I have been using the QLPreviewController in an app for some time now and have always gotten a flurry of constraint warnings when it launches which I have ignored. I have looked at them and don't believe they are due to my code and the app seems to work. Tried to attach a simple app that loads a ViewController with a single button that when pressed creates an object that generates and displays a CSV file via QLPreviewController but can't. First warning: Invalid content type identifier com.apple.pktransaction specified in extension com.apple.Passbook.QuicklookPreviewExtension Second warning: Unable to simultaneously satisfy constraints. 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:0x60000213ae40 h=-&- v=--& UINavigationBar:0x10621ddf0.minY == 0 (active, names: '|':UILayoutContainerView:0x106208830 )>", "<NSAutoresizingMaskLayoutConstraint:0x60000213ae90 h=-&- v=--& UINavigationBar:0x10621ddf0.height == 44 (active)>", "<NSLayoutConstraint:0x600002137890 V:[UINavigationBar:0x10621ddf0]-(0)-[UIFocusContainerGuide:0x600003d04000'UINavigationControllerContentFocusContainerGuide'] (active)>", "<NSLayoutConstraint:0x600002137020 UIFocusContainerGuide:0x600003d04000'UINavigationControllerContentFocusContainerGuide'.bottom == UILayoutContainerView:0x106208830.bottom (active)>", "<NSLayoutConstraint:0x6000021366c0 V:|-(0)-[UILayoutContainerView:0x106208830] (active, names: QLPreviewControllerView:0x10631de80, '|':QLPreviewControllerView:0x10631de80 )>", "<NSLayoutConstraint:0x600002134d20 V:[UILayoutContainerView:0x106208830]-(0)-| (active, names: QLPreviewControllerView:0x10631de80, '|':QLPreviewControllerView:0x10631de80 )>", "<NSLayoutConstraint:0x60000211dcc0 'UIView-Encapsulated-Layout-Height' QLPreviewControllerView.height == 0 (active, names: QLPreviewControllerView:0x10631de80 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x600002137890 V:[UINavigationBar:0x10621ddf0]-(0)-[UIFocusContainerGuide:0x600003d04000'UINavigationControllerContentFocusContainerGuide'] (active)> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful. dealloc Query controller [A899BAB1-6730-4B7D-9CBE-488EC6641B6B] Unable to simultaneously satisfy constraints. 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:0x6000021229e0 h=--& v=--& _UIToolbarContentView:0x10641e920.width == 0 (active)>", "<NSLayoutConstraint:0x60000213a6c0 H:|-(0)-[_UIButtonBarStackView:0x106507620] (active, names: '|':_UIToolbarContentView:0x10641e920 )>", "<NSLayoutConstraint:0x60000213a710 H:[_UIButtonBarStackView:0x106507620]-(0)-| (active, names: '|':_UIToolbarContentView:0x10641e920 )>", "<NSLayoutConstraint:0x600002146bc0 'IB_Leading_Leading' H:|-(16)-[_UIModernBarButton:0x106519cd0] (active, names: '|':_UIButtonBarButton:0x106519ab0 )>", "<NSLayoutConstraint:0x600002146c60 'IB_Trailing_Trailing' H:[_UIModernBarButton:0x106519cd0]-(16)-| (active, names: '|':_UIButtonBarButton:0x106519ab0 )>", "<NSLayoutConstraint:0x600002147f70 'UISV-canvas-connection' UILayoutGuide:0x600003b050a0'UIViewLayoutMarginsGuide'.leading == _UIButtonBarButton:0x106519ab0.leading (active)>", "<NSLayoutConstraint:0x60000213b020 'UISV-canvas-connection' UILayoutGuide:0x600003b050a0'UIViewLayoutMarginsGuide'.trailing == UIView:0x10651c300.trailing (active)>", "<NSLayoutConstraint:0x60000213bde0 'UISV-spacing' H:[_UIButtonBarButton:0x106519ab0]-(0)-[UIView:0x10651c300] (active)>", "<NSLayoutConstraint:0x60000213a5d0 'UIView-leftMargin-guide-constraint' H:|-(0)-[UILayoutGuide:0x600003b050a0'UIViewLayoutMarginsGuide'](LTR) (active, names: '|':_UIButtonBarStackView:0x106507620 )>", "<NSLayoutConstraint:0x60000213a670 'UIView-rightMargin-guide-constraint' H:[UILayoutGuide:0x600003b050a0'UIViewLayoutMarginsGuide']-(0)-|(LTR) (active, names: '|':_UIButtonBarStackView:0x106507620 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x600002146c60 'IB_Trailing_Trailing' H:[_UIModernBarButton:0x106519cd0]-(16)-| (active, names: '|':_UIButtonBarButton:0x106519ab0 )> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful. Unable to simultaneously satisfy constraints. 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. ( "<NSLayoutConstraint:0x6000021374d0 UILayoutGuide:0x600003b21340'TitleView(layout=0x106416a30)'.leading >= UILayoutGuide:0x600003b216c0'UIViewLayoutMarginsGuide'.leading (active)>", "<NSLayoutConstraint:0x6000021372f0 UILayoutGuide:0x600003b21340'TitleView(layout=0x106416a30)'.trailing <= UILayoutGuide:0x600003b216c0'UIViewLayoutMarginsGuide'.trailing (active)>", "<NSLayoutConstraint:0x60000216ce60 'UIView-Encapsulated-Layout-Width' _UINavigationBarContentView:0x106416700.width == 0 (active)>", "<NSLayoutConstraint:0x600002134f50 'UIView-leftMargin-guide-constraint' H:|-(16)-[UILayoutGuide:0x600003b216c0'UIViewLayoutMarginsGuide'](LTR) (active, names: '|':_UINavigationBarContentView:0x106416700 )>", "<NSLayoutConstraint:0x600002134b90 'UIView-rightMargin-guide-constraint' H:[UILayoutGuide:0x600003b216c0'UIViewLayoutMarginsGuide']-(16)-|(LTR) (active, names: '|':_UINavigationBarContentView:0x106416700 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x6000021372f0 UILayoutGuide:0x600003b21340'TitleView(layout=0x106416a30)'.trailing <= UILayoutGuide:0x600003b216c0'UIViewLayoutMarginsGuide'.trailing (active)> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.

I am updating my app to display correctly in dark mode and one of the things it does is provide the ability to view a log file. The file is a CSV file and I use QLPreviewController to display it. However, I notice that in dark mode the QLPreviewController is still white background and black text. I would think it would change to black background with white text like the rest of the views. I attempted to set the background color myself in a subclass of QLPreviewContrller but was unsuccessul. Am I misunderstanding the point of dark mode? Is there a way to make it work as I am describing?