WebXR Layers API Level 1

navigator.xr.requestSession('immersive-vr', {
    optionalFeatures: ['layers']
  }

enum XRLayerLayout {
  "default",
  "mono",
  "stereo",
  "stereo-left-right",
  "stereo-top-bottom"
};

[Exposed=Window] interface XRCompositionLayer : XRLayer {
  readonly attribute XRLayerLayout layout;

  attribute boolean blendTextureSourceAlpha;
  attribute boolean? chromaticAberrationCorrection;
  readonly attribute unsigned long mipLevels;

  readonly attribute boolean needsRedraw;

  undefined destroy();
};

When the underlying resources of a layer are lost for an XRCompositionLayer layer, the user agent MUST run the following steps:

1. Set layer’s needsRedraw to true.

2. If layer is not an XRProjectionLayer, queue a task to fire an event named redraw on layer.

To intialize a composition layer with a XRSession session and an optional instance of a WebGLRenderingContext or a WebGL2RenderingContext context, the user agent MUST run the following steps:

1. Set this session to session.

2. If context is defined, set this context to context.

3. Set this blendTextureSourceAlpha to true.

4. Initialize this chromaticAberrationCorrection as follows:

   If the user agent supports chromatic aberration correction

   Set this chromaticAberrationCorrection to true or false depending on the user agent’s preference.

   Otherwise

   Set this chromaticAberrationCorrection to null.

When calling destroy(), the user agent MUST run the following steps:

1. Set this colorTextures array to an empty array.

2. Set this depthStencilTextures array to an empty array.

3. Destroy the underlying GL attachments.

When setting the space on a layer with XRSpace space and XRCompositionLayer layer, the user agent MUST run the following steps to validate if the space is valid:

1. If space is null, throw TypeError and abort these steps.

2. If space’s session is not equal to the layer’s session, throw TypeError and abort these steps.

[Exposed=Window] interface XRProjectionLayer : XRCompositionLayer {
  readonly attribute unsigned long textureWidth;
  readonly attribute unsigned long textureHeight;
  readonly attribute unsigned long textureArrayLength;

  readonly attribute boolean ignoreDepthValues;
  attribute float? fixedFoveation;
};

[Exposed=Window] interface XRQuadLayer : XRCompositionLayer {
  attribute XRSpace space;
  attribute XRRigidTransform transform;

  attribute float width;
  attribute float height;

  // Events
  attribute EventHandler onredraw;
};

When initializing an XRQuadLayer layer with an XRQuadLayerInit init, the user agent MUST run the following steps:

1. Initialize layer’s width to init’s width.

2. Initialize layer’s height to init’s height.

3. Let layer’s space be the init’s space.

4. Initialize layer’s transform as follows:

   If init’s transform is set

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer initialized with position and orientation of init’s transform.

   Otherwise

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer initialized with a DOMPointInit position of { x: 0.0, y: 0.0, z: 0.0, w: 1.0 }.

5. Initialize layer’s isStatic to init’s isStatic

[Exposed=Window] interface XRCylinderLayer : XRCompositionLayer {
  attribute XRSpace space;
  attribute XRRigidTransform transform;

  attribute float radius;
  attribute float centralAngle;
  attribute float aspectRatio;

  // Events
  attribute EventHandler onredraw;
};

When initializing an XRCylinderLayer layer with an XRCylinderLayerInit init, the user agent MUST run the following steps:

1. Initialize layer’s radius to init’s radius.

2. Initialize layer’s centralAngle to init’s centralAngle.

3. Initialize layer’s aspectRatio to init’s aspectRatio.

4. Let layer’s space be the init’s space.

5. Initialize layer’s transform as follows:

   If init’s transform is set

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer initialized with position and orientation of init’s transform.

   Otherwise

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer initialized with a DOMPointInit position of { x: 0.0, y: 0.0, z: 0.0, w: 1.0 }.

6. Initialize layer’s isStatic to init’s isStatic

[Exposed=Window] interface XREquirectLayer : XRCompositionLayer {
  attribute XRSpace space;
  attribute XRRigidTransform transform;

  attribute float radius;
  attribute float centralHorizontalAngle;
  attribute float upperVerticalAngle;
  attribute float lowerVerticalAngle;

  // Events
  attribute EventHandler onredraw;
};

When setting the space on an equirect layer with XRSpace space and XREquirectLayer layer, the user agent MUST run the following steps to validate if the space is valid:

1. If init’s space is not an instance of type XRReferenceSpace, throw TypeError and abort these steps.

2. If init’s space has a type of "viewer", throw TypeError and abort these steps.

3. Run setting the space on a layer with space and layer.

When initializing an XREquirectLayer layer with an XREquirectLayerInit init, the user agent MUST run the following steps:

1. Initialize layer’s radius to init’s radius.

2. Initialize layer’s centralHorizontalAngle to init’s centralHorizontalAngle.

3. Initialize layer’s upperVerticalAngle to init’s upperVerticalAngle.

4. Initialize layer’s lowerVerticalAngle to init’s lowerVerticalAngle.

5. Let layer’s space be the init’s space.

6. Initialize layer’s transform as follows:

   If init’s transform is set

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer initialized with position and orientation of init’s transform.

   Otherwise

   Let layer’s transform be a new XRRigidTransform in the relevant realm of layer.

7. Initialize layer’s isStatic to init’s isStatic

[Exposed=Window] interface XRCubeLayer : XRCompositionLayer {
  attribute XRSpace space;
  attribute DOMPointReadOnly orientation;

  // Events
  attribute EventHandler onredraw;
};

When setting the space on an cube layer with XRSpace space and XRCubeLayer layer, the user agent MUST run the following steps to validate if the space is valid:

1. If init’s space is not an instance of type XRReferenceSpace, throw TypeError and abort these steps.

2. If init’s space has a type of "viewer", throw TypeError and abort these steps.

3. Run setting the space on a layer with space and layer.

[Exposed=Window] interface XRSubImage {
  [SameObject] readonly attribute XRViewport viewport;
};

[Exposed=Window] interface XRWebGLSubImage : XRSubImage {
  [SameObject] readonly attribute WebGLTexture colorTexture;
  [SameObject] readonly attribute WebGLTexture? depthStencilTexture;
  readonly attribute unsigned long? imageIndex;
  readonly attribute unsigned long textureWidth;
  readonly attribute unsigned long textureHeight;
};

enum XRTextureType {
  "texture",
  "texture-array"
};

dictionary XRProjectionLayerInit {
  XRTextureType textureType = "texture";
  GLenum colorFormat = 0x1908; // RGBA
  GLenum depthFormat = 0x1902; // DEPTH_COMPONENT
  double scaleFactor = 1.0;
};

dictionary XRLayerInit {
  required XRSpace space;
  GLenum colorFormat = 0x1908; // RGBA
  GLenum? depthFormat;
  unsigned long mipLevels = 1;
  required unsigned long viewPixelWidth;
  required unsigned long viewPixelHeight;
  XRLayerLayout layout = "mono";
  boolean isStatic = false;
};

dictionary XRQuadLayerInit : XRLayerInit {
  XRTextureType textureType = "texture";
  XRRigidTransform? transform;
  float width = 1.0;
  float height = 1.0;
};

dictionary XRCylinderLayerInit : XRLayerInit {
  XRTextureType textureType = "texture";
  XRRigidTransform? transform;
  float radius = 2.0;
  float centralAngle = 0.78539;
  float aspectRatio = 2.0;
};

dictionary XREquirectLayerInit : XRLayerInit {
  XRTextureType textureType = "texture";
  XRRigidTransform? transform;
  float radius = 0;
  float centralHorizontalAngle = 6.28318;
  float upperVerticalAngle = 1.570795;
  float lowerVerticalAngle = -1.570795;
};

dictionary XRCubeLayerInit : XRLayerInit {
  DOMPointReadOnly? orientation;
};

[Exposed=Window] interface XRWebGLBinding {
  constructor(XRSession session, XRWebGLRenderingContext context);

  readonly attribute double nativeProjectionScaleFactor;
  readonly attribute boolean usesDepthValues;

  XRProjectionLayer createProjectionLayer(optional XRProjectionLayerInit init = {});
  XRQuadLayer createQuadLayer(optional XRQuadLayerInit init = {});
  XRCylinderLayer createCylinderLayer(optional XRCylinderLayerInit init = {});
  XREquirectLayer createEquirectLayer(optional XREquirectLayerInit init = {});
  XRCubeLayer createCubeLayer(optional XRCubeLayerInit init = {});

  XRWebGLSubImage getSubImage(XRCompositionLayer layer, XRFrame frame, optional XREye eye = "none");
  XRWebGLSubImage getViewSubImage(XRProjectionLayer layer, XRView view);
};

The XRWebGLBinding(session, context) constructor MUST perform the following steps when invoked:

1. Let binding be a new XRWebGLBinding in the relevant realm of session.

2. If session’s ended value is true, throw an InvalidStateError and abort these steps.

3. If context is lost, throw an InvalidStateError and abort these steps.

4. If session is not an immersive session, throw an InvalidStateError and abort these steps.

5. If context’s XR compatible boolean is false, throw an InvalidStateError and abort these steps.

6. Initialize binding’s context to context.

7. Initialize binding’s session to session.

8. Return binding.

To determine the layout attribute using an XRTextureType textureType, an XRWebGLRenderingContext context and an XRLayerLayout layout, the user agent MUST run the following steps:

1. If context is not an WebGL2RenderingContext and textureType is "texture-array", throw TypeError and abort these steps.

2. If textureType is "texture-array" and not all of the session’s views in the list of views have the same recommended WebGL texture resolution, throw a NotSupportedError and abort these steps.

3. If layout is "mono", return layout and abort these steps.

4. If layout is "default", run the following steps:

   1. If the size of list of views is 1, return "mono" and abort these steps.

   2. If textureType is "texture-array", return layout and abort these steps.

5. If layout is "default" or "stereo" and textureType is "texture", run the following steps:

   1. If the user agent prefers "stereo-left-right" layout, return "stereo-left-right" and abort these steps.

   2. If the user agent prefers "stereo-top-bottom" layout, return "stereo-top-bottom" and abort these steps.

6. return layout.

To determine the maximum scalefactor using an XRSession session, an XRWebGLRenderingContext context and an XRLayerLayout layout, the user agent MUST run the following steps:

1. Let largest width be the largest width of the recommended WebGL texture resolution from the session’s list of views excluding the secondary views.

2. Let largest height be the largest height of the recommended WebGL texture resolution from the session’s list of views excluding the secondary views.

3. If layout is "stereo-left-right" layout, multiply largest width by 2.

4. If layout is "stereo-top-bottom" layout, multiply largest height by 2.

5. Let largest view dimension be the largest of largest width or largest height.

6. Let largest texture dimension be the largest dimension of a WebGLTexture created by context.

7. return largest texture dimension divided by largest view dimension.

To allocate color textures for projection layers using an XRProjectionLayer layer, an XRTextureType textureType, a GLenum textureFormat and a float scaleFactor, the user agent MUST run the following steps:

1. Let array be a new array in the relevant realm of context.

2. Let context be layer’s context.

3. Let session be layer’s session.

4. Let numViews be the number of the session’s list of views excluding the secondary views.

5. Let view be the first entry in the session’s list of views that is not a secondary views.

6. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

7. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

8. If textureFormat is not in the list of color formats for projection layers, throw a NotSupportedError and abort these steps.

9. If layer’s layout is "mono" or "default":

   If textureType is "texture-array":

   If the session’s views in the list of views don’t all have the same recommended WebGL texture resolution excluding the secondary views, throw a NotSupportedError and abort these steps.

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with numViews layers using context, textureFormat, width and height.

   Return array and abort these steps.

   Otherwise

   For each view in the session’s list of views:

   1. If view is a secondary view, continue.

   2. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   3. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   4. let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context, textureFormat, width and height.

   5. Append texture to array.

   Return array and abort these steps.

10. If the session’s views in the list of views don’t all have the same recommended WebGL texture resolution excluding the secondary views, throw a NotSupportedError and abort these steps.

11. If layer’s layout is stereo-left-right, initialize array with 1 new instance of opaque texture in the relevant realm of context created as a textureType texture using context , textureFormat, numViews multiplied by width and height.

12. If layer’s layout is stereo-top-bottom, initialize array with 1 new instance of opaque texture in the relevant realm of context created as a textureType texture using context , textureFormat, width and numViews multiplied by height.

13. return array.

To allocate depth textures for projection layers using an XRProjectionLayer layer, an XRTextureType textureType, a GLenum textureFormat and a float scaleFactor, the user agent MUST run the following steps:

1. Let array be a new array in the relevant realm of context.

2. Let context be layer’s context.

3. Let session be layer’s session.

4. If textureFormat is 0, return array and abort these steps.

5. If context is a WebGLRenderingContext and the WEBGL_depth_texture extension is not enabled in context, return array and abort these steps.

6. If textureFormat is not in the list of depth formats for projection layers, throw a NotSupportedError and abort these steps.

7. let numViews be the number of the session’s list of views excluding the secondary views.

8. Let view be the first entry in the session’s list of views that is not a secondary view.

9. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

10. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

11. If layer’s layout is "mono" or "default":

    If textureType is "texture-array":

    Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with numViews layers using context, textureFormat, stencil, width and height.

    Return array and abort these steps.

    Otherwise

    For each view in the session’s list of views:

    1. If view is a secondary view, continue.

    2. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

    3. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

    4. let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context, textureFormat, stencil, width and height.

    5. Append texture to array.

    Return array and abort these steps.

12. If the session’s views in the list of views don’t all have the same recommended WebGL texture resolution excluding the secondary views, throw a NotSupportedError and abort these steps.

13. If layer’s layout is stereo-left-right, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context, textureFormat, stencil, numViews multiplied by width and height.

14. If layer’s layout is stereo-top-bottom, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context, textureFormat, stencil, width and numViews multiplied by height.

15. return array.

To allocate the color textures for the secondary views using an XRProjectionLayer layer, an XRTextureType textureType, a GLenum textureFormat and a float scaleFactor, the user agent MUST run the following steps:

1. Let context be layer’s context.

2. Let session be layer’s session.

3. Let array be a new array in the relevant realm of context.

4. If textureFormat is not in the list of color formats for projection layers, throw a NotSupportedError and abort these steps.

5. For each view in the session’s list of views:

   1. If view is not a secondary view, continue.

   2. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   3. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   4. Initialize texture as follows:

      If textureType is "texture-array":

      Let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with context, textureFormat, width and height.

      Otherwise

      Let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context, textureFormat, width and height.

   5. Append texture to array.

6. Return array and abort these steps.

To allocate the depth textures for the secondary views using an XRProjectionLayer layer, an XRTextureType textureType, a GLenum textureFormat and a float scaleFactor, the user agent MUST run the following steps:

1. Let context be layer’s context.

2. Let session be layer’s session.

3. If textureFormat is 0, return array and abort these steps.

4. If context is a WebGLRenderingContext and the WEBGL_depth_texture extension is not enabled in context, return array and abort these steps.

5. If textureFormat is not in the list of depth formats for projection layers, throw a NotSupportedError and abort these steps.

6. Let array be a new array in the relevant realm of context.

7. For each view in the session’s list of views:

   1. If view is not a secondary view, continue.

   2. Let width be the width of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   3. Let height be the height of view’s recommended WebGL texture resolution multiplied by scaleFactor.

   4. Initialize texture as follows:

      If textureType is "texture-array":

      Let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with context, textureFormat, stencil, width and height.

      Otherwise

      Let texture be a new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context, textureFormat, stencil, width and height.

   5. Append texture to array.

8. Return array and abort these steps.

To allocate color textures using an XRCompositionLayer layer, an XRTextureType textureType and an XRLayerInit init, the user agent MUST run the following steps:

1. let array be a new array in the relevant realm of context.

2. let context be layer’s context.

3. If init’s colorFormat is not in the list of color formats for non-projection layers, throw a NotSupportedError and abort these steps.

4. If init’s mipLevels is smaller than 1, throw a InvalidStateError and abort these steps.

5. If init’s mipLevels is larger than 1 and viewPixelWidth and viewPixelHeight are not powers of 2, throw a InvalidStateError and abort these steps

6. If layer’s layout is "mono":

   If textureType is "texture-array":

   Initialize array with 1 new instance of an opaque texture in the relevant realm of this context created as a TEXTURE_2D_ARRAY texture with 1 internal texture using context and init’s colorFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Otherwise

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context and init’s colorFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

7. If layer’s layout is "stereo":

   If textureType is "texture-array":

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with 2 layers using context and init’s colorFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Return array and abort these steps.

   Otherwise

   Initialize array with 2 new instances of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context and init’s colorFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Return array and abort these steps.

8. If layer’s layout is stereo-left-right, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context and init’s colorFormat, mipLevels, double of viewPixelWidth and viewPixelHeight values.

9. If layer’s layout is stereo-top-bottom, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context and init’s colorFormat, mipLevels, viewPixelWidth and double of viewPixelHeight values.

10. return array.

To allocate depth textures using an XRCompositionLayer layer, an XRTextureType textureType and an XRLayerInit init, the user agent MUST run the following steps:

1. let array be a new array in the relevant realm of context.

2. let context be layer’s context.

3. If init’s depthFormat is not set, return array and abort these steps.

4. If init’s depthFormat is not in the list of depth formats for non-projection layers, throw a NotSupportedError and abort these steps.

5. If init’s mipLevels is smaller than 1, throw a InvalidStateError and abort these steps.

6. If init’s mipLevels is larger than 1 and viewPixelWidth and viewPixelHeight are not powers of 2, throw a InvalidStateError and abort these steps.

7. If layer’s layout is "mono":

   If textureType is "texture-array":

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with 1 internal texture using context and init’s depthFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Otherwise

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context and init’s depthFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

8. If layer’s layout is "stereo":

   If textureType is "texture-array":

   Initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a TEXTURE_2D_ARRAY texture with 2 layers using context and init’s depthFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Return array and abort these steps.

   Otherwise

   Initialize array with 2 new instances of an opaque texture in the relevant realm of context created as a TEXTURE_2D texture with context and init’s depthFormat, mipLevels, viewPixelWidth and viewPixelHeight values.

   Return array and abort these steps.

9. If layer’s layout is stereo-left-right, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context and init’s depthFormat, mipLevels, double of viewPixelWidth and viewPixelHeight values.

10. If layer’s layout is stereo-top-bottom, initialize array with 1 new instance of an opaque texture in the relevant realm of context created as a textureType texture using context and init’s depthFormat, mipLevels, viewPixelWidth and double of viewPixelHeight values.

11. return array.

The createProjectionLayer(optional XRProjectionLayerInit init) method creates a new XRProjectionLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. Let context be this context.

3. Let layer be a new XRProjectionLayer in the relevant realm of this.

4. If session’s ended value is true, throw InvalidStateError and abort these steps.

5. If context is lost, throw InvalidStateError and abort these steps.

6. Run intialize a composition layer on layer with session and context.

7. Initialize layer’s isStatic to false.

8. Initialize layer’s ignoreDepthValues as follows:

   If init’s depthFormat is false and the XR Compositor will make use of depth values

   Initialize layer’s ignoreDepthValues to false

   Otherwise

   Initialize layer’s ignoreDepthValues to true

9. Initialize layer’s fixedFoveation to 0.

10. let layout be the result of determining the layout attribute with init’s textureType, context and "default".

11. Let maximum scalefactor be the result of determining the maximum scalefactor with session, context and layout.

12. If scaleFactor is larger than maximum scalefactor, set scaleFactor to maximum scalefactor.

13. Initialize layer’s layout to layout.

14. Initialize layer’s needsRedraw to true.

15. let layer’s colorTextures be the result of allocating color textures for projection layers with layer, init’s textureType, init’s colorFormat and init’s scaleFactor.

16. let layer’s depthStencilTextures be the result of allocating depth textures for projection layers with layer, init’s textureType, init’s depthFormat and init’s scaleFactor.

17. Initialize the colortextures for secondary views as follows:

    If the session was created with "secondary-views" enabled

    Let colortextures for secondary views be the result of allocate the color textures for the secondary views with layer, init’s textureType, init’s colorFormat and init’s scaleFactor.

    Otherwise

    Let colortextures for secondary views be null.

18. Initialize the depthstenciltextures for secondary views as follows:

    If the session was created with "secondary-views" enabled

    Let depthstenciltextures for secondary views be the result of allocate the depth textures for the secondary views with layer, init’s textureType, init’s depthFormat and init’s scaleFactor.

    Otherwise

    Let depthstenciltextures for secondary views be null.

19. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

20. Return layer.

The createQuadLayer(XRQuadLayerInit init) method creates a new XRQuadLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. Let context be this context.

4. If session’s ended value is true, throw InvalidStateError and abort these steps.

5. If context is lost, throw InvalidStateError and abort these steps.

6. If layout is "default", throw TypeError and abort these steps.

7. Let layer be a new XRQuadLayer in the relevant realm of this.

8. Run intialize a composition layer on layer with session and context.

9. Run initialize a quad layer with layer and init.

10. let layout be the result of determining the layout attribute with init’s textureType, context and init’s layout.

11. Initialize layer’s layout to layout.

12. Initialize layer’s needsRedraw to true.

13. let layer’s colorTextures be the result of allocating color textures with layer, init’s textureType and init.

14. let layer’s depthStencilTextures be the result of allocating depth textures with layer, init’s textureType and init.

15. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

16. return layer.

The createCylinderLayer(XRCylinderLayerInit init) method creates a new XRCylinderLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. Let context be this context.

4. If session’s ended value is true, throw InvalidStateError and abort these steps.

5. If context is lost, throw InvalidStateError and abort these steps.

6. If layout is "default", throw TypeError and abort these steps.

7. Let layer be a new XRCylinderLayer in the relevant realm of this.

8. Run intialize a composition layer on layer with session and context.

9. Run initialize a cylinder layer with layer and init.

10. let layout be the result of determining the layout attribute with init’s textureType, context and init’s layout.

11. Initialize layer’s layout to layout.

12. Initialize layer’s needsRedraw to true.

13. let layer’s colorTextures be the result of allocating color textures with layer, init’s textureType and init.

14. let layer’s depthStencilTextures be the result of allocating depth textures with layer, init’s textureType and init.

15. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

16. return layer.

The createEquirectLayer(XREquirectLayerLayerInit init) method creates a new XREquirectLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. Let context be this context.

4. If session’s ended value is true, throw InvalidStateError and abort these steps.

5. If context is lost, throw InvalidStateError and abort these steps.

6. If layout is "default", throw TypeError and abort these steps.

7. If init’s space is not an instance of type XRReferenceSpace, throw TypeError and abort these steps.

8. If init’s space has a type of "viewer", throw TypeError and abort these steps.

9. Let layer be a new XREquirectLayer in the relevant realm of this.

10. Run intialize a composition layer on layer with session and context.

11. Run initialize a equirect layer with layer and init.

12. let layout be the result of determining the layout attribute with init’s textureType, context and init’s layout.

13. Initialize layer’s layout to layout.

14. Initialize layer’s needsRedraw to true.

15. let layer’s colorTextures be the result of allocating color textures with layer, init’s textureType and init.

16. let layer’s depthStencilTextures be the result of allocating depth textures with layer, init’s textureType and init.

17. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

18. return layer.

The createCubeLayer(XRCubeLayerInit init) method creates a new XRCubeLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. Let context be this context.

4. If session’s ended value is true, throw InvalidStateError and abort these steps.

5. If context is not a WebGL2RenderingContext context, throw InvalidStateError and abort these steps.

6. If context is lost, throw InvalidStateError and abort these steps.

7. If init’s space is not an instance of type XRReferenceSpace, throw TypeError and abort these steps.

8. If init’s space has a type of "viewer", throw TypeError and abort these steps.

9. Let layer be a new XRCubeLayer in the relevant realm of this.

10. Run intialize a composition layer on layer with session and context.

11. Let layer’s space be the init’s space.

12. Initialize layer’s isStatic to init’s isStatic

13. Initialize layer’s orientation as follows:

    If init’s orientation is set

    Let layer’s orientation be the result of running fromPoint with init’s orientation.

    Otherwise

    Let layer’s orientation be a new DOMPointReadOnly in the relevant realm of this.

14. let layout be init’s layout.

15. Initialize layer’s needsRedraw to true.

16. If layout is "default" or "stereo-left-right" or "stereo-top-bottom", throw TypeError and abort these steps.

17. Let layer’s colorTextures be a new array in the relevant realm of this XRCubeLayer.

18. Initialize layer’s colorTextures as follows, based on the value of layout:

    "mono":

    Initialize colorTextures with 1 new instance of an opaque texture in the relevant realm of this XRCubeLayer created as a TEXTURE_CUBE_MAP texture with context and init’s colorFormat, viewPixelWidth and viewPixelHeight values.

    Otherwise

    Initialize colorTextures with 2 new instances of an opaque texture in the relevant realm of this XRCubeLayer created as a TEXTURE_CUBE_MAP texture with context and init’s colorFormat, viewPixelWidth and viewPixelHeight values.

19. Let layer’s depthStencilTextures be a new array in the relevant realm of this XRCubeLayer.

20. If init’s depthFormat is set, initialize layer’s depthStencilTextures as follows:

    If context is not a WebGL2RenderingContext and the WEBGL_depth_texture extension is not enabled in context

    Throw TypeError and abort these steps.

    Else if layout is "mono"

    Initialize depthStencilTextures with 1 new instance of an opaque texture in the relevant realm of this XRCubeLayer created as a TEXTURE_CUBE_MAP texture with context and init’s depthFormat, viewPixelWidth and viewPixelHeight values.

    Otherwise

    Initialize depthStencilTextures with 2 new instances of an opaque texture in the relevant realm of this XRCubeLayer created as a TEXTURE_CUBE_MAP texture with context and init’s depthFormat, viewPixelWidth and viewPixelHeight values.

21. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

22. return layer.

To validate the state of the XRWebGLSubImage creation function of an XRWebGLBinding binding with parameters of XRCompositionLayer layer and XRFrame frame, the user agent MUST run the following steps:

1. If frame’s session is not equal to layer’s session, return false and abort these steps.

2. If frame’s active boolean is false, return false and abort these steps.

3. If frame’s animationFrame boolean is false, return false and abort these steps.

4. If binding’s session is not equal to layer’s session, return false and abort these steps.

5. If binding’s context is not equal to layer’s context, return false and abort these steps.

6. If the layer’s colorTextures array is empty or missing, return false and abort these steps.

7. If the layer’s isStatic is true and layer’s needsRedraw is false, return false and abort these steps.

8. return true.

To initialize the viewport of an XRViewport viewport with a opaque texture texture, a XRLayerLayout layout, an integer offset and a integer num, the user agent MUST run the following steps:

1. Set viewport’s x to 0.

2. Set viewport’s y to 0.

3. Set viewport’s width to the pixel width of texture.

4. Set viewport’s height to the pixelh eight of texture.

5. Update viewport as follows:

   If layout is "stereo-left-right"

   Set viewport’s x to the pixel width of texture multiplied by offset and divided by num.

   Set viewport’s width to the pixel width of subimage’s texture divided by num.

   Else if layout is "stereo-top-bottom"

   Set viewport’s y to the pixel height of texture multiplied by offset and divided by num.

   Set viewport’s height to the pixel height of subimage’s texture divided by num.

The getSubImage(XRCompositionLayer layer, XRFrame frame, optional XREye eye = "none") method creates a new XRWebGLSubImage.

When this method is invoked on an XRWebGLBinding binding, it MUST run the following steps:

1. Initialize subimage as follows:

   If getSubImage() was called previously with the same binding, layer and eye, the user agent MAY

   Let subimage be the same XRWebGLSubImage object as returned by an earlier call with the same arguments.

   Otherwise

   Let subimage be a new XRWebGLSubImage in the relevant realm of this.

   Let subimage’s viewport be a new XRViewport in the relevant realm of this.

2. Let session be this session.

3. If layer is not in the session’s layers array, throw a TypeError and abort these steps.

4. If layer’s type is XRProjectionLayer, throw a TypeError and abort these steps.

5. If layer’s layout attribute is "default", throw a TypeError and abort these steps.

6. Let index be 0.

7. If layer’s layout attribute is "stereo":

   1. If eye is "none", throw a TypeError and abort these steps.

   2. If eye is "right", set index to 1.

8. If validate the state of the XRWebGLSubImage creation function with layer and frame is false, throw an InvalidStateError and abort these steps.

9. Initialize subimage’s imageIndex as follows:

   If the layer was created with a textureType of "texture-array"

   Initialize subimage’s imageIndex with index.

   Otherwise

   Initialize subimage’s imageIndex with 0.

10. Initialize subimage’s colorTexture as follows:

    If the layer was created with a textureType of "texture"

    Initialize subimage’s colorTexture with the element at offset index of the layer’s colorTextures array.

    Otherwise

    Initialize subimage’s colorTexture with the first element of the layer’s colorTextures array.

11. Initialize subimage’s depthStencilTexture as follows:

    If the layer’s depthStencilTextures is an empty array

    Initialize subimage’s depthStencilTexture with null.

    Else the layer was created with a textureType of "texture"

    Initialize subimage’s depthStencilTexture with the element at offset index of the layer’s depthStencilTextures array.

    Otherwise

    Initialize subimage’s depthStencilTexture with the first element of layer’s depthStencilTextures array.

12. Set subimage’s textureWidth to the pixel width of subimage’s colorTexture.

13. Set subimage’s textureHeight to the pixel height of subimage’s colorTexture.

14. Let viewsPerTexture be 1.

15. If layer’s layout attribute is "stereo-left-right" or "stereo-top-bottom", set viewsPerTexture to 2.

16. Run initialize the viewport on subimage’s viewport with subimage’s colorTexture, layer’s layout, index and viewsPerTexture.

17. Queue a task to set needsRedraw to false.

18. return subimage.

The getViewSubImage(XRProjectionLayer layer, XRView view) method creates a new XRWebGLSubImage.

When this method is invoked on an XRWebGLBinding binding, it MUST run the following steps:

1. Initialize subimage as follows:

   If getViewSubImage() was called previously with the same binding, layer and view, the user agent MAY

   Let subimage be the same XRWebGLSubImage object as returned by an earlier call with the same arguments.

   Otherwise

   Let subimage be a new XRWebGLSubImage in the relevant realm of this.

   Let subimage’s viewport be a new XRViewport in the relevant realm of this.

2. Let frame be view’s frame.

3. Let session be this session.

4. If validate the state of the XRWebGLSubImage creation function with layer and frame is false, throw an InvalidStateError and abort these steps.

5. If layer is not in the session’s layers array, throw a TypeError and abort these steps.

6. If view’s active flag is false, throw an InvalidStateError and abort these steps.

7. Initialize index as follows:

   If view is a secondary view from session’s list of views

   Let index be the offset of view’s view in session’s list of views excluding the primary views.

   Otherwise

   Let index be the offset of view’s view in session’s list of views excluding the secondary views.

8. Initialize subimage’s imageIndex as follows:

   If the layer was created with a textureType of "texture-array":

   Initialize subimage’s imageIndex with index.

   Otherwise

   Initialize subimage’s imageIndex to 0.

9. Initialize subimage’s colorTexture as follows:

   If view is a secondary view from session’s list of views

   Initialize subimage’s colorTexture with the element at offset index of the layer’s colorTextures for secondary views.

   Else if the layer’s layout is "default" and the layer was created with a textureType of "texture"

   Initialize subimage’s colorTexture with the element at offset index of the layer’s colorTextures array.

   Otherwise

   Initialize subimage’s colorTexture with the first element of the layer’s colorTextures array.

10. Initialize subimage’s depthStencilTexture as follows:

    If the layer’s depthStencilTextures is an empty array

    Initialize subimage’s depthStencilTexture with null.

    Else if view is a secondary view from session’s list of views

    Initialize subimage’s colorTexture with the element at offset index of the layer’s depthStencilTextures for secondary views.

    Else if the layer’s layout is "default" and the layer was created with a textureType of "texture"

    Initialize subimage’s depthStencilTexture with the element at offset index of the layer’s depthStencilTextures array.

    Otherwise

    Initialize subimage’s depthStencilTexture with the first element of layer’s depthStencilTextures array.

11. Set subimage’s textureWidth to the pixel width of subimage’s colorTexture.

12. Set subimage’s textureHeight to the pixel height of subimage’s colorTexture.

13. Run initialize the viewport on subimage’s viewport with subimage’s colorTexture, layer’s layout, index and the number of the session’s list of views.

14. Set needsRedraw to false.

15. return subimage

dictionary XRMediaLayerInit {
  required XRSpace space;
  XRLayerLayout layout = "mono";
  boolean invertStereo = false;
};

dictionary XRMediaQuadLayerInit : XRMediaLayerInit {
  XRRigidTransform? transform;
  float? width;
  float? height;
};

dictionary XRMediaCylinderLayerInit : XRMediaLayerInit {
  XRRigidTransform? transform;
  float radius = 2.0;
  float centralAngle = 0.78539;
  float? aspectRatio;
};

dictionary XRMediaEquirectLayerInit : XRMediaLayerInit {
  XRRigidTransform? transform;
  float radius = 0.0;
  float centralHorizontalAngle = 6.28318;
  float upperVerticalAngle = 1.570795;
  float lowerVerticalAngle = -1.570795;
};

[Exposed=Window] interface XRMediaBinding {
  constructor(XRSession session);

  XRQuadLayer createQuadLayer(HTMLVideoElement video, optional XRMediaQuadLayerInit init = {});
  XRCylinderLayer createCylinderLayer(HTMLVideoElement video, optional XRMediaCylinderLayerInit init = {});
  XREquirectLayer createEquirectLayer(HTMLVideoElement video, optional XRMediaEquirectLayerInit init = {});
};

When an XRCompositionLayer layer with a HTMLVideoElement media needs to be rendered, the user agent MUST run the following steps:

1. Let usability be the result of checking the usability of media.

2. If usability is bad, then fill the layer with opaque black and abort these steps.

3. Fill the layer with the content of the media element.

The XRMediaBinding(XRSession session) constructor MUST perform the following steps when invoked:

1. If session’s ended value is true, throw an InvalidStateError and abort these steps.

2. If session is not an immersive session, throw an InvalidStateError and abort these steps.

3. Let binding be a new XRMediaBindingin the relevant realm of session.

4. Initialize binding’s session to session.

5. Return binding.

To calculate the aspect ratio of an HTMLVideoElement video and an XRLayerLayout layout, run the following steps:

1. Let width be the video’s videoWidth.

2. Let height be the video’s videoHeight.

3. If layout is "stereo-left-right", divide width by 2.

4. If layout is "stereo-top-bottom", divide height by 2.

5. Return width divided by height.

The createQuadLayer(HTMLVideoElement video, XRMediaQuadLayerInit init) method creates a new XRQuadLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. If session’s ended value is true, throw InvalidStateError and abort these steps.

4. If init’s layout is "default", throw a TypeError and abort these steps.

5. Let layer be a new XRQuadLayer in the relevant realm of this.

6. Run intialize a composition layer on layer with session.

7. Initialize layer’s media to video.

8. Initialize layer’s needsRedraw to false.

9. Let aspectRatio be the result of calculate the aspect ratio with video and init’s layout.

10. If init’s width and height are undefined, set width to 1.

11. If init’s height is undefined, set height to width divided by aspectRatio.

12. If init’s width is undefined, set width to height multiplied by aspectRatio.

13. Run initialize a quad layer with layer and init.

14. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

15. return layer.

The createCylinderLayer(HTMLVideoElement video, XRMediaCylinderLayerInit init) method creates a new XRCylinderLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. If session’s ended value is true, throw InvalidStateError and abort these steps.

4. If init’s layout is "default", throw a TypeError and abort these steps.

5. Let layer be a new XRCylinderLayer in the relevant realm of this.

6. Run intialize a composition layer on layer with session.

7. Initialize layer’s media to video.

8. Initialize layer’s needsRedraw to false.

9. Let aspectRatio be the result of calculate the aspect ratio with video and init’s layout.

10. If init’s aspectRatio is undefined, set aspectRatio to aspectRatio.

11. Run initialize a cylinder layer with layer and init.

12. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

13. return layer.

The createEquirectLayer(HTMLVideoElement video, XRMediaEquirectLayerInit init) method creates a new XREquirectLayer layer.

When this method is invoked, the user agent MUST run the following steps:

1. Let session be this session.

2. If session was not created with "layers" enabled, throw a NotSupportedError and abort these steps.

3. If session’s ended value is true, throw InvalidStateError and abort these steps.

4. If init’s layout is "default", throw a TypeError and abort these steps.

5. If init’s space is not an instance of type XRReferenceSpace, throw InvalidStateError and abort these steps.

6. If init’s space has a type of "viewer", throw InvalidStateError and abort these steps.

7. Let layer be a new XREquirectLayer in the relevant realm of this.

8. Run intialize a composition layer on layer with session.

9. Initialize layer’s media to video.

10. Initialize layer’s needsRedraw to false.

11. Run initialize a equirect layer with layer and init.

12. If the XR Compositor knows that it will be unable to create the resources for the layer for any reason, throw an OperationError and abort these steps.

13. return layer.

[SecureContext, Exposed=Window] interface XRLayerEvent : Event {
  constructor(DOMString type, XRLayerEventInit eventInitDict);
  [SameObject] readonly attribute XRLayer layer;
};

dictionary XRLayerEventInit : EventInit {
  required XRLayer layer;
};

[SecureContext, Exposed=Window] partial interface XRRenderState {
  readonly attribute FrozenArray<XRLayer> layers;
};

This module replaces the steps given by initialize the render state. Instead when an XRRenderState object state is created for an XRSession session, the user agent MUST initialize the render state by running the following steps:

1. Initialize state by running the original steps to initialize the render state.

2. Initialize state’s layers with a new empty array in the relevant realm of session.

This module replaces the steps given by "update the pending layers state" from the WebXR specification. Instead when the user agent will update the pending layers state with XRSession session and XRRenderStateInit newState, it must run the following steps:

1. If both newState’s baseLayer and newState’s layers are set, throw a NotSupportedError and abort these steps.

2. Let activeState be session’s active render state.

3. If newState’s baseLayer is set:

   1. If session’s pending render state is null, set it to a copy of activeState.

   2. Set session’s pending render state's layers to null.

4. If newState’s layers is set:

   1. If session was not created with "layers" enabled and newState’s layers contains more than 1 instance, throw a NotSupportedError and abort these steps.

   2. If session’s pending render state is null, set it to a copy of activeState.

   3. If newState’s layers contains duplicate instances, throw a TypeError and abort these steps.

   4. For each layer in newState’s layers:

      1. If layer is an XRCompositionLayer and layer’s session is different from session, throw a TypeError and abort these steps.

      2. If layer is an XRWebGLLayer and layer’s session is different from session, throw a TypeError and abort these steps.

   5. Set session’s pending render state's baseLayer to null.

   6. Set session’s pending render state's layers to newState’s layers.

This module replaces the steps given by "check the layers state" from the WebXR specification. Instead to check the layers state with renderState state, the user agent MUST run the following steps:

1. If state’s baseLayer is not null, return true.

2. If state’s layers is not empty, return true.

3. return false.