Feature request: minimum refresh rate for VRR

[mgabor3141]

Problem

With variable-refresh-rate enabled, my monitors drop to 48Hz when idle. At this low refresh rate, both of my monitors show intermittent brightness flickering in bright areas of the screen. Moving the mouse or triggering any animation immediately stops the flickering since the refresh rate goes back up.

This happens on two different monitors, both with a 48Hz as their lowest rate. The flickering is subtle and doesn't happen 100% of the time, but it's noticeable enough to be annoying. From what I've read, this is a common panel-level issue at very low refresh rates.

Why on-demand VRR doesn't work for me

I know I can use variable-refresh-rate on-demand=true and add window rules for games, but I also want VRR for browsers so videos display with correct frame timing. If I add a rule for Firefox/Chrome, then I get the low refresh rate flickering whenever I'm reading a webpage with no video playing.

Proposed solution

A min-rate option that prevents the refresh rate from dropping below a threshold:

output "DP-1" {
    variable-refresh-rate min-rate=60
}

Niri would force redraws at the minimum rate when nothing else is updating the screen.

This seems doable since the redraw loop already uses timers for frame pacing, and the skip-cursor-only-updates-during-vrr flag shows that conditional redraw logic based on VRR state already exists.

Related

• Discussion "is-maximized" window rule for VRR #2487 is about the same underlying problem with a different approach
• Discussions VRR on-demand fullscreen window-rule #1725, VRR enabled with consistent refresh rate on the desktop. #2407
• KDE has a similar minimum refresh rate setting

Setup

• NVIDIA GPU on Wayland
• niri from CachyOS repos
• Dell S2721D (DP-2) and Gigabyte M32U (DP-1)