fix: Added missing widget state utilities (#411)

packages/mix/lib/src/attributes/spacing/spacing_util.dart

@@ -105,8 +105,7 @@ final class SpacingDirectionalUtility<T extends Attribute>
 }
 
 @immutable
-final class SpacingSideUtility<T extends Attribute>
-    extends MixUtility<T, double> {
+class SpacingSideUtility<T extends Attribute> extends MixUtility<T, double> {
   const SpacingSideUtility(super.builder);
 
   T call(double value) => builder(value);

packages/mix/lib/src/core/widget_state/widget_state_controller.dart

@@ -15,27 +15,68 @@ enum MixWidgetState {
   static const hasStateOf = MixWidgetStateModel.hasStateOf;
 }
 
+/// A controller that manages the state of a widget.
+///
+/// [MixWidgetStateController] tracks various states of a widget, such as
+/// [disabled], [hovered], [focused], [pressed], [dragged], [selected], and
+/// [longPressed]. These states are stored in a [Set] called [value].
+///
+/// The controller extends [ChangeNotifier], allowing listeners to be notified
+/// when the state of the widget changes.
 class MixWidgetStateController extends ChangeNotifier {
+  /// The current set of states for the widget.
+  ///
+  /// This is annotated with `@visibleForTesting` to indicate that it is
+  /// accessible for testing purposes.
   @visibleForTesting
   Set<MixWidgetState> value = {};
 
+  /// Whether the widget is currently in the disabled state.
   bool get disabled => value.contains(MixWidgetState.disabled);
+
+  /// Whether the widget is currently being hovered over.
   bool get hovered => value.contains(MixWidgetState.hovered);
+
+  /// Whether the widget currently has focus.
   bool get focused => value.contains(MixWidgetState.focused);
+
+  /// Whether the widget is currently being pressed.
   bool get pressed => value.contains(MixWidgetState.pressed);
+
+  /// Whether the widget is currently being dragged.
   bool get dragged => value.contains(MixWidgetState.dragged);
+
+  /// Whether the widget is currently in the selected state.
   bool get selected => value.contains(MixWidgetState.selected);
+
+  /// Whether the widget is currently being long-pressed.
   bool get longPressed => value.contains(MixWidgetState.longPressed);
 
+  /// Sets whether the widget is in the disabled state.
   set disabled(bool value) => update(MixWidgetState.disabled, value);
+
+  /// Sets whether the widget is being hovered over.
   set hovered(bool value) => update(MixWidgetState.hovered, value);
+
+  /// Sets whether the widget has focus.
   set focused(bool value) => update(MixWidgetState.focused, value);
+
+  /// Sets whether the widget is being pressed.
   set pressed(bool value) => update(MixWidgetState.pressed, value);
+
+  /// Sets whether the widget is being dragged.
   set dragged(bool value) => update(MixWidgetState.dragged, value);
+
+  /// Sets whether the widget is in the selected state.
   set selected(bool value) => update(MixWidgetState.selected, value);
 
+  /// Sets whether the widget is being long-pressed.
   set longPressed(bool value) => update(MixWidgetState.longPressed, value);
 
+  /// Updates the state of the widget for a given [key].
+  ///
+  /// If [add] is true, the [key] state is added to [value]. If false, it is
+  /// removed. Listeners are notified if the state has changed.
   // ignore: prefer-named-boolean-parameters
   void update(MixWidgetState key, bool add) {
     final valueHasChanged = add ? value.add(key) : value.remove(key);
@@ -45,6 +86,11 @@ class MixWidgetStateController extends ChangeNotifier {
     }
   }
 
+  /// Batch updates the state of the widget with multiple state changes.
+  ///
+  /// [updates] is a list of tuples, where each tuple contains a state [key]
+  /// and a boolean [add] indicating whether to add or remove the state.
+  /// Listeners are notified if any state has changed.
   void batch(List<(MixWidgetState, bool)> updates) {
     var valueHasChanged = false;
     for (final update in updates) {
@@ -62,5 +108,6 @@ class MixWidgetStateController extends ChangeNotifier {
     }
   }
 
+  /// Checks if the widget is currently in the given state [key].
   bool has(MixWidgetState key) => value.contains(key);
 }

packages/mix/lib/src/variants/context_variant_util/on_util.dart

@@ -35,6 +35,9 @@ class OnContextVariantUtility {
   late final enabled = const OnNotVariant(OnDisabledVariant());
   late final disabled = const OnDisabledVariant();
   late final longPress = const OnLongPressVariant();
+  late final selected = const OnSelectedVariant();
+  late final unselected = const OnNotVariant(OnSelectedVariant());
+  late final dragged = const OnDraggedVariant();
 
   /// Creates an [OnNotVariant] with the specified [variant].
   ///

packages/mix/lib/src/widgets/pressable_widget.dart

@@ -87,6 +87,7 @@ class Pressable extends StatefulWidget {
     this.semanticButtonLabel,
     this.onKeyEvent,
     this.unpressDelay = kDefaultAnimationDuration,
+    this.controller,
     this.actions,
   });
 
@@ -143,6 +144,8 @@ class Pressable extends StatefulWidget {
   /// Actions to be bound to the widget
   final Map<Type, Action<Intent>>? actions;
 
+  final MixWidgetStateController? controller;
+
   /// The duration to wait after the press is released before the state of pressed is removed
   final Duration unpressDelay;
 
@@ -152,7 +155,13 @@ class Pressable extends StatefulWidget {
 
 @visibleForTesting
 class PressableWidgetState extends State<Pressable> {
-  final _controller = MixWidgetStateController();
+  late final MixWidgetStateController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = widget.controller ?? MixWidgetStateController();
+  }
 
   @override
   void dispose() {