fix: Reimplement setLayoutSize to only notify once

packages/flame/lib/src/experimental/layout_component.dart

@@ -29,20 +29,30 @@ abstract class LayoutComponent extends PositionComponent {
   double? get layoutSizeX => _layoutSizeX;
   double? get layoutSizeY => _layoutSizeY;
 
-  /// Avoid using within layout logic.
-  /// Instead, use [setLayoutAxisLength], as it allows selective setting of
-  /// vector components, and subsequently selective setting of the
-  /// size components.
+  /// Sets both layout axes at the same time, and consequently, sets the [size]
+  /// in one go.
+  /// If you intend to only selectively set one axis length at a time, use
+  /// [setLayoutAxisLength].
+  ///
+  /// This is *not* equivalent to calling [setLayoutAxisLength] for both
+  /// axes. Doing so would result size listeners being called twice: once for
+  /// the x axis, and again for the y axis.
   void setLayoutSize(double? layoutSizeX, double? layoutSizeY) {
-    setLayoutAxisLength(LayoutAxis.x, layoutSizeX);
-    setLayoutAxisLength(LayoutAxis.y, layoutSizeY);
+    _layoutSizeX = layoutSizeX;
+    _layoutSizeY = layoutSizeY;
+    resetSize();
   }
 
-  /// A helper function to set the appropriate layout dimension based on
-  /// [axis]. This is needed because currently there's no other way, at the
-  /// [LayoutComponent] level, to selective set width or height without setting
-  /// both.
-  /// e.g. if [axis] is [LayoutAxis.y], then that's the y axis.
+  /// Sets the appropriate layout dimension based on [axis]. This is needed
+  /// because currently there's no other way, at the [LayoutComponent] level,
+  /// to selectively set width or height without setting both.
+  /// e.g. to set Y axis to 100, `setLayoutAxisLength(LayoutAxis.y, 100)`
+  ///
+  /// If you intend to set both axes at the same time, use [setLayoutSize]
+  ///
+  /// This is *not* equivalent to calling [setLayoutSize] with one of the axes
+  /// set to null. Doing so would actually set the axis to the intrinsic length
+  /// of that dimension.
   void setLayoutAxisLength(LayoutAxis axis, double? value) {
     // This is necessary because we cannot extend the accessor assignment of
     // NullableVector2 to trigger some extra functionality
@@ -65,8 +75,10 @@ abstract class LayoutComponent extends PositionComponent {
   /// Reset the size of this [LayoutComponent] to either the layout dimensions
   /// or the [intrinsicSize].
   void resetSize() {
-    width = _layoutSizeX ?? intrinsicSize.x;
-    height = _layoutSizeY ?? intrinsicSize.y;
+    size.setValues(
+      _layoutSizeX ?? intrinsicSize.x,
+      _layoutSizeY ?? intrinsicSize.y,
+    );
   }
 
   bool isShrinkWrappedIn(LayoutAxis axis) {

packages/flame/test/experimental/linear_layout_component_test.dart

@@ -483,6 +483,36 @@ void main() {
           expect(textBoxComponent.boxConfig.maxWidth, layoutComponent.width);
         },
       );
+      testWithFlameGame(
+        'setLayoutSize and setLayoutAxisLength each notify once',
+        (game) async {
+          final layoutComponent = ColumnComponent();
+          await game.ensureAdd(layoutComponent);
+          var setLayoutSizeCallCount = 0;
+          var setLayoutAxisLengthCallCount = 0;
+          void firstListener() {
+            setLayoutSizeCallCount += 1;
+          }
+
+          void secondListener() {
+            setLayoutAxisLengthCallCount += 1;
+          }
+
+          layoutComponent.size.addListener(firstListener);
+          layoutComponent.setLayoutSize(100, 100);
+          await game.lifecycleEventsProcessed;
+          layoutComponent.size.removeListener(firstListener);
+          expect(setLayoutSizeCallCount, 1);
+          expect(layoutComponent.size, Vector2(100, 100));
+
+          layoutComponent.size.addListener(secondListener);
+          layoutComponent.setLayoutAxisLength(LayoutAxis.x, 200);
+          await game.lifecycleEventsProcessed;
+          layoutComponent.size.removeListener(secondListener);
+          expect(setLayoutAxisLengthCallCount, 1);
+          expect(layoutComponent.size, Vector2(200, 100));
+        },
+      );
     });
   });
 }