Federighi: iPhone Duo Hinge API Exposes Device Pose to Developers

Federighi said an API lets developers read the angle of the hinge with an accuracy of around five degrees, as well as read what Apple describes as the “pose” of the device. Apple itself uses the hinge angle in several ways, including the way the outer screen defocuses into a preview of the inner one as the phone opens. He told Donald Decodes that the feature is subtle but magical.

He described the design goal as automatic perception rather than a flashy animation. “The goal was not a fancy animation you’d think about, but something you’d perceive automatically: the screen becomes translucent, a window to what’s below,” he said. Continuity between the experience when the device is closed and what appears when it is opened is fundamental to the device, he added. “Seeing through the screen above to what’s about to be revealed below eases that journey in the most natural way. We’re really delighted with how it came out. It’s subtle but magical.”

Federighi said he is confident developers will do creative and exciting things with the hinge information exposed, just as they have with other iPhone data made available to them. For most developers, he said, Apple is focused on communicating the pose of the device: whether it is in book pose, on-table pose, or tent pose. Developers do not have to work with how many degrees open it is. By communicating the pose, frameworks can react automatically and deliver a consistent experience across apps, he said. For creative experiences, such as Apple’s own animation, developers can get closer to the raw information.

He pointed to Apple’s history of exposing gyroscope and accelerometer data to developers, which he said they have used in interesting ways over time. “One of the ways this device expresses itself is through its poses and the hinge, and we’re excited to see what developers do with it,” Federighi said.

Federighi also said Apple has worked to make it easier for developers to create apps that take full advantage of the iPhone Duo’s capabilities. He said the company built its platform on high-level frameworks like UIKit and SwiftUI that abstract away many of the harder layout problems, so apps often inherit new behaviors automatically. Over time, Apple has added more high-level constructs that adapt automatically, making the transition nearly automatic for many developers. He added that Apple supports agentic coding tools to enable developers to adapt existing apps almost completely automatically. The interview can be watched in the video published with the report.