1. Set |activeState|'s [=XRRenderState/composition disabled=] and [=XRRenderState/output canvas=] as follows:

: If |session|'s [=XRSession/mode=] is {{XRSessionMode/"inline"}} and |baseLayer| is an instance of an {{XRWebGLLayer}} with [=XRWebGLLayer/composition disabled=] set to `true`:

:: Set |activeState|'s [=XRRenderState/composition disabled=] boolean to `true`.

:: Set |activeState|'s [=XRRenderState/composition disabled=] boolean to `false`.

Each {{XRSession}} has a <dfn for="XRSession">list of views</dfn>, which is a [=/list=] of [=view=]s corresponding to the views provided by the [=XRSession/XR device=]. If the {{XRSession}}'s {{XRSession/renderState}}'s [=XRRenderState/composition disabled=] boolean is set to `true` the [=list of views=] MUST contain a single [=view=]. The [=XRSession/list of views=] is immutable during the {{XRSession}} and MUST contain any [=views=] that may be surfaced during the session, including [=secondary views=] that may not initially be [=view/active=].

Each {{XRRenderState}} also has <dfn for="XRRenderState">composition disabled</dfn> boolean, which is initially `false`. The {{XRRenderState}} is considered to be have [=XRRenderState/composition disabled=] if rendering commands performed for an {{XRSessionMode/"inline"}} {{XRSession}} are executed in such a way that they are directly displayed into [=XRRenderState/output canvas=], rather than first being processed by the [=XR Compositor=].

Note: At this point the {{XRRenderState}} will only have an [=XRRenderState/output canvas=] if it has [=XRRenderState/composition disabled=], but future versions of the specification are likely to introduce methods for setting [=XRRenderState/output canvas=]' that support more advanced uses like mirroring and layer compositing that will require composition.

1. If |session|'s [=ended=] value is `true`, return '0' and abort these steps.

1. Initialize |layer|'s [=XRWebGLLayer/composition disabled=] boolean as follows:

:: Initialize |layer|'s [=XRWebGLLayer/composition disabled=] to `true`.

:: Initialize |layer|'s [=XRWebGLLayer/composition disabled=] boolean to `false`.

: If |layer|'s [=XRWebGLLayer/composition disabled=] boolean is `false`:

Note: If an {{XRWebGLLayer}}'s [=XRWebGLLayer/composition disabled=] boolean is set to `true` all values on the {{XRWebGLLayerInit}} object are ignored, since the {{WebGLRenderingContext}}'s default framebuffer was already allocated using the context's [=actual context parameters=] and cannot be overridden.

Each {{XRWebGLLayer}} has a <dfn for="XRWebGLLayer">composition disabled</dfn> boolean which is initially set to `false`. If set to `true` it indicates that the {{XRWebGLLayer}} MUST NOT allocate its own {{WebGLFramebuffer}}, and all properties of the {{XRWebGLLayer}} that reflect {{XRWebGLLayer/framebuffer}} properties MUST instead reflect the properties of the [=XRWebGLLayer/context=]'s default framebuffer.

The <dfn attribute for="XRWebGLLayer">framebuffer</dfn> attribute of an {{XRWebGLLayer}} is an instance of a {{WebGLFramebuffer}} which has been marked as [=opaque framebuffer|opaque=] if [=XRWebGLLayer/composition disabled=] is `false`, and `null` otherwise. The {{framebuffer}} size cannot be adjusted by the developer after the {{XRWebGLLayer}} has been created.

Each {{XRWebGLLayer}} has a <dfn for="XRWebGLLayer">target framebuffer</dfn>, which is the {{XRWebGLLayer/framebuffer}} if [=XRWebGLLayer/composition disabled=] is `false`, and the [=XRWebGLLayer/context=]'s default framebuffer otherwise.

Each {{XRWebGLLayer}} MUST have a <dfn>list of full-sized viewports</dfn> which is a [=/list=] containing one [=WebGL viewport=] for each [=view=] the {{XRSession}} may expose, including [=secondary views=] that are not currently [=view/active=] but may become [=view/active=] for the current session. The viewports MUST have a {{XRViewport/width}} and {{XRViewport/height}} greater than `0` and MUST describe a rectangle that does not exceed the bounds of the [=target framebuffer=]. The viewports MUST NOT be overlapping. If [=XRWebGLLayer/composition disabled=] is `true`, the [=list of full-sized viewports=] MUST contain a single [=WebGL viewport=] that covers the [=XRWebGLLayer/context=]'s entire default framebuffer.