]
pub type AUHostMusicalContextBlock = *mut block2::DynBlock<
    dyn Fn(
        *mut c_double,
        *mut c_double,
        *mut NSInteger,
        *mut c_double,
        *mut NSInteger,
        *mut c_double,
    ) -> Bool,
>;

/// Block by which hosts are informed of an audio unit having enabled or disabled a
/// MIDI-CI profile.
///
/// Parameter `cable`: The virtual MIDI cable on which the event occured.
///
/// Parameter `channel`: The MIDI channel on which the profile was enabled or disabled.
///
/// Parameter `profile`: The MIDI-CI profile.
///
/// Parameter `enabled`: YES if the profile was enabled, NO if the profile was disabled.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aumidiciprofilechangedblock?language=objc)
#[cfg(all(feature = "block2", feature = "objc2-core-midi"))]
pub type AUMIDICIProfileChangedBlock =
    *mut block2::DynBlock<dyn Fn(u8, MIDIChannelNumber, NonNull<MIDICIProfile>, Bool)>;

/// Flags describing the host's transport state.
///
/// True if, since the callback was last called, there was a change to the state of, or
/// discontinuities in, the host's transport. Can indicate such state changes as
/// start/stop, or seeking to another position in the timeline.
///
/// True if the transport is moving.
///
/// True if the host is recording, or prepared to record. Can be true with or without the
/// transport moving.
///
/// True if the host is cycling or looping.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auhosttransportstateflags?language=objc)
// NS_OPTIONS
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct AUHostTransportStateFlags(pub NSUInteger);
bitflags::bitflags! {
    impl AUHostTransportStateFlags: NSUInteger {
        #[doc(alias = "AUHostTransportStateChanged")]
        const Changed = 1;
        #[doc(alias = "AUHostTransportStateMoving")]
        const Moving = 2;
        #[doc(alias = "AUHostTransportStateRecording")]
        const Recording = 4;
        #[doc(alias = "AUHostTransportStateCycling")]
        const Cycling = 8;
    }
}

unsafe impl Encode for AUHostTransportStateFlags {
    const ENCODING: Encoding = NSUInteger::ENCODING;
}

unsafe impl RefEncode for AUHostTransportStateFlags {
    const ENCODING_REF: Encoding = Encoding::Pointer(&Self::ENCODING);
}

/// Block by which hosts provide information about their transport state.
///
/// Parameter `transportStateFlags`: The current state of the transport.
///
/// Parameter `currentSamplePosition`: The current position in the host's timeline, in samples at the audio unit's output sample
/// rate.
///
/// Parameter `cycleStartBeatPosition`: If cycling, the starting beat position of the cycle.
///
/// Parameter `cycleEndBeatPosition`: If cycling, the ending beat position of the cycle.
///
/// If the host app provides this block to an AUAudioUnit (as its transportStateBlock), then
/// the block may be called at the beginning of each render cycle to obtain information about
/// the current transport state.
///
/// Any of the provided parameters may be null to indicate that the audio unit is not interested
/// in that particular piece of information.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auhosttransportstateblock?language=objc)
#[cfg(feature = "block2")]
pub type AUHostTransportStateBlock = *mut block2::DynBlock<
    dyn Fn(*mut AUHostTransportStateFlags, *mut c_double, *mut c_double, *mut c_double) -> Bool,
>;

extern_class!(
    /// An audio unit instance.
    ///
    /// AUAudioUnit is a host interface to an audio unit. Hosts can instantiate either version 2 or
    /// version 3 units with this class, and to some extent control whether an audio unit is
    /// instantiated in-process or in a separate extension process.
    ///
    /// Implementors of version 3 audio units can and should subclass AUAudioUnit. To port an
    /// existing version 2 audio unit easily, AUAudioUnitV2Bridge can be subclassed.
    ///
    /// These are the ways in which audio unit components can be registered:
    ///
    /// - (v2) Packaged into a component bundle containing an `AudioComponents` Info.plist entry,
    /// referring to an `AudioComponentFactoryFunction`. See AudioComponent.h.
    ///
    /// - (v2) AudioComponentRegister(). Associates a component description with an
    /// AudioComponentFactoryFunction. See AudioComponent.h.
    ///
    /// - (v3) Packaged into an app extension containing an AudioComponents Info.plist entry.
    /// The principal class must conform to the AUAudioUnitFactory protocol, which will typically
    /// instantiate an AUAudioUnit subclass.
    ///
    /// - (v3) `+[AUAudioUnit registerSubclass:asComponentDescription:name:version:]`. Associates
    /// a component description with an AUAudioUnit subclass.
    ///
    /// A host need not be aware of the concrete subclass of AUAudioUnit that is being instantiated.
    /// `initWithComponentDescription:options:error:` ensures that the proper subclass is used.
    ///
    /// When using AUAudioUnit with a v2 audio unit, or the C AudioComponent and AudioUnit API's
    /// with a v3 audio unit, all major pieces of functionality are bridged between the
    /// two API's. This header describes, for each v3 method or property, the v2 equivalent.
    ///
    /// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounit?language=objc)
    #[unsafe(super(NSObject))]
    #[derive(Debug, PartialEq, Eq, Hash)]
    pub struct AUAudioUnit;
);

extern_conformance!(
    unsafe impl NSObjectProtocol for AUAudioUnit {}
);

impl AUAudioUnit {
    extern_methods!(
        #[unsafe(method(init))]
        #[unsafe(method_family = init)]
        pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>;

        #[cfg(feature = "AudioComponent")]
        /// Designated initializer.
        ///
        /// Parameter `componentDescription`: A single AUAudioUnit subclass may implement multiple audio units, for example, an effect
        /// that can also function as a generator, or a cluster of related effects. The component
        /// description specifies the component which was instantiated.
        ///
        /// Parameter `options`: Options for loading the unit in-process or out-of-process.
        ///
        /// Parameter `outError`: Returned in the event of failure.
        #[unsafe(method(initWithComponentDescription:options:error:_))]
        #[unsafe(method_family = init)]
        pub unsafe fn initWithComponentDescription_options_error(
            this: Allocated<Self>,
            component_description: AudioComponentDescription,
            options: AudioComponentInstantiationOptions,
        ) -> Result<Retained<Self>, Retained<NSError>>;

        #[cfg(feature = "AudioComponent")]
        /// Convenience initializer (omits options).
        #[unsafe(method(initWithComponentDescription:error:_))]
        #[unsafe(method_family = init)]
        pub unsafe fn initWithComponentDescription_error(
            this: Allocated<Self>,
            component_description: AudioComponentDescription,
        ) -> Result<Retained<Self>, Retained<NSError>>;

        #[cfg(all(feature = "AudioComponent", feature = "block2"))]
        /// Asynchronously create an AUAudioUnit instance.
        ///
        /// Parameter `componentDescription`: The AudioComponentDescription of the audio unit to instantiate.
        ///
        /// Parameter `options`: See the discussion of AudioComponentInstantiationOptions in AudioToolbox/AudioComponent.h.
        ///
        /// Parameter `completionHandler`: Called in a thread/dispatch queue context internal to the implementation. The client should
        /// retain the supplied AUAudioUnit.
        ///
        /// Certain types of AUAudioUnits must be instantiated asynchronously -- see
        /// the discussion of kAudioComponentFlag_RequiresAsyncInstantiation in
        /// AudioToolbox/AudioComponent.h.
        ///
        /// Note: Do not block the main thread while waiting for the completion handler to be called;
        /// this can deadlock.
        #[unsafe(method(instantiateWithComponentDescription:options:completionHandler:))]
        #[unsafe(method_family = none)]
        pub unsafe fn instantiateWithComponentDescription_options_completionHandler(
            component_description: AudioComponentDescription,
            options: AudioComponentInstantiationOptions,
            completion_handler: &block2::DynBlock<dyn Fn(*mut AUAudioUnit, *mut NSError)>,
        );

        #[cfg(feature = "AudioComponent")]
        /// The AudioComponentDescription with which the audio unit was created.
        #[unsafe(method(componentDescription))]
        #[unsafe(method_family = none)]
        pub unsafe fn componentDescription(&self) -> AudioComponentDescription;

        #[cfg(feature = "AudioComponent")]
        /// The AudioComponent which was found based on componentDescription when the
        /// audio unit was created.
        #[unsafe(method(component))]
        #[unsafe(method_family = none)]
        pub unsafe fn component(&self) -> AudioComponent;

        /// The unit's component's name.
        ///
        /// By convention, an audio unit's component name is its manufacturer's name, plus ": ",
        /// plus the audio unit's name. The audioUnitName and manufacturerName properties are derived
        /// from the component name.
        #[unsafe(method(componentName))]
        #[unsafe(method_family = none)]
        pub unsafe fn componentName(&self) -> Option<Retained<NSString>>;

        /// The audio unit's name.
        #[unsafe(method(audioUnitName))]
        #[unsafe(method_family = none)]
        pub unsafe fn audioUnitName(&self) -> Option<Retained<NSString>>;

        /// The manufacturer's name.
        #[unsafe(method(manufacturerName))]
        #[unsafe(method_family = none)]
        pub unsafe fn manufacturerName(&self) -> Option<Retained<NSString>>;

        /// A short name for the audio unit.
        ///
        /// Audio unit host applications can display this name in situations where the audioUnitName
        /// might be too long. The recommended length is up to 16 characters. Host applications may
        /// truncate it.
        #[unsafe(method(audioUnitShortName))]
        #[unsafe(method_family = none)]
        pub unsafe fn audioUnitShortName(&self) -> Option<Retained<NSString>>;

        /// The unit's component's version.
        #[unsafe(method(componentVersion))]
        #[unsafe(method_family = none)]
        pub unsafe fn componentVersion(&self) -> u32;

        /// Allocate resources required to render.
        ///
        /// Hosts must call this before beginning to render. Subclassers should call the superclass
        /// implementation.
        ///
        /// Bridged to the v2 API AudioUnitInitialize().
        #[unsafe(method(allocateRenderResourcesAndReturnError:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn allocateRenderResourcesAndReturnError(&self)
            -> Result<(), Retained<NSError>>;

        /// Deallocate resources allocated by allocateRenderResourcesAndReturnError:
        ///
        /// Hosts should call this after finishing rendering. Subclassers should call the superclass
        /// implementation.
        ///
        /// Bridged to the v2 API AudioUnitUninitialize().
        #[unsafe(method(deallocateRenderResources))]
        #[unsafe(method_family = none)]
        pub unsafe fn deallocateRenderResources(&self);

        /// returns YES if the unit has render resources allocated.
        #[unsafe(method(renderResourcesAllocated))]
        #[unsafe(method_family = none)]
        pub unsafe fn renderResourcesAllocated(&self) -> bool;

        /// Reset transitory rendering state to its initial state.
        ///
        /// Hosts should call this at the point of a discontinuity in the input stream being provided to
        /// an audio unit, for example, when seeking forward or backward within a track. In response,
        /// implementations should clear delay lines, filters, etc. Subclassers should call the
        /// superclass implementation.
        ///
        /// Bridged to the v2 API AudioUnitReset(), in the global scope.
        #[unsafe(method(reset))]
        #[unsafe(method_family = none)]
        pub unsafe fn reset(&self);

        /// An audio unit's audio input connection points.
        ///
        /// Subclassers must override this property's getter. The implementation should return the same
        /// object every time it is asked for it, since clients can install KVO observers on it.
        #[unsafe(method(inputBusses))]
        #[unsafe(method_family = none)]
        pub unsafe fn inputBusses(&self) -> Retained<AUAudioUnitBusArray>;

        /// An audio unit's audio output connection points.
        ///
        /// Subclassers must override this property's getter. The implementation should return the same
        /// object every time it is asked for it, since clients can install KVO observers on it.
        #[unsafe(method(outputBusses))]
        #[unsafe(method_family = none)]
        pub unsafe fn outputBusses(&self) -> Retained<AUAudioUnitBusArray>;

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// Block which hosts use to ask the unit to render.
        ///
        /// Before invoking an audio unit's rendering functionality, a host should fetch this block and
        /// cache the result. The block can then be called from a realtime context without the
        /// possibility of blocking and causing an overload at the Core Audio HAL level.
        ///
        /// This block will call a subclass' internalRenderBlock, providing all realtime events
        /// scheduled for the current render time interval, bracketed by calls to any render observers.
        ///
        /// Subclassers should override internalRenderBlock, not this property.
        ///
        /// Bridged to the v2 API AudioUnitRender().
        ///
        /// # Safety
        ///
        /// - The returned block's argument 1 must be a valid pointer.
        /// - The returned block's argument 2 must be a valid pointer.
        /// - The returned block's argument 5 must be a valid pointer.
        /// - The returned block's argument 6 must be a valid pointer or null.
        #[unsafe(method(renderBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn renderBlock(&self) -> AURenderBlock;

        #[cfg(all(
            feature = "AUParameters",
            feature = "AudioUnitProperties",
            feature = "block2"
        ))]
        /// Block which hosts use to schedule parameters.
        ///
        /// As with renderBlock, a host should fetch and cache this block before calling
        /// allocateRenderResources, if it intends to schedule parameters.
        ///
        /// The block is safe to call from any thread context, including realtime audio render
        /// threads.
        ///
        /// Subclassers should not override this; it is implemented in the base class and will schedule
        /// the events to be provided to the internalRenderBlock.
        ///
        /// Bridged to the v2 API AudioUnitScheduleParameters().
        #[unsafe(method(scheduleParameterBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn scheduleParameterBlock(&self) -> AUScheduleParameterBlock;

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// Add a block to be called on each render cycle.
        ///
        /// The supplied block is called at the beginning and ending of each render cycle. It should
        /// not make any blocking calls.
        ///
        /// This method is implemented in the base class AUAudioUnit, and should not be overridden.
        ///
        /// Bridged to the v2 API AudioUnitAddRenderNotify().
        ///
        /// Parameter `observer`: The block to call.
        ///
        /// Returns: A token to be used when removing the observer.
        ///
        /// # Safety
        ///
        /// `observer` must be a valid pointer.
        #[unsafe(method(tokenByAddingRenderObserver:))]
        #[unsafe(method_family = none)]
        pub unsafe fn tokenByAddingRenderObserver(&self, observer: AURenderObserver) -> NSInteger;

        /// Remove an observer block added via tokenByAddingRenderObserver:
        ///
        /// Parameter `token`: The token previously returned by tokenByAddingRenderObserver:
        ///
        /// Bridged to the v2 API AudioUnitRemoveRenderNotify().
        #[unsafe(method(removeRenderObserver:))]
        #[unsafe(method_family = none)]
        pub unsafe fn removeRenderObserver(&self, token: NSInteger);

        /// The maximum number of frames which the audio unit can render at once.
        ///
        /// This must be set by the host before render resources are allocated. It cannot be changed
        /// while render resources are allocated.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_MaximumFramesPerSlice.
        #[unsafe(method(maximumFramesToRender))]
        #[unsafe(method_family = none)]
        pub unsafe fn maximumFramesToRender(&self) -> AUAudioFrameCount;

        /// Setter for [`maximumFramesToRender`][Self::maximumFramesToRender].
        #[unsafe(method(setMaximumFramesToRender:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setMaximumFramesToRender(&self, maximum_frames_to_render: AUAudioFrameCount);

        #[cfg(feature = "AUParameters")]
        /// An audio unit's parameters, organized in a hierarchy.
        ///
        /// Returns: A parameter tree object, or nil if the unit has no parameters.
        ///
        /// Audio unit hosts can fetch this property to discover a unit's parameters. KVO notifications
        /// are issued on this member to notify the host of changes to the set of available parameters.
        ///
        /// AUAudioUnit has an additional pseudo-property, "allParameterValues", on which KVO
        /// notifications are issued in response to certain events where potentially all parameter
        /// values are invalidated. This includes changes to currentPreset, fullState, and
        /// fullStateForDocument.
        ///
        /// Hosts should not attempt to set this property.
        ///
        /// Subclassers should implement the parameterTree getter to expose parameters to hosts. They
        /// should cache as much as possible and send KVO notifications on "parameterTree" when altering
        /// the structure of the tree or the static information (ranges, etc) of parameters.
        ///
        /// This is similar to the v2 properties kAudioUnitProperty_ParameterList and
        /// kAudioUnitProperty_ParameterInfo.
        ///
        /// Note that it is not safe to modify this property in a real-time context.
        #[unsafe(method(parameterTree))]
        #[unsafe(method_family = none)]
        pub unsafe fn parameterTree(&self) -> Option<Retained<AUParameterTree>>;

        #[cfg(feature = "AUParameters")]
        /// Setter for [`parameterTree`][Self::parameterTree].
        #[unsafe(method(setParameterTree:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setParameterTree(&self, parameter_tree: Option<&AUParameterTree>);

        /// Returns the audio unit's `count` most important parameters.
        ///
        /// This property allows a host to query an audio unit for some small number of parameters which
        /// are its "most important", to be displayed in a compact generic view.
        ///
        /// An audio unit subclass should return an array of NSNumbers representing the addresses
        /// of the `count` most important parameters.
        ///
        /// The base class returns an empty array regardless of count.
        ///
        /// Partially bridged to kAudioUnitProperty_ParametersForOverview (v2 hosts can use that
        /// property to access this v3 method of an audio unit).
        #[unsafe(method(parametersForOverviewWithCount:))]
        #[unsafe(method_family = none)]
        pub unsafe fn parametersForOverviewWithCount(
            &self,
            count: NSInteger,
        ) -> Retained<NSArray<NSNumber>>;

        #[unsafe(method(allParameterValues))]
        #[unsafe(method_family = none)]
        pub unsafe fn allParameterValues(&self) -> bool;

        /// Specifies whether an audio unit responds to MIDI events.
        ///
        /// This is implemented in the base class and returns YES if the component type is music
        /// device or music effect.
        #[unsafe(method(isMusicDeviceOrEffect))]
        #[unsafe(method_family = none)]
        pub unsafe fn isMusicDeviceOrEffect(&self) -> bool;

        /// The number of virtual MIDI cables implemented by a music device or effect.
        ///
        /// A music device or MIDI effect can support up to 256 virtual MIDI cables of input; this
        /// property expresses the number of cables supported by the audio unit.
        #[unsafe(method(virtualMIDICableCount))]
        #[unsafe(method_family = none)]
        pub unsafe fn virtualMIDICableCount(&self) -> NSInteger;

        #[cfg(all(feature = "AudioUnitProperties", feature = "block2"))]
        /// Block used to schedule MIDI events.
        ///
        /// As with renderBlock, a host should fetch and cache this block before calling
        /// allocateRenderResources if it intends to schedule MIDI events.
        ///
        /// This is implemented in the base class. It is nil when musicDeviceOrEffect is NO.
        ///
        /// Subclasses should not override. When hosts schedule events via this block, they are
        /// sent to the Audio Unit via the list of AURenderEvents delivered to
        /// internalRenderBlock.
        ///
        /// All events sent via this block will be delivered to the internalRenderBlock in the MIDI
        /// protocol returned by the AudioUnitMIDIProtocol property. For example, if AudioUnitMIDIProtocol
        /// returns kMIDIProtocol_2_0, incoming events will be translated to MIDI 2.0 if necessary.
        /// If AudioUnitMIDIProtocol is not set, events will be delivered as legacy MIDI.
        ///
        /// This bridged to the v2 API MusicDeviceMIDIEvent.
        ///
        /// # Safety
        ///
        /// The returned block's argument 4 must be a valid pointer.
        #[unsafe(method(scheduleMIDIEventBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn scheduleMIDIEventBlock(&self) -> AUScheduleMIDIEventBlock;

        /// Count, and names of, a plug-in's MIDI outputs.
        ///
        /// A plug-in may override this method to inform hosts about its MIDI outputs. The size of the
        /// array is the number of outputs the Audio Unit supports. Each item in the array is the name
        /// of the MIDI output at that index.
        ///
        /// This is bridged to the v2 API property kAudioUnitProperty_MIDIOutputCallbackInfo.
        #[unsafe(method(MIDIOutputNames))]
        #[unsafe(method_family = none)]
        pub unsafe fn MIDIOutputNames(&self) -> Retained<NSArray<NSString>>;

        /// Specifies whether an audio unit provides UI (normally in the form of a view controller).
        ///
        /// Implemented in the framework and should not be overridden by implementators. The
        /// framework detects whether any subclass has implemented
        /// `requestViewControllerWithCompletionHandler:` or is implemented by an AU extension whose
        /// extension point identifier is `com.apple.AudioUnit-UI`. See also
        /// `requestViewControllerWithCompletionHandler:` in
        /// <CoreAudioKit
        /// /AUViewController.h>
        #[unsafe(method(providesUserInterface))]
        #[unsafe(method_family = none)]
        pub unsafe fn providesUserInterface(&self) -> bool;

        #[cfg(all(feature = "AudioUnitProperties", feature = "block2"))]
        /// Block used by the host to access the MIDI output generated by an Audio Unit.
        ///
        /// The host can set this block and the plug-in can call it in its renderBlock to provide to the
        /// host the MIDI data associated with the current render cycle.
        ///
        /// All events sent via this block will be delivered to the host in the MIDI protocol returned by
        /// the hostMIDIProtocol property. For example, if hostMIDIProtocol is set to
        /// kMIDIProtocol_2_0, incoming events will be translated to MIDI 2.0. If hostMIDIProtocol
        /// is not set, events will be delivered as legacy MIDI.
        ///
        /// Note: AUMIDIEventListBlock should be preferred over this block going forward.
        ///
        /// This is bridged to the v2 API property kAudioUnitProperty_MIDIOutputCallback.
        ///
        /// # Safety
        ///
        /// The returned block's argument 4 must be a valid pointer.
        #[unsafe(method(MIDIOutputEventBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn MIDIOutputEventBlock(&self) -> AUMIDIOutputEventBlock;

        #[cfg(all(feature = "AudioUnitProperties", feature = "block2"))]
        /// Setter for [`MIDIOutputEventBlock`][Self::MIDIOutputEventBlock].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `midi_output_event_block` must be a valid pointer or null.
        #[unsafe(method(setMIDIOutputEventBlock:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setMIDIOutputEventBlock(
            &self,
            midi_output_event_block: AUMIDIOutputEventBlock,
        );

        #[cfg(feature = "objc2-core-midi")]
        /// The MIDI protocol used by the Audio Unit for receiving MIDIEventList data.
        ///
        /// Subclassers should override to return the desired protocol in which the Audio Unit wants
        /// to receive input MIDI data, otherwise the Audio Unit will default to receiving legacy MIDI.
        ///
        /// All translatable messages will be converted (if necessary) to this protocol prior to delivery
        /// to the Audio Unit.
        ///
        /// This is bridged to the v2 API property kAudioUnitProperty_AudioUnitMIDIProtocol.
        #[unsafe(method(AudioUnitMIDIProtocol))]
        #[unsafe(method_family = none)]
        pub unsafe fn AudioUnitMIDIProtocol(&self) -> MIDIProtocolID;

        #[cfg(feature = "objc2-core-midi")]
        /// The MIDI protocol to be used by the host for receiving MIDIEventList data.
        ///
        /// Hosts should set this property to the protocol they wish to receive MIDIEventList data
        /// from the Audio Unit. This should be set prior to initialization, all translatable messages
        /// will be converted  (if necessary) to this property's protocol prior to delivery to the host.
        ///
        /// Host should setup in the following order:
        /// - Set hostMIDIProtocol
        /// - Set MIDIOutputEventListBlock
        /// - Call allocateRenderResourcesAndReturnError
        ///
        /// This is bridged to the v2 API property kAudioUnitProperty_HostMIDIProtocol.
        ///
        /// Notes:
        /// - If overriding this property, subclassers must call [super setHostMIDIProtocol:]
        /// - hostMIDIProtocol should be set before attempting to query AudioUnitMIDIProtocol
        /// or calling allocateRenderResourcesAndReturnError to allow Audio Units to
        /// optionally match their input MIDI protocol to the desired host protocol and prevent
        /// protocol conversion.
        #[unsafe(method(hostMIDIProtocol))]
        #[unsafe(method_family = none)]
        pub unsafe fn hostMIDIProtocol(&self) -> MIDIProtocolID;

        #[cfg(feature = "objc2-core-midi")]
        /// Setter for [`hostMIDIProtocol`][Self::hostMIDIProtocol].
        #[unsafe(method(setHostMIDIProtocol:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setHostMIDIProtocol(&self, host_midi_protocol: MIDIProtocolID);

        /// A persistable snapshot of the Audio Unit's properties and parameters, suitable for
        /// saving as a user preset.
        ///
        /// Hosts may use this property to save and restore the state of an Audio Unit being used in a
        /// user preset or document. The Audio Unit should not persist transitory properties such as
        /// stream formats, but should save and restore all parameters and custom properties.
        ///
        /// The base class implementation of this property saves the values of all parameters
        /// currently in the parameter tree. A subclass which dynamically produces multiple variants
        /// of the parameter tree needs to be aware that the serialization method does a depth-first
        /// preorder traversal of the tree.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_ClassInfo.
        #[unsafe(method(fullState))]
        #[unsafe(method_family = none)]
        pub unsafe fn fullState(&self) -> Option<Retained<NSDictionary<NSString, AnyObject>>>;

        /// Setter for [`fullState`][Self::fullState].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `full_state` generic should be of the correct type.
        #[unsafe(method(setFullState:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setFullState(&self, full_state: Option<&NSDictionary<NSString, AnyObject>>);

        /// A persistable snapshot of the audio unit's properties and parameters, suitable for
        /// saving in a user's document.
        ///
        /// This property is distinct from fullState in that some state is suitable for saving in user
        /// presets, while other state is not. For example, a synthesizer's master tuning setting could
        /// be considered global state, inappropriate for storing in reusable presets, but desirable
        /// for storing in a document for a specific live performance.
        ///
        /// Hosts saving documents should use this property. If the audio unit does not implement it,
        /// the base class simply sets/gets fullState.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_ClassInfoFromDocument.
        #[unsafe(method(fullStateForDocument))]
        #[unsafe(method_family = none)]
        pub unsafe fn fullStateForDocument(
            &self,
        ) -> Option<Retained<NSDictionary<NSString, AnyObject>>>;

        /// Setter for [`fullStateForDocument`][Self::fullStateForDocument].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `full_state_for_document` generic should be of the correct type.
        #[unsafe(method(setFullStateForDocument:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setFullStateForDocument(
            &self,
            full_state_for_document: Option<&NSDictionary<NSString, AnyObject>>,
        );

        /// A collection of presets provided by the audio unit's developer.
        ///
        /// A preset provides users of an audio unit with an easily-selectable, fine-tuned set of
        /// parameters provided by the developer. This property returns all of the available factory presets.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_FactoryPresets.
        #[unsafe(method(factoryPresets))]
        #[unsafe(method_family = none)]
        pub unsafe fn factoryPresets(&self) -> Option<Retained<NSArray<AUAudioUnitPreset>>>;

        /// A collection of presets saved by the user
        ///
        /// In addition to factory presets, provided by the audio unit vendor, users have the ability to
        /// save the values of the parameters of an audio unit into a user preset. These users presets
        /// can be accessed using this property.
        ///
        /// The default implementation of this method will load the user presets from an internal
        /// location that might not be directly accessible to the audio unit host application or to the
        /// audio unit. Instead of accessing this path directly, the audio unit should rely on the
        /// superclass implementation of this method to retrieve the presets.
        ///
        /// Audio Units are free to override this method to load their user presets via different means
        /// (e.g. from their iCloud container).
        #[unsafe(method(userPresets))]
        #[unsafe(method_family = none)]
        pub unsafe fn userPresets(&self) -> Retained<NSArray<AUAudioUnitPreset>>;

        /// Persistently save the current state of the audio unit into a userPreset
        ///
        /// The new preset will be added to userPresets and will become selectable by assigning it
        /// to the currentPreset property.
        /// If a preset with the provided name already exists then it will be overwritten.
        ///
        /// For user presets, the preset number is required to be negative.
        /// If a positive number is passed, the sign will be changed to negative.
        /// If zero is passed, the number will be set to -1.
        /// These changes will be reflected on the userPreset argument.
        ///
        /// The default implementation of this method will save the user preset to an internal
        /// location.
        ///
        /// Audio Units are free to override this method to operate on a different location (e.g. their
        /// iCloud container).
        ///
        /// Parameter `userPreset`: The preset under which the current state will be saved.
        ///
        /// Parameter `outError`: In the event of a failure, the method will return NO and outError will be set to an
        /// NSError, describing the problem.
        /// Some possible errors:
        /// - domain: NSOSStatusErrorDomain code: kAudioUnitErr_NoConnection
        /// - domain: NSOSStatusErrorDomain    code: kAudioUnitErr_InvalidFilePath
        /// - domain: NSOSStatusErrorDomain    code: kAudioUnitErr_MissingKey
        ///
        /// Returns: YES for success. NO in the event of a failure, in which case the error is returned in
        /// outError.
        #[unsafe(method(saveUserPreset:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn saveUserPreset_error(
            &self,
            user_preset: &AUAudioUnitPreset,
        ) -> Result<(), Retained<NSError>>;

        /// Remove a user preset.
        ///
        /// The user preset will be removed from userPresets and will be permanently deleted.
        ///
        /// The default implementation of this method will delete the user preset from an internal
        /// location.
        ///
        /// Audio Units are free to override this method to operate on a different location (e.g. their
        /// iCloud container).
        ///
        /// Parameter `userPreset`: The preset to be deleted.
        ///
        /// Parameter `outError`: In the event of a failure, the method will return NO and outError will be set to an
        /// NSError, describing the problem.
        /// Some possible errors:
        /// - domain: NSOSStatusErrorDomain code: kAudioUnitErr_NoConnection
        /// - domain: NSPOSIXErrorDomain    code: ENOENT
        /// - domain: NSOSStatusErrorDomain    code: kAudioUnitErr_InvalidFilePath
        ///
        /// Returns: YES for success. NO in the event of a failure, in which case the error is returned in
        /// outError.
        #[unsafe(method(deleteUserPreset:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn deleteUserPreset_error(
            &self,
            user_preset: &AUAudioUnitPreset,
        ) -> Result<(), Retained<NSError>>;

        /// Retrieve the state stored in a user preset
        ///
        /// This method allows access to the contents of a preset without having to set that preset as
        /// current. The returned dictionary is assignable to the audio unit's fullState and/or
        /// fullStateForDocument properties.
        ///
        /// Audio units can override this method in order to vend user presets from a different location
        /// (e.g. their iCloud container).
        ///
        /// In order to restore the state from a user preset, the audio unit should override the setter
        /// for the currentPreset property and check the preset number to determine the type of preset.
        /// If the preset number is >= 0 then the preset is a factory preset.
        /// If the preset number is
        /// <
        /// 0 then it is a user preset.
        ///
        /// This method can then be called to retrieve the state stored in a user preset and the audio
        /// unit can assign this to fullState or fullStateForDocument.
        ///
        ///
        /// Parameter `userPreset`: The preset to be selected.
        ///
        /// Parameter `outError`: In the event of a failure, the method will return nil and outError will be set to an
        /// NSError, describing the problem.
        /// Some possible errors:
        /// - domain: NSOSStatusErrorDomain code: kAudioUnitErr_NoConnection
        /// - domain: NSPOSIXErrorDomain    code: ENOENT
        /// - domain: NSCocoaErrorDomain    code: NSCoderReadCorruptError
        ///
        /// Returns: Returns nil if there was an error, otherwise returns a dictionary containing the full state
        /// of the audio unit saved in the preset.
        /// For details on the possible keys present in the full state dictionary, please see the
        /// documentation for kAudioUnitProperty_ClassInfo.
        /// The minimal set of keys and their type is:
        /// : NSNumber,
        /// : NSNumber,
        /// : NSNumber,
        /// : NSNumber,
        /// : NSString,
        /// : NSNumber,
        /// : NSData
        #[unsafe(method(presetStateFor:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn presetStateFor_error(
            &self,
            user_preset: &AUAudioUnitPreset,
        ) -> Result<Retained<NSDictionary<NSString, AnyObject>>, Retained<NSError>>;

        /// Specifies whether an audio unit supports loading and saving user presets
        ///
        /// The audio unit should set this property to YES if a user preset can be assigned to
        /// currentPreset.
        ///
        /// Audio unit host applications should query this property to determine whether the audio unit
        /// supports user presets.
        ///
        /// Assigning a user preset to the currentPreset property of an audio unit that does not support
        /// restoring state from user presets may result in incorrect behavior.
        #[unsafe(method(supportsUserPresets))]
        #[unsafe(method_family = none)]
        pub unsafe fn supportsUserPresets(&self) -> bool;

        /// Set to YES when an AUAudioUnit is loaded in-process
        ///
        /// If the AUAudioUnit is instantiated with kAudioComponentInstantiation_LoadInProcess, but the
        /// audio unit is not packaged properly to support loading in-process, the system will silently
        /// fall back to loading the audio unit out-of-process.
        ///
        /// This property can be used to determine whether the instantiation succeeded as intended and
        /// the audio unit is running in-process.
        ///
        /// The presence of an extension process is not sufficient indication that the audio unit failed
        /// to load in-process, since the framework might launch the audio unit extension process to
        /// fulfill auxiliary functionality. If the audio unit is loaded in-process then rendering is
        /// done in the host process. Other operations that are not essential to rendering audio, might
        /// be done in the audio unit's extension process.
        #[unsafe(method(isLoadedInProcess))]
        #[unsafe(method_family = none)]
        pub unsafe fn isLoadedInProcess(&self) -> bool;

        /// The audio unit's last-selected preset.
        ///
        /// Hosts can let the user select a preset by setting this property. Note that when getting
        /// this property, it does not reflect whether parameters may have been modified since the
        /// preset was selected.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_PresentPreset.
        #[unsafe(method(currentPreset))]
        #[unsafe(method_family = none)]
        pub unsafe fn currentPreset(&self) -> Option<Retained<AUAudioUnitPreset>>;

        /// Setter for [`currentPreset`][Self::currentPreset].
        #[unsafe(method(setCurrentPreset:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setCurrentPreset(&self, current_preset: Option<&AUAudioUnitPreset>);

        /// The audio unit's processing latency, in seconds.
        ///
        /// This property reflects the delay between when an impulse in the unit's audio unit stream
        /// arrives in the input vs. output streams. This should reflect the delay due
        /// to signal processing (e.g. filters, FFT's, etc.), not delay or reverberation which is
        /// being applied as an effect.
        ///
        /// Note that a latency that varies with parameter settings, including bypass, is generally not
        /// useful to hosts. A host is usually only prepared to add delays before starting to render and
        /// those delays need to be fixed. A variable delay would introduce artifacts even if the host
        /// could track it. If an algorithm has a variable latency it should be adjusted upwards to some
        /// fixed latency within the audio unit. If for some reason this is not possible, then latency
        /// could be regarded as an unavoidable consequence of the algorithm and left unreported (i.e.
        /// with a value of 0).
        ///
        /// Bridged to the v2 property kAudioUnitProperty_Latency.
        #[unsafe(method(latency))]
        #[unsafe(method_family = none)]
        pub unsafe fn latency(&self) -> NSTimeInterval;

        /// The audio unit's tail time, in seconds.
        ///
        /// This property reflects the time interval between when the input stream ends or otherwise
        /// transitions to silence, and when the output stream becomes silent. Unlike latency, this
        /// should reflect the duration of a delay or reverb effect.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_TailTime.
        #[unsafe(method(tailTime))]
        #[unsafe(method_family = none)]
        pub unsafe fn tailTime(&self) -> NSTimeInterval;

        /// Provides a trade-off between rendering quality and CPU load.
        ///
        /// The range of valid values is 0-127.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_RenderQuality.
        #[unsafe(method(renderQuality))]
        #[unsafe(method_family = none)]
        pub unsafe fn renderQuality(&self) -> NSInteger;

        /// Setter for [`renderQuality`][Self::renderQuality].
        #[unsafe(method(setRenderQuality:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setRenderQuality(&self, render_quality: NSInteger);

        /// Directs an effect to route input directly to output, without any processing.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_BypassEffect.
        #[unsafe(method(shouldBypassEffect))]
        #[unsafe(method_family = none)]
        pub unsafe fn shouldBypassEffect(&self) -> bool;

        /// Setter for [`shouldBypassEffect`][Self::shouldBypassEffect].
        #[unsafe(method(setShouldBypassEffect:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setShouldBypassEffect(&self, should_bypass_effect: bool);

        /// Expresses whether an audio unit can process in place.
        ///
        /// In-place processing is the ability for an audio unit to transform an input signal to an
        /// output signal in-place in the input buffer, without requiring a separate output buffer.
        ///
        /// A host can express its desire to process in place by using null mData pointers in the output
        /// buffer list. The audio unit may process in-place in the input buffers. See the discussion of
        /// renderBlock.
        ///
        /// Partially bridged to the v2 property kAudioUnitProperty_InPlaceProcessing; in v3 it is not
        /// settable.
        ///
        /// Defaults to NO. Subclassers can override to return YES.
        #[unsafe(method(canProcessInPlace))]
        #[unsafe(method_family = none)]
        pub unsafe fn canProcessInPlace(&self) -> bool;

        /// Communicates to an audio unit that it is rendering offline.
        ///
        /// A host should set this property when using an audio unit in a context where there are no
        /// realtime deadlines, before asking the unit to allocate render resources. An audio unit may
        /// respond by using a more expensive signal processing algorithm, or allowing itself to block
        /// at render time if data being generated on secondary work threads is not ready in time.
        /// (Normally, in a realtime thread, this data would have to be dropped).
        ///
        /// Bridged to the v2 property kAudioUnitProperty_OfflineRender.
        #[unsafe(method(isRenderingOffline))]
        #[unsafe(method_family = none)]
        pub unsafe fn isRenderingOffline(&self) -> bool;

        /// Setter for [`isRenderingOffline`][Self::isRenderingOffline].
        #[unsafe(method(setRenderingOffline:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setRenderingOffline(&self, rendering_offline: bool);

        /// Expresses valid combinations of input and output channel counts.
        ///
        /// Elements are NSNumber containing integers; [0]=input count, [1]=output count, [2]=2nd input
        /// count, [3]=2nd output count, etc.
        ///
        /// An input, output count of (2, 2) signifies that the audio unit can process 2 input channels
        /// to 2 output channels.
        ///
        /// Negative numbers (-1, -2) indicate *any* number of channels. (-1, -1) means any number
        /// of channels on input and output as long as they are the same. (-1, -2) means any number of
        /// channels on input or output, without the requirement that the counts are the same.
        ///
        /// A negative number less than -2 is used to indicate a total number of channels across every
        /// bus in that scope, regardless of how many channels are set on any particular bus. For
        /// example, (-16, 2) indicates that a unit can accept up to 16 channels of input across its
        /// input busses, but will only produce 2 channels of output.
        ///
        /// Zero on either side (though typically input) means "not applicable", because there are no
        /// elements on that side.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_SupportedNumChannels.
        #[unsafe(method(channelCapabilities))]
        #[unsafe(method_family = none)]
        pub unsafe fn channelCapabilities(&self) -> Option<Retained<NSArray<NSNumber>>>;

        #[cfg(feature = "block2")]
        /// A callback for the AU to call the host for musical context information.
        ///
        /// Note that an audio unit implementation accessing this property should cache it in
        /// realtime-safe storage before beginning to render.
        ///
        /// Bridged to the HostCallback_GetBeatAndTempo and HostCallback_GetMusicalTimeLocation
        /// callback members in kAudioUnitProperty_HostCallbacks.
        ///
        /// # Safety
        ///
        /// - The returned block's argument 1 must be a valid pointer or null.
        /// - The returned block's argument 2 must be a valid pointer or null.
        /// - The returned block's argument 3 must be a valid pointer or null.
        /// - The returned block's argument 4 must be a valid pointer or null.
        /// - The returned block's argument 5 must be a valid pointer or null.
        /// - The returned block's argument 6 must be a valid pointer or null.
        #[unsafe(method(musicalContextBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn musicalContextBlock(&self) -> AUHostMusicalContextBlock;

        #[cfg(feature = "block2")]
        /// Setter for [`musicalContextBlock`][Self::musicalContextBlock].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `musical_context_block` must be a valid pointer or null.
        #[unsafe(method(setMusicalContextBlock:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setMusicalContextBlock(
            &self,
            musical_context_block: AUHostMusicalContextBlock,
        );

        #[cfg(feature = "block2")]
        /// A callback for the AU to call the host for transport state information.
        ///
        /// Note that an audio unit implementation accessing this property should cache it in
        /// realtime-safe storage before beginning to render.
        ///
        /// Bridged to the HostCallback_GetTransportState and HostCallback_GetTransportState2
        /// callback members in kAudioUnitProperty_HostCallbacks.
        ///
        /// # Safety
        ///
        /// - The returned block's argument 1 must be a valid pointer or null.
        /// - The returned block's argument 2 must be a valid pointer or null.
        /// - The returned block's argument 3 must be a valid pointer or null.
        /// - The returned block's argument 4 must be a valid pointer or null.
        #[unsafe(method(transportStateBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn transportStateBlock(&self) -> AUHostTransportStateBlock;

        #[cfg(feature = "block2")]
        /// Setter for [`transportStateBlock`][Self::transportStateBlock].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `transport_state_block` must be a valid pointer or null.
        #[unsafe(method(setTransportStateBlock:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setTransportStateBlock(
            &self,
            transport_state_block: AUHostTransportStateBlock,
        );

        /// Information about the host context in which the audio unit is connected, for display
        /// in the audio unit's view.
        ///
        /// For example, a host could set "track 3" as the context, so that the audio unit's view could
        /// then display to the user "My audio unit on track 3".
        ///
        /// Bridged to the v2 property kAudioUnitProperty_ContextName.
        #[unsafe(method(contextName))]
        #[unsafe(method_family = none)]
        pub unsafe fn contextName(&self) -> Option<Retained<NSString>>;

        /// Setter for [`contextName`][Self::contextName].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        #[unsafe(method(setContextName:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setContextName(&self, context_name: Option<&NSString>);

        /// Information for migrating data from other audio plug-ins to the v3 Audio Unit architecture.
        ///
        /// This can be used to migrate settings from an older Audio Unit; this allows manufacturers
        /// to deprecate older Audio Units and replace them with new ones. The data for the older Audio Unit is
        /// an array of NSData representing byte encoded AudioUnitOtherPluginDescs to migrate from.
        /// Can also be used to migrate from a v2 to a v3 Audio Unit.
        ///
        /// Bridged to the v2 property kAudioUnitMigrateProperty_FromPlugin.
        #[unsafe(method(migrateFromPlugin))]
        #[unsafe(method_family = none)]
        pub unsafe fn migrateFromPlugin(&self) -> Retained<NSArray>;

        /// Specifies whether an audio unit supports Multi-dimensional Polyphonic Expression.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_SupportsMPE.
        #[unsafe(method(supportsMPE))]
        #[unsafe(method_family = none)]
        pub unsafe fn supportsMPE(&self) -> bool;

        /// Specify a mapping of input channels to output channels.
        ///
        /// Converter and input/output audio units may support re-ordering or splitting of input
        /// channels to output channels. The number of channels in the channel map is the number of
        /// channels of the destination (output format). The channel map entries contain a channel
        /// number of the source channel that should be mapped to that destination channel. If -1 is
        /// specified, then that destination channel will not contain any channel from the source (so it
        /// will be silent).
        ///
        /// If the property value is nil, then the audio unit does not support this property.
        ///
        /// Bridged to the v2 property kAudioOutputUnitProperty_ChannelMap.
        #[unsafe(method(channelMap))]
        #[unsafe(method_family = none)]
        pub unsafe fn channelMap(&self) -> Option<Retained<NSArray<NSNumber>>>;

        /// Setter for [`channelMap`][Self::channelMap].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        #[unsafe(method(setChannelMap:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setChannelMap(&self, channel_map: Option<&NSArray<NSNumber>>);

        #[cfg(feature = "objc2-core-midi")]
        /// Given a MIDI cable and channel number, return the supported MIDI-CI Profiles.
        ///
        /// Parameter `cable`: The virtual MIDI cable for which the profiles are requested.
        ///
        /// Parameter `channel`: The MIDI channel for which the profiles are requested.
        ///
        /// Returns: A MIDICIProfileState object containing all the supported MIDI-CI profiles for this channel
        /// on this cable.
        #[unsafe(method(profileStateForCable:channel:))]
        #[unsafe(method_family = none)]
        pub unsafe fn profileStateForCable_channel(
            &self,
            cable: u8,
            channel: MIDIChannelNumber,
        ) -> Retained<MIDICIProfileState>;

        #[cfg(feature = "objc2-core-midi")]
        /// Enable a MIDI-CI Profile on the specified cable/channel.
        ///
        /// Parameter `profile`: The MIDI-CI profile to be enabled.
        ///
        /// Parameter `cable`: The virtual MIDI cable.
        ///
        /// Parameter `channel`: The MIDI channel.
        ///
        /// Parameter `outError`: Returned in the event of failure.
        ///
        /// Returns: YES for success. NO in the event of a failure, in which case the error is returned
        /// in outError.
        #[unsafe(method(enableProfile:cable:onChannel:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn enableProfile_cable_onChannel_error(
            &self,
            profile: &MIDICIProfile,
            cable: u8,
            channel: MIDIChannelNumber,
        ) -> Result<(), Retained<NSError>>;

        #[cfg(feature = "objc2-core-midi")]
        /// Disable a MIDI-CI Profile on the specified cable/channel.
        ///
        /// Parameter `profile`: The MIDI-CI profile to be disabled.
        ///
        /// Parameter `cable`: The virtual MIDI cable.
        ///
        /// Parameter `channel`: The MIDI channel.
        ///
        /// Parameter `outError`: Returned in the event of failure.
        ///
        /// Returns: YES for success. NO in the event of a failure, in which case the error is returned
        /// in outError.
        #[unsafe(method(disableProfile:cable:onChannel:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn disableProfile_cable_onChannel_error(
            &self,
            profile: &MIDICIProfile,
            cable: u8,
            channel: MIDIChannelNumber,
        ) -> Result<(), Retained<NSError>>;

        #[cfg(all(feature = "block2", feature = "objc2-core-midi"))]
        /// A block called when a device notifies that a MIDI-CI profile has been enabled or
        /// disabled.
        ///
        /// Since enabling / disabling MIDI-CI profiles is an asynchronous operation, the host can set
        /// this block and the audio unit is expected to call it every time the state of a MIDI-CI
        /// profile has changed.
        ///
        /// # Safety
        ///
        /// The returned block's argument 3 must be a valid pointer.
        #[unsafe(method(profileChangedBlock))]
        #[unsafe(method_family = none)]
        pub unsafe fn profileChangedBlock(&self) -> AUMIDICIProfileChangedBlock;

        #[cfg(all(feature = "block2", feature = "objc2-core-midi"))]
        /// Setter for [`profileChangedBlock`][Self::profileChangedBlock].
        ///
        /// # Safety
        ///
        /// `profile_changed_block` must be a valid pointer or null.
        #[unsafe(method(setProfileChangedBlock:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setProfileChangedBlock(
            &self,
            profile_changed_block: AUMIDICIProfileChangedBlock,
        );

        /// Returns an object for bidirectional communication between an Audio Unit and its host.
        ///
        /// Message channels provide a flexible way for custom data exchange between an Audio Unit and its host.
        /// An Audio Unit can support multiple message channels which are identified by the `channelName`.
        /// The message channel object's lifetime is managed by the host. Message channel objects should be designed
        /// in such a way that they could outlive the AU that vended them.
        /// For further details see discussion for `AUMessageChannel`.
        ///
        /// Parameter `channelName`: The name of the message channel to be returned by the Audio Unit if supported.
        ///
        /// Returns: An object that conforms to the `AUMessageChannel` protocol.
        #[unsafe(method(messageChannelFor:))]
        #[unsafe(method_family = none)]
        pub unsafe fn messageChannelFor(
            &self,
            channel_name: &NSString,
        ) -> Retained<ProtocolObject<dyn AUMessageChannel>>;
    );
}

/// Methods declared on superclass `NSObject`.
impl AUAudioUnit {
    extern_methods!(
        #[unsafe(method(new))]
        #[unsafe(method_family = new)]
        pub unsafe fn new() -> Retained<Self>;
    );
}

/// Block to notify the client of an I/O unit that input is available.
///
/// Parameter `actionFlags`: Pointer to action flags.
///
/// Parameter `timestamp`: The HAL time at which the input data was captured. If there is a sample rate conversion
/// or time compression/expansion downstream, the sample time will not be valid.
///
/// Parameter `frameCount`: The number of sample frames of input available.
///
/// Parameter `inputBusNumber`: The index of the input bus from which input is available.
///
/// The input data is obtained by calling the render block of the audio unit.
/// The AUAudioUnit is not provided since it is not safe to message an Objective C
/// object in a real time context.
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auinputhandler?language=objc)
#[cfg(all(
    feature = "AUComponent",
    feature = "block2",
    feature = "objc2-core-audio-types"
))]
pub type AUInputHandler = *mut block2::DynBlock<
    dyn Fn(
        NonNull<AudioUnitRenderActionFlags>,
        NonNull<AudioTimeStamp>,
        AUAudioFrameCount,
        NSInteger,
    ),
>;

/// AUAudioInputOutputUnit.
///
/// Additional methods for audio units which can do input/output.
///
/// These methods will fail if the audio unit is not an input/output audio unit.
impl AUAudioUnit {
    extern_methods!(
        /// Whether the I/O device can perform input.
        #[unsafe(method(canPerformInput))]
        #[unsafe(method_family = none)]
        pub unsafe fn canPerformInput(&self) -> bool;

        /// Whether the I/O device can perform output.
        #[unsafe(method(canPerformOutput))]
        #[unsafe(method_family = none)]
        pub unsafe fn canPerformOutput(&self) -> bool;

        /// Flag enabling audio input from the unit.
        ///
        /// Input is disabled by default. This must be set to YES if input audio is desired.
        /// Setting to YES will have no effect if canPerformInput is false.
        #[unsafe(method(isInputEnabled))]
        #[unsafe(method_family = none)]
        pub unsafe fn isInputEnabled(&self) -> bool;

        /// Setter for [`isInputEnabled`][Self::isInputEnabled].
        #[unsafe(method(setInputEnabled:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setInputEnabled(&self, input_enabled: bool);

        /// Flag enabling audio output from the unit.
        ///
        /// Output is enabled by default.
        /// Setting to YES will have no effect if canPerformOutput is false.
        #[unsafe(method(isOutputEnabled))]
        #[unsafe(method_family = none)]
        pub unsafe fn isOutputEnabled(&self) -> bool;

        /// Setter for [`isOutputEnabled`][Self::isOutputEnabled].
        #[unsafe(method(setOutputEnabled:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setOutputEnabled(&self, output_enabled: bool);

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// The block that the output unit will call to get audio to send to the output.
        ///
        /// This block must be set if output is enabled.
        ///
        /// # Safety
        ///
        /// - The returned block's argument 1 must be a valid pointer.
        /// - The returned block's argument 2 must be a valid pointer.
        /// - The returned block's argument 5 must be a valid pointer.
        #[unsafe(method(outputProvider))]
        #[unsafe(method_family = none)]
        pub unsafe fn outputProvider(&self) -> AURenderPullInputBlock;

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// Setter for [`outputProvider`][Self::outputProvider].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `output_provider` must be a valid pointer or null.
        #[unsafe(method(setOutputProvider:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setOutputProvider(&self, output_provider: AURenderPullInputBlock);

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// The block that the output unit will call to notify when input is available.
        ///
        /// See discussion for AUInputHandler.
        ///
        /// # Safety
        ///
        /// - The returned block's argument 1 must be a valid pointer.
        /// - The returned block's argument 2 must be a valid pointer.
        #[unsafe(method(inputHandler))]
        #[unsafe(method_family = none)]
        pub unsafe fn inputHandler(&self) -> AUInputHandler;

        #[cfg(all(
            feature = "AUComponent",
            feature = "block2",
            feature = "objc2-core-audio-types"
        ))]
        /// Setter for [`inputHandler`][Self::inputHandler].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `input_handler` must be a valid pointer or null.
        #[unsafe(method(setInputHandler:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setInputHandler(&self, input_handler: AUInputHandler);

        /// Get the I/O hardware device.
        #[unsafe(method(deviceID))]
        #[unsafe(method_family = none)]
        pub unsafe fn deviceID(&self) -> AUAudioObjectID;

        /// Set the I/O hardware device.
        ///
        /// Parameter `deviceID`: The device to select.
        ///
        /// Parameter `outError`: Returned in the event of failure.
        #[unsafe(method(setDeviceID:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn setDeviceID_error(
            &self,
            device_id: AUAudioObjectID,
        ) -> Result<(), Retained<NSError>>;

        /// The audio device's input latency, in seconds.
        ///
        /// Bridged to the HAL property kAudioDevicePropertyLatency, which is implemented
        /// by v2 input/output units.
        #[unsafe(method(deviceInputLatency))]
        #[unsafe(method_family = none)]
        pub unsafe fn deviceInputLatency(&self) -> NSTimeInterval;

        /// The audio device's output latency, in seconds.
        ///
        /// Bridged to the HAL property kAudioDevicePropertyLatency, which is implemented
        /// by v2 input/output units.
        #[unsafe(method(deviceOutputLatency))]
        #[unsafe(method_family = none)]
        pub unsafe fn deviceOutputLatency(&self) -> NSTimeInterval;

        /// The audio device's running state.
        #[unsafe(method(isRunning))]
        #[unsafe(method_family = none)]
        pub unsafe fn isRunning(&self) -> bool;

        /// Starts the audio hardware.
        ///
        /// Parameter `outError`: Returned in the event of failure.
        #[unsafe(method(startHardwareAndReturnError:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn startHardwareAndReturnError(&self) -> Result<(), Retained<NSError>>;

        /// Stops the audio hardware.
        #[unsafe(method(stopHardware))]
        #[unsafe(method_family = none)]
        pub unsafe fn stopHardware(&self);
    );
}

extern_class!(
    /// Container for an audio unit's input or output busses.
    ///
    /// Hosts can observe a bus property across all busses by using KVO on this object, without
    /// having to observe it on each individual bus. (One could add listeners to individual busses,
    /// but that means one has to observe bus count changes and add/remove listeners in response.
    /// Also, NSArray's addObserver:toObjectsAtIndexes:forKeyPath:options:context: is problematic;
    /// it does not let the individual objects override the observation request, and so a bus which
    /// is proxying a bus in an extension process does not get the message.)
    ///
    /// Some audio units (e.g. mixers) support variable numbers of busses, via subclassing. When the
    /// bus count changes, a KVO notification is sent on "inputBusses" or "outputBusses," as
    /// appropriate.
    ///
    /// Subclassers should see also the AUAudioUnitBusImplementation category.
    ///
    /// The bus array is bridged to the v2 property kAudioUnitProperty_ElementCount.
    ///
    /// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounitbusarray?language=objc)
    #[unsafe(super(NSObject))]
    #[derive(Debug, PartialEq, Eq, Hash)]
    pub struct AUAudioUnitBusArray;
);

extern_conformance!(
    unsafe impl NSFastEnumeration for AUAudioUnitBusArray {}
);

extern_conformance!(
    unsafe impl NSObjectProtocol for AUAudioUnitBusArray {}
);

impl AUAudioUnitBusArray {
    extern_methods!(
        #[unsafe(method(init))]
        #[unsafe(method_family = init)]
        pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>;

        /// Initializes by making a copy of the supplied bus array.
        #[unsafe(method(initWithAudioUnit:busType:busses:))]
        #[unsafe(method_family = init)]
        pub unsafe fn initWithAudioUnit_busType_busses(
            this: Allocated<Self>,
            owner: &AUAudioUnit,
            bus_type: AUAudioUnitBusType,
            bus_array: &NSArray<AUAudioUnitBus>,
        ) -> Retained<Self>;

        /// Initializes an empty bus array.
        #[unsafe(method(initWithAudioUnit:busType:))]
        #[unsafe(method_family = init)]
        pub unsafe fn initWithAudioUnit_busType(
            this: Allocated<Self>,
            owner: &AUAudioUnit,
            bus_type: AUAudioUnitBusType,
        ) -> Retained<Self>;

        #[unsafe(method(count))]
        #[unsafe(method_family = none)]
        pub unsafe fn count(&self) -> NSUInteger;

        #[unsafe(method(objectAtIndexedSubscript:))]
        #[unsafe(method_family = none)]
        pub unsafe fn objectAtIndexedSubscript(
            &self,
            index: NSUInteger,
        ) -> Retained<AUAudioUnitBus>;

        /// Whether the array can have a variable number of busses.
        ///
        /// The base implementation returns false.
        #[unsafe(method(isCountChangeable))]
        #[unsafe(method_family = none)]
        pub unsafe fn isCountChangeable(&self) -> bool;

        /// Change the number of busses in the array.
        #[unsafe(method(setBusCount:error:_))]
        #[unsafe(method_family = none)]
        pub unsafe fn setBusCount_error(&self, count: NSUInteger) -> Result<(), Retained<NSError>>;

        /// Add a KVO observer for a property on all busses in the array.
        ///
        /// # Safety
        ///
        /// - `observer` should be of the correct type.
        /// - `context` must be a valid pointer or null.
        #[unsafe(method(addObserverToAllBusses:forKeyPath:options:context:))]
        #[unsafe(method_family = none)]
        pub unsafe fn addObserverToAllBusses_forKeyPath_options_context(
            &self,
            observer: &NSObject,
            key_path: &NSString,
            options: NSKeyValueObservingOptions,
            context: *mut c_void,
        );

        /// Remove a KVO observer for a property on all busses in the array.
        ///
        /// # Safety
        ///
        /// - `observer` should be of the correct type.
        /// - `context` must be a valid pointer or null.
        #[unsafe(method(removeObserverFromAllBusses:forKeyPath:context:))]
        #[unsafe(method_family = none)]
        pub unsafe fn removeObserverFromAllBusses_forKeyPath_context(
            &self,
            observer: &NSObject,
            key_path: &NSString,
            context: *mut c_void,
        );

        /// The audio unit that owns the bus.
        ///
        /// # Safety
        ///
        /// This is not retained internally, you must ensure the object is still alive.
        #[unsafe(method(ownerAudioUnit))]
        #[unsafe(method_family = none)]
        pub unsafe fn ownerAudioUnit(&self) -> Retained<AUAudioUnit>;

        /// Which bus array this is (input or output).
        #[unsafe(method(busType))]
        #[unsafe(method_family = none)]
        pub unsafe fn busType(&self) -> AUAudioUnitBusType;
    );
}

/// Methods declared on superclass `NSObject`.
impl AUAudioUnitBusArray {
    extern_methods!(
        #[unsafe(method(new))]
        #[unsafe(method_family = new)]
        pub unsafe fn new() -> Retained<Self>;
    );
}

extern_class!(
    /// An input or output connection point on an audio unit.
    ///
    /// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounitbus?language=objc)
    #[unsafe(super(NSObject))]
    #[derive(Debug, PartialEq, Eq, Hash)]
    pub struct AUAudioUnitBus;
);

extern_conformance!(
    unsafe impl NSObjectProtocol for AUAudioUnitBus {}
);

impl AUAudioUnitBus {
    extern_methods!(
        /// Controls the audio unit's allocation strategy for a bus.
        ///
        /// Hosts can set this flag to communicate whether an audio unit should allocate its own buffer.
        /// By default this flag is set to true.
        ///
        /// On the output side, shouldAllocateBuffer=false means the AU can assume that it will be
        /// called with non-null output buffers. If shouldAllocateBuffer=true (the default), the AU must
        /// be prepared to be called with null pointers and replace them with pointers to its internally
        /// allocated buffer.
        ///
        /// On the input side, shouldAllocateBuffer=false means the AU can pull for input using a buffer
        /// list with null buffer pointers, and assume that the pull input block will provide pointers.
        /// If shouldAllocateBuffer=true (the default), the AU must pull with non-null pointers while
        /// still being prepared for the source to replace them with pointers of its own.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_ShouldAllocateBuffer.
        #[unsafe(method(shouldAllocateBuffer))]
        #[unsafe(method_family = none)]
        pub unsafe fn shouldAllocateBuffer(&self) -> bool;

        /// Setter for [`shouldAllocateBuffer`][Self::shouldAllocateBuffer].
        #[unsafe(method(setShouldAllocateBuffer:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setShouldAllocateBuffer(&self, should_allocate_buffer: bool);

        /// Whether the bus is active.
        ///
        /// Hosts must enable input busses before using them. The reason for this is to allow a unit
        /// such as a mixer to be prepared to render a large number of inputs, but avoid the work
        /// of preparing to pull inputs which are not in use.
        ///
        /// Bridged to the v2 properties kAudioUnitProperty_MakeConnection and
        /// kAudioUnitProperty_SetRenderCallback.
        #[unsafe(method(isEnabled))]
        #[unsafe(method_family = none)]
        pub unsafe fn isEnabled(&self) -> bool;

        /// Setter for [`isEnabled`][Self::isEnabled].
        #[unsafe(method(setEnabled:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setEnabled(&self, enabled: bool);

        /// A name for the bus. Can be set by host.
        #[unsafe(method(name))]
        #[unsafe(method_family = none)]
        pub unsafe fn name(&self) -> Option<Retained<NSString>>;

        /// Setter for [`name`][Self::name].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        #[unsafe(method(setName:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setName(&self, name: Option<&NSString>);

        /// The index of this bus in the containing array.
        #[unsafe(method(index))]
        #[unsafe(method_family = none)]
        pub unsafe fn index(&self) -> NSUInteger;

        /// The AUAudioUnitBusType.
        #[unsafe(method(busType))]
        #[unsafe(method_family = none)]
        pub unsafe fn busType(&self) -> AUAudioUnitBusType;

        /// The audio unit that owns the bus.
        ///
        /// # Safety
        ///
        /// This is not retained internally, you must ensure the object is still alive.
        #[unsafe(method(ownerAudioUnit))]
        #[unsafe(method_family = none)]
        pub unsafe fn ownerAudioUnit(&self) -> Retained<AUAudioUnit>;

        /// This is an array of NSNumbers representing AudioChannelLayoutTag.
        #[unsafe(method(supportedChannelLayoutTags))]
        #[unsafe(method_family = none)]
        pub unsafe fn supportedChannelLayoutTags(&self) -> Option<Retained<NSArray<NSNumber>>>;

        /// Information about latency in the audio unit's processing context.
        ///
        /// This should not be confused with the audio unit's latency property, where the audio unit
        /// describes to the host any processing latency it introduces between its input and its output.
        ///
        /// A host may set this property to describe to the audio unit the presentation latency of its
        /// input and/or output audio data. Latency is described in seconds. A value of zero means
        /// either no latency or an unknown latency.
        ///
        /// A host should set this property on each active bus, since, for example, the audio routing
        /// path to each of multiple output busses may differ.
        ///
        /// For input busses:
        /// Describes how long ago the audio arriving on this bus was acquired. For instance, when
        /// reading from a file to the first audio unit in a chain, the input presentation latency
        /// is zero. For audio input from a device, this initial input latency is the presentation
        /// latency of the device itself, i.e. the device's safety offset and latency.
        ///
        /// A second chained audio unit's input presentation latency will be the input presentation
        /// latency of the first unit, plus the processing latency of the first unit.
        ///
        /// For output busses:
        /// Describes how long it will be before the output audio of an audio unit is presented. For
        /// instance, when writing to a file, the output presentation latency of the last audio unit
        /// in a chain is zero. When the audio from that audio unit is to be played to a device,
        /// then that initial presentation latency will be the presentation latency of the device
        /// itself, which is the I/O buffer size, plus the device's safety offset and latency
        ///
        /// A previous chained audio unit's output presentation latency is the last unit's
        /// presentation latency plus its processing latency.
        ///
        /// So, for a given audio unit anywhere within a mixing graph, the input and output presentation
        /// latencies describe to that unit how long from the moment of generation it has taken for its
        /// input to arrive, and how long it will take for its output to be presented.
        ///
        /// Bridged to the v2 property kAudioUnitProperty_PresentationLatency.
        #[unsafe(method(contextPresentationLatency))]
        #[unsafe(method_family = none)]
        pub unsafe fn contextPresentationLatency(&self) -> NSTimeInterval;

        /// Setter for [`contextPresentationLatency`][Self::contextPresentationLatency].
        #[unsafe(method(setContextPresentationLatency:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setContextPresentationLatency(
            &self,
            context_presentation_latency: NSTimeInterval,
        );
    );
}

/// Methods declared on superclass `NSObject`.
impl AUAudioUnitBus {
    extern_methods!(
        #[unsafe(method(init))]
        #[unsafe(method_family = init)]
        pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>;

        #[unsafe(method(new))]
        #[unsafe(method_family = new)]
        pub unsafe fn new() -> Retained<Self>;
    );
}

extern_class!(
    /// A collection of parameter settings provided by the audio unit implementor, producing a
    /// useful sound or starting point.
    ///
    /// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/auaudiounitpreset?language=objc)
    #[unsafe(super(NSObject))]
    #[derive(Debug, PartialEq, Eq, Hash)]
    pub struct AUAudioUnitPreset;
);

extern_conformance!(
    unsafe impl NSCoding for AUAudioUnitPreset {}
);

extern_conformance!(
    unsafe impl NSObjectProtocol for AUAudioUnitPreset {}
);

extern_conformance!(
    unsafe impl NSSecureCoding for AUAudioUnitPreset {}
);

impl AUAudioUnitPreset {
    extern_methods!(
        /// The preset's unique numeric identifier.
        #[unsafe(method(number))]
        #[unsafe(method_family = none)]
        pub unsafe fn number(&self) -> NSInteger;

        /// Setter for [`number`][Self::number].
        #[unsafe(method(setNumber:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setNumber(&self, number: NSInteger);

        /// The preset's name.
        #[unsafe(method(name))]
        #[unsafe(method_family = none)]
        pub unsafe fn name(&self) -> Retained<NSString>;

        /// Setter for [`name`][Self::name].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        #[unsafe(method(setName:))]
        #[unsafe(method_family = none)]
        pub unsafe fn setName(&self, name: &NSString);
    );
}

/// Methods declared on superclass `NSObject`.
impl AUAudioUnitPreset {
    extern_methods!(
        #[unsafe(method(init))]
        #[unsafe(method_family = init)]
        pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>;

        #[unsafe(method(new))]
        #[unsafe(method_family = new)]
        pub unsafe fn new() -> Retained<Self>;
    );
}

/// Block that hosts provide to AU message channels to be called back by the AU.
///
/// Parameter `message`: An NSDictionary with custom data. The allowed classes for key and value types are
/// NSArray, NSDictionary, NSOrderedSet, NSSet, NSString, NSData, NSNull, NSNumber, NSDate
///
/// Returns: An NSDictionary with custom data. The allowed classes for key and value types are
/// NSArray, NSDictionary, NSOrderedSet, NSSet, NSString, NSData, NSNull, NSNumber, NSDate
///
/// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/callhostblock?language=objc)
#[cfg(feature = "block2")]
pub type CallHostBlock =
    *mut block2::DynBlock<dyn Fn(NonNull<NSDictionary>) -> NonNull<NSDictionary>>;

extern_protocol!(
    /// The protocol which objects returned from `[AUAudioUnit messageChannelFor:]` have to conform to.
    ///
    /// Audio Units and hosts that have special needs of communication, e.g. to exchange musical context required for better audio processing,
    /// can implement a communication object to exchange messages in form of NSDictionaries. An Audio Unit would need to implement
    /// a class conforming to the AUMessageChannel protocol and return an instance via `[AUAudioUnit messageChannelFor:]`. A host can query
    /// the instance via the channel name.
    /// The protocol offers a method to send messages to the AU and a block to send messages to the host.
    ///
    /// See also [Apple's documentation](https://developer.apple.com/documentation/audiotoolbox/aumessagechannel?language=objc)
    pub unsafe trait AUMessageChannel {
        /// Calls the Audio Unit with custom data message.
        ///
        /// Parameter `message`: An NSDictionary with custom data. The allowed classes for key and value types are
        /// NSArray, NSDictionary, NSOrderedSet, NSSet, NSString, NSData, NSNull, NSNumber, NSDate
        ///
        /// Returns: An NSDictionary with custom data. The allowed classes for key and value types are
        /// NSArray, NSDictionary, NSOrderedSet, NSSet, NSString, NSData, NSNull, NSNumber, NSDate
        ///
        /// # Safety
        ///
        /// `message` generic should be of the correct type.
        #[optional]
        #[unsafe(method(callAudioUnit:))]
        #[unsafe(method_family = none)]
        unsafe fn callAudioUnit(&self, message: &NSDictionary) -> Retained<NSDictionary>;

        #[cfg(feature = "block2")]
        /// A callback for the AU to send a message to the host.
        ///
        /// The host has to set a block on this property.
        ///
        /// # Safety
        ///
        /// The returned block's argument must be a valid pointer.
        #[optional]
        #[unsafe(method(callHostBlock))]
        #[unsafe(method_family = none)]
        unsafe fn callHostBlock(&self) -> CallHostBlock;

        #[cfg(feature = "block2")]
        /// Setter for [`callHostBlock`][Self::callHostBlock].
        ///
        /// This is [copied][objc2_foundation::NSCopying::copy] when set.
        ///
        /// # Safety
        ///
        /// `call_host_block` must be a valid pointer or null.
        #[optional]
        #[unsafe(method(setCallHostBlock:))]
        #[unsafe(method_family = none)]
        unsafe fn setCallHostBlock(&self, call_host_block: CallHostBlock);
    }
);

/// IntendedSpatialExperience.
impl AUAudioUnit {
    extern_methods!();
}