Use the same UI as Android when tapping a link to a private room.

ElementX/Sources/Screens/JoinRoomScreen/JoinRoomScreenModels.swift

@@ -43,6 +43,14 @@ struct JoinRoomScreenViewState: BindableState {
         roomDetails?.name ?? L10n.screenJoinRoomTitleNoPreview
     }
 
+    var subtitle: String? {
+        switch mode {
+        case .loading: nil
+        case .unknown: L10n.screenJoinRoomSubtitleNoPreview
+        case .invited, .join, .knock: roomDetails?.canonicalAlias
+        }
+    }
+
     var avatar: RoomAvatar {
         .room(id: roomID, name: title, avatarURL: roomDetails?.avatarURL)
     }

ElementX/Sources/Screens/JoinRoomScreen/JoinRoomScreenViewModel.swift

@@ -22,6 +22,7 @@ typealias JoinRoomScreenViewModelType = StateStoreViewModel<JoinRoomScreenViewSt
 class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewModelProtocol {
     private let roomID: String
     private let via: [String]
+    private let allowKnocking: Bool // For preview tests only, actions aren't sent.
     private let clientProxy: ClientProxyProtocol
     private let userIndicatorController: UserIndicatorControllerProtocol
 
@@ -32,11 +33,13 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
 
     init(roomID: String,
          via: [String],
+         allowKnocking: Bool = false,
          clientProxy: ClientProxyProtocol,
          mediaProvider: MediaProviderProtocol,
          userIndicatorController: UserIndicatorControllerProtocol) {
         self.roomID = roomID
         self.via = via
+        self.allowKnocking = allowKnocking
         self.clientProxy = clientProxy
         self.userIndicatorController = userIndicatorController
 
@@ -81,6 +84,8 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
         switch await clientProxy.roomPreviewForIdentifier(roomID, via: via) {
         case .success(let roomDetails):
             state.roomDetails = roomDetails
+        case .failure(.roomPreviewIsPrivate):
+            break // Handled by the mode, we don't need an error indicator.
         case .failure:
             userIndicatorController.submitIndicator(UserIndicator(title: L10n.errorUnknown))
         }
@@ -96,8 +101,8 @@ class JoinRoomScreenViewModel: JoinRoomScreenViewModelType, JoinRoomScreenViewMo
             state.mode = .join
         } else if roomDetails.isInvited {
             state.mode = .invited
-        } else if roomDetails.canKnock { // Knocking is not supported yet, treat it as .unknown
-            state.mode = .unknown
+        } else if roomDetails.canKnock, allowKnocking { // Knocking is not supported yet, the flag is purely for preview tests.
+            state.mode = .knock
         } else {
             state.mode = .unknown
         }

ElementX/Sources/Screens/JoinRoomScreen/View/JoinRoomScreen.swift

@@ -51,10 +51,11 @@ struct JoinRoomScreen: View {
                     .foregroundStyle(.compound.textPrimary)
                     .multilineTextAlignment(.center)
 
-                if let alias = context.viewState.roomDetails?.canonicalAlias {
-                    Text(alias)
+                if let subtitle = context.viewState.subtitle {
+                    Text(subtitle)
                         .font(.compound.bodyMD)
                         .foregroundStyle(.compound.textSecondary)
+                        .multilineTextAlignment(.center)
                 }
 
                 if let memberCount = context.viewState.roomDetails?.memberCount {
@@ -168,6 +169,7 @@ struct JoinRoomScreen_Previews: PreviewProvider, TestablePreview {
 
         return JoinRoomScreenViewModel(roomID: "1",
                                        via: [],
+                                       allowKnocking: true,
                                        clientProxy: clientProxy,
                                        mediaProvider: MockMediaProvider(),
                                        userIndicatorController: ServiceLocator.shared.userIndicatorController)

ElementX/Sources/Services/Client/ClientProxy.swift

@@ -481,6 +481,8 @@ class ClientProxy: ClientProxyProtocol {
         do {
             let roomPreview = try await client.getRoomPreviewFromRoomId(roomId: identifier, viaServers: via)
             return .success(.init(roomPreview))
+        } catch let error as ClientError where error.code == .forbidden {
+            return .failure(.roomPreviewIsPrivate)
         } catch {
             MXLog.error("Failed retrieving preview for room: \(identifier) with error: \(error)")
             return .failure(.sdkError(error))

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -43,6 +43,7 @@ enum ClientProxyError: Error {
     case invalidMedia
     case invalidUserIDServerName
     case failedUploadingMedia(Error, MatrixErrorCode)
+    case roomPreviewIsPrivate
 }
 
 enum SlidingSyncConstants {