Class OpenXRCustomLayerHandler<T>

Provides a base implementation for the OpenXRLayerProvider.ILayerHandler interface. You can implement the required methods of this abstract class to create a concrete layer handler.

Inheritance
object
OpenXRCustomLayerHandler<T>
Implements
Inherited Members
object.Equals(object)
object.Equals(object, object)
object.GetHashCode()
object.GetType()
object.MemberwiseClone()
Namespace: UnityEngine.XR.OpenXR.CompositionLayers
Assembly: Unity.XR.OpenXR.dll
Syntax
public abstract class OpenXRCustomLayerHandler<T> : OpenXRLayerProvider.ILayerHandler, IDisposable where T : struct
Type Parameters
Name Description
T

The native OpenXR structure of the composition layer to handle.
Remarks

The OpenXRLayerProvider.ILayerHandler methods that this class implements handle adding and removing composition layers from native arrays, swap chain creation dispatching and other tasks required by the Unity side of the API.

The abstract methods that you must implement handle the custom aspects of your layer. These methods include:

You are not required to implement a custom layer handler based on this abstract class, but doing so should be easier than implementing the OpenXRLayerProvider.ILayerHandler interface in its entirety.

You must register your concrete layer handler object with RegisterLayerHandler(Type, ILayerHandler).

Constructors

OpenXRCustomLayerHandler()

Initializes and returns an instance of this OpenXRCustomLayerHandler<T> while also setting the singleton instance member.

Declaration
protected OpenXRCustomLayerHandler()

Fields

Instance

Singleton instance of this specific handler.

Declaration
protected static OpenXRCustomLayerHandler<T> Instance
Field Value
Type Description
OpenXRCustomLayerHandler<T>

actionsForMainThread

Thread safe queue used to dispatch callbacks that may come from other threads such as the swapchain creation on the graphics thread.

Declaration
protected ConcurrentQueue<Action> actionsForMainThread
Field Value
Type Description
ConcurrentQueue<Action>

m_nativeLayers

Mapping of instance ids and native layer structs to help determine what layers are currently set to be active.

Declaration
protected Dictionary<int, T> m_nativeLayers
Field Value
Type Description
Dictionary<int, T>

Methods

ActiveNativeLayer(LayerInfo, ref T)

Override this method to modify a native composition layer struct in response to when it is active. An active compositon layer will invoke this every frame.

Declaration
protected virtual bool ActiveNativeLayer(CompositionLayerManager.LayerInfo layerInfo, ref T nativeLayer)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer that is active.
T nativeLayer

A reference to the native OpenXR structure of the composition layer that is active.
Returns
Type Description
bool

Bool indicating success or failure. A failure case will result in the native composition layer struct not being added into the final XrFrameEndInfo struct.

CreateLayer(LayerInfo)

Implements the OpenXRLayerProvider.ILayerHandler method that is called by the OpenXRLayerProvider when a new layer has been created. This implementation triggers the creation of a swapchain before the actual native layer struct is created.

Declaration
public void CreateLayer(CompositionLayerManager.LayerInfo layerInfo)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer being created.

CreateNativeLayer(LayerInfo, SwapchainCreatedOutput, out T)

Declaration
protected abstract bool CreateNativeLayer(CompositionLayerManager.LayerInfo layerInfo, OpenXRCustomLayerHandler<T>.SwapchainCreatedOutput swapchainOutput, out T nativeLayer)
Parameters
Type Name Description
LayerInfo layerInfo
OpenXRCustomLayerHandler<T>.SwapchainCreatedOutput swapchainOutput
T nativeLayer
Returns
Type Description
bool

CreateSwapchain(LayerInfo, out SwapchainCreateInfo)

Declaration
protected abstract bool CreateSwapchain(CompositionLayerManager.LayerInfo layerInfo, out OpenXRCustomLayerHandler<T>.SwapchainCreateInfo swapchainCreateInfo)
Parameters
Type Name Description
LayerInfo layerInfo
OpenXRCustomLayerHandler<T>.SwapchainCreateInfo swapchainCreateInfo
Returns
Type Description
bool

CreateSwapchainAsync(LayerInfo)

Calls CreateSwapchain(LayerInfo, out SwapchainCreateInfo) to create a OpenXRCustomLayerHandler<T>.SwapchainCreateInfo struct that is then passed to the UnityOpenXR lib to actually create the swapchain on the graphics thread. The static OnCreatedSwapchainCallback(int, ulong) method is passed as a callback and invoked when the swapchain has been created.

Declaration
protected virtual void CreateSwapchainAsync(CompositionLayerManager.LayerInfo layerInfo)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer that was just created.

Dispose()

Implements method from IDisposable that is called by the OpenXRLayerProvider when this custom layer handler instance is disposed.

Declaration
public void Dispose()

Dispose(bool)

Clears all maps and disposes any created native arrays.

Declaration
protected virtual void Dispose(bool disposing)
Parameters
Type Name Description
bool disposing

Determines if this method was called from the Dispose() method or the finalizer.

~OpenXRCustomLayerHandler()

Declaration
protected ~OpenXRCustomLayerHandler()

ModifyLayer(LayerInfo)

Implements the OpenXRLayerProvider.ILayerHandler method that is called by the OpenXRLayerProvider when a layer or attached extension has been modified. This implementation asks the subclass for any changes that must be made to the layer via ModifyNativeLayer(LayerInfo, ref T) by sending a reference to the native layer struct.

Declaration
public virtual void ModifyLayer(CompositionLayerManager.LayerInfo layerInfo)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer that was modified.

ModifyNativeLayer(LayerInfo, ref T)

Override this method to modify a native composition layer struct in response to changes on the associated Unity.XR.CompositionLayers.Layers.LayerData object or any extension components on the Unity.XR.CompositionLayers.CompositionLayer GameObject.

Declaration
protected abstract bool ModifyNativeLayer(CompositionLayerManager.LayerInfo layerInfo, ref T nativeLayer)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer that was modified.
T nativeLayer

A reference to the native OpenXR structure of the composition layer that was modified. The concrete implementation of this method should update the values of the structure as appropriate.
Returns
Type Description
bool

A bool indicating success or failure.
Remarks

You must reinitialize the Next pointer with OpenXRLayerUtility.GetExtensionsChain(CompositionLayerManager.LayerInfo, Unity.XR.CompositionLayers.CompositionLayerExtension.ExtensionTarget) to get any potential updates from extension components.

Examples

Modifies an XrCompositionLayerQuad struct with new transform and extension information.

protected override bool ModifyNativeLayer(CompositionLayerManager.LayerInfo layerInfo, ref XrCompositionLayerQuad nativeLayer)
{
    var data = layerInfo.Layer.LayerData as QuadLayerData;
    var transform = layerInfo.Layer.GetComponent<Transform>();

    nativeLayer.Pose = new XrPosef(transform.position, transform.rotation);
    nativeLayer.Size = new XrExtend2Df()
    {
        width = data.GetScaledSize(transform.lossyScale).x,
        height = data.GetScaledSize(transform.lossyScale).y
    };

    unsafe
    {
        nativeLayer.Next = OpenXRLayerUtility.GetExtensionsChain(layerInfo, CompositionLayerExtension.ExtensionTarget.Layer);
    }
    return true;
}

OnCreatedSwapchain(LayerInfo, SwapchainCreatedOutput)

This method is dispatched to the main thread inside OnCreatedSwapchainCallback(int, ulong) and asks this subclass to create the native layer struct by invoking CreateNativeLayer(LayerInfo, SwapchainCreatedOutput, out T).

Declaration
protected virtual void OnCreatedSwapchain(CompositionLayerManager.LayerInfo layerInfo, OpenXRCustomLayerHandler<T>.SwapchainCreatedOutput swapchainOutput)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer that was just created.
OpenXRCustomLayerHandler<T>.SwapchainCreatedOutput swapchainOutput

Information regarding the swapchain that was created for this layer, such as the associated swapchain handle.

OnUpdate()

Implements the OpenXRLayerProvider.ILayerHandler method that is called by the OpenXRLayerProvider during the Unity update loop.

Declaration
public virtual void OnUpdate()
Remarks

This implementation carries out two tasks. It dequeues actions for the main thread like dispatch when the swapchain has been created and it adds all the active layers to the endFrameInfo struct in the native UnityOpenXR lib.

RemoveLayer(int)

Implements the OpenXRLayerProvider.ILayerHandler method that is called by the OpenXRLayerProvider when a layer is destroyed or disabled.

Declaration
public virtual void RemoveLayer(int removedLayerId)
Parameters
Type Name Description
int removedLayerId

The instance id of the CompositionLayer component that was removed.

ResizeNativeArrays()

Ensures that the native arrays are of the same size as the m_nativeLayers map.

Declaration
protected virtual void ResizeNativeArrays()

SetActiveLayer(LayerInfo)

Implements the OpenXRLayerProvider.ILayerHandler method that is called by the OpenXRLayerProvider when a layer is considered to be currently active.

Declaration
public virtual void SetActiveLayer(CompositionLayerManager.LayerInfo layerInfo)
Parameters
Type Name Description
LayerInfo layerInfo

Container for the instance id and CompositionLayer component of the composition layer being set to active.

Implements

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