perf(player): isolate high-frequency playback updates

lib/widgets/mini_player.dart

@@ -23,8 +23,7 @@ class _MiniPlayerState extends ConsumerState<MiniPlayer> {
     final mediaItem = ref.watch(currentMediaItemProvider).value;
     if (mediaItem == null) return const SizedBox.shrink();
 
-    final playback = ref.watch(playbackStateProvider).value;
-    final isPlaying = playback?.playing ?? false;
+    final isPlaying = ref.watch(playbackPlayingProvider);
     if (mediaItem.id == _dismissedItemId && !isPlaying) {
       return const SizedBox.shrink();
     }
@@ -32,10 +31,6 @@ class _MiniPlayerState extends ConsumerState<MiniPlayer> {
     final controller = ref.read(musicPlayerControllerProvider);
     final colorScheme = Theme.of(context).colorScheme;
 
-    final duration = mediaItem.duration?.inMilliseconds ?? 0;
-    final position = playback?.position.inMilliseconds ?? 0;
-    final progress = duration > 0 ? (position / duration).clamp(0.0, 1.0) : 0.0;
-
     return Dismissible(
       key: ValueKey('mini-player-${mediaItem.id}'),
       direction: DismissDirection.horizontal,
@@ -64,9 +59,8 @@ class _MiniPlayerState extends ConsumerState<MiniPlayer> {
             child: Column(
               mainAxisSize: MainAxisSize.min,
               children: [
-                LinearProgressIndicator(
-                  value: progress,
-                  minHeight: 2,
+                _MiniPlayerProgress(
+                  duration: mediaItem.duration ?? Duration.zero,
                   backgroundColor: colorScheme.surfaceContainerHighest,
                 ),
                 Padding(
@@ -136,3 +130,27 @@ class _MiniPlayerState extends ConsumerState<MiniPlayer> {
     );
   }
 }
+
+class _MiniPlayerProgress extends ConsumerWidget {
+  final Duration duration;
+  final Color backgroundColor;
+
+  const _MiniPlayerProgress({
+    required this.duration,
+    required this.backgroundColor,
+  });
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final durationMs = duration.inMilliseconds;
+    final positionMs = ref.watch(playbackPositionProvider).inMilliseconds;
+    final progress = durationMs > 0
+        ? (positionMs / durationMs).clamp(0.0, 1.0)
+        : 0.0;
+    return LinearProgressIndicator(
+      value: progress,
+      minHeight: 2,
+      backgroundColor: backgroundColor,
+    );
+  }
+}

lib/widgets/preview_button.dart

@@ -17,9 +17,9 @@ class PreviewButton extends ConsumerWidget {
       await ref.read(previewPlayerProvider.notifier).toggle(track.previewUrl);
     } catch (_) {
       if (!context.mounted) return;
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text(context.l10n.previewUnavailable)),
-      );
+      ScaffoldMessenger.of(
+        context,
+      ).showSnackBar(SnackBar(content: Text(context.l10n.previewUnavailable)));
     }
   }
 
@@ -41,8 +41,7 @@ class PreviewButton extends ConsumerWidget {
     // it (consistent with the mini player) rather than the preview snippet.
     final mainItem = ref.watch(currentMediaItemProvider).value;
     if (_isCurrentMainTrack(mainItem)) {
-      final isPlaying =
-          ref.watch(playbackStateProvider).value?.playing ?? false;
+      final isPlaying = ref.watch(playbackPlayingProvider);
       return Transform.translate(
         offset: const Offset(18, 0),
         child: IconButton(
@@ -57,9 +56,12 @@ class PreviewButton extends ConsumerWidget {
                 : Icons.play_circle_fill_rounded,
             color: colorScheme.primary,
           ),
-          tooltip: isPlaying ? context.l10n.previewStop : context.l10n.previewPlay,
-          onPressed: () =>
-              ref.read(musicPlayerControllerProvider).togglePlayPause(isPlaying),
+          tooltip: isPlaying
+              ? context.l10n.previewStop
+              : context.l10n.previewPlay,
+          onPressed: () => ref
+              .read(musicPlayerControllerProvider)
+              .togglePlayPause(isPlaying),
         ),
       );
     }
@@ -92,10 +94,7 @@ class PreviewButton extends ConsumerWidget {
         tooltip = context.l10n.previewStop;
         break;
       case PreviewStatus.paused:
-        icon = Icon(
-          Icons.play_circle_fill_rounded,
-          color: colorScheme.primary,
-        );
+        icon = Icon(Icons.play_circle_fill_rounded, color: colorScheme.primary);
         tooltip = context.l10n.previewPlay;
         break;
       case PreviewStatus.idle: