Using iPhone Duo's hinge angle API without breaking your layout

What the API actually gives you

In SwiftUI, the onHingeChange modifier and in UIKit, UIHingeInteraction expose the hinge status as one of three discrete states — closed, partially open, or fully open — alongside a continuous angle value that updates as the device folds and unfolds.

Why Apple says not to use it for layout

Apple's guidance is explicit: use these APIs for interactive effects, not layout logic. The examples given are things like pitch-bending an audio effect as the hinge angle changes, or driving a 3D perspective shift in a game or visualization as the device opens. For actual layout decisions — what content goes where, how much space each part of your interface gets — the guidance points developers toward ArrangementView and ReservedRegion instead, which we cover in our companion guide to adaptive layouts.

Why the distinction matters

The practical risk of building layout logic on top of hinge angle is that it locks your interface to the exact mechanical range of the current hardware. If a future iPhone Duo ships with a different maximum hinge angle, a redesigned hinge assembly, or a different resting position for tabletop mode, any layout logic keyed to specific angle thresholds breaks immediately. ArrangementView and reserved regions are designed to abstract that away, so your layout continues working even if the hinge mechanics themselves change generation to generation.

Where hinge angle is the right tool

That said, the API exists for a reason, and interactive effects are a legitimate and, based on early developer previews, fairly popular use case. A few examples worth considering if your app has a tabletop or partially-folded interaction mode: adjusting a virtual camera's perspective as the device opens, driving a subtle parallax effect on background art, or triggering haptic feedback at specific fold thresholds as a physical-feeling confirmation.

If you are building anything camera-related that also needs to respond to device pose, see our piece on Virtual Front Camera and camera continuity, which touches on a related but separate set of APIs.