If I change the tracking speed of my USB mouse then literally nothing happens. It tracks at the exact same speed:
It appears to remember the setting and it makes defaults read -g com.apple.mouse.scaling return different results, but the actual mouse tracking speed never changes. Is there any way to debug this? I'm using MacOS 10.15.6.
Ah I just figured it out! I was using a KVM with a "fast switching mode" where you can hit the side of the screen with your mouse twice to switch inputs. Somehow this got turned on. (It also explains why it was randomly switching inputs without me asking!)
As soon as you turn it off (Scroll lock, Scroll lock, F12 for the one I'm using), the mouse works perfectly again. My guess is that in order to know when you hit the side of the screen, the KVM has to be in charge of the position of the cursor on the screen, so it must set the mouse to absolute mode, and then the OS sensitivity has no effect.
Would be nice if something in the UI said the mouse is operating in absolute mode (I didn't even know that was possible, though I guess graphics tablets use it).
In my case, I had installed USB Overdrive long ago for use with a bluetooth mouse, and was using the "Any Mouse" settings profile for it. When I plugged in the wired mouse recently the acceleration was wrong.
Once I finally remembered USB Overdrive was installed, I upgraded it to the latest version then gave the bluetooth and wired mice devices their own profiles instead of using the default "any mouse" panel.
Overdrive also let me use the MacOS settings for the wired mouse movement, but override the acceleration (UO's accel setting is much more adjustable than Apple's.)
I forgot how useful UO was. Really the worst thing about it is that you can forget it's there after a couple years, and there is no indication in System Settings that the mouse is being overridden.
