Auto-Layout: What Creates Constraints Named Uiview-Encapsulated-Layout-Width & Height

Auto-layout: What creates constraints named UIView-Encapsulated-Layout-Width & Height?

Based on a ton of observation I believe (but cannot know for certain) that the constraints named UIView-Encapsulated-Layout-Width and UIView-Encapsulated-Layout-Height are created by UICollectionView and friends, and exist to enforce the size returned by the sizeForItemAtIndexPath delegate method. I guess it's there to ensure that the UICollectionViewCell set up by cellForItemAtIndexPath ends up the size that it was told it would be.

Which answers my initial question here. A second question is why were the constraints unsatisfiable? The cell's intrinsic height should have been the same as UIView-Encapsulated-Layout-Height. Again, I don't know for certain, but I suspect it was a rounding error (i.e. intrinsic height came to 200.1 pixels, the UIView-Encapsulated-Layout-Height maybe rounded to 200. The fix I came up with was to just lower the priority of the relevant cell constraint to allow UIView-Encapsulated-Layout-Height to have the last word.

iOS 8.3 'UIView-Encapsulated-Layout-Width' in Custom Keyboard

    Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSAutoresizingMaskLayoutConstraint:0x15dd1da0 h=-&- v=-&- Keyboard:0x15db2b00.width == UIView:0x15da7b90.width - 320>",
    "<NSLayoutConstraint:0x15dd2520 'UIView-Encapsulated-Layout-Width' H:[UIView:0x15da7b90(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x15dd2520 'UIView-Encapsulated-Layout-Width' H:[UIView:0x15da7b90(0)]>

It is telling you that it can't satisfy all constraints at once.

You have a constraint <NSAutoresizingMaskLayoutConstraint:0x15dd1da0 h=-&- v=-&- Keyboard:0x15db2b00.width == UIView:0x15da7b90.width - 320>, which dictates the width of the keyboard equals the width of the UIView at 0x15da7b90 minus 320 (check the debugger which one this is, I usually look at the GUI debugger if I know what UIViews might be causing the problem).

The other conflicting constraint is <NSLayoutConstraint:0x15dd2520 'UIView-Encapsulated-Layout-Width' H:[UIView:0x15da7b90(0)]>, which dictates the width of the UIView at 0x15da7b90 (same one) to be 0. It cannot satisfy both this one and the one above, so it breaks this one.

I see that your first constraint is one of the type NSAutoresizingMaskLayoutConstraint, so you can try to set setTranslatesAutoresizingMaskIntoConstraints to false on your view, which will probably remove the first constraint, thus removing the conflict.

Other helpful documentation:

• Visual Format Language, the format that Xcode uses in the log, helps to know this language to debug them better.
• View Debugging in Xcode, helps to identify which views are where and at what address.

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