Drop into AppKit/UIKit to reliably set/unset preferred color scheme

Shared/Preferences/PreferencesModel.swift

@@ -1,19 +1,53 @@
 import SwiftUI
 
 class PreferencesModel: ObservableObject {
-    @Environment(\.colorScheme) var currentColorScheme
-    @Published var preferredColorScheme: ColorScheme = .light
+    /* We're stuck dropping into AppKit/UIKit to set light/dark schemes for now,
+     * because setting the .preferredColorScheme modifier on views in SwiftUI is
+     * currently unreliable.
+     *
+     * Feedback submitted to Apple:
+     *
+     * FB8382883: "On macOS 11β4, preferredColorScheme modifier does not respect .light ColorScheme"
+     * FB8383053: "On iOS 14β4/macOS 11β4, it is not possible to unset preferredColorScheme after setting
+     *              it to either .light or .dark"
+     */
+
+    #if os(iOS)
+    var window: UIWindow? {
+        guard let scene = UIApplication.shared.connectedScenes.first,
+              let windowSceneDelegate = scene.delegate as? UIWindowSceneDelegate,
+              let window = windowSceneDelegate.window else {
+            return nil
+        }
+        return window
+    }
+    #endif
+
+    @Published var selectedColorScheme: ColorScheme?
     @Published var appearance: Int = 0 {
         didSet {
             switch appearance {
-            case 0:
-                preferredColorScheme = currentColorScheme
             case 1:
-                preferredColorScheme = .light
+//                selectedColorScheme = .light
+                #if os(macOS)
+                NSApp.appearance = NSAppearance(named: .aqua)
+                #else
+                window?.overrideUserInterfaceStyle = .light
+                #endif
             case 2:
-                preferredColorScheme = .dark
+//                selectedColorScheme = .dark
+                #if os(macOS)
+                NSApp.appearance = NSAppearance(named: .darkAqua)
+                #else
+                window?.overrideUserInterfaceStyle = .dark
+                #endif
             default:
-                print("Unknown option selected, failing gracefully...")
+//                selectedColorScheme = .none
+                #if os(macOS)
+                NSApp.appearance = nil
+                #else
+                window?.overrideUserInterfaceStyle = .unspecified
+                #endif
             }
         }
     }

Shared/WriteFreely_MultiPlatformApp.swift

@@ -18,7 +18,7 @@ struct WriteFreely_MultiPlatformApp: App {
     var body: some Scene {
         WindowGroup {
             ContentView(postStore: store, preferences: preferences, account: account)
-                .preferredColorScheme(preferences.preferredColorScheme)
+//                .preferredColorScheme(preferences.selectedColorScheme)    // See PreferencesModel for info.
         }
 
         #if os(macOS)
@@ -39,7 +39,7 @@ struct WriteFreely_MultiPlatformApp: App {
             }
             .frame(minWidth: 300, maxWidth: 300, minHeight: 200, maxHeight: 200)
             .padding()
-            .preferredColorScheme(preferences.preferredColorScheme)
+//            .preferredColorScheme(preferences.selectedColorScheme)    // See PreferencesModel for info.
         }
         #endif
     }

WriteFreely-MultiPlatform.xcodeproj/xcuserdata/angelo.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -7,12 +7,12 @@
 		<key>WriteFreely-MultiPlatform (iOS).xcscheme_^#shared#^_</key>
 		<dict>
 			<key>orderHint</key>
-			<integer>1</integer>
+			<integer>0</integer>
 		</dict>
 		<key>WriteFreely-MultiPlatform (macOS).xcscheme_^#shared#^_</key>
 		<dict>
 			<key>orderHint</key>
-			<integer>0</integer>
+			<integer>1</integer>
 		</dict>
 	</dict>
 </dict>

iOS/Settings/SettingsView.swift

@@ -18,7 +18,7 @@ struct SettingsView: View {
                 }
             }
         }
-        .preferredColorScheme(preferences.preferredColorScheme)
+//        .preferredColorScheme(preferences.selectedColorScheme)    // See PreferencesModel for info.
     }
 }