Add tooltips for SegmentedButton (#128501)

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

@@ -17,6 +17,7 @@ import 'segmented_button_theme.dart';
 import 'text_button.dart';
 import 'text_button_theme.dart';
 import 'theme.dart';
+import 'tooltip.dart';
 
 /// Data describing a segment of a [SegmentedButton].
 class ButtonSegment<T> {
@@ -27,6 +28,7 @@ class ButtonSegment<T> {
     required this.value,
     this.icon,
     this.label,
+    this.tooltip,
     this.enabled = true,
   }) : assert(icon != null || label != null);
 
@@ -41,6 +43,9 @@ class ButtonSegment<T> {
   /// Optional label displayed in the segment.
   final Widget? label;
 
+  /// Optional tooltip for the segment
+  final String? tooltip;
+
   /// Determines if the segment is available for selection.
   final bool enabled;
 }
@@ -335,11 +340,18 @@ class SegmentedButton<T> extends StatelessWidget {
             child: label,
           );
 
+      final Widget buttonWithTooltip = (segment.tooltip != null)
+        ? Tooltip(
+            message: segment.tooltip,
+            child: button,
+          )
+        : button;
+
       return MergeSemantics(
         child: Semantics(
           checked: segmentSelected,
           inMutuallyExclusiveGroup: multiSelectionEnabled ? null : true,
-          child: button,
+          child: buttonWithTooltip,
         ),
       );
     }

packages/flutter/test/material/segmented_button_test.dart

@@ -533,4 +533,59 @@ testWidgets('SegmentedButton shows checkboxes for selected segments', (WidgetTes
     expect(overlayColor(), paints..rect()..rect(color: theme.colorScheme.onSurface.withOpacity(0.12)));
     expect(material.textStyle?.color, theme.colorScheme.onSurface);
   });
+
+  testWidgets('SegmentedButton has no tooltips by default', (WidgetTester tester) async {
+    final ThemeData theme = ThemeData(useMaterial3: true);
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: theme,
+        home: Scaffold(
+          body: Center(
+            child: SegmentedButton<int>(
+              segments: const <ButtonSegment<int>>[
+                ButtonSegment<int>(value: 1, label: Text('1')),
+                ButtonSegment<int>(value: 2, label: Text('2')),
+                ButtonSegment<int>(value: 3, label: Text('3'), enabled: false),
+              ],
+              selected: const <int>{2},
+              onSelectionChanged: (Set<int> selected) { },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(find.byType(Tooltip), findsNothing);
+  });
+
+  testWidgets('SegmentedButton has correct tooltips', (WidgetTester tester) async {
+    final ThemeData theme = ThemeData(useMaterial3: true);
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: theme,
+        home: Scaffold(
+          body: Center(
+            child: SegmentedButton<int>(
+              segments: const <ButtonSegment<int>>[
+                ButtonSegment<int>(value: 1, label: Text('1')),
+                ButtonSegment<int>(value: 2, label: Text('2'), tooltip: 't2'),
+                ButtonSegment<int>(
+                    value: 3,
+                    label: Text('3'),
+                    tooltip: 't3',
+                    enabled: false,
+                ),
+              ],
+              selected: const <int>{2},
+              onSelectionChanged: (Set<int> selected) { },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(find.byType(Tooltip), findsNWidgets(2));
+    expect(find.byTooltip('t2'), findsOneWidget);
+    expect(find.byTooltip('t3'), findsOneWidget);
+  });
 }