Corrected OverflowBar layout when it is wider that its intrinsic width (#82380)

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

@@ -510,17 +510,25 @@ class _RenderOverflowBar extends RenderBox
       }
       size = constraints.constrain(Size(constraints.maxWidth, y - overflowSpacing));
     } else {
-      // Default horizontal layout
-      child = rtl ? lastChild : firstChild;
-      RenderBox? nextChild() => rtl ? childBefore(child!) : childAfter(child!);
-      double x  = 0;
+      // Default horizontal layout.
+      size = constraints.constrain(Size(actualWidth, maxChildHeight));
+      child = firstChild;
+      double x = rtl ? size.width - child!.size.width : 0;
       while (child != null) {
         final _OverflowBarParentData childParentData = child.parentData! as _OverflowBarParentData;
         childParentData.offset = Offset(x, (maxChildHeight - child.size.height) / 2);
-        x += child.size.width + spacing;
-        child = nextChild();
+        // x is the horizontal origin of child. To advance x to the next child's
+        // origin for LTR: add the width of the current child. To advance x to
+        // the origin of the next child for RTL: subtract the width of the next
+        // child (if there is one).
+        if (!rtl) {
+          x += child.size.width + spacing;
+        }
+        child = childAfter(child);
+        if (rtl && child != null) {
+          x -= child.size.width + spacing;
+        }
       }
-      size = constraints.constrain(Size(actualWidth, maxChildHeight));
     }
   }
 

packages/flutter/test/widgets/overflow_bar_test.dart

@@ -234,4 +234,41 @@ void main() {
     await tester.pumpWidget(buildFrame(maxWidth: 150));
     expect(tester.getSize(find.byType(OverflowBar)).height, 166); // 166 = 50 + 8 + 25 + 8 + 75
   });
+
+
+  testWidgets('OverflowBar is wider that its intrinsic width', (WidgetTester tester) async {
+    final Key key0 = UniqueKey();
+    final Key key1 = UniqueKey();
+    final Key key2 = UniqueKey();
+
+    Widget buildFrame(TextDirection textDirection) {
+      return Directionality(
+        textDirection: textDirection,
+        child: SizedBox(
+          width: 800,
+          // intrinsic width = 50 + 10 + 60 + 10 + 70 = 200
+          child: OverflowBar(
+            spacing: 10,
+            children: <Widget>[
+              SizedBox(key: key0, width: 50, height: 50),
+              SizedBox(key: key1, width: 60, height: 50),
+              SizedBox(key: key2, width: 70, height: 50),
+            ],
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildFrame(TextDirection.ltr));
+    expect(tester.getSize(find.byType(OverflowBar)), const Size(800.0, 600.0));
+    expect(tester.getTopLeft(find.byKey(key0)).dx, 0);
+    expect(tester.getTopLeft(find.byKey(key1)).dx, 60);
+    expect(tester.getTopLeft(find.byKey(key2)).dx, 130);
+
+    await tester.pumpWidget(buildFrame(TextDirection.rtl));
+    expect(tester.getSize(find.byType(OverflowBar)), const Size(800.0, 600.0));
+    expect(tester.getTopLeft(find.byKey(key0)).dx, 750);
+    expect(tester.getTopLeft(find.byKey(key1)).dx, 680);
+    expect(tester.getTopLeft(find.byKey(key2)).dx, 600);
+  });
 }