Clean up Share Extension theme override management

SignalServiceKit/Util/AppContext.swift

@@ -31,11 +31,9 @@ public enum AppContextType: CaseIterable, CustomStringConvertible {
 
 public protocol AppContext {
     var type: AppContextType { get }
-    var isMainApp: Bool { get }
     var isMainAppAndActive: Bool { get }
     @MainActor
     var isMainAppAndActiveIsolated: Bool { get }
-    var isNSE: Bool { get }
     /// Whether the user is using a right-to-left language like Arabic.
     var isRTL: Bool { get }
     var isRunningTests: Bool { get }
@@ -99,6 +97,31 @@ public protocol AppContext {
     var debugLogsDirPath: String { get }
 }
 
+extension AppContext {
+    public var isMainApp: Bool {
+        return switch type {
+        case .main: true
+        case .nse, .share: false
+        }
+    }
+
+    public var isNSE: Bool {
+        switch type {
+        case .nse: true
+        case .main, .share: false
+        }
+    }
+
+    public var isShareExtension: Bool {
+        switch type {
+        case .share: true
+        case .main, .nse: false
+        }
+    }
+}
+
+// MARK: -
+
 public final class AppContextObjCBridge: NSObject {
     @objc
     @available(swift, obsoleted: 1)
@@ -116,6 +139,8 @@ public final class AppContextObjCBridge: NSObject {
     }
 }
 
+// MARK: -
+
 // These are fired whenever the corresponding "main app" or "app extension"
 // notification is fired.
 //
@@ -130,6 +155,8 @@ public extension Notification.Name {
     static let OWSApplicationDidBecomeActive = Notification.Name("OWSApplicationDidBecomeActiveNotification")
 }
 
+// MARK: -
+
 private var currentAppContext: (any AppContext)?
 
 public func CurrentAppContext() -> any AppContext {
@@ -143,13 +170,3 @@ public func SetCurrentAppContext(_ appContext: any AppContext, isRunningTests: B
     owsPrecondition(currentAppContext == nil || isRunningTests)
     currentAppContext = appContext
 }
-
-extension AppContext {
-    public var isMainApp: Bool {
-        type == .main
-    }
-
-    public var isNSE: Bool {
-        type == .nse
-    }
-}

SignalUI/Appearance/Theme.swift

@@ -9,11 +9,6 @@ public extension Notification.Name {
     static let themeDidChange = Notification.Name("ThemeDidChangeNotification")
 }
 
-@objc
-public extension NSNotification {
-    static var ThemeDidChange: NSString { Notification.Name.themeDidChange.rawValue as NSString }
-}
-
 final public class Theme {
 
     private static var shared = Theme(themeDataStore: ThemeDataStore())
@@ -108,12 +103,16 @@ final public class Theme {
     private var cachedIsDarkThemeEnabled: Bool?
     private var cachedCurrentMode: ThemeDataStore.Appearance?
 
-    public static var shareExtensionThemeOverride: UIUserInterfaceStyle = .unspecified {
+    public static var shareExtensionInterfaceStyleOverride: UIUserInterfaceStyle = .unspecified {
         didSet {
-            guard !CurrentAppContext().isMainApp else {
-                return owsFailDebug("Should only be set in share extension")
+            owsPrecondition(
+                CurrentAppContext().isShareExtension,
+                "Must only be set in the share extension!"
+            )
+
+            if oldValue != shareExtensionInterfaceStyleOverride {
+                shared.themeDidChange()
             }
-            shared.themeDidChange()
         }
     }
 
@@ -131,7 +130,7 @@ final public class Theme {
 
         // Always respect the system theme in extensions.
         guard CurrentAppContext().isMainApp else {
-            return switch Self.shareExtensionThemeOverride {
+            return switch Self.shareExtensionInterfaceStyleOverride {
             case .dark:
                 true
             case .light:

SignalUI/RecipientPickers/ConversationPicker.swift

@@ -207,13 +207,11 @@ open class ConversationPickerViewController: OWSTableViewController2 {
             object: nil
         )
 
-        DispatchQueue.main.async {
-            if
-                !CurrentAppContext().isMainApp,
-                self.traitCollection.userInterfaceStyle != UITraitCollection.current.userInterfaceStyle
-            {
-                Theme.shareExtensionThemeOverride = self.traitCollection.userInterfaceStyle
-            }
+        // Works around a mysterious issue in which UITraitCollection.current's
+        // userInterfaceStyle doesn't match that of this view controller, which
+        // results in wonky colors.
+        DispatchQueue.main.async { [self] in
+            configureThemeForShareExtension()
         }
     }
 
@@ -224,19 +222,24 @@ open class ConversationPickerViewController: OWSTableViewController2 {
         presentationTime = presentationTime ?? Date()
     }
 
+    // MARK: -
+
     open override func themeDidChange() {
         super.themeDidChange()
-
         updateTableContents(shouldReload: false)
     }
 
+    /// Manually observe `UITraitCollection` changes to manage `Theme`. This is
+    /// typically done by `OWSWindow`, but in the Share Extension we don't have
+    /// an `OWSWindow` to do this for us.
     open override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
         super.traitCollectionDidChange(previousTraitCollection)
+        configureThemeForShareExtension()
+    }
 
-        let userInterfaceStyleDidChange = previousTraitCollection?.userInterfaceStyle != traitCollection.userInterfaceStyle
-        if !CurrentAppContext().isMainApp, userInterfaceStyleDidChange {
-            Theme.shareExtensionThemeOverride = traitCollection.userInterfaceStyle
-        }
+    private func configureThemeForShareExtension() {
+        guard CurrentAppContext().isShareExtension else { return }
+        Theme.shareExtensionInterfaceStyleOverride = traitCollection.userInterfaceStyle
     }
 
     // MARK: - ConversationCollection