Frame presentation timing queries/control? #3634

As far as I can tell (but maybe I didn't look hard enough), WebGPU does not currently provide a way to query the time at which previous video frames were presented to a screen, nor does it provide a way to check or control the time at which the frame currently being rendered should be presented to the screen, assuming that its rendering is completed in due time.

These features are useful in applications where minimal compute-to-display latency is desired, such as fast-paced interactive gaming or pro audio visualization. In this context, they can be used to slightly delay the rendering of a frame when the rendering time is known to be fairly reproducible and much smaller than the refresh rate, in order to make sure that the generated image will be presented to the screen as soon as possible after the underlying data has been collected.

These features are also useful when trying to avoid the jarring visual effect of fluctuations in said latency when rendering animated content (known as "jitter", "stutter" or "jank"). In this context, minimizing latency is not the primary goal, the main goal is rather to keep it as constant as possible in order to sync up with outgoing audio streams and to make sure that what is meant to be a constant-speed smooth animation on the application side does not become variable-speed irregular movement on the display side.

If you can confirm that this feature is not present in the existing WebGPU spec and would be of interest, we can discuss further what it should look like. For now, I'll just drop a bunch of links to reference material:

• Optimization of controller-to-display latency in Call of Duty: https://www.activision.com/cdn/research/Hogge_Akimitsu_Controller_to_display.pdf
• Slide deck from Croteam adressing the same issue (unfortunately, I couldn't find a 60fps recording of the presentation, which would be needed to enjoy their demos as they are meant to be seen): https://www.gdcvault.com/play/1025407/Advanced-Graphics-Techniques-Tutorial-The
• Exploration of the same issue in an UI rendering context, with lots of extra reference links:
  • https://raphlinus.github.io/ui/graphics/2020/09/13/compositor-is-evil.html
  • https://raphlinus.github.io/ui/graphics/gpu/2021/10/22/swapchain-frame-pacing.html
• Discussion of some existing system-specific APIs to do this : https://stackoverflow.com/questions/61031850/how-to-get-the-next-frame-presentation-time-in-vulkan .