RangeSlider overlap properly (#60549)

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

@@ -328,8 +328,7 @@ enum Thumb {
 /// {@macro flutter.material.slider.seeAlso.rangeSliderTickMarkShape}
 @immutable
 class SliderThemeData with Diagnosticable {
-  /// Create a [SliderThemeData] given a set of exact values. All the values
-  /// must be specified.
+  /// Create a [SliderThemeData] given a set of exact values.
   ///
   /// This will rarely be used directly. It is used by [lerp] to
   /// create intermediate themes based on two themes.
@@ -2513,29 +2512,11 @@ class RoundRangeSliderThumbShape extends RangeSliderThumbShape {
     // Add a stroke of 1dp around the circle if this thumb would overlap
     // the other thumb.
     if (isOnTop == true) {
-      bool showValueIndicator;
-      switch (sliderTheme.showValueIndicator) {
-        case ShowValueIndicator.onlyForDiscrete:
-          showValueIndicator = isDiscrete;
-          break;
-        case ShowValueIndicator.onlyForContinuous:
-          showValueIndicator = !isDiscrete;
-          break;
-        case ShowValueIndicator.always:
-          showValueIndicator = true;
-          break;
-        case ShowValueIndicator.never:
-          showValueIndicator = false;
-          break;
-      }
-
-      if (!showValueIndicator || activationAnimation.value == 0) {
-        final Paint strokePaint = Paint()
-          ..color = sliderTheme.overlappingShapeStrokeColor
-          ..strokeWidth = 1.0
-          ..style = PaintingStyle.stroke;
-        canvas.drawCircle(center, radius, strokePaint);
-      }
+      final Paint strokePaint = Paint()
+        ..color = sliderTheme.overlappingShapeStrokeColor
+        ..strokeWidth = 1.0
+        ..style = PaintingStyle.stroke;
+      canvas.drawCircle(center, radius, strokePaint);
     }
 
     final Color color = colorTween.evaluate(enableAnimation);

packages/flutter/test/material/range_slider_test.dart

@@ -1662,6 +1662,86 @@ void main() {
     await gesture.up();
   });
 
+  testWidgets('Range Slider thumb gets stroked when overlapping', (WidgetTester tester) async {
+    RangeValues values = const RangeValues(0.3, 0.7);
+
+    final ThemeData theme = ThemeData(
+      platform: TargetPlatform.android,
+      primarySwatch: Colors.blue,
+      sliderTheme: const SliderThemeData(
+        valueIndicatorColor: Color(0xff000001),
+        showValueIndicator: ShowValueIndicator.onlyForContinuous,
+      ),
+    );
+    final SliderThemeData sliderTheme = theme.sliderTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Directionality(
+          textDirection: TextDirection.ltr,
+          child: StatefulBuilder(
+            builder: (BuildContext context, StateSetter setState) {
+              return Material(
+                child: Center(
+                  child: Theme(
+                    data: theme,
+                    child: RangeSlider(
+                      values: values,
+                      labels: RangeLabels(values.start.toStringAsFixed(2), values.end.toStringAsFixed(2)),
+                      onChanged: (RangeValues newValues) {
+                        setState(() {
+                          values = newValues;
+                        });
+                      },
+                    ),
+                  ),
+                ),
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    // Get the bounds of the track by finding the slider edges and translating
+    // inwards by the overlay radius.
+    final Offset topLeft = tester.getTopLeft(find.byType(RangeSlider)).translate(24, 0);
+    final Offset bottomRight = tester.getBottomRight(find.byType(RangeSlider)).translate(-24, 0);
+    final Offset middle = topLeft + bottomRight / 2;
+
+    // Drag the thumbs towards the center.
+    final Offset leftTarget = topLeft + (bottomRight - topLeft) * 0.3;
+    await tester.dragFrom(leftTarget, middle - leftTarget);
+    await tester.pumpAndSettle();
+    final Offset rightTarget = topLeft + (bottomRight - topLeft) * 0.7;
+    await tester.dragFrom(rightTarget, middle - rightTarget);
+    await tester.pumpAndSettle();
+    expect(values.start, closeTo(0.5, 0.03));
+    expect(values.end, closeTo(0.5, 0.03));
+    final TestGesture gesture = await tester.startGesture(middle);
+    await tester.pumpAndSettle();
+
+    /// The first circle is the thumb, the second one is the overlapping shape
+    /// circle, and the last one is the second thumb.
+    expect(
+        find.byType(RangeSlider),
+        paints
+          ..circle()
+          ..circle(color: sliderTheme.overlappingShapeStrokeColor)
+          ..circle()
+    );
+
+    await gesture.up();
+
+    expect(
+        find.byType(RangeSlider),
+        paints
+          ..circle()
+          ..circle(color: sliderTheme.overlappingShapeStrokeColor)
+          ..circle()
+    );
+  });
+
   testWidgets('Range Slider implements debugFillProperties', (WidgetTester tester) async {
     final DiagnosticPropertiesBuilder builder = DiagnosticPropertiesBuilder();