Add ability to customize the default Slider padding (#156143)

Fixes [Ability to change Sliders padding](https://github.com/flutter/flutter/issues/40098)

Add ability to override default padding so the Slider can fit better in a layout.

### Code sample

<details>
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  double _sliderValue = 0.5;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        sliderTheme: const SliderThemeData(
          padding: EdgeInsets.symmetric(vertical: 4.0),
          thumbColor: Colors.red,
          inactiveTrackColor: Colors.amber,
        ),
      ),
      home: Scaffold(
        body: Directionality(
          textDirection: TextDirection.ltr,
          child: Center(
            child: Card(
              shape: const RoundedRectangleBorder(
                borderRadius: BorderRadius.all(Radius.circular(4.0)),
              ),
              color: Theme.of(context).colorScheme.surfaceContainerHighest,
              margin: const EdgeInsets.symmetric(horizontal: 16.0),
              child: Padding(
                padding: const EdgeInsets.all(16.0),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    const Placeholder(fallbackHeight: 100.0),
                    Slider(
                      value: _sliderValue,
                      onChanged: (double value) {
                        setState(() {
                          _sliderValue = value;
                        });
                      },
                    ),
                    const Placeholder(fallbackHeight: 100.0),

                  ],
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}
```

</details>

### Before
(Cannot adjust default `Slider` padding to fill the horizontal space in a `Column` and reduce the padded height)

<img width="717" alt="Screenshot 2024-10-03 at 15 45 18" src="https://github.com/user-attachments/assets/e9d9a4d1-3087-45b4-8607-b94411e2bd23">

### After 
Can adjust default `Slider` padding via `SliderTheme`)

<img width="717" alt="Screenshot 2024-10-03 at 15 46 25" src="https://github.com/user-attachments/assets/cd455881-6d52-46cb-8ac6-cc33f50a13ff">

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

@@ -196,6 +196,7 @@ class Slider extends StatefulWidget {
     this.focusNode,
     this.autofocus = false,
     this.allowedInteraction,
+    this.padding,
   }) : _sliderType = _SliderType.material,
        assert(min <= max),
        assert(value >= min && value <= max,
@@ -238,6 +239,7 @@ class Slider extends StatefulWidget {
     this.autofocus = false,
     this.allowedInteraction,
   }) : _sliderType = _SliderType.adaptive,
+       padding = null,
        assert(min <= max),
        assert(value >= min && value <= max,
          'Value $value is not between minimum $min and maximum $max'),
@@ -550,6 +552,14 @@ class Slider extends StatefulWidget {
   /// Defaults to [SliderInteraction.tapAndSlide].
   final SliderInteraction? allowedInteraction;
 
+  /// Determines the padding around the [Slider].
+  ///
+  /// If specified, this padding overrides the default vertical padding of
+  /// the [Slider], defaults to the height of the overlay shape, and the
+  /// horizontal padding, defaults to the width of the thumb shape or
+  /// overlay shape, whichever is larger.
+  final EdgeInsetsGeometry? padding;
+
   final _SliderType _sliderType ;
 
   @override
@@ -853,6 +863,7 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
       valueIndicatorShape: valueIndicatorShape,
       showValueIndicator: sliderTheme.showValueIndicator ?? defaultShowValueIndicator,
       valueIndicatorTextStyle: valueIndicatorTextStyle,
+      padding: widget.padding ?? sliderTheme.padding,
     );
     final MouseCursor effectiveMouseCursor = MaterialStateProperty.resolveAs<MouseCursor?>(widget.mouseCursor, states)
       ?? sliderTheme.mouseCursor?.resolve(states)
@@ -899,6 +910,36 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
       : MediaQuery.textScalerOf(context);
     final double effectiveTextScale = textScaler.scale(fontSizeToScale) / fontSizeToScale;
 
+    Widget result = CompositedTransformTarget(
+      link: _layerLink,
+      child: _SliderRenderObjectWidget(
+        key: _renderObjectKey,
+        value: _convert(widget.value),
+        secondaryTrackValue: (widget.secondaryTrackValue != null) ? _convert(widget.secondaryTrackValue!) : null,
+        divisions: widget.divisions,
+        label: widget.label,
+        sliderTheme: sliderTheme,
+        textScaleFactor: effectiveTextScale,
+        screenSize: screenSize(),
+        onChanged: (widget.onChanged != null) && (widget.max > widget.min) ? _handleChanged : null,
+        onChangeStart: _handleDragStart,
+        onChangeEnd: _handleDragEnd,
+        state: this,
+        semanticFormatterCallback: widget.semanticFormatterCallback,
+        hasFocus: _focused,
+        hovering: _hovering,
+        allowedInteraction: effectiveAllowedInteraction,
+      ),
+    );
+
+    final EdgeInsetsGeometry? padding = widget.padding ?? sliderTheme.padding;
+    if (padding != null) {
+      result = Padding(
+        padding: padding,
+        child: result,
+      );
+    }
+
     return Semantics(
       container: true,
       slider: true,
@@ -912,27 +953,7 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
         onShowFocusHighlight: _handleFocusHighlightChanged,
         onShowHoverHighlight: _handleHoverChanged,
         mouseCursor: effectiveMouseCursor,
-        child: CompositedTransformTarget(
+        child: result,
-          link: _layerLink,
-          child: _SliderRenderObjectWidget(
-            key: _renderObjectKey,
-            value: _convert(widget.value),
-            secondaryTrackValue: (widget.secondaryTrackValue != null) ? _convert(widget.secondaryTrackValue!) : null,
-            divisions: widget.divisions,
-            label: widget.label,
-            sliderTheme: sliderTheme,
-            textScaleFactor: effectiveTextScale,
-            screenSize: screenSize(),
-            onChanged: (widget.onChanged != null) && (widget.max > widget.min) ? _handleChanged : null,
-            onChangeStart: _handleDragStart,
-            onChangeEnd: _handleDragEnd,
-            state: this,
-            semanticFormatterCallback: widget.semanticFormatterCallback,
-            hasFocus: _focused,
-            hovering: _hovering,
-            allowedInteraction: effectiveAllowedInteraction,
-          ),
-        ),
       ),
     );
   }
@@ -1145,8 +1166,13 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   // centered on the track.
   double get _maxSliderPartWidth => _sliderPartSizes.map((Size size) => size.width).reduce(math.max);
   double get _maxSliderPartHeight => _sliderPartSizes.map((Size size) => size.height).reduce(math.max);
+  double get _thumbSizeHeight => _sliderTheme.thumbShape!.getPreferredSize(isInteractive, isDiscrete).height;
+  double get _overlayHeight => _sliderTheme.overlayShape!.getPreferredSize(isInteractive, isDiscrete).height;
   List<Size> get _sliderPartSizes => <Size>[
-    _sliderTheme.overlayShape!.getPreferredSize(isInteractive, isDiscrete),
+    Size(
+      _sliderTheme.overlayShape!.getPreferredSize(isInteractive, isDiscrete).width,
+      _sliderTheme.padding != null ? _thumbSizeHeight : _overlayHeight
+    ),
     _sliderTheme.thumbShape!.getPreferredSize(isInteractive, isDiscrete),
     _sliderTheme.tickMarkShape!.getPreferredSize(isEnabled: isInteractive, sliderTheme: sliderTheme),
   ];

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

@@ -296,6 +296,7 @@ class SliderThemeData with Diagnosticable {
     this.thumbSelector,
     this.mouseCursor,
     this.allowedInteraction,
+    this.padding,
   });
 
   /// Generates a SliderThemeData from three main colors.
@@ -588,6 +589,14 @@ class SliderThemeData with Diagnosticable {
   /// If specified, overrides the default value of [Slider.allowedInteraction].
   final SliderInteraction? allowedInteraction;
 
+  /// Determines the padding around the [Slider].
+  ///
+  /// If specified, this padding overrides the default vertical padding of
+  /// the [Slider], defaults to the height of the overlay shape, and the
+  /// horizontal padding, defaults to the width of the thumb shape or
+  /// overlay shape, whichever is larger.
+  final EdgeInsetsGeometry? padding;
+
   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   SliderThemeData copyWith({
@@ -623,6 +632,7 @@ class SliderThemeData with Diagnosticable {
     RangeThumbSelector? thumbSelector,
     MaterialStateProperty<MouseCursor?>? mouseCursor,
     SliderInteraction? allowedInteraction,
+    EdgeInsetsGeometry? padding,
   }) {
     return SliderThemeData(
       trackHeight: trackHeight ?? this.trackHeight,
@@ -657,6 +667,7 @@ class SliderThemeData with Diagnosticable {
       thumbSelector: thumbSelector ?? this.thumbSelector,
       mouseCursor: mouseCursor ?? this.mouseCursor,
       allowedInteraction: allowedInteraction ?? this.allowedInteraction,
+      padding: padding ?? this.padding,
     );
   }
 
@@ -700,6 +711,7 @@ class SliderThemeData with Diagnosticable {
       thumbSelector: t < 0.5 ? a.thumbSelector : b.thumbSelector,
       mouseCursor: t < 0.5 ? a.mouseCursor : b.mouseCursor,
       allowedInteraction: t < 0.5 ? a.allowedInteraction : b.allowedInteraction,
+      padding: EdgeInsetsGeometry.lerp(a.padding, b.padding, t),
     );
   }
 
@@ -737,6 +749,7 @@ class SliderThemeData with Diagnosticable {
       thumbSelector,
       mouseCursor,
       allowedInteraction,
+      padding,
     ),
   );
 
@@ -780,7 +793,8 @@ class SliderThemeData with Diagnosticable {
         && other.minThumbSeparation == minThumbSeparation
         && other.thumbSelector == thumbSelector
         && other.mouseCursor == mouseCursor
-        && other.allowedInteraction == allowedInteraction;
+        && other.allowedInteraction == allowedInteraction
+        && other.padding == padding;
   }
 
   @override
@@ -819,6 +833,7 @@ class SliderThemeData with Diagnosticable {
     properties.add(DiagnosticsProperty<RangeThumbSelector>('thumbSelector', thumbSelector, defaultValue: defaultData.thumbSelector));
     properties.add(DiagnosticsProperty<MaterialStateProperty<MouseCursor?>>('mouseCursor', mouseCursor, defaultValue: defaultData.mouseCursor));
     properties.add(EnumProperty<SliderInteraction>('allowedInteraction', allowedInteraction, defaultValue: defaultData.allowedInteraction));
+    properties.add(DiagnosticsProperty<EdgeInsetsGeometry>('padding', padding, defaultValue: defaultData.padding));
   }
 }
 
@@ -1535,9 +1550,9 @@ mixin BaseSliderTrackShape {
     assert(overlayWidth >= 0);
     assert(trackHeight >= 0);
 
-    final double trackLeft = offset.dx + math.max(overlayWidth / 2, thumbWidth / 2);
+    final double trackLeft = offset.dx + (sliderTheme.padding == null ?  math.max(overlayWidth / 2, thumbWidth / 2) : 0);
     final double trackTop = offset.dy + (parentBox.size.height - trackHeight) / 2;
-    final double trackRight = trackLeft + parentBox.size.width - math.max(thumbWidth, overlayWidth);
+    final double trackRight = trackLeft + parentBox.size.width - (sliderTheme.padding == null ? math.max(thumbWidth, overlayWidth) : 0);
     final double trackBottom = trackTop + trackHeight;
     // If the parentBox's size less than slider's size the trackRight will be less than trackLeft, so switch them.
     return Rect.fromLTRB(math.min(trackLeft, trackRight), trackTop, math.max(trackLeft, trackRight), trackBottom);

packages/flutter/test/material/slider_test.dart

@@ -4598,4 +4598,93 @@ void main() {
       paints..path(color: const Color(0xff000000))..paragraph(),
     );
   }, variant: TargetPlatformVariant.desktop());
+
+  testWidgets('Slider.padding can override the default Slider padding', (WidgetTester tester) async {
+    Widget buildSlider({ EdgeInsetsGeometry? padding }) {
+      return MaterialApp(
+        home: Material(
+          child: Center(
+            child: IntrinsicHeight(
+              child: Slider(
+                padding: padding,
+                value: 0.5,
+                onChanged: (double value) {},
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    RenderBox sliderRenderBox() {
+      return tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderSlider') as RenderBox;
+    }
+
+    // Test Slider height and tracks spacing with zero padding.
+    await tester.pumpWidget(buildSlider(padding: EdgeInsets.zero));
+    await tester.pumpAndSettle();
+
+    // The height equals to the default thumb height.
+    expect(sliderRenderBox().size, const Size(800, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(398.0, 8.0, 800.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 402.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+
+    // Test Slider height and tracks spacing with directional padding.
+    const double startPadding = 100;
+    const double endPadding = 20;
+    await tester.pumpWidget(buildSlider(
+      padding: const EdgeInsetsDirectional.only(
+        start: startPadding,
+        end: endPadding,
+      ),
+    ));
+    await tester.pumpAndSettle();
+
+    expect(sliderRenderBox().size, const Size(800 - startPadding - endPadding, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(338.0, 8.0, 680.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 342.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+
+
+    // Test Slider height and tracks spacing with top and bottom padding.
+    const double topPadding = 100;
+    const double bottomPadding = 20;
+    const double trackHeight = 20;
+    await tester.pumpWidget(buildSlider(padding: const EdgeInsetsDirectional.only(top: topPadding, bottom: bottomPadding)));
+    await tester.pumpAndSettle();
+
+    expect(tester.getSize(find.byType(Slider)), const Size(800, topPadding + trackHeight + bottomPadding));
+    expect(sliderRenderBox().size, const Size(800, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(398.0, 8.0, 800.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 402.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+  });
 }

packages/flutter/test/material/slider_theme_test.dart

@@ -2551,6 +2551,95 @@ void main() {
     expect(const RoundedRectSliderTrackShape().isRounded, isTrue);
   });
 
+  testWidgets('SliderThemeData.padding can override the default Slider padding', (WidgetTester tester) async {
+    Widget buildSlider({ EdgeInsetsGeometry? padding }) {
+      return MaterialApp(
+        theme: ThemeData(sliderTheme: SliderThemeData(padding: padding)),
+        home: Material(
+          child: Center(
+            child: IntrinsicHeight(
+              child: Slider(
+                value: 0.5,
+                onChanged: (double value) {},
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    RenderBox sliderRenderBox() {
+      return tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderSlider') as RenderBox;
+    }
+
+    // Test Slider height and tracks spacing with zero padding.
+    await tester.pumpWidget(buildSlider(padding: EdgeInsets.zero));
+    await tester.pumpAndSettle();
+
+    // The height equals to the default thumb height.
+    expect(sliderRenderBox().size, const Size(800, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(398.0, 8.0, 800.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 402.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+
+    // Test Slider height and tracks spacing with directional padding.
+    const double startPadding = 100;
+    const double endPadding = 20;
+    await tester.pumpWidget(buildSlider(
+      padding: const EdgeInsetsDirectional.only(
+        start: startPadding,
+        end: endPadding,
+      ),
+    ));
+    await tester.pumpAndSettle();
+
+    expect(sliderRenderBox().size, const Size(800 - startPadding - endPadding, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(338.0, 8.0, 680.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 342.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+
+
+    // Test Slider height and tracks spacing with top and bottom padding.
+    const double topPadding = 100;
+    const double bottomPadding = 20;
+    const double trackHeight = 20;
+    await tester.pumpWidget(buildSlider(padding: const EdgeInsetsDirectional.only(top: topPadding, bottom: bottomPadding)));
+    await tester.pumpAndSettle();
+
+    expect(tester.getSize(find.byType(Slider)), const Size(800, topPadding + trackHeight + bottomPadding));
+    expect(sliderRenderBox().size, const Size(800, 20));
+    expect(
+      find.byType(Slider),
+      paints
+        // Inactive track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(398.0, 8.0, 800.0, 12.0,  const Radius.circular(2.0)),
+        )
+        // Active track.
+        ..rrect(
+          rrect: RRect.fromLTRBR(0.0, 7.0, 402.0, 13.0,  const Radius.circular(3.0)),
+        ),
+    );
+  });
+
   group('Material 2', () {
     // These tests are only relevant for Material 2. Once Material 2
     // support is deprecated and the APIs are removed, these tests