Bug 173442 – Eventual Variable Refresh Rate support (HTML 5.3)

• Status: NEW
• Component: Canvas

[mdrejhon]

Long Term Enhancement Project: Support for variable refresh rates in WebKit

With the proliferation of variable refresh capable displays (FreeSync, GSYNC, VESA Adaptive-Sync, HDMI 2.1 VRR, Apple ProMotion), there is a need to prepare the WebKit engine over the coming few years as the new iPad and the new Microsoft XBox both support variable refresh rates, as several HDTVs shown off at CES 2017.

Variable refresh rate displays lets software decide when to begin refresh cycles.  

The goal is animations run at a specific frame rate (e.g. 48 fps or 75 fps), the display refresh rate follows along for the dominant element (e.g. full screen canvas, WebGL, video, etc).  The refresh rate changes seamlessly even every refresh cycle, if necessary -- so sudden framerate changes are seamlessly possible without stutters (software simulation via frame interpolation -- http://www.testufo.com/#test=stutter&demo=gsync ...) as modern variable refresh rate displays can change refresh rates with no visual flash or disruption unlike previous displays.,

Currently, as an Invited Expert to W3C Web Platform Working Group, work is currently ongoing to prepare browser engines for emerging dynamic variable refresh rate operation capability -- https://github.com/w3c/html/issues/375

Specific potential pre-alpha proposals towards variable refresh rate support are located at:
PHASE 1 -- No API changes -- https://github.com/w3c/html/issues/375#issuecomment-306591154
PHASE 2 -- New API changes -- https://github.com/w3c/html/issues/375#issuecomment-306603305

While this is very early to report this to Webkit, I'm adding this because I'm aware of ongoing work to refactor the animation engines in WebKit, and it needs to have a migration path to become VRR-compatible -- to avoid coding into a corner between a rock and hard place.

[mdrejhon]

Also a very useful comments thread I've also posted on the potential gotchas, and considerations:
https://github.com/w3c/html/issues/375#issuecomment-306590982

[Brent Fulgham]

Feature Request (may be largely complete now)

[Radar WebKit Bug Importer]

<rdar://problem/97220919>

[Simon Fraser (smfr)]

Our proposed API for animation with different frame rates is at https://github.com/WebKit/explainers/tree/main/animation-frame-rate