Some WebXR Implementations pause the 2D browser page in XR, make this optional?

[AdaRoseCannon]

Some WebXR Implementations pause the 2D browser page in WebXR, this is a performance improvement and is technically correct since the page isn't visible. Unfortunately it can cause issues if you are tying bits of your WebGL scene to DOM based animations and transitions. The ability to opt out of this behaviour would be handy for developers.

Related #1316 since this would also keep the animations running.

/agenda to discuss.

[AdaRoseCannon]

/facetoface lets talk about this at the face to face

[emmanueljl]

Do you have a link to a WebXR app that does this? The system keyboard integration, for example, is dependent on interacting with a text input element on the page. I'd like to test whether that has issues with this "pausing".

[mkeblx]

Here's a basic example page where a CSS animation value is used to drive a WebXR object's position.
https://mkeblx.github.io/css2webxr/

This fails to work in WebXR if the WebXR implementation pauses the 2D browser page (e.g. like Meta Browser currently). On desktop you can see the working scenario using the Immersive Web Emulator.