iOS dual pane with UIArrangementViewController (parked)

[erkamyaman]

iOS 27.1 adds UIArrangementViewController, Apple's way to arrange two child view controllers around the fold (UISplitArrangement side by side or stacked, UIOverlayArrangement one over the other), with animated transitions.

Findings (2026-09-20, from the Xcode 27.1 SDK): it holds exactly two view controllers. A Capacitor app is one WKWebView in one view controller, so a plain arrangement gains nothing over the fold position, segments and CSS variables the plugin already reports. There is nothing to put in the second placement.

The only version worth building is a dual-pane feature, the iOS twin of Android's startDualScreen():

await Foldable.startSplitPane({ url: 'second.html' });
await Foldable.stopSplitPane();

The plugin would host a second web view in the secondary placement, with the system handling the split and the animation.

Open questions:

• The second web view has no Capacitor bridge, the same limitation as Android dual screen. Is that acceptable?
• The app has to host Capacitor's view controller inside a UIArrangementViewController, which means a storyboard change, like the MainViewController recipe in the iPhone Duo guide.
• Does anyone actually want it? Nobody has asked yet.

Decision: parked. Plain arrangement support is not worth it. Revisit the dual-pane idea after iPhone Duo ships on October 23 and we see real demand.

[erkamyaman]

Read the iOS 27.1 headers and the Swift interface.

What it is. UIArrangementViewController holds exactly two child view controllers, a primary and a secondary, and arranges them with either UISplitArrangement (side by side or stacked, with minimum, preferred and maximum sizes per pane and a layout priority) or UIOverlayArrangement (one over the other, with z-index and hidden state). The system animates between arrangements, so it is Apple's building block for "show two things when the phone is open, one when it is closed".

Why it does not fit as it stands. A Capacitor app is one WKWebView in one view controller. Handing that single web view to a split arrangement gains nothing over what the plugin already reports: the fold position, the segments and the CSS variables, which the web layout can use directly. There is nothing to put in the second placement.

Where it could pay off. As a dual-pane feature, the same idea as startDualScreen() on Android: the plugin hosts a second web view in the secondary placement, so an app can show a different page on the other half of the fold.

await Foldable.startSplitPane({ url: 'second.html' });
await Foldable.stopSplitPane();

That would mirror the Android API, with the system handling the split and the animation. Open questions: the second web view has no bridge (the same limitation as Android dual screen), and it needs the Capacitor view controller to be hosted inside a UIArrangementViewController, which means touching the app's storyboard, like the MainViewController recipe in the iPhone Duo guide.

Suggestion: leave the plain arrangement support closed, and decide separately whether the dual-pane feature is worth it after iPhone Duo ships.