Recent Spec Changes - from 2019-05-08 to 2019-06-17

Edit on Github
<https://github.com/immersive-web/administrivia/blob/master/newsletter/2019-05-08-to-2019-06-17-Recent_Spec_Changes.md>
.
Rename reference space types
<https://github.com/immersive-web/webxr/pull/640>

Merged Tue May 14 2019 - [image: ed:explainer] [image: ed:spec] [image:
potential breaking change]

Rename reference space types (#640)

Renames several reference space types for clarity, as recommended in issue
#633. Intent is to better communicate which reference spaces are
floor-aligned and avoid potential developer confusion that may arise from
use of the term "stationary".

Renamed reference spaces:

   - eye-level -> local
   - floor-level -> local-floor
   - bounded -> bounded-floor

Change inputSources getter from method to attrib.
<https://github.com/immersive-web/webxr/pull/624>

Merged Tue May 14 2019 - [image: ed:explainer] [image: ed:spec]

Change inputSources getter from method to attrib. (#624)

Changes the getInputSources() method on XRSesssion to a readonly attribute
inputSources. This better reflects the expected behavior of the returned
array being a live object that is updated in-place as input sources are
added and removed.

In order to facilitate that change the XRInputSourceArray interface was
also added, since FrozenArray doesn't support the live changes that are
required for this attribute.
Single-canvas inline, drop XRPresentationContext
<https://github.com/immersive-web/webxr/pull/656>

Merged Thu Jun 13 2019 - [image: ed:explainer] [image: ed:spec]

Single-canvas inline, drop XRPresentationContext (#656)

This change adds a path for using a single WebGL canvas to drive inline
sessions, rather than needing both a WebGL context and an
XRPresentationContext before the inline session can function. With this
change XRWebGLLayers will automatically stop allocating a framebuffer with
inline sessions, which causes WebGL commands to naturally "fall through" to
the underlying default framebuffer.

In addition to the above, this change removes the XRPresentationContext
entirely, and along with it the ability to do desktop mirroring (and more
advanced inline scenarios.) This is to simplify the core API, and
equivalent functionality will be reconsidered in the future because the
functionality that they represent is valuable.
Fix multiplication order for transforms
<https://github.com/immersive-web/webxr/pull/649>

Merged Thu May 16 2019 - [image: ed:spec]

Fix multiplication order for transforms

The multiplication order in the spec needs to match the matrix semantics
we've agreed on, and the usage appeared to be backwards.

Specific justifications following.

getViewerPose: if |offset| is the view offset of an eye view, the expected
semantics would be that it's a pose-like transform where the transform's
position is the eye view's coordinates in XRViewerPose space. The
corresponding matrix is viewerFromEye. XRViewerPose contains the viewer
pose in the base reference space, so its transform's position is the viewer
position in base space coordinates, and the transform is baseFromViewer.

Chaining these transforms works as follows:

offset.matrix = viewerFromEye;
viewerPose.transform.matrix = baseFromViewer;

view.transform.matrix = baseFromEye
                      = baseFromViewer * viewerFromEye
                      = viewerPose.transform.matrix * offset.matrix

For originOffset, the logic is similar:

let offsetASpace = baseSpace.getOffsetReferenceSpace(offsetAInBase);
// offsetAInBase.matrix = baseFromA
let offsetBSpace = offsetASpace.getOffsetReferenceSpace(offsetBInA);
// offsetBInA.matrix = AFromB

// equivalent to:
let offsetBSpace = baseSpace.getOffsetReferenceSpace(offsetBInBase);
// offsetBInBase.matrix = baseFromA * AFromB = offsetAInBase.matrix *
offsetBInA.matrix

Lastly, for XRRay, the convention is to transform points or vectors by
premultiplying the transform matrix from the left, I've rephrased those
usages to make that explicit. The current text was basically saying
"multiply vector by matrix" which would be backwards.
Some matrix clarifications <https://github.com/immersive-web/webxr/pull/654>

Merged Fri May 17 2019 - [image: ed:spec]

Some matrix clarifications (#654)

Add note clarifying what the matrix describes and a different way to
multiply matrices. Also clarifies which direction XRView.transform works in.
Describe how the input source list is maintained
<https://github.com/immersive-web/webxr/pull/628>

Merged Tue May 14 2019 - [image: ed:spec]

Describe how the input source list is maintained (#628)

Defines what should happen as input sources for a session are added,
removed, and changed. Also clarifies the definitions for some of the
related concepts.
Explicitly spec out when requestReferenceSpace() can reject queries
<https://github.com/immersive-web/webxr/pull/651>

Merged Fri May 17 2019 - [image: ed:spec]

Explicitly spec out when requestReferenceSpace() can reject queries (#651)

Provides a more explicit algorithm for determining if a given
XRReferenceSpaceType is supported for a given XRSession. It's anticipated
that this criteria will be expanded in the future as we finalize privacy
considerations, but for now it's focused on the device capabilities.
Simplify available spaces <https://github.com/immersive-web/webxr/pull/626>

Merged Thu May 09 2019 - [image: ed:explainer] [image: ed:spec]

Simplify available spaces (#626)

Removes the position-disabled reference space from the spec and explainers.
Developers that wish to display the types of content this reference space
supported (primarily 360 media) should instead manually zero-out the
position of the XRView transforms when rendering.

Also consolidates the viewerSpace attribute and the identity reference
space into a single new reference space called viewer. This new space is
functionally equivalent to the previous viewerSpace but fetched via
requestReferenceSpace() with the same guarantee of availability as identity
had previously. All other spaces relate to it like any other space.
Change blur/focus to visibilitychange
<https://github.com/immersive-web/webxr/pull/687>

Merged Fri Jun 14 2019 - [image: ed:explainer] [image: ed:spec]

Change blur/focus to visibilitychange (#687)

Fixes #488 Fixes #468

Changes the blur and focus events to visibilitychange, along with a
visibilityState attribute on the XRSession. The visibilityState may be
visible, visible-blurred, or hidden. This is pretty close to the
document.visibilityState attribute and associated event, with the exception
of the visible-blurredstate.
Define event order of input sources
<https://github.com/immersive-web/webxr/pull/629>

Merged Tue May 14 2019 - [image: ed:spec]

Define event order of input sources (#629)

Makes the order of select, selectstart, and selectend events generated by
the API explicit, as well as their timing relative to certain non-XR input
events in the case of transient input types (mouse, touch, etc.)
Clarify when the reset event gets fired
<https://github.com/immersive-web/webxr/pull/637>

Merged Tue May 14 2019 - [image: ed:spec]

Clarify when the reset event gets fired (#637)

Clarify when the reset event gets fired
Updated the explainer with new origin offset mechanics.
<https://github.com/immersive-web/webxr/pull/642>

Merged Sat May 25 2019 - [image: ed:explainer] [image: ed:spec]

Updated the explainer with new origin offset mechanics. (#642)
requestSession(): Group steps to run when promise is rejected
<https://github.com/immersive-web/webxr/pull/646>

Merged Wed May 15 2019 - [image: ed:spec]

requestSession(): Group steps to run when promise is rejected (#646)

This makes the algorithm a little easier to read.
Clarify assumptions for local and local-floor tracking
<https://github.com/immersive-web/webxr/pull/648>

Merged Wed May 15 2019 - [image: ed:explainer]

Clarify assumptions for local and local-floor tracking (#648)
Rename getPose arg referenceSpace->baseSpace
<https://github.com/immersive-web/webxr/pull/659>

Merged Mon May 20 2019 - [image: ed:spec]

Rename getPose arg referenceSpace->baseSpace (#659)

The use of referenceSpace here may inadvertently suggest that it only takes
an XRReferenceSpace object, when in reality it can take any XRSpace. Using
baseSpace as a replacement at the suggestion of @klausw and @thetuvix.

Plus it's fun to say: getPose finds the place of your space in the
baseSpace's space! ;D
Update Explainer Text for new requestReferenceSpace modes names
<https://github.com/immersive-web/webxr/pull/662>

Merged Tue May 21 2019 - [image: ed:spec]

Update Explainer Text for new requestReferenceSpace modes names
Handle detached arrays <https://github.com/immersive-web/webxr/pull/684>

Merged Wed Jun 05 2019 - [image: ed:spec]

Handle detached arrays (#684)

Handle detached arrays in XRRigidTransform.matrix and XRRay.matrix
Move racy parts of requestSession() to the main thread
<https://github.com/immersive-web/webxr/pull/706>

Merged Mon Jun 17 2019 - [image: ed:spec]

Move racy parts of requestSession() to the main thread (#706)

Move racy parts of requestSession() to the main thread.
Remove redundant "abort these steps" in requestSession() algorithm
<https://github.com/immersive-web/webxr/pull/645>

Merged Wed May 15 2019 - [image: ed:spec]

Remove redundant "abort these steps"

"and abort these steps" is unnecessary as the steps are aborted two steps
later. This would also prevent "pending immersive session" from being
cleared.
Make XRRay.matrix unique, add steps for obtaining it
<https://github.com/immersive-web/webxr/pull/655>

Merged Tue May 28 2019 - [image: ed:spec]

Make XRRay.matrix unique, add steps for obtaining it (#655)

Adds an algorithm for how XRRay.matrix must be calculated to ensure
compatibility between UAs.
Properly format conditionals
<https://github.com/immersive-web/webxr/pull/657>

Merged Mon May 20 2019 - [image: ed:spec]

Properly format conditionals (#657)
Replace 'list of pending render states' with 'pending render state'
<https://github.com/immersive-web/webxr/pull/701>

Merged Fri Jun 14 2019 - [image: ed:spec]

Replace 'list of pending render states' with 'pending render state' (#701)

Replace 'list of pending render states' with 'pending render state'
Some XRRenderState clarifications
<https://github.com/immersive-web/webxr/pull/703>

Merged Fri Jun 14 2019 - [image: ed:spec]

Some XRRenderState clarifications
Clarify that small overlay UIs are allowed in exclusive access
<https://github.com/immersive-web/webxr/pull/709>

Merged Mon Jun 17 2019 - [image: ed:spec]

Clarify that small overlay UIs are allowed in exclusive access (#709)

Clarify that small overlay UIs are allowed in exclusive access
Remove XRWebGLLayer.requestViewportScaling()
<https://github.com/immersive-web/webxr/pull/631>

Merged Thu May 09 2019 - [image: ed:explainer] [image: ed:spec]

Remove XRWebGLLayer.requestViewportScaling()

This method has been identified as a target for deferring until a future
version of the API, due to it's difficulty to use effectively and overlap
with framebuffer scaling for quality control.
Add none variant to XREye <https://github.com/immersive-web/webxr/pull/641>

Merged Tue May 14 2019 - [image: ed:explainer] [image: ed:feature] [image:
ed:spec]

Add none variant to XREye (#641)

Fixes #620
Added non-normative note about gamepad liveness.
<https://github.com/immersive-web/webxr/pull/650>

Merged Wed May 15 2019 - [image: ed:spec]

Added non-normative note about gamepad liveness.
Clarify what value a touchpad should report when not being touched.
<https://github.com/immersive-web/webxr/pull/660>

Merged Tue May 21 2019 - [image: ed:spec]

Clarify what value a touchpad should report when not being touched. (#660)

Specify that untouched touchpads report axis values of 0.
Better define gamepad placeholder buttons and axes
<https://github.com/immersive-web/webxr/pull/661>

Merged Tue May 21 2019 - [image: ed:spec]

Better define gamepad placeholder buttons and axes (#661)

Define what values are expected for placeholder elements and when it is
appropriate to omit them.
Remove XRLayer base type. <https://github.com/immersive-web/webxr/pull/688>

Merged Mon Jun 10 2019 - [image: ed:explainer] [image: ed:spec]

Remove XRLayer base type. (#688)

Also changed baseLayer to only accept an XRWebGLLayer. This can be extended
in the future in a few ways:

   - Re-introduce XRLayer and change baseLayer to take one.
   - Update baseLayer to accept a union of layer types.
   - Leave baseLayer as WebGL-only and enforce that new layer types must
   use whatever layer array mechanism is introduced.

Change required gamepad index to -1
<https://github.com/immersive-web/webxr/pull/690>

Merged Tue Jun 11 2019 - [image: ed:spec]

Change required gamepad index to -1 (#690)