}

[SecureContext, Exposed=Window] interface XRSession : EventTarget {

readonly attribute XREnvironmentBlendMode environmentBlendMode;

readonly attribute XRRenderState renderState;

interface XRWebGLLayer : XRLayer {

readonly attribute XRWebGLRenderingContext context;

readonly attribute boolean antialias;

readonly attribute boolean ignoreDepthValues;

readonly attribute unsigned long framebufferWidth;

[SecureContext, Exposed=Window] interface XRSession : EventTarget {

// Attributes

readonly attribute XREnvironmentBlendMode environmentBlendMode;

readonly attribute XRRenderState renderState;

readonly attribute XRSpace viewerSpace;

};

When an {{XRSession}} is created, the user agent MUST <dfn>initialize the session</dfn> by running the following steps:

1. Let |session| be the newly created {{XRSession}} object.

1. Let |mode| be the {{XRSessionMode}} passed to {{requestSession()}}.

1. [=Initialize the render state=].

1. If no other features of the user agent have done so already, perform the necessary platform-specific steps to initialize the device's tracking and rendering capabilities.

1. If |session|'s [=list of pending render states=] is not empty, [=apply pending render states=].

1. If |session|'s {{XRSession/renderState}}'s {{XRRenderState/baseLayer}} is <code>null</code>, abort these steps.

1. Let |callbacks| be a list of the entries in |session|'s [=list of animation frame callback=], in the order in which they were added to the list.

1. Set |session|'s [=list of animation frame callbacks=] to the empty list.

1. Set |frame|'s [=active=] boolean to <code>true</code>.

1. If |type| is {{identity}} let |referenceSpace| be a new {{XRReferenceSpace}}.

1. If |type| is {{stationary}} and |options| does not have a {{XRReferenceSpaceOptions/subtype}} field, throw {{TypeError}}.

1. Else if |type| is {{bounded}} or {{unbounded}} and |options| has a {{XRReferenceSpaceOptions/subtype}} field, throw a {{TypeError}}.

1. Else if |type| is {{bounded}}, let |referenceSpace| be a new {{XRBoundedReferenceSpace}}.

1. Else if |type| is {{unbounded}}, let |referenceSpace| be a new {{XRUnboundedReferenceSpace}}.

1. Return |referenceSpace|.

interface XRStationaryReferenceSpace : XRReferenceSpace {

};

XRBoundedReferenceSpace {#xrboundedreferencespace-interface}

----------------------------

readonly attribute XRWebGLRenderingContext context;

readonly attribute boolean antialias;

readonly attribute boolean ignoreDepthValues;

readonly attribute WebGLFramebuffer framebuffer;

1. If |context|'s [=XR compatible=] boolean is false, throw an {{InvalidStateError}} and abort these steps.

1. Initialize |layer|'s {{XRWebGLLayer/context}} to |context|.

1. Initialize |layer|'s {{XRWebGLLayer/antialias}} to |layerInit|'s {{XRWebGLLayerInit/antialias}} value.

1. If |layerInit|'s {{XRWebGLLayerInit/ignoreDepthValues}} value is <code>false</code> and the [=XR Compositor=] will make use of depth values, Initialize |layer|'s {{XRWebGLLayer/ignoreDepthValues}} to <code>false</code>.

1. Else Initialize |layer|'s {{XRWebGLLayer/ignoreDepthValues}} to <code>true</code>

1. Initialize |layer|'s {{XRWebGLLayer/framebuffer}} to a new [=opaque framebuffer=] created with |context|.

The <dfn attribute for="XRWebGLLayer">antialias</dfn> attribute is <code>true</code> if the {{framebuffer}} supports antialiasing using a technique of the UAs choosing, and <code>false</code> if no antialiasing will be performed.

The <dfn attribute for="XRWebGLLayer">ignoreDepthValues</dfn> attribute, if <code>true</code>, indicates the [=XR Compositor=] MUST NOT make use of values in the depth buffer attachment when rendering. When the attribute is <code>false</code> it indicates that the content of the depth buffer attachment will be used by the [=XR Compositor=] and is expected to be representative of the scene rendered into the layer.

Depth values stored in the buffer are expected to be between <code>0.0</code> and <code>1.0</code>, with <code>0.0</code> representing the distance of {{XRRenderState/depthNear}} and <code>1.0</code> representing the distance of {{XRRenderState/depthFar}}, with intermediate values interpolated linearly. This is the default behavior of WebGL. (See documentation for the <a href="https://www.khronos.org/registry/OpenGL-Refpages/es2.0/xhtml/glDepthRangef.xml">depthRange function</a> for additional details.))

The [=native WebGL framebuffer resolution=] is determined by running the following steps:

1. Let |session| be the target {{XRSession}}.