[Public WebGL] frame timing

[Florian Bösch <pyalot@gmail.com>]

A while back there was a discussion on introducing timer queries. Far as I recall, this discussion stalled on these points:

• About 50% of desktops support them and only a fraction of mobiles
• They're non-intuitive on tiled renderers
• The implementations that exist may report garbage and/or slow things down considerably (unfit to deploy in production)
• Disagreement on the API format

Considering timer queries dead and burried, it would still be nice to have a way to measure per frame time that doesn't require gl.finish() (or mocking gl.finish with readPixels), that isn't hampered by tiled-rendering and that can capture performance regardless/beyond the 60fps cap (and without having to disable vsync browserwide).

I'd like to explore if there's a viable path to that goal:

• Disjoint timer queries (for mobile) and timer queries (for desktop) have some support. Would it be viable to use this capability in principle to achieve frame timing results?
• Would browser vendors be able to black/whitelist vendors/devices/drivers where timer queries behave anomalously?
• Lacking timer queries, or lacking their reliable functioning, would it be possible to achieve still relevant timings for a frame by other means for the UA?
• As an API to that functionality, would something like a WEBGL_frame_timer extension that just has one function like ext.getLastFrameTime() be satisfactory?