Added AlertDialog.actionsAlignment OverflowBar configuration (#85260)

Added AlertDialog.actionsAlignment OverflowBar configuration.

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

@@ -276,6 +276,7 @@ class AlertDialog extends StatelessWidget {
     this.contentTextStyle,
     this.actions,
     this.actionsPadding = EdgeInsets.zero,
+    this.actionsAlignment,
     this.actionsOverflowDirection,
     this.actionsOverflowButtonSpacing,
     this.buttonPadding,
@@ -383,6 +384,15 @@ class AlertDialog extends StatelessWidget {
   /// * [ButtonBar], which [actions] configures to lay itself out.
   final EdgeInsetsGeometry actionsPadding;
 
+  /// Defines the horizontal layout of the [actions] according to the same
+  /// rules as for [Row.mainAxisAlignment].
+  ///
+  /// This parameter is passed along to the dialog's [OverflowBar].
+  ///
+  /// If this parameter is null (the default) then [MainAxisAlignment.end]
+  /// is used.
+  final MainAxisAlignment? actionsAlignment;
+
   /// The vertical direction of [actions] if the children overflow
   /// horizontally.
   ///
@@ -534,21 +544,17 @@ class AlertDialog extends StatelessWidget {
       );
     }
 
-
     if (actions != null) {
       final double spacing = (buttonPadding?.horizontal ?? 16) / 2;
       actionsWidget = Padding(
-        padding: actionsPadding,
-        child: Container(
-          alignment: AlignmentDirectional.centerEnd,
-          padding: EdgeInsets.all(spacing),
-          child: OverflowBar(
-            spacing: spacing,
-            overflowAlignment: OverflowBarAlignment.end,
-            overflowDirection: actionsOverflowDirection ?? VerticalDirection.down,
-            overflowSpacing: actionsOverflowButtonSpacing ?? 0,
-            children: actions!,
-          ),
+        padding: actionsPadding.add(EdgeInsets.all(spacing)),
+        child: OverflowBar(
+          alignment: actionsAlignment ?? MainAxisAlignment.end,
+          spacing: spacing,
+          overflowAlignment: OverflowBarAlignment.end,
+          overflowDirection: actionsOverflowDirection ?? VerticalDirection.down,
+          overflowSpacing: actionsOverflowButtonSpacing ?? 0,
+          children: actions!,
         ),
       );
     }

packages/flutter/test/material/dialog_test.dart

@@ -50,7 +50,7 @@ RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text)
 // is now a Container with an OverflowBar child. The Container's size and location
 // match the original ButtonBar's size and location.
 Finder _findButtonBar() {
-  return find.ancestor(of: find.byType(OverflowBar), matching: find.byType(Container)).first;
+  return find.ancestor(of: find.byType(OverflowBar), matching: find.byType(Padding)).first;
 }
 
 const ShapeBorder _defaultDialogShape = RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(4.0)));
@@ -517,6 +517,8 @@ void main() {
           child: const Text('button'),
         ),
       ],
+      // The OverflowBar is inset by the buttonPadding/2 + actionsPadding
+      buttonPadding: EdgeInsets.zero,
       actionsPadding: const EdgeInsets.all(30.0), // custom padding value
     );
 
@@ -536,7 +538,7 @@ void main() {
         matching: find.byType(Material),
       ).first,
     );
-    final Size actionsSize = tester.getSize(_findButtonBar());
+    final Size actionsSize = tester.getSize(find.byType(OverflowBar));
 
     expect(actionsSize.width, dialogSize.width - (30.0 * 2));
   });
@@ -2066,6 +2068,58 @@ void main() {
     await tester.restoreFrom(restorationData);
     expect(find.byType(AlertDialog), findsOneWidget);
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/33615
+
+  testWidgets('AlertDialog.actionsAlignment', (WidgetTester tester) async {
+    final Key actionKey = UniqueKey();
+
+    Widget buildFrame(MainAxisAlignment? alignment) {
+      return MaterialApp(
+        home: Scaffold(
+          body: AlertDialog(
+            content: const SizedBox(width: 800),
+            actionsAlignment: alignment,
+            actions: <Widget>[SizedBox(key: actionKey, width: 20, height: 20)],
+            buttonPadding: EdgeInsets.zero,
+            insetPadding: EdgeInsets.zero,
+          ),
+        ),
+      );
+    }
+
+    // Default configuration
+    await tester.pumpWidget(buildFrame(null));
+    expect(tester.getTopLeft(find.byType(AlertDialog)).dx, 0);
+    expect(tester.getTopRight(find.byType(AlertDialog)).dx, 800);
+    expect(tester.getSize(find.byType(OverflowBar)).width, 800);
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, 800 - 20);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, 800);
+
+    // All possible alginment values
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.start));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, 0);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, 20);
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.center));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, (800 - 20) / 2);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, (800 - 20) / 2 + 20);
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.end));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, 800 - 20);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, 800);
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.spaceBetween));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, 0);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, 20);
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.spaceAround));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, (800 - 20) / 2);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, (800 - 20) / 2 + 20);
+
+    await tester.pumpWidget(buildFrame(MainAxisAlignment.spaceEvenly));
+    expect(tester.getTopLeft(find.byKey(actionKey)).dx, (800 - 20) / 2);
+    expect(tester.getTopRight(find.byKey(actionKey)).dx, (800 - 20) / 2 + 20);
+  });
 }
 
 class _RestorableDialogTestWidget extends StatelessWidget {