Open Radar

 
Summary:
With the Accessibility Inspector (or another assistive application) open, the iOS simulator is plagued by frequent hangs and pinwheels.

Steps to Reproduce:
1. Make sure that no assistive applications are open. These include Accessibility Inspector, Moom, Zoom/2, and other apps that allow you to move windows around in any means the than clicking and dragging.
2. Run any app in the iOS simulator. Apps with scroll views are best, because it’s easiest to tell when they’re pinwheeling.
3. Interact with the app for a few seconds. Make sure everything is working normally, and there are no weird hangs or pinwheels.
4. Open Accessibility Inspector or another assistive application.
5. Again, interact with the app in the simulator.

Expected Results:
App’s performance is not affected.

Actual Results:
App performs normally for a second or two, then hangs for long enough to cause the simulator to pinwheel (which I believe is at least 2 seconds). It seems to coalesce all your clicks and drags, then plays them all back in quick succession, then starts pinwheeling again. Quitting the assistive application seems to fix the problem.

Regression:
This was not a problem in Xcode 7.0 as far as I know.

Notes:
You can’t see the pinwheels in the attached video, because QuickTime screen recording doesn’t capture them, so look for the app being unresponsive and listen for when I say that it’s pinwheeling.
Also attaching the app from the video, but I’ve seen it in multiple Obj-C and Swift apps in both the iOS 8.4 and iOS 9.1 simulators.