John SiracusaMar 31, 2023

I've been tracking this one down for a few days. Ever since I updated to macOS 13.3, window dragging sometimes looks like this.

It happens with any window in any app. It stops when I hide some(?) other windows. Not sure why and which windows, but I'm working on it…

Show threadJohn SiracusaApr 24, 2023

Here's a better screen recording of the laggy-window-dragging bug I described earlier (currently filed with Apple as FB12122106)

https://youtu.be/h0bKmcsMFvw

FB12122106 Demonstration

YouTube
Show threadSteve Troughton-SmithApr 24, 2023
@siracusa that jittering tells me some other process is trying to update the window position as you're dragging it
Doug LandonApr 25, 2023
Show threadJohn Siracusa
@stroughtonsmith I’ve been assuming it’s the snap-to-window-edge feature that was added to macOS several years ago, but somehow going haywire since 13.3 was released.
Apr 24, 2023 at 7:24pmIvory for iOS
Show threadJohn SiracusaApr 24, 2023
@stroughtonsmith Notice how it chills out once the number of visible windows is reduced. It’s like a bad algorithm for window placement that goes off a cliff once N gets too big.
Show threadGeorge NachmanApr 25, 2023
@siracusa does it happen with your own app’s window? If so set a breakpoint in windowDidMove and you can tell from the call stack if accessibility caused it. That would implicate a third party app.
Show threadSteve Troughton-SmithApr 24, 2023
@siracusa I would be very surprised if it’s not at all related to third party software. It looks like something is looping over your window list and reading/setting frames 👀 I can open a hundred TextEdit windows here without seeing any slowdown to snap, and I'm just on a Mac mini
Show threadJoshua ShapiroApr 24, 2023
@stroughtonsmith @siracusa are you accusing Front and Center?
Show threadSteve Troughton-SmithApr 24, 2023
@jashapiro @siracusa alas all the window management solutions on the MAS are paid upfront, so I can't test against any of them here
Show threadJohn SiracusaApr 24, 2023

@stroughtonsmith @jashapiro For the record, it happens when my apps are not running at all. (Also, my apps have nothing to do with window dragging.)

I also uninstalled all third-party kexts and system extensions, with no change.

Show threadJoshua ShapiroApr 24, 2023
@siracusa @stroughtonsmith For the record, I was joking! (Even if I hadn’t remembered that John said it was with all 3rd party apps closed & kexts removed, I would have assumed it)
Show threadJohn SiracusaApr 24, 2023
@stroughtonsmith It started immediately after I updated to macOS 13.3, so if it’s third-party, then it’s a third-party conflict with 13.3.
Show threadSteve Troughton-SmithApr 24, 2023
@siracusa could be something like the window list API changed internally to something slower than before, another one of those 'hope nobody notices' things?
Show threadJohn SiracusaApr 24, 2023
@stroughtonsmith Maybe, but then what’s reading the list? And if it’s the window server (or WindowManager) then why isn’t it happening to everyone? Mysterious. I will continue investigating…
Show threadDKMJApr 24, 2023
@siracusa @stroughtonsmith I saw similar erratic behaviour as result of wrong refresh frequency on external monitor, immediately after upgrading to 13.3
Show threadChris TurnerApr 25, 2023
@siracusa have you tried doing an strace (or whatever the macOS equivalent is) of windowmanager with and without the bug occurring? it would be a lot of output to mull through but you might see a difference that could be helpful
Show threadChris TurnerApr 25, 2023
@siracusa looks like it’s dtruss and you need to disable SIP to use it. Meh. If I can manage to reproduce on one of my macs I’ll try it and report back.
Show threadJohn SiracusaApr 25, 2023
@megachris sc_usage and fs_usage can get you a lot too, but I already did spindumps which cover a lot of the same area.
Show threadJohn SiracusaApr 24, 2023
@stroughtonsmith Also, it’s not the size of the window list that matters, it’s the number of *visible* windows, as demonstrated in my screen recording when merely hiding all the windows makes it behave normally again.
Show threadSteve Troughton-SmithApr 24, 2023
@siracusa I'm seeing if I can find an easy repro case, but those options /are/ available through API so I would be suspicious
Show threadJohn SiracusaApr 24, 2023
@stroughtonsmith If it helps, the windows in my video are the only ones visible on the screen. (There aren’t more outside the frame of the screen capture.) So you can see the the number of windows required for reproduction is pretty small! Also, it takes some time (minutes to hours) after a reboot to start happening again. (It doesn’t stop after it starts.)
Show threadTimo HetzelApr 24, 2023
@siracusa @stroughtonsmith maybe something from some app got stuck in Accessibility settings? Empty out those plist files?
Show threadMike Schreiber Apr 24, 2023
@siracusa I'm attempting to repro on my own Mac Pro now - only a 5K display, not 6K, and with the lowest-end GPU, so not *exactly* the same device, but closer than many. I'll reply here if I get a repro over time.
Show threadAdam Bell Apr 24, 2023
@siracusa @stroughtonsmith sounds like we're gonna need a third party app to undo the changes to windows made by third party apps
Show threadAndreas HartlApr 24, 2023
@stroughtonsmith @siracusa if it’s a M1/2 mini vs an Intel + AMD Mac Pro then trying to reproduce it on another graphics subsystem might help to isolate the culprit of this behaviour.
Show threadDan Morgan Apr 24, 2023
@stroughtonsmith @siracusa It is Adobe Type Manager. Make sure it loads first. #ClassicMac
Show threadJason Petersen (he)Apr 25, 2023
@stroughtonsmith but is it an _Intel_ Mac Mini?
Show threadDavid AnsonApr 24, 2023
@siracusa @stroughtonsmith Have you tried a fresh OS on a USB key or external drive? I don’t trust that it’s not a side effect of something you added to the system. (No offense!)