Simplify broadcast extension setup with standard format for identifiers (livekit#573)

When configuring a broadcast extension, manually setting the info keys
`RTCAppGroupIdentifier` and `RTCScreenSharingExtension` is no longer
required when using the standard format. The standard format is as
follows:
- App group: `group.<main-app-bundle-id>`
- Broadcast extension: `<main-app-bundle-id>.broadcast`

---------

Co-authored-by: Hiroshi Horie <[email protected]>

Author: ladvoc

.nanpa/broadcast-identifier-defaults.kdl

@@ -0,0 +1 @@
+patch type="change" "Simplify broadcast extension setup with standard format for identifiers"

Docs/ios-screen-sharing.md

@@ -44,15 +44,17 @@ flowchart LR
 
 To use the Broadcast Capture mode, follow these steps to add a Broadcast Upload Extension target and associated configuration to your project. You can also refer to the [example app](https://github.com/livekit-examples/swift-example), which demonstrates this configuration.
 
-#### 1. Add Broadcast Upload Extension Target
 
+#### 1. Add Broadcast Upload Extension Target
 
 <img src="Resources/new-target-options.png" width="500" />
 
 1. In Xcode, Choose "File" > "New > "Target"
 2. From the template chooser, select "Broadcast Upload Extension"
-3. Name the extension (e.g. "BroadcastExtension"). Take note of the extension's bundle identifier, as it will be needed later.
-4. Replace the default content of `SampleHandler.swift` in the new target with the following:
+3. Name the extension (e.g. "BroadcastExtension").
+4. Press "Finish"
+5. From the "Signing & Capabilities" tab of the new target, change the bundle identifier to be the same as your main app with `.broadcast` added to the end. To use a custom identifier, see *[Custom Identifiers](#custom-identifiers)* below.
+6. Replace the default content of `SampleHandler.swift` in the new target with the following:
 
 ```swift
 import LiveKit
@@ -75,14 +77,9 @@ In order for the broadcast extension to communicate with your app, they must be
 2. Select the "Signing & Capabilities" tab and press the "+ Capability" button.
 3. Add the "App Groups" capability.
 4. Press "+" to add a new app group.
-5. Enter an app group identifier in the format `group.<domain>.<group_name>`. Be sure to use the same identifier for both targets.
-
-#### 3. Add Properties to Info.plist
-
-1. Set `RTCAppGroupIdentifier` in the Info.plist of **both targets** to the group identifier from the previous step.
-2. Set `RTCScreenSharingExtension` in the Info.plist of your **primary app target** to the broadcast extension's bundle identifier.
+5. Add the target to the group `group.<main-app-bundle-id>`. To use a custom identifier, see *[Custom Identifiers](#custom-identifiers)* below.
 
-#### 4. Begin Screen Share
+#### 3. Begin Screen Share
 
 With setup of the broadcast extension complete, broadcast capture will be used by default when enabling screen share:
 ```swift
@@ -102,6 +99,8 @@ While running your app in a debug session in Xcode, check the debug console for
 
 ### Advanced Usage
 
+#### Manual Track Publication
+
 When using broadcast capture, a broadcast can be initiated externally (for example, via control center). By default, when a broadcast begins, the local participant automatically publishes a screen share track. In some cases, however, you may want to handle track publication manually. You can achieve this by using `BroadcastManager`:
 
 First, disable automatic track publication:
@@ -111,7 +110,7 @@ BroadcastManager.shared.shouldPublishTrack = false
 
 Then, use one of the two methods for detecting changes in the broadcast state:
 
-#### Combine Publisher
+##### Combine Publisher
 ```swift
 let subscription = BroadcastManager.shared
     .isBroadcastingPublisher
@@ -120,7 +119,7 @@ let subscription = BroadcastManager.shared
     }
 ```
 
-#### Delegate
+##### Delegate
 ```swift
 class MyDelegate: BroadcastManagerDelegate {
     func broadcastManager(didChangeState isBroadcasting: Bool) {
@@ -129,3 +128,8 @@ class MyDelegate: BroadcastManagerDelegate {
 }
 BroadcastManager.shared.delegate = MyDelegate()
 ```
+
+#### Custom Identifiers
+
+By default, the app group identifier is expected to be `group.<main-app-bundle-id>`, and the broadcast extension's bundle identifier is expected to be `<main-app-bundle-id>.broadcast`.
+To override these values, set `RTCAppGroupIdentifier` in Info.plist for both targets (both broadcast extension and main app), and set `RTCScreenSharingExtension` in Info.plist for your main app.

Sources/LiveKit/Broadcast/BroadcastBundleInfo.swift

@@ -20,12 +20,19 @@ import Foundation
 
 enum BroadcastBundleInfo {
     /// Identifier of the app group shared by the primary app and broadcast extension.
-    @BundleInfo("RTCAppGroupIdentifier")
-    static var groupIdentifier: String?
-
+    static var groupIdentifier: String? {
+        if let override = groupIdentifierOverride { return override }
+        guard let bundleIdentifier = Bundle.main.bundleIdentifier else { return nil }
+        let appBundleIdentifier = bundleIdentifier.dropSuffix(".\(extensionSuffix)") ?? bundleIdentifier
+        return "group.\(appBundleIdentifier)"
+    }
+    
     /// Bundle identifier of the broadcast extension.
-    @BundleInfo("RTCScreenSharingExtension")
-    static var screenSharingExtension: String?
+    static var screenSharingExtension: String? {
+        if let override = screenSharingExtensionOverride { return override }
+        guard let bundleIdentifier = Bundle.main.bundleIdentifier else { return nil }
+        return "\(bundleIdentifier).\(extensionSuffix)"
+    }
 
     /// Path to the socket file used for interprocess communication.
     static var socketPath: String? {
@@ -37,7 +44,14 @@ enum BroadcastBundleInfo {
     static var hasExtension: Bool {
         socketPath != nil && screenSharingExtension != nil
     }
+    
+    @BundleInfo("RTCAppGroupIdentifier")
+    private static var groupIdentifierOverride: String?
 
+    @BundleInfo("RTCScreenSharingExtension")
+    private static var screenSharingExtensionOverride: String?
+
+    private static let extensionSuffix = "broadcast"
     private static let socketFileDescriptor = "rtc_SSFD"
 
     private static func socketPath(for groupIdentifier: String) -> String? {
@@ -48,4 +62,12 @@ enum BroadcastBundleInfo {
     }
 }
 
+private extension String {
+    func dropSuffix(_ suffix: String) -> Self? {
+        guard hasSuffix(suffix) else { return nil }
+        let trailingIndex = index(endIndex, offsetBy: -suffix.count)
+        return String(self[..<trailingIndex])
+    }
+}
+
 #endif

Sources/LiveKit/Broadcast/BundleInfo.swift

@@ -28,10 +28,7 @@ struct BundleInfo<Value>: Sendable {
     }
 
     var wrappedValue: Value? {
-        guard let value = bundle.infoDictionary?[key] as? Value else {
-            logger.warning("Missing bundle property with key `\(key)`")
-            return nil
-        }
+        guard let value = bundle.infoDictionary?[key] as? Value else { return nil }
         return value
     }
 }