I've looked at the UIKit docs for UIView reservedRegions(kind:options:). I've watched the video "Strike a pose with adaptive layouts on iPhone Duo".
So I know how to get the current reserved regions. But I can't find the APIs to know when the reserved regions change. This means I can setup my custom view controller with the reserved regions that exist when the view controller is first displayed. But if the user changes the Duo, say from fully open to partially open, what API is triggered that lets me know that I need to call reservedRegions(kind:options:) and update the layout as needed?
I played around with UIHingeInteraction but that isn't the right approach. In most cases I tried calling reservedRegions(kind:options:) on each call to the interaction handler but I almost always got the wrong results (maybe a simulator issue?). And of course that interactiion handler will be called a lot just to report the new fold angle. I also tried various UIViewController methods for size changes and registered for size class changes. None of these were appropriate.
I just need a single notification that the Duo went from fully open to partially open, partially open to fully open, and partially open between landscape/portrait so that I can call reservedRegions(kind:options:) and get the correct, current divider info.
What am I missing?
My use case is for a custom fullscreen view controller that needs to layout a few items based on whether the Duo is fully open or partially open and whether the fold is horizontal or vertical. Unless I'm mistaken this precludes the use of UIArrangementViewController since I only have one view controller with one set of content to display. Showing the view controller as a form sheet, page sheet, or popover won't work since I need this to be fullscreen. I just need the fullscreen content to adjust for any fold (reserved region).