improved performance and battery usage on older devices

lib/widget/chat_background.dart

@@ -8,6 +8,7 @@ import '../state/app/modules/settings/bloc/settings_cubit.dart';
 import '../storage/chat_background_settings.dart';
 import '../theming/app_theme.dart';
 import '../utils/app_paths.dart';
+import '../utils/screen_bound_image.dart';
 
 /// Renders the configurable chat background behind [child].
 ///
@@ -24,7 +25,13 @@ class ChatBackground extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final s = context.watch<SettingsCubit>().val().chatBackgroundSettings;
+    // Value snapshot: the settings object is mutated in place, so only copied
+    // values can tell whether the background actually changed.
+    context.select((SettingsCubit c) {
+      final s = c.state.chatBackgroundSettings;
+      return (s.type, s.fit, s.colorValue, s.imageVersion, s.dim, s.blur);
+    });
+    final s = context.read<SettingsCubit>().val().chatBackgroundSettings;
     final dark = AppTheme.isDarkMode(context);
 
     final Widget background;
@@ -32,7 +39,9 @@ class ChatBackground extends StatelessWidget {
       case ChatBackgroundType.none:
         background = ColoredBox(color: Theme.of(context).colorScheme.surface);
       case ChatBackgroundType.color:
-        background = ColoredBox(color: Color(s.colorValue ?? _fallbackColor.toARGB32()));
+        background = ColoredBox(
+          color: Color(s.colorValue ?? _fallbackColor.toARGB32()),
+        );
       case ChatBackgroundType.pattern:
         background = _imageLayer(
           const AssetImage('assets/background/chat.png'),
@@ -41,12 +50,17 @@ class ChatBackground extends StatelessWidget {
           isPattern: true,
         );
       case ChatBackgroundType.image:
+        final image = FileImage(File(AppPaths.chatBackgroundImage));
         background = KeyedSubtree(
           // imageVersion changes on every replacement, forcing a fresh subtree
           // alongside the explicit ImageCache evict in the settings handler.
           key: ValueKey(s.imageVersion),
+          // Only "cover" scales the photo to the screen; tile/center render
+          // it unscaled, so those keep the natural size.
           child: _imageLayer(
-            FileImage(File(AppPaths.chatBackgroundImage)),
+            s.fit == ChatBackgroundFit.cover
+                ? screenBoundImage(context, image)
+                : image,
             s,
             dark,
             isPattern: false,
@@ -57,7 +71,9 @@ class ChatBackground extends StatelessWidget {
     return Stack(
       fit: StackFit.expand,
       children: [
-        Positioned.fill(child: background),
+        // Own layer: without it every scroll frame of the message list above
+        // repaints the (possibly tiled or blurred) background as well.
+        Positioned.fill(child: RepaintBoundary(child: background)),
         if (s.dim > 0)
           Positioned.fill(
             child: ColoredBox(color: Colors.black.withValues(alpha: s.dim)),