Hello WebKit,

I'd like to ask for WebKit's position on the dynamic viewport scaling feature that's part of the WebXR API. This is intended to let applications render to a subset of the full viewport and adjust that scale on a per-frame basis if needed to reach target framerates.

Specification: Part of WebXR, see for example https://immersive-web.github.io/webxr/#dom-xrview-requestviewportscale

Explainer: https://github.com/immersive-web/webxr/blob/master/explainer.md#dynamic-viewport-scaling

This was discussed in https://github.com/immersive-web/webxr/issues/1091 and multiple calls with the immersive-web group. The changes were merged into the main specification via https://github.com/immersive-web/webxr/pull/1132 , but to the best of my knowledge this hasn't been launched in any other browser yet.

Could I get your position on this?

For context, the goal is that this API is optional for UAs. It would be a valid implementation to provide a requestViewportScale method that does nothing. If it is supported, the UA can optionally provide a recommendedViewportScale numeric attribute based on internal heuristics, but it's also valid to keep that undefined.

Thank you,

Klaus Weidner