display-access

Display Access (iOS)

Use MWDATDisplay to render content on Meta Ray-Ban Display glasses.

Use this skill with getting-started and permissions-registration when creating a full app. A Display app still needs Wearables.configure() at launch, Info.plist URL scheme configuration, URL callbacks through Wearables.shared.handleUrl(_:), and completed Meta AI registration before it can create a session.

Add the Display module

Add MWDATDisplay to the same app target that already uses MWDATCore. Import it next to core:

import MWDATCore
import MWDATDisplay

Display-specific app configuration

Use the getting-started Info.plist setup, then mirror the DisplayAccess sample for Display sessions:

• Keep the CFBundleURLTypes URL scheme and route callbacks to Wearables.shared.handleUrl(_:).
• Under MWDAT, set AppLinkURLScheme, MetaAppID, ClientToken, and TeamID. MetaAppID = 0 is for Developer Mode; production apps should use Wearables Developer Center values for MetaAppID and ClientToken, plus the Apple Developer Team ID.
• Include UISupportedExternalAccessoryProtocols with com.meta.ar.wearable, UIBackgroundModes entries for external-accessory and bluetooth-central, and NSBluetoothAlwaysUsageDescription. The DisplayAccess sample also includes bluetooth-peripheral and processing.
• For high-bandwidth Display/video fallback, include a non-empty NSLocalNetworkUsageDescription and NSBonjourServices. Display acquires link leases: core device discovery/session setup uses medium then low links, while Display uses medium then high links when available.

Select a display-capable device

Use the public display filter when creating an automatic selector:

let wearables = Wearables.shared
let deviceSelector = AutoDeviceSelector(
  wearables: wearables,
  filter: { device in device.supportsDisplay() }
)

Use SpecificDeviceSelector(device: selectedDevice.identifier) instead when your UI lets the user pick a specific Device. The initializer takes a DeviceIdentifier, not the whole Device.

AutoDeviceSelector updates from devicesStream(). Create it before the user taps the Display action, or wait for activeDeviceStream() to yield a non-nil device before calling createSession(deviceSelector:); otherwise createSession can throw DeviceSessionError.noEligibleDevice.

For a picker or Settings screen, list devices from Wearables.shared.devicesStream(), then look up metadata from deviceForIdentifier(_:). The DisplayAccess sample shows nameOrId(), deviceType().rawValue, linkState, and compatibility() and keeps addLinkStateListener / addCompatibilityListener tokens alive while rows are visible. If compatibility() == .deviceUpdateRequired, surface a firmware update action through Wearables.shared.openFirmwareUpdate().

Attach Display after the session starts

Create and start the DeviceSession, wait for .started, then add and start Display. Keep the state listener token alive for as long as you need updates, and observe session.errorStream() for async session failures.

import MWDATCore
import MWDATDisplay

@MainActor
final class DisplayController {
  private var deviceSession: DeviceSession?
  private var display: Display?
  private var displayStateToken: AnyListenerToken?
  private var sessionErrorTask: Task<Void, Never>?

  func connect() async {
    do {
      let wearables = Wearables.shared
      let selector = AutoDeviceSelector(
        wearables: wearables,
        filter: { $0.supportsDisplay() }
      )

      let session = try wearables.createSession(deviceSelector: selector)
      deviceSession = session
      sessionErrorTask = Task { [weak self] in
        for await error in session.errorStream() {
          await self?.showError(error.localizedDescription)
        }
      }

      let sessionStarted = Task {
        for await state in session.stateStream() {
          if state == .started {
            return
          }
        }
      }
      do {
        try session.start()
        await sessionStarted.value
      } catch {
        sessionStarted.cancel()
        throw error
      }

      let capability = try session.addDisplay()
      display = capability
      displayStateToken = capability.statePublisher.listen { [weak self] state in
        Task { @MainActor in
          if state == .started {
            self?.showStatusCard()
          }
        }
      }

      capability.start()
    } catch DeviceSessionError.datAppOnTheGlassesUpdateRequired {
      showDATGlassesAppUpdate()
    } catch {
      showError(error.localizedDescription)
    }
  }

  func disconnect() async {
    display?.onPlaybackEvent = nil
    display?.stop()
    deviceSession?.stop()
    sessionErrorTask?.cancel()
    sessionErrorTask = nil
    displayStateToken = nil
    display = nil
    deviceSession = nil
  }
}

For user-triggered content, match the sample's pending-action pattern: if the user taps "Try it" before Display is connected, store the send as a pending async action, attach to Display, and run the action when DisplayState.started arrives. Reset the display session when registration changes to .available or .unavailable.

Send display UI

Build exactly one root DisplayableView per send(_:) call. Each send replaces the previous content on the glasses and replaces the active tap handlers. Use a root FlexBox for UI, or a root VideoPlayer for video. Do not send Text, Button, Image, or Icon as the root; place them inside a FlexBox.

If a file also imports SwiftUI, Display DSL names such as Text, Button, and Image can be ambiguous. Prefer keeping Display builders in files that import MWDATDisplay without SwiftUI, or qualify the symbols as MWDATDisplay.Text, MWDATDisplay.Button, and MWDATDisplay.Image.

func showStatusCard() {
  Task {
    do {
      try await display?.send(
        FlexBox(direction: .column, spacing: 12) {
          Text("Bike ride", style: .heading)
          Text("Turn right in 200 ft", style: .body, color: .secondary)
          Button(
            label: "Done",
            style: .primary,
            iconName: .checkmark,
            onClick: { print("Done tapped") }
          )
        }
        .padding(24)
        .background(.card)
        .onTap { print("Card tapped") }
      )
    } catch {
      showError((error as? DisplayError)?.description ?? error.localizedDescription)
    }
  }
}

Use images and built-in icons

Use HTTPS image URLs for image content, and use the IconName enum for built-in icons. Do not invent raw icon strings.

try await display.send(
  FlexBox(direction: .row, spacing: 8, crossAlignment: .center) {
    Image(
      uri: "https://example.com/thumbnail.png",
      sizePreset: .fill,
      cornerRadius: .medium
    )
    Icon(name: .gear, style: .filled)
    Text("Device settings", style: .body)
  }
  .padding(24)
)

Send video

For URL-based video, send a root VideoPlayer. Use VideoPlayer(onError:) for video-specific errors, and use display.onPlaybackEvent for playback events. Set onPlaybackEvent before sending the video, clear it after terminal events if the flow is complete, and call sendVideoStop() if the user exits playback early. Blank or non-HTTP(S) URLs throw DisplayError.invalidVideoURL.

display.onPlaybackEvent = { event in
  if event.type == .ended || event.type == .stopped {
    Task { @MainActor in
      display.onPlaybackEvent = nil
      showStatusCard()
    }
  }
}

try await display.send(
  VideoPlayer(
    provider: .uri("https://example.com/tutorial.mp4"),
    codec: .mp4,
    onError: { error in
      Task { @MainActor in
        showError(error.localizedDescription)
      }
    }
  )
)

Display rules

• Call Wearables.configure() at app launch and complete registration before creating the session.
• Include the DisplayAccess sample's link-lease Info.plist keys when building a full Display app.
• Wait for the DeviceSession to reach .started before calling addDisplay().
• Handle DeviceSessionError.datAppOnTheGlassesUpdateRequired separately and offer Wearables.shared.openDATGlassesAppUpdate().
• Call display.start(), then wait for DisplayState.started through statePublisher before sending user-triggered content.
• Observe session.errorStream() so async session failures are surfaced.
• Keep listener tokens alive; dropping a token stops that listener.
• Use the getting-started setup for Info.plist URL schemes and route app-open URLs to Wearables.shared.handleUrl(_:).
• Use nameOrId(), deviceType(), linkState, and compatibility() for device rows; keep link/compatibility listener tokens until the row is gone.
• Use FlexBox.onTap and Button(label:onClick:) for interactions. The callbacks belong to the most recent sent view.
• Use only public Display DSL names: FlexBox, Text, Button, Image, Icon, VideoPlayer, IconName, TextStyle, TextColor, ButtonStyle, ImageSize, CornerRadius, Direction, Alignment, Background, Edge, and EdgeInsets.
• Clear display.onPlaybackEvent when the video flow is finished if you no longer need playback callbacks.
• Stop Display before stopping the parent DeviceSession when the display experience ends.

Sample app

Use the Display Access sample app for a complete flow: registration, device selection, display attachment, interactive content, and video.

Links

• iOS API reference
• Developer documentation