theme support on older devices

app/lib/core/providers/defaults.dart

@@ -0,0 +1,11 @@
+import 'package:flutter/material.dart';
+import 'package:riverpod/riverpod.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'defaults.g.dart';
+
+@Riverpod(keepAlive: true)
+Color lightSeedColorFallback(Ref ref) => const Color(0xFF167C80);
+
+@Riverpod(keepAlive: true)
+Color darkSeedColorFallback(Ref ref) => const Color(0xFF167C80);

app/lib/core/providers/defaults.g.dart

@@ -0,0 +1,46 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'defaults.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+String _$lightSeedColorFallbackHash() =>
+    r'af151d3293d372f5df451aa8c3a75136377b6ce1';
+
+/// See also [lightSeedColorFallback].
+@ProviderFor(lightSeedColorFallback)
+final lightSeedColorFallbackProvider = Provider<Color>.internal(
+  lightSeedColorFallback,
+  name: r'lightSeedColorFallbackProvider',
+  debugGetCreateSourceHash: const bool.fromEnvironment('dart.vm.product')
+      ? null
+      : _$lightSeedColorFallbackHash,
+  dependencies: null,
+  allTransitiveDependencies: null,
+);
+
+@Deprecated('Will be removed in 3.0. Use Ref instead')
+// ignore: unused_element
+typedef LightSeedColorFallbackRef = ProviderRef<Color>;
+String _$darkSeedColorFallbackHash() =>
+    r'9418cf71e3d80c8a2142e0d3a8820989b29bff86';
+
+/// See also [darkSeedColorFallback].
+@ProviderFor(darkSeedColorFallback)
+final darkSeedColorFallbackProvider = Provider<Color>.internal(
+  darkSeedColorFallback,
+  name: r'darkSeedColorFallbackProvider',
+  debugGetCreateSourceHash: const bool.fromEnvironment('dart.vm.product')
+      ? null
+      : _$darkSeedColorFallbackHash,
+  dependencies: null,
+  allTransitiveDependencies: null,
+);
+
+@Deprecated('Will be removed in 3.0. Use Ref instead')
+// ignore: unused_element
+typedef DarkSeedColorFallbackRef = ProviderRef<Color>;
+// ignore_for_file: type=lint
+// ignore_for_file: subtype_of_sealed_class, invalid_use_of_internal_member, invalid_use_of_visible_for_testing_member, deprecated_member_use_from_same_package

app/lib/main.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import 'package:home_widget/home_widget.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:lensai/core/error_observer.dart';
+import 'package:lensai/core/providers/defaults.dart';
 import 'package:lensai/domain/services/app_initialization.dart';
 import 'package:lensai/features/user/domain/repositories/general_settings.dart';
 import 'package:lensai/presentation/hooks/on_initialization.dart';
@@ -36,14 +37,35 @@ void main() async {
 
           return DynamicColorBuilder(
             builder: (lightDynamic, darkDynamic) {
+              ColorScheme lightColorScheme;
+              ColorScheme darkColorScheme;
+
+              if (lightDynamic != null && darkDynamic != null) {
+                // On Android S+ devices, use the provided dynamic color scheme.
+                // (Recommended) Harmonize the dynamic color scheme' built-in semantic colors.
+                lightColorScheme = lightDynamic.harmonized();
+
+                // Repeat for the dark color scheme.
+                darkColorScheme = darkDynamic.harmonized();
+              } else {
+                // Otherwise, use fallback schemes.
+                lightColorScheme = ColorScheme.fromSeed(
+                  seedColor: ref.read(lightSeedColorFallbackProvider),
+                );
+                darkColorScheme = ColorScheme.fromSeed(
+                  seedColor: ref.read(darkSeedColorFallbackProvider),
+                  brightness: Brightness.dark,
+                );
+              }
+
               return MainApp(
                 theme: ThemeData(
                   useMaterial3: true,
-                  colorScheme: lightDynamic?.harmonized(),
+                  colorScheme: lightColorScheme,
                 ),
                 darkTheme: ThemeData(
                   useMaterial3: true,
-                  colorScheme: darkDynamic?.harmonized(),
+                  colorScheme: darkColorScheme,
                 ),
                 themeMode: themeMode,
               );