Open Radar

 
Summary:
I am changing navigation bar global appearance directly before presenting a MFMessageComposeViewController and again in the presentations completion block in one method.

When I call this method about 10 times, it becomes exponentially slower to present the modal. The app hangs and the screen even goes black before presenting the messages modal.

When connected to the debugger I get the follow timeout message in my log:
<CKSMSComposeRemoteViewController: 0x15feac8b0> timed out waiting for fence barrier from com.apple.mobilesms.compose

This does not happen if I am not changing global UIAppearance.

Steps to Reproduce:
1. Write a method that changes uiappearance colors (globally), presents a MFMessageComposeViewController and in the completion block of the presentation change the uiappearance colors back to their initial states.

2. Create a button and that calls this method. 

3. Implement MFMessageComposeViewController's didFinishWithResult: to dismiss the MFMessageComposeViewController.

4. Run your app on a device, and click this button to present the message VC and then cancel the message modal around 8 - 12 times. 

5. Notice the exponentially increased lag. 
If you are connected to the debugger you will see this in the log:
<CKSMSComposeRemoteViewController: 0x15feac8b0> timed out waiting for fence barrier from com.apple.mobilesms.compose

Expected Results:
We expect to see no lag, no matter how many times the modal is presented.

Actual Results:
The app hangs and the screen even goes black before presenting the messages modal after presenting the MFMessageViewController multiple times. 

Version:
7.1(11D167)

Notes:
This bug also happens on iOS 8 (beta) on an iPhone 5S.

Configuration:
iPhone 5S