Mesa Vulkan KHR_present_wait Support Extended To Wayland

[phoronix]

Phoronix: Mesa Vulkan KHR_present_wait Support Extended To Wayland

VK_KHR_present_wait is an extension originally started by Keith Packard working for Valve on improving the Linux graphics stack. The VK_KHR_present_wait extension allows for waiting for present operations to complete and can be used for monitoring/pacing the application by managing the number of images not yet presented. This Vulkan extension had been supported by Mesa Vulkan drivers under X.Org and now is being enabled for Wayland environments too...

https://www.phoronix.com/news/Mesa-KHR_present_wait-Wayland

[V1tol]

Patch applies cleanly over 23.1.0-rc4 if anyone interested

[Calinou]

In a nutshell, this allows enforcing double-buffered V-Sync instead of triple-buffered V-Sync: https://github.com/godotengine/godot-proposals/issues/4065.

Double-buffered V-Sync has lower latency (1 less frame = -16.7 ms at 60 Hz), but framerate will fully drop to the next divisor if the application can't sustain the display refresh rate. For example, if you have a 60 Hz display, the app will appear to run at 30 FPS whenever it can't reach 60 FPS. This makes double-buffered V-Sync a good choice for applications that are nearly always locked to the target framerate, but a bad choice otherwise.

Remember that the Steam Deck's display doesn't support VRR, so this will definitely be handy in situations where you don't want tearing but don't want too much input lag from V-Sync.