It may sound like a trivial feature, but this sort of thing matters, and not only to gamers
In a sign of how display handling is evolving, the GNOME desktop’s 3D-compositing Mutter window manager is gaining support for variable refresh rate (VRR, also known as Adaptive Sync) displays. Mutter is an important chunk of code. As the project page says, it’s «a Wayland display server and X11 window manager and compositor library.»
It’s the basis of GNOME Shell, which is implemented [PDF] as a Mutter plug-in, but other desktops use it as well. For instance, the PIXEL desktop of the Raspberry Pi OS. It’s also used in Pop! _OS’s Cosmic desktop. Cinnamon uses a fork of it called Muffin. Its name comes from Metacity + Clutter. Metacity was the old GNOME 2 window manager, which used Gtk2 to render to the screen, and Clutter used to be GNOME’s OpenGL rendering library. The long-outstanding change to give it VRR support has finally lost its «work-in-progress» tag. Once merged, it will be visible in the GNOME Control Center as a simple on/off toggle. Many modern chipsets, such as Intel’s Arc, support «Adaptive Sync.» Even plain old X.org has supported it for a while, and HDMI has since 2017. In brief, it enables the monitor’s refresh rate to change to match the frame rate of the program driving the display.
