When projection layers are created, they use the current number of views

[asajeffrey]

In https://immersive-web.github.io/layers/#allocate-color-textures-for-projection-layers, the algorithm for allocating textures for projection layers says "Let numViews be the number of the session’s list of views..." and allocates that many textures. But over in https://immersive-web.github.io/webxr/#update-the-viewports, there is text for "When the list of views changes", which implies the list of views may change over time.

[asajeffrey]

See also immersive-web/webxr#1094

[cabanier]

Yes, PR #176 fixes this.
Can you take a look to make sure I didn't miss something?

[asajeffrey]

I don't see how that language copes with the list of views changing?

[cabanier]

I don't see how that language copes with the list of views changing?

yes, that seems problematic. I made these changes assumes that the list of exposed XRViews would change but not the list of views.
@Manishearth, how can we allocate texture if we can't be sure about the maximum number of views?

[Manishearth]

Yeah so in the current spec situation the "list of views" is a mutable quantity. There is a "list of viewports" which isn't. I could introduce a concept of active views, or a separate "list of possible views" list.

[Manishearth]

Note that you can be sure of the maximum number of views already: the list of viewports language mentions that it is for all possible views that may be exposed. I'll fix this up a bit

[cabanier]

Yeah so in the current spec situation the "list of views" is a mutable quantity. There is a "list of viewports" which isn't. I could introduce a concept of active views, or a separate "list of possible views" list.

The layers spec calculates the viewports from the list of views.

[cabanier]

Note that you can be sure of the maximum number of views already: the list of viewports language mentions that it is for all possible views that may be exposed. I'll fix this up a bit

ok. I'll make a similar change

[cabanier]

Note that you can be sure of the maximum number of views already: the list of viewports language mentions that it is for all possible views that may be exposed. I'll fix this up a bit

ok. I'll make a similar change

Having to add that the {{XRSession}} may expose everywhereI I use list of views is a bit verbose.
Can you define the concept in the WebXR spec instead?

[Manishearth]

Yes I'm about to do that. I'll introduce a concept of active view and mandate that the full list of views be immutable

[cabanier]

@Manishearth's PR makes it so we don't have to change the layers spec. Closing.