fix: [#3073] graphics system allows parents without transforms

closes #3073

CHANGELOG.md

@@ -26,6 +26,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed issue where `ex.SpriteFont` did not respect scale when measuring text
 - Fixed issue where negative transforms would cause collision issues because polygon winding would change.
 - Fixed issue where removing and re-adding an actor would cause subsequent children added not to function properly with regards to their parent/child transforms
+- Fixed issue where `ex.GraphicsSystem` would crash if a parent entity did not have a `ex.TransformComponent`
 
 ### Updates
 

src/engine/Graphics/GraphicsSystem.ts

@@ -255,16 +255,15 @@ export class GraphicsSystem extends System {
     for (const ancestor of ancestors) {
       const transform = ancestor?.get(TransformComponent);
       const optionalBody = ancestor?.get(BodyComponent);
-      let tx = transform.get();
-      if (optionalBody) {
-        if (this._engine.fixedUpdateFps && optionalBody.__oldTransformCaptured && optionalBody.enableFixedUpdateInterpolate) {
-          // Interpolate graphics if needed
-          const blend = this._engine.currentFrameLagMs / (1000 / this._engine.fixedUpdateFps);
-          tx = blendTransform(optionalBody.oldTransform, transform.get(), blend, this._targetInterpolationTransform);
-        }
-      }
-
       if (transform) {
+        let tx = transform.get();
+        if (optionalBody) {
+          if (this._engine.fixedUpdateFps && optionalBody.__oldTransformCaptured && optionalBody.enableFixedUpdateInterpolate) {
+            // Interpolate graphics if needed
+            const blend = this._engine.currentFrameLagMs / (1000 / this._engine.fixedUpdateFps);
+            tx = blendTransform(optionalBody.oldTransform, transform.get(), blend, this._targetInterpolationTransform);
+          }
+        }
         this._graphicsContext.z = transform.globalZ;
         this._graphicsContext.translate(tx.pos.x, tx.pos.y);
         this._graphicsContext.scale(tx.scale.x, tx.scale.y);

src/spec/GraphicsSystemSpec.ts

@@ -396,4 +396,25 @@ describe('A Graphics ECS System', () => {
     engine.graphicsContext.flush();
     await expectAsync(engine.canvas).toEqualImage('src/spec/images/GraphicsSystemSpec/sword-flip-both-offset.png');
   });
+
+  it('can add graphics+transform to a parent without a transform', () => {
+    const world = engine.currentScene.world;
+    const sut = new ex.GraphicsSystem(world);
+    engine.currentScene.camera.update(engine, 1);
+    engine.currentScene._initialize(engine);
+    engine.screen.setCurrentCamera(engine.currentScene.camera);
+    sut.initialize(world, engine.currentScene);
+    sut.preupdate();
+
+    const parent = new ex.Entity();
+    const child = new ex.Entity();
+    child.addComponent(new ex.TransformComponent());
+    child.addComponent(new ex.GraphicsComponent());
+    parent.addChild(child);
+
+    sut.query.checkAndAdd(parent);
+    sut.query.checkAndAdd(child);
+
+    expect(() => sut.update(1)).not.toThrow();
+  });
 });