iOS 7, corrupt UINavigationBar when swiping back fast using the default interactivePopGestureRecognizer

Question

I have an issue that I\'m stuck on, but I have no idea why it even happens; If I push a detail controller on the stack, and I swipe back very quickly using the default left edge

Answer 1

After investigating this issue for some time with debug console, Instruments and Reveal, I have found out the following:

1) On simulator the bug can be recreated every time, if using Profile/Automation Template and adding the following script:

var target = UIATarget.localTarget();
var appWindow = target.frontMostApp().mainWindow();
appWindow.buttons()[0].tap();
target.delay(1);
target.flickFromTo({x:2, y: 100}, {x:160, y: 100});

2) On real device (iPhone 5s, iOS 7.1) this script never causes the bug. I tried various options for flick coordinates and the delay.

3) UINavigationBar consists of:

_UINavigationBarBackground (doesn't seem to be related to the bug)
      _UIBackdropView
           _UIBackgropEffectView
           UIView
      UIImageView
UINavigationItemView
      UILabel (visible in the bug)
_UINavigationBarBackIndicatorView (visible in the bug)

4) When bug happens UILabel looks half transparent and in the wrong position, but the actual properties of the UILabel are correct (alpha: 1 and frame as in normal situation). Also _UINavigationBarBackIndicatorView looks doesn't correspond to actual properties - it is visible although it's alpha is 0.

From this I conclude that it's a bug of Simulator and that you can't even detect from the code that something is wrong.

So @troop231 - are you 100% sure this also happens on device?