iOS 10: "[App] if we're in the real pre-commit handler we can't actually add any new fences due to CA restriction"

Solution 1:

in your Xcode:

• Click on your active scheme name right next to the Stop button
• Click on Edit Scheme....
• in Run (Debug) select the Arguments tab
• in Environment Variables click +
• add variable: OS_ACTIVITY_MODE = disable

Solution 2:

It comes from +[UIWindow _synchronizeDrawingAcrossProcessesOverPort:withPreCommitHandler:] via os_log API. It doesn't depend from another components/frameworks that you are using(only from UIKit) - it reproduces in clean single view application project on changing interface orientation.

This method consists from 2 parts:

1. adding passed precommit handler to list of handlers;
2. do some work, that depends on current finite state machine state.

When second part fails (looks like prohibited transition), it prints message above to error log. However, I think that this problem is not fatal: there are 2 additional assert cases in this method, that will lead to crash in debug.

Seems that radar is the best we can do.