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• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• All existing tests are passing: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/DevelopmentWorkflow.md#running-unit-tests-application.
• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

No issue exists yet; this comes out of building an app against the iPhone Duo simulator (Xcode 27.1 / iOS 27.1) and hitting the problems below. Reference: Preparing your app for iPhone Duo.

What is the current behavior?

iPhone Duo has two displays. A scene moves between them as the device opens and closes, and UIScreen.main is always the outer display (there are two UIScreens while open; window.screen follows the scene). Core assumes the scene matches the main screen in two places:

1. A Frame or TabView hosted in a NativeScript view is never laid out. On iOS both have no-op layoutNativeView()/_setNativeViewFrame(), which is right when a UIKit container controller places them (window root, TabView items, modals). When one is hosted directly in a NativeScript view instead — a TabView as a Page's content (the usual Angular TabView in a routed component), or a Frame in a layout (GridLayout > page-router-outlet) — nothing sizes or positions the controller's view. It keeps the UIScreen.main bounds UIKit creates it with, at the container's origin; the autoresizing mask then only tracks later container changes. This affects every device: a Frame or TabView in <GridLayout rows="50, *"> row 1 covers row 0. On iPhone Duo it also means the wrong display's size. Measured in apps/toolbox with its root Frame wrapped in a GridLayout, cold-launched with the device open:

A TabView as Page content shows the same thing: launched on the inner display it stays 466 wide, with the vertical bar in the middle of the screen. Launching closed and then opening happens to work, which hides the problem.

2. Screen.mainScreen goes stale. It caches the first UIScreen it resolves, so after the scene moves displays widthDIPs/heightDIPs (and the pixel sizes media queries match against) keep reporting the previous display: 951x669 while on the 466x678 outer display.

3. ActionItems can't take part in vertical bars well. iOS 27.1 presents bars vertically on iPhone Duo, where fewer items fit and the rest move to an overflow menu that shows image + title. Core creates image-only UIBarButtonItems when icon is set (the text is only used for accessibility), and there is no way to reach the new visibilityPriority / axisBehavior properties.

What is the new behavior?

• fix(ios) Frame and TabView: when hosted directly in a NativeScript view (IOSHelper.isHostedInView), they take the regular View frame path from their layout slot. Their safe-area handling differs from other views: an edge that lies on the container's safe-area edge extends out to the container's bounds (IOSHelper.extendUnderContainerSafeArea), since the controller insets its own content. expandBeyondSafeArea can't be reused here because it measures against view.viewController.view, which for these views is the view itself. Frames and TabViews under a UIKit container (window root, TabView items, SplitView, modals) are untouched.
• fix(ios) Screen: bounds are read from the window's current screen. scale still uses the cached screen: it is on hot paths and is identical on both displays, the invariant layout-helper already relies on.
• feat(action-bar):
  • text is kept as the UIBarButtonItem title when an icon is set. Bars still render only the image (checked on iOS 26.5 and 27.1); the overflow menu now has a title to show.
  • ios.visibilityPriority: 'high' | 'standard' | 'low' | number
  • ios.axisBehavior: 'automatic' | 'horizontalOnly' | 'verticalPreferred'
  • Both are ignored where the API doesn't exist (respondsToSelector). The 27.1 symbols aren't in types-ios yet, so they are declared locally in action-bar/index.ios.ts; those declarations can go once the typings are regenerated against the 27.1 SDK.

<ActionItem icon="sys://star" text="Favorite" ios.position="right" ios.visibilityPriority="high" />
<ActionItem icon="sys://tag" text="Tag" ios.position="right" ios.visibilityPriority="low" />
<ActionItem icon="sys://printer" text="Print" ios.position="right" ios.axisBehavior="horizontalOnly" />

Verified on the iPhone Duo simulator with the new apps/toolbox action-items page: with a horizontal and a vertical bar both present, the horizontalOnly item stays in the horizontal bar while the rest stack vertically; with the closed device in landscape (the tightest bar) both low items and the last standard one moved to the overflow menu, listed by icon and title, while the high item kept its place.

Testing

• npx nx run core:test — passing.
• apps/automated on an iPhone 17 Pro simulator (iOS 26.5) — 1820 OK, 0 failed, including:
  • two ActionItem tests (title kept alongside the icon; placement settings applied where available and harmless where not);
  • two Frame/TabView tests (frame-tests.ios.ts): each is hosted in row 1 of <GridLayout rows="50, *"> and must start below the header and fill the rest of the grid. Both fail without the fix (Actual: 0 Expected: 112).
• The Screen fix has no automated test: it only shows up when the scene's screen differs from UIScreen.main, which needs the iPhone Duo simulator.
• On the iPhone Duo simulator, an Angular app with a TabView as Page content and no layout workarounds: cold launch on the open inner display, close, reopen, and book posture all give a TabView frame equal to its container. The same app with its root page-router-outlet in row 1 of a GridLayout under a header keeps the header visible on the outer display. To reproduce the Frame case in toolbox, wrap the root Frame of apps/toolbox/src/app-root.xml in a GridLayout and cold-launch with the device open.

Not in this PR

• Media queries are correct when evaluated but are not re-evaluated when the scene moves between displays (no orientation change fires).
• UILayoutViewController copies an ancestor's top safe-area inset onto itself assuming its owner is a TabView item; any other hosted view with a parent picks that up too.
• Regenerating types-ios for the 27.1 SDK, and any first-class API for hinge state or reserved regions.