perf(tv): cut semantics work during card navigation

lib/focus/focusable_wrapper.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter/rendering.dart';
 
 import '../widgets/clickable_cursor.dart';
 import '../utils/text_input_diagnostics.dart';
@@ -21,6 +22,62 @@ void _logFocusableWrapper(String message) {
   TextInputDiagnostics.log('FocusableWrapper', message);
 }
 
+/// Applies a visual scale without changing hit-test or semantics geometry.
+///
+/// Focus scale is paint-only: animating a [Transform] marks the transformed
+/// subtree's semantics dirty on every frame, which is costly for dense TV
+/// grids. Keeping layout and semantics static preserves the same visible
+/// motion without rebuilding the accessibility tree.
+class _PaintScale extends SingleChildRenderObjectWidget {
+  const _PaintScale({required this.scale, required super.child});
+
+  final double scale;
+
+  @override
+  RenderObject createRenderObject(BuildContext context) => _RenderPaintScale(scale);
+
+  @override
+  void updateRenderObject(BuildContext context, _RenderPaintScale renderObject) {
+    renderObject.scale = scale;
+  }
+}
+
+class _RenderPaintScale extends RenderProxyBox {
+  _RenderPaintScale(double scale) : _scale = scale;
+
+  final Matrix4 _transform = Matrix4.identity();
+  double _scale;
+
+  set scale(double value) {
+    if (_scale == value) return;
+    _scale = value;
+    markNeedsPaint();
+  }
+
+  @override
+  void paint(PaintingContext context, Offset offset) {
+    if (child == null) return;
+    if (_scale == 1) {
+      layer = null;
+      super.paint(context, offset);
+      return;
+    }
+
+    _transform
+      ..setIdentity()
+      ..setEntry(0, 0, _scale)
+      ..setEntry(1, 1, _scale)
+      ..setTranslationRaw((1 - _scale) * size.width / 2, (1 - _scale) * size.height / 2, 0);
+    layer = context.pushTransform(
+      needsCompositing,
+      offset,
+      _transform,
+      super.paint,
+      oldLayer: layer is TransformLayer ? layer as TransformLayer? : null,
+    );
+  }
+}
+
 /// A wrapper widget that makes its child focusable with D-pad navigation support.
 ///
 /// Provides:
@@ -475,46 +532,46 @@ class _FocusableWrapperState extends State<FocusableWrapper> with SingleTickerPr
         controller.duration = duration;
       }
 
+      final shouldScale = showFocus && !widget.disableScale;
+      // Keep the card subtree outside the scale builder. Rebuilding media-card
+      // semantics on every animation tick is substantially more expensive than
+      // changing the paint transform alone on dense TV grids.
+      Widget card;
+      if (widget.delegateFocusBorder) {
+        card = CardFocusScope(showFocus: showFocus, child: widget.child);
+      } else {
+        final focusDecoration = widget.useBackgroundFocus
+            ? FocusTheme.focusBackgroundDecoration(
+                isFocused: showFocus,
+                borderRadius: widget.borderRadius,
+                radii: widget.borderRadii,
+              )
+            : FocusTheme.focusDecoration(
+                context,
+                isFocused: showFocus,
+                borderRadius: widget.borderRadius,
+                radii: widget.borderRadii,
+                color: widget.focusColor,
+              );
+        card = AnimatedContainer(
+          duration: duration,
+          curve: Curves.easeOutCubic,
+          decoration: focusDecoration,
+          child: widget.child,
+        );
+      }
+      if (widget.useFocusGlow) {
+        card = FocusGlowOverlay(
+          isFocused: showFocus,
+          borderRadius: widget.borderRadius,
+          color: widget.focusColor ?? FocusTheme.getFocusBorderColor(context),
+          child: card,
+        );
+      }
       inner = AnimatedBuilder(
         animation: _scaleAnimation!,
-        builder: (context, child) {
-          final shouldScale = showFocus && !widget.disableScale;
-          // The glow (full-bleed cards) is drawn in an overlay above siblings so
-          // it stays symmetric; the in-card decoration only carries the border.
-          Widget card;
-          if (widget.delegateFocusBorder) {
-            card = CardFocusScope(showFocus: showFocus, child: widget.child);
-          } else {
-            final focusDecoration = widget.useBackgroundFocus
-                ? FocusTheme.focusBackgroundDecoration(
-                    isFocused: showFocus,
-                    borderRadius: widget.borderRadius,
-                    radii: widget.borderRadii,
-                  )
-                : FocusTheme.focusDecoration(
-                    context,
-                    isFocused: showFocus,
-                    borderRadius: widget.borderRadius,
-                    radii: widget.borderRadii,
-                    color: widget.focusColor,
-                  );
-            card = AnimatedContainer(
-              duration: duration,
-              curve: Curves.easeOutCubic,
-              decoration: focusDecoration,
-              child: widget.child,
-            );
-          }
-          if (widget.useFocusGlow) {
-            card = FocusGlowOverlay(
-              isFocused: showFocus,
-              borderRadius: widget.borderRadius,
-              color: widget.focusColor ?? FocusTheme.getFocusBorderColor(context),
-              child: card,
-            );
-          }
-          return Transform.scale(scale: shouldScale ? _scaleAnimation!.value : 1.0, child: card);
-        },
+        child: card,
+        builder: (context, child) => _PaintScale(scale: shouldScale ? _scaleAnimation!.value : 1.0, child: child!),
       );
     }
 

lib/widgets/media_card.dart

@@ -303,7 +303,9 @@ class MediaCardState extends State<MediaCard> with ContextMenuTapMixin<MediaCard
 
     final semanticLabel = mediaCardSemanticLabel(item);
     final enableDetailLinks = widget.onTap == null;
-    final preserveDetailSemantics = enableDetailLinks && item is MediaItem && _hasPointerDetailLinks(item);
+    final preservePointerDetailSemantics = !PlatformDetector.isTV() || MediaQuery.accessibleNavigationOf(context);
+    final preserveDetailSemantics =
+        preservePointerDetailSemantics && enableDetailLinks && item is MediaItem && _hasPointerDetailLinks(item);
     final localPosterPath = _getLocalPosterPath(context, item);
 
     Widget cardWidget = viewMode == ViewMode.grid

lib/widgets/tv_browse_rail.dart

@@ -18,6 +18,7 @@ import '../navigation/main_screen_scope.dart';
 import '../media/media_hub.dart';
 import '../media/media_item.dart';
 import '../screens/hub_detail_screen.dart';
+import '../services/device_performance.dart';
 import '../services/settings_service.dart';
 import '../theme/mono_tokens.dart';
 import '../utils/media_image_helper.dart';
@@ -407,6 +408,7 @@ class TvBrowseRailState extends State<TvBrowseRail> {
   final FocusNode _focusNode = FocusNode(debugLabel: 'tv_browse_rail');
   final Map<String, ScrollController> _scrollControllers = {};
   final ScrollController _verticalController = ScrollController();
+  final SnapshotController _verticalScrollSnapshotController = SnapshotController();
   final Map<int, GlobalKey> _hubSectionKeys = {};
   final Map<String, GlobalKey<MediaCardState>> _mediaCardKeys = {};
   final Map<String, TvBrowseRailLayoutMetrics> _metricsByHub = {};
@@ -429,6 +431,7 @@ class TvBrowseRailState extends State<TvBrowseRail> {
   VoidCallback? _gestureSignalListener;
   bool _suppressSelectUntilKeyUp = false;
   bool _hasUserChangedHub = false;
+  int _verticalScrollGeneration = 0;
   bool _hasUserChangedItem = false;
 
   MediaHub? get _activeHub => widget.hubs.isEmpty ? null : widget.hubs[_hubIndex.clamp(0, widget.hubs.length - 1)];
@@ -610,6 +613,8 @@ class TvBrowseRailState extends State<TvBrowseRail> {
       controller.dispose();
     }
     _verticalController.dispose();
+    _verticalScrollGeneration++;
+    _verticalScrollSnapshotController.dispose();
     super.dispose();
   }
 
@@ -797,14 +802,16 @@ class TvBrowseRailState extends State<TvBrowseRail> {
       if (_verticalController.hasClients && _hubIndex >= 0 && _hubIndex < _sectionOffsets.length) {
         final target = _sectionOffsets[_hubIndex].clamp(0.0, _sectionMaxScrollExtent).toDouble();
         if (animate) {
-          unawaited(
-            _verticalController.animateTo(
+          _startVerticalScrollAnimation(
+            () => _verticalController.animateTo(
               target,
               duration: const Duration(milliseconds: 250),
               curve: Curves.easeOutCubic,
             ),
           );
         } else {
+          _verticalScrollGeneration++;
+          _verticalScrollSnapshotController.allowSnapshotting = false;
           _verticalController.jumpTo(target);
         }
         return;
@@ -813,18 +820,39 @@ class TvBrowseRailState extends State<TvBrowseRail> {
       final key = _hubSectionKeys[_hubIndex];
       final context = key?.currentContext;
       if (context == null) return;
-
-      unawaited(
-        Scrollable.ensureVisible(
-          context,
-          alignment: 0,
-          duration: animate ? const Duration(milliseconds: 250) : Duration.zero,
-          curve: Curves.easeOutCubic,
-        ),
-      );
+      if (animate) {
+        _startVerticalScrollAnimation(
+          () => Scrollable.ensureVisible(
+            context,
+            alignment: 0,
+            duration: const Duration(milliseconds: 250),
+            curve: Curves.easeOutCubic,
+          ),
+        );
+      } else {
+        _verticalScrollGeneration++;
+        _verticalScrollSnapshotController.allowSnapshotting = false;
+        unawaited(Scrollable.ensureVisible(context, alignment: 0, duration: Duration.zero));
+      }
     });
   }
 
+  void _startVerticalScrollAnimation(Future<void> Function() animate) {
+    final generation = ++_verticalScrollGeneration;
+    // Full-tier row effects must stay live. The reduced tier has already
+    // resolved those short effects to their final state before this snapshot.
+    final useSnapshots = DevicePerformance.isReduced;
+    if (useSnapshots) {
+      _verticalScrollSnapshotController.allowSnapshotting = true;
+    }
+    unawaited(
+      animate().whenComplete(() {
+        if (!mounted || generation != _verticalScrollGeneration) return;
+        _verticalScrollSnapshotController.allowSnapshotting = false;
+      }),
+    );
+  }
+
   void _setHoveredItem(MediaHub hub, int index) {
     final active = _activeHub;
     if (active == null || _hubKey(active) != _hubKey(hub) || index >= hub.items.length || _itemIndex == index) {
@@ -1195,31 +1223,36 @@ class TvBrowseRailState extends State<TvBrowseRail> {
         // below is passed through as a stable child.
         bool isActiveHub() => _focusModel.hubIndex == hubIndex;
 
-        return SizedBox(
-          key: _hubSectionKeys.putIfAbsent(hubIndex, () => GlobalKey()),
-          height: sectionHeight,
-          child: Column(
-            crossAxisAlignment: .stretch,
-            children: [
-              ListenableSelector<bool>(
-                listenable: _focusModel,
-                selector: isActiveHub,
-                builder: (context, isActive, _) =>
-                    _buildHubHeader(context, hub: hub, hubIndex: hubIndex, isActive: isActive, scale: scale),
-              ),
-              SizedBox(height: TvBrowseRailLayout.hubStripGapForScale(scale)),
-              _buildHubRail(
-                hub: hub,
-                hubIndex: hubIndex,
-                episodePosterMode: modes[hubIndex],
-                metrics: metrics,
-                scale: scale,
-                fullCardLayout: fullCardLayout,
-                leftOverflow: leftOverflow,
-                interactionExpansion: interactionExpansion,
-                railViewportWidth: railViewportWidth,
-              ),
-            ],
+        return SnapshotWidget(
+          controller: _verticalScrollSnapshotController,
+          mode: SnapshotMode.permissive,
+          autoresize: true,
+          child: SizedBox(
+            key: _hubSectionKeys.putIfAbsent(hubIndex, () => GlobalKey()),
+            height: sectionHeight,
+            child: Column(
+              crossAxisAlignment: .stretch,
+              children: [
+                ListenableSelector<bool>(
+                  listenable: _focusModel,
+                  selector: isActiveHub,
+                  builder: (context, isActive, _) =>
+                      _buildHubHeader(context, hub: hub, hubIndex: hubIndex, isActive: isActive, scale: scale),
+                ),
+                SizedBox(height: TvBrowseRailLayout.hubStripGapForScale(scale)),
+                _buildHubRail(
+                  hub: hub,
+                  hubIndex: hubIndex,
+                  episodePosterMode: modes[hubIndex],
+                  metrics: metrics,
+                  scale: scale,
+                  fullCardLayout: fullCardLayout,
+                  leftOverflow: leftOverflow,
+                  interactionExpansion: interactionExpansion,
+                  railViewportWidth: railViewportWidth,
+                ),
+              ],
+            ),
           ),
         );
       },