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I got a purple warning border of some sort on my OS X Photos app.

It was described in this Apple Support community thread and got a solution. The problem was caused by NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints being set.

This is a screenshot from my own computer:

enter image description here

Would it be safe to remove the purple warning without addressing the problem causing it? Why did I get a purple warning in the first place?

  • What aspect are you concerned about being safe? The command line solution maybe? – Graham Miln Nov 29 '15 at 13:11
  • See my comment to your answer. Thanks and hope your holidays was delightful! : ) – MacProGirl Dec 28 '15 at 18:36
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Enabling and disabling NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints is safe. This feature allows developers to debug their application's layout problems.

Autolayout and Constraints

Constraint based layout is a mechanism Apple recommends developers use to craft their user interfaces. The mechanism is often called Autolayout in developer documentation.

Autolayout is tough to get right. It is possible to have constraints that conflict. Apple have added numerous features to help flag these conflicts and to help developer's fix them.

The NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints flag is one such tool to aid developers.

Autolayout debug

Not Intended for Users

I presume you did not enable NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints yourself. Preassuming this, it suggests Photos.app's engineers have an autolayout bug or that some other process has enabled this flag on Photos.app.

Either way, the purple interface was rightly concerning as a user. No user should ever see, or need, this debugging tool. Somewhere a mistake was made or a bug exists within OS X.

Safe to Disable

The suggested solution in the discussion thread deletes any value associated with NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints. This is safe:

 defaults delete com.apple.Photos NSConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints
  • I don't understand. Do I still have full functionality? If not then that's what I want. Thanks. – MacProGirl Dec 23 '15 at 15:13
  • I am not sure I understand. Feel free to edit your question to clarify what you need addressing. – Graham Miln Dec 24 '15 at 17:51
  • Was the purple warning I got not a real warning for something that is wrong in my computer so I can dismiss it? It feels a bit unsafe to go under the hood and change system settings and hope all is fine. Thanks! – MacProGirl Dec 28 '15 at 18:34
  • You can safely make the defaults change. Apple will likely fix the problem in an update. If the purple warning appears again, please add to this question and we can try to find the underlying cause. – Graham Miln Dec 28 '15 at 19:22
  • You are assuming that it is a general problem and not specific for just my app/computer. I still wonder what I did that others haven't that triggered it. Now that I start up Photos there is no problem. Strange since I haven't done anything. I rarely open the app so I cannot figure what is causing or fixing it. Thanks anyway! – MacProGirl Jan 2 '16 at 8:51

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