TabBar: add themeable mouse cursor (#96737)

Author: TahaTesser

packages/flutter/lib/src/material/tab_bar_theme.dart

@@ -37,6 +37,7 @@ class TabBarTheme with Diagnosticable {
     this.unselectedLabelStyle,
     this.overlayColor,
     this.splashFactory,
+    this.mouseCursor,
   });
 
   /// Default value for [TabBar.indicator].
@@ -70,6 +71,11 @@ class TabBarTheme with Diagnosticable {
   /// Default value for [TabBar.splashFactory].
   final InteractiveInkFeatureFactory? splashFactory;
 
+  /// {@macro flutter.material.tabs.mouseCursor}
+  ///
+  /// If specified, overrides the default value of [TabBar.mouseCursor].
+  final MaterialStateProperty<MouseCursor?>? mouseCursor;
+
   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   TabBarTheme copyWith({
@@ -82,6 +88,7 @@ class TabBarTheme with Diagnosticable {
     TextStyle? unselectedLabelStyle,
     MaterialStateProperty<Color?>? overlayColor,
     InteractiveInkFeatureFactory? splashFactory,
+    MaterialStateProperty<MouseCursor?>? mouseCursor,
   }) {
     return TabBarTheme(
       indicator: indicator ?? this.indicator,
@@ -93,6 +100,7 @@ class TabBarTheme with Diagnosticable {
       unselectedLabelStyle: unselectedLabelStyle ?? this.unselectedLabelStyle,
       overlayColor: overlayColor ?? this.overlayColor,
       splashFactory: splashFactory ?? this.splashFactory,
+      mouseCursor: mouseCursor ?? this.mouseCursor,
     );
   }
 
@@ -120,6 +128,7 @@ class TabBarTheme with Diagnosticable {
       unselectedLabelStyle: TextStyle.lerp(a.unselectedLabelStyle, b.unselectedLabelStyle, t),
       overlayColor: _LerpColors(a.overlayColor, b.overlayColor, t),
       splashFactory: t < 0.5 ? a.splashFactory : b.splashFactory,
+      mouseCursor: t < 0.5 ? a.mouseCursor : b.mouseCursor,
     );
   }
 
@@ -135,6 +144,7 @@ class TabBarTheme with Diagnosticable {
       unselectedLabelStyle,
       overlayColor,
       splashFactory,
+      mouseCursor,
     );
   }
 
@@ -153,7 +163,8 @@ class TabBarTheme with Diagnosticable {
         && other.unselectedLabelColor == unselectedLabelColor
         && other.unselectedLabelStyle == unselectedLabelStyle
         && other.overlayColor == overlayColor
-        && other.splashFactory == splashFactory;
+        && other.splashFactory == splashFactory
+        && other.mouseCursor == mouseCursor;
   }
 }
 

packages/flutter/lib/src/material/tabs.dart

@@ -803,10 +803,23 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
   /// {@macro flutter.widgets.scrollable.dragStartBehavior}
   final DragStartBehavior dragStartBehavior;
 
+  /// {@template flutter.material.tabs.mouseCursor}
   /// The cursor for a mouse pointer when it enters or is hovering over the
   /// individual tab widgets.
   ///
-  /// If this property is null, [SystemMouseCursors.click] will be used.
+  /// If [mouseCursor] is a [MaterialStateProperty<MouseCursor>],
+  /// [MaterialStateProperty.resolve] is used for the following [MaterialState]s:
+  ///
+  ///  * [MaterialState.selected].
+  /// {@endtemplate}
+  ///
+  /// If null, then the value of [TabBarTheme.mouseCursor] is used. If
+  /// that is also null, then [MaterialStateMouseCursor.clickable] is used.
+  ///
+  /// See also:
+  ///
+  ///  * [MaterialStateMouseCursor], which can be used to create a [MouseCursor]
+  ///    that is also a [MaterialStateProperty<MouseCursor>].
   final MouseCursor? mouseCursor;
 
   /// Whether detected gestures should provide acoustic and/or haptic feedback.
@@ -1222,8 +1235,16 @@ class _TabBarState extends State<TabBar> {
     // the same share of the tab bar's overall width.
     final int tabCount = widget.tabs.length;
     for (int index = 0; index < tabCount; index += 1) {
+      final Set<MaterialState> states = <MaterialState>{
+        if (index == _currentIndex) MaterialState.selected,
+      };
+
+      final MouseCursor effectiveMouseCursor = MaterialStateProperty.resolveAs<MouseCursor?>(widget.mouseCursor, states)
+        ?? tabBarTheme.mouseCursor?.resolve(states)
+        ?? MaterialStateMouseCursor.clickable.resolve(states);
+
       wrappedTabs[index] = InkWell(
-        mouseCursor: widget.mouseCursor ?? SystemMouseCursors.click,
+        mouseCursor: effectiveMouseCursor,
         onTap: () { _handleTap(index); },
         enableFeedback: widget.enableFeedback ?? true,
         overlayColor: widget.overlayColor ?? tabBarTheme.overlayColor,

packages/flutter/test/material/tab_bar_theme_test.dart

@@ -6,6 +6,7 @@
 // machines.
 @Tags(<String>['reduced-test-set'])
 
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -67,6 +68,7 @@ void main() {
     expect(const TabBarTheme().unselectedLabelStyle, null);
     expect(const TabBarTheme().overlayColor, null);
     expect(const TabBarTheme().splashFactory, null);
+    expect(const TabBarTheme().mouseCursor, null);
   });
 
   testWidgets('Tab bar defaults - label style and selected/unselected label colors', (WidgetTester tester) async {
@@ -302,6 +304,22 @@ void main() {
     );
   });
 
+  testWidgets('Tab bar theme overrides tab mouse cursor', (WidgetTester tester) async {
+    const TabBarTheme tabBarTheme = TabBarTheme(mouseCursor: MaterialStateMouseCursor.textable);
+
+    await tester.pumpWidget(_withTheme(tabBarTheme));
+
+    final Offset tabBar = tester.getCenter(
+      find.ancestor(of: find.text('tab 1'),matching: find.byType(TabBar)),
+    );
+    final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
+    await gesture.addPointer();
+    addTearDown(gesture.removePointer);
+    await gesture.moveTo(tabBar);
+    await tester.pumpAndSettle();
+    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+  });
+
   testWidgets('Tab bar theme - custom tab indicator', (WidgetTester tester) async {
     final TabBarTheme tabBarTheme = TabBarTheme(
       indicator: BoxDecoration(