[ad8e]

> Delay rendering until just before VSync: If you get it slightly wrong and your frame takes slightly more time to render than you thought, your frame may not be done in time for VSync. Then it will have to wait a whole extra frame and the previous frame will be displayed twice, causing a hitch in any animations.

According to docs, there are extensions WGL_EXT_swap_control_tear/GLX_EXT_swap_control_tear [0], that cause late frames to tear instead of wait a full frame. They don't work on my machine (my Intel HD 4000 reports that it is supported and then silently fails), but this should be the ideal swap mechanism.

[0]: https://registry.khronos.org/OpenGL/extensions/EXT/GLX_EXT_s...

[modeless]

I discuss tearing here: https://james.darpinian.com/blog/latency-techniques#tearing-... and here https://james.darpinian.com/blog/latency-platform-considerat...

Tearing is a pretty bad artifact so I wouldn't say that enabling it is ideal. I'm a stickler for low latency but even I don't think it's worth it in most cases. It's possible to achieve great latency without tearing. The ideal swap mechanism would be VRR when available.

Those GL extensions likely predate modern composition window managers and fail to work when compositing is enabled. As I discuss in the platform specific considerations section, tearing on Windows requires either full screen, or Multiplane Overlay which is not supported by OpenGL.

[ad8e]

On a non-VRR display, I believe it's nicer to have a momentary tearline near the top of the screen than a momentary frame skip. The stutter is more noticeable than the tearline. (Some feature of how GPUs work means that tearlines landing exactly at vsync are mysteriously delayed half a frame. Maybe someone else knows why, since I don't and neither do the people I talked to.)