Fixes the reactive theme service to properly follow the system brightness

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/src/services/reactive_theme/reactive_theme_extensions.dart

@@ -15,7 +15,7 @@ extension DarkMode on BuildContext {
   /// }
   /// ```
   bool get isDarkMode {
-    final brightness = MediaQuery.of(this).platformBrightness;
+    final brightness = MediaQuery.platformBrightnessOf(this);
     return brightness == Brightness.dark;
   }
 }

lib/src/services/reactive_theme/reactive_theme_service.dart

@@ -1,3 +1,5 @@
+import "dart:async";
+
 import "package:arcane_framework/arcane_framework.dart";
 import "package:flutter/material.dart";
 
@@ -8,7 +10,7 @@ part "reactive_theme_extensions.dart";
 /// `ArcaneReactiveTheme` allows switching between light and dark themes and provides
 /// methods to customize the themes. The current theme mode can be accessed, and the
 /// theme can be switched at runtime.
-class ArcaneReactiveTheme extends ArcaneService {
+class ArcaneReactiveTheme extends ArcaneService with WidgetsBindingObserver {
   /// The singleton instance of `ArcaneReactiveTheme`.
   static final ArcaneReactiveTheme _instance = ArcaneReactiveTheme._internal();
 
@@ -17,13 +19,24 @@ class ArcaneReactiveTheme extends ArcaneService {
 
   ArcaneReactiveTheme._internal();
 
+  // Whether to follow system theme
+  bool _followingSystemTheme = false;
+
   final ValueNotifier<ThemeMode> _systemThemeNotifier =
-      ValueNotifier(ThemeMode.light);
+      ValueNotifier(ThemeMode.system);
 
-  final ValueNotifier<ThemeMode> _currentThemeNotifier =
-      ValueNotifier(ThemeMode.light);
+  final StreamController<ThemeMode> _themeStreamController =
+      StreamController<ThemeMode>.broadcast(
+    onCancel: () {
+      I._themeStreamController.close();
+    },
+  );
 
-  ThemeMode get currentTheme => I._currentThemeNotifier.value;
+  Stream<ThemeMode> get currentThemeStream => I._themeStreamController.stream;
+
+  ThemeMode _currentTheme = ThemeMode.light;
+
+  ThemeMode get currentTheme => _currentTheme;
 
   /// A listenable that notifies listeners when the system theme mode changes.
   ThemeMode get systemTheme => I._systemThemeNotifier.value;
@@ -52,21 +65,17 @@ class ArcaneReactiveTheme extends ArcaneService {
   /// ArcaneReactiveTheme.I.switchTheme();
   /// ```
   ArcaneReactiveTheme switchTheme({ThemeMode? themeMode}) {
-    if (I._systemThemeNotifier.hasListeners) {
-      _systemThemeNotifier.removeListener(_systemThemeListener);
-    }
+    _followingSystemTheme = false;
 
     if (themeMode != null) {
-      _currentThemeNotifier.value = themeMode;
+      _updateTheme(themeMode);
     } else {
-      _currentThemeNotifier.value =
-          _currentThemeNotifier.value == ThemeMode.light
-              ? ThemeMode.dark
-              : ThemeMode.light;
+      _updateTheme(
+        currentTheme == ThemeMode.dark ? ThemeMode.light : ThemeMode.dark,
+      );
     }
 
     notifyListeners();
-
     return I;
   }
 
@@ -79,21 +88,33 @@ class ArcaneReactiveTheme extends ArcaneService {
   /// final ThemeMode mode = Arcane.theme.systemTheme.value;
   /// ```
   ArcaneReactiveTheme followSystemTheme(BuildContext context) {
-    final ThemeMode systemMode =
-        context.isDarkMode ? ThemeMode.dark : ThemeMode.light;
+    if (!_followingSystemTheme) {
+      _followingSystemTheme = true;
 
-    if (!I._systemThemeNotifier.hasListeners) {
-      I._systemThemeNotifier.addListener(_systemThemeListener);
-    }
-
-    if (systemMode != currentTheme) {
-      _systemThemeNotifier.value = systemMode;
-      notifyListeners();
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        checkSystemTheme(context);
+      });
     }
 
     return I;
   }
 
+  /// Check and apply the system theme if we're following it
+  void checkSystemTheme(BuildContext context) {
+    if (!_followingSystemTheme) return;
+
+    final Brightness systemBrightness =
+        MediaQuery.platformBrightnessOf(context);
+
+    final ThemeMode systemMode =
+        systemBrightness == Brightness.dark ? ThemeMode.dark : ThemeMode.light;
+
+    if (systemMode != _currentTheme) {
+      _updateTheme(systemMode);
+      notifyListeners();
+    }
+  }
+
   /// Sets a custom `ThemeData` for the dark theme.
   ///
   /// This allows you to customize the dark theme and notify listeners to apply the
@@ -128,15 +149,13 @@ class ArcaneReactiveTheme extends ArcaneService {
   void reset() {
     _darkTheme.value = ThemeData.dark();
     _lightTheme.value = ThemeData.light();
-    _systemThemeNotifier.value = ThemeMode.light;
-    _currentThemeNotifier.value = ThemeMode.light;
+    _followingSystemTheme = false;
+    _updateTheme(ThemeMode.light);
     notifyListeners();
   }
 
-  void _systemThemeListener() {
-    if (currentTheme != _systemThemeNotifier.value) {
-      _currentThemeNotifier.value = _systemThemeNotifier.value;
-      notifyListeners();
-    }
+  void _updateTheme(ThemeMode themeMode) {
+    _currentTheme = themeMode;
+    _themeStreamController.add(themeMode);
   }
 }