Expose padding on RawScrollbar (#107756)

Author: Piinks

packages/flutter/lib/src/widgets/scrollbar.dart

@@ -944,6 +944,7 @@ class RawScrollbar extends StatefulWidget {
     this.scrollbarOrientation,
     this.mainAxisMargin = 0.0,
     this.crossAxisMargin = 0.0,
+    this.padding,
     @Deprecated(
       'Use thumbVisibility instead. '
       'This feature was deprecated after v2.9.0-1.0.pre.',
@@ -1366,6 +1367,13 @@ class RawScrollbar extends StatefulWidget {
   /// Must not be null and defaults to 0.
   final double crossAxisMargin;
 
+  /// The insets by which the scrollbar thumb and track should be padded.
+  ///
+  /// When null, the inherited [MediaQueryData.padding] is used.
+  ///
+  /// Defaults to null.
+  final EdgeInsets? padding;
+
   @override
   RawScrollbarState<RawScrollbar> createState() => RawScrollbarState<RawScrollbar>();
 }
@@ -1593,7 +1601,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
       ..textDirection = Directionality.of(context)
       ..thickness = widget.thickness ?? _kScrollbarThickness
       ..radius = widget.radius
-      ..padding = MediaQuery.of(context).padding
+      ..padding = widget.padding ?? MediaQuery.of(context).padding
       ..scrollbarOrientation = widget.scrollbarOrientation
       ..mainAxisMargin = widget.mainAxisMargin
       ..shape = widget.shape

packages/flutter/test/widgets/scrollbar_test.dart

@@ -2612,7 +2612,7 @@ void main() {
     // Go without throw.
   });
 
-  testWidgets('Track offset respects padding', (WidgetTester tester) async {
+  testWidgets('Track offset respects MediaQuery padding', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/106834
     final ScrollController scrollController = ScrollController();
     await tester.pumpWidget(
@@ -2640,7 +2640,39 @@ void main() {
       find.byType(RawScrollbar),
       paints
         ..rect(rect: const Rect.fromLTRB(744.0, 50.0, 750.0, 550.0)) // track
-        ..rect(rect: const Rect.fromLTRB(744.0, 50.0, 750.0, 71.0))
+        ..rect(rect: const Rect.fromLTRB(744.0, 50.0, 750.0, 71.0)) // thumb
+    ); // thumb
+  });
+
+  testWidgets('RawScrollbar.padding replaces MediaQueryData.padding', (WidgetTester tester) async {
+    final ScrollController scrollController = ScrollController();
+    await tester.pumpWidget(
+        Directionality(
+            textDirection: TextDirection.ltr,
+            child: MediaQuery(
+              data: const MediaQueryData(
+                padding: EdgeInsets.all(50.0),
+              ),
+              child: RawScrollbar(
+                controller: scrollController,
+                minThumbLength: 21,
+                minOverscrollLength: 8,
+                thumbVisibility: true,
+                padding: const EdgeInsets.all(100),
+                child: SingleChildScrollView(
+                  controller: scrollController,
+                  child: const SizedBox(width: 1000.0, height: 50000.0),
+                ),
+              ),
+            )
+        )
+    );
+    await tester.pumpAndSettle();
+    expect(
+        find.byType(RawScrollbar),
+        paints
+          ..rect(rect: const Rect.fromLTRB(694.0, 100.0, 700.0, 500.0)) // track
+          ..rect(rect: const Rect.fromLTRB(694.0, 100.0, 700.0, 121.0)) // thumb
     ); // thumb
   });
 }