Custom apps are facing an incorrect behavior of NSRulerViews when running in full screen: The height of the horizontal ruler is increased, obscuring the top of the clipview. I observed this issue with one of my apps, but was able to replicate it with the attached minimal sample app, using a scrollable text view with rulers: Just launch the app, enter some (different) text lines and switch to full screen. For your convenience I attached two screenshots with the different results.In my app I could aviid this behavior by setting translatesAutoresizingMaskIntoConstraints to false - but this was only a dirty hack with several unwanted side effects.

RulerTest - Window.png
RulerTest - FullScreen.png