I was trying to fix some (what I thought to be) minor alignment bugs that came up during QA for one of our apps, when I stumbled on one of the more strange bugs I've seen recently.
In this app, the first screen presents you with the options to log in or create an account. The login screen is two text fields and the first part of the account creation is one large one. The QA came back with a bug where the email field on the login screen wasn't properly centered during editing: before tapping to edit: after tapping: At first, I couldn't even reproduce the bug until they gave me this set of steps: Launch the app Look at the account creation screen (which sets the first textfield as first responder automatically) Go back the splash screen Click the login button start editing the text in the email box voila, broken centering After rounding up the usual suspects, nothing seemed to make sense. Plus the only way to cause it was to view an unrelated view. Not only is the account creation screen completely different from the login screen, but once you back out of the account creation screen, it is deallocated and shouldn't have any effect on anything. Yet somehow, just having the cursor in the field was enough to spawn two entangled particles somewhere in the depths of UIKit that linked this view and the one that will be created (note it is not even in memory yet) when the login view is initialized (and the original field has already been deallocated). These two views that were never resident in memory at the same time, used the magic of (presumably) quantum physics to communicate across time and space with the goal of breaking my simple text centering. After proceeding through the five stages of grief about what I assumed to be yet another rare, unsolvable quirk in UIKit, I found this Stack Overflow question: http://stackoverflow.com/questions/24184302/uitextfield-horizontal-text-alignment-text-not-centered?rq=1 There was some mention that the height of the field affected the centering. This isn't my issue because the field in question has a reasonable height. But it got me thinking, what could have caused this? I'm still not sure. But what I do know is that it only happens if you start editing a UITextField where the height is set by a constraint such as V:|-[viewInQuestion]-|. Once you begin editing that field (which itself acts just as you would expect), you can edit the other field and observe the jump: This only happens the first time you begin editing the normally sized field. Every subsequent entry into the field results in the normal lack-of-crazy-jump that you've come to expect from UIKit. Additionally, editing a similarly laid out text field with secureTextEntry set to TRUE does not display the same behavior. For now, I can change the constraint aligning the text field which is the source of the problem, but I thought that this discovery might be of interest to the cocoa-dev list (and hopefully to someone at Apple ;-] ). As such, I created a new project from the ground up with a (mostly) minimal setup to reproduce the bug under the conditions that I saw it (multiple view controllers). That project can be found here: https://github.com/danblakemore/QuantumEntanglement -- Daniel Blakemore Pixio Software _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
