refactor(mix): reduce style pipeline overhead

packages/mix/lib/src/animation/style_animation_builder.dart

@@ -32,17 +32,20 @@ class StyleAnimationBuilder<S extends Spec<S>> extends StatefulWidget {
 class _StyleAnimationBuilderState<S extends Spec<S>>
     extends State<StyleAnimationBuilder<S>>
     with TickerProviderStateMixin {
-  late StyleAnimationDriver<S> animationDriver;
+  StyleAnimationDriver<S>? _animationDriver;
 
   @override
   void initState() {
     super.initState();
     final spec = widget.spec;
     final config = spec.animation;
-    animationDriver = _createAnimationDriver(config: config, initialSpec: spec);
+    _animationDriver = _createAnimationDriver(
+      config: config,
+      initialSpec: spec,
+    );
   }
 
-  StyleAnimationDriver<S> _createAnimationDriver({
+  StyleAnimationDriver<S>? _createAnimationDriver({
     required AnimationConfig? config,
     required StyleSpec<S> initialSpec,
   }) {
@@ -73,14 +76,13 @@ class _StyleAnimationBuilderState<S extends Spec<S>>
         initialSpec: initialSpec,
         context: context,
       ),
-      // ignore: avoid-undisposed-instances
-      null => NoAnimationDriver(vsync: this, initialSpec: initialSpec),
+      null => null,
     };
   }
 
   @override
   void dispose() {
-    animationDriver.dispose();
+    _animationDriver?.dispose();
     super.dispose();
   }
 
@@ -92,22 +94,27 @@ class _StyleAnimationBuilderState<S extends Spec<S>>
     final oldConfig = oldWidget.spec.animation;
 
     if ((oldConfig.runtimeType == config.runtimeType) && config != null) {
-      animationDriver.updateDriver(config);
+      _animationDriver!.updateDriver(config);
     } else {
-      animationDriver.dispose();
-      animationDriver = _createAnimationDriver(
+      _animationDriver?.dispose();
+      _animationDriver = _createAnimationDriver(
         config: config ?? oldConfig,
         initialSpec: oldWidget.spec,
       );
     }
 
     if (oldWidget.spec != widget.spec) {
-      animationDriver.didUpdateSpec(oldWidget.spec, widget.spec);
+      _animationDriver?.didUpdateSpec(oldWidget.spec, widget.spec);
     }
   }
 
   @override
   Widget build(BuildContext context) {
+    final animationDriver = _animationDriver;
+    if (animationDriver == null) {
+      return widget.builder(context, widget.spec);
+    }
+
     return AnimatedBuilder(
       animation: animationDriver.animation,
       builder: (context, child) {

packages/mix/lib/src/core/providers/widget_state_provider.dart

@@ -42,6 +42,14 @@ class WidgetStateProvider extends InheritedModel<WidgetState> {
     );
   }
 
+  /// Whether a [WidgetStateProvider] exists above [context].
+  ///
+  /// Unlike [of], this lookup does not register a dependency on any state
+  /// aspect.
+  static bool hasProvider(BuildContext context) {
+    return context.getInheritedWidgetOfExactType<WidgetStateProvider>() != null;
+  }
+
   /// Checks if a specific [WidgetState] is currently active.
   ///
   /// Returns false if no [WidgetStateProvider] is found in the widget tree.

packages/mix/lib/src/core/style.dart

@@ -72,6 +72,24 @@ abstract class Style<S extends Spec<S>> extends Mix<StyleSpec<S>>
         .toSet();
   }
 
+  /// Whether this style reacts to a state produced by automatic pointer
+  /// tracking.
+  @internal
+  bool get needsPointerTracking {
+    final variants = $variants;
+    if (variants == null) return false;
+
+    for (final variantStyle in variants) {
+      final variant = variantStyle.variant;
+      if (variant is WidgetStateVariant &&
+          (variant.state == .hovered || variant.state == .pressed)) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   /// Merges all active variants with their nested variants recursively.
   ///
   /// This method evaluates which variants should be active based on the current
@@ -88,8 +106,13 @@ abstract class Style<S extends Spec<S>> extends Mix<StyleSpec<S>>
     BuildContext context, {
     required Set<NamedVariant> namedVariants,
   }) {
+    final variants = $variants;
+    if (variants == null || variants.isEmpty) {
+      return this;
+    }
+
     // Filter variants that should be active in this context
-    final activeVariants = ($variants ?? [])
+    final activeVariants = variants
         .where(
           (variantAttr) => switch (variantAttr.variant) {
             (ContextVariant variant) => variant.when(context),

packages/mix/lib/src/core/style_builder.dart

@@ -46,45 +46,8 @@ class StyleBuilder<S extends Spec<S>> extends StatefulWidget {
   State<StyleBuilder<S>> createState() => _StyleBuilderState<S>();
 }
 
-class _StyleBuilderState<S extends Spec<S>> extends State<StyleBuilder<S>>
-    with TickerProviderStateMixin {
-  late WidgetStatesController _controller;
-
-  /// Tracks whether we created the controller internally (and thus own it)
-  bool _ownsController = false;
-
-  @override
-  void initState() {
-    super.initState();
-    _initController();
-  }
-
-  void _initController() {
-    if (widget.controller != null) {
-      _controller = widget.controller!;
-      _ownsController = false;
-    } else {
-      _controller = WidgetStatesController();
-      _ownsController = true;
-    }
-  }
-
-  void _handleControllerChange(StyleBuilder<S> oldWidget) {
-    // Dispose old internal controller if we owned it
-    if (_ownsController) {
-      _controller.dispose();
-    }
-
-    // Set up new controller
-    if (widget.controller != null) {
-      _controller = widget.controller!;
-      _ownsController = false;
-    } else {
-      // Create internal controller, preserving state from old external controller
-      _controller = WidgetStatesController(oldWidget.controller?.value ?? {});
-      _ownsController = true;
-    }
-  }
+class _StyleBuilderState<S extends Spec<S>> extends State<StyleBuilder<S>> {
+  WidgetStatesController? _preservedController;
 
   Style<S> _buildStyle(BuildContext context) {
     final inheritedStyle = Style.maybeOf<S>(context);
@@ -105,31 +68,28 @@ class _StyleBuilderState<S extends Spec<S>> extends State<StyleBuilder<S>>
   void didUpdateWidget(covariant StyleBuilder<S> oldWidget) {
     super.didUpdateWidget(oldWidget);
 
-    // Handle controller changes
-    if (oldWidget.controller != widget.controller) {
-      _handleControllerChange(oldWidget);
+    if (oldWidget.controller == widget.controller) return;
+
+    if (widget.controller != null) {
+      _preservedController?.dispose();
+      _preservedController = null;
+    } else {
+      _preservedController = WidgetStatesController(
+        oldWidget.controller?.value ?? {},
+      );
     }
   }
 
   @override
   void dispose() {
-    // Only dispose controllers we created internally
-    if (_ownsController) {
-      _controller.dispose();
-    }
-
+    _preservedController?.dispose();
     super.dispose();
   }
 
   @override
   Widget build(BuildContext context) {
     final style = _buildStyle(context);
-
-    // Calculate interactivity need early
-    final needsToTrackWidgetState =
-        widget.controller == null && style.widgetStates.isNotEmpty;
-
-    final alreadyHasWidgetStateScope = WidgetStateProvider.of(context) != null;
+    final externalController = widget.controller;
 
     Widget current = Builder(
       builder: (context) {
@@ -142,14 +102,15 @@ class _StyleBuilderState<S extends Spec<S>> extends State<StyleBuilder<S>>
       },
     );
 
-    if (needsToTrackWidgetState && !alreadyHasWidgetStateScope) {
-      // If we need interactivity and no MixWidgetStateModel is present,
-      // wrap in MixInteractionDetector
-      current = MixInteractionDetector(controller: _controller, child: current);
-    } else if (widget.controller != null) {
-      // If we have an external controller, wrap with _ExternalControllerProvider
+    if (externalController != null) {
       current = _ExternalControllerProvider(
-        controller: _controller,
+        controller: externalController,
+        child: current,
+      );
+    } else if (style.needsPointerTracking &&
+        !WidgetStateProvider.hasProvider(context)) {
+      current = MixInteractionDetector(
+        controller: _preservedController,
         child: current,
       );
     }