I know I’m kind of hypersensitive. That’s why I have a Studio Display XDR in the first place. Everything is noticeably smoother and more responsive at 120hz over 60hz. (display refreshing 120 times a second, over 60 times, as with my old LG 5k displays).
When I started using the display, something was immediately off. Moving windows didn’t feel as smooth as everything else. Am I crazy? I investigated.
Moving the mouse cursor was smooth. Resizing windows felt smooth, so did scrolling and the animation when switching to mission control. The only thing that seemed off was moving windows.
Unfortunately, macOS’s own recording feature maxes out at 60 fps. I also wanted to avoid any processing issue, so I did what anyone would do who feels like their window movements aren’t entirely smooth: I recorded a 120fps video of the display using my tripod.
In this video (slowed down to 24 fps), we can see:
- smooth mouse cursor
- smooth scrolling
- smooth resize
- smooth mission control
- moving window only updates every 2 frames!
I’m not crazy. (or am I, for doing this?)
I also tested the same on my built-in MacBook Pro Display. It doesn’t happen there. It’s only on the Studio Display XDR.
There might be better a better way to debug this. It looks like this is an issue below Quartz. When using QuartzDebug to “Flash screen updates”, everything is yellow while dragging a window, but when investigating (via taking a picture of the screen, since Quartz debug happens after what I’d otherwise take a screenshot of), it looks like the Quartz debug flashes themselves only update at 60fps.
Either way, I filed a bug report with Apple. Wild. I hope I can move windows smoothly soon.
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