perf(Renderer): accumulate actors and volumes without concat

Sources/Rendering/Core/Renderer/index.js

@@ -13,6 +13,26 @@ function notImplemented(method) {
   return () => vtkErrorMacro(`vtkRenderer::${method} - NOT IMPLEMENTED`);
 }
 
+// Props may return an array or a single object (e.g. vtkImageSlice).
+// Append array elements individually; append other values as one element.
+function collectFromProps(props, getFromProp) {
+  const collected = [];
+  props.forEach((prop) => {
+    const items = getFromProp(prop);
+    if (Array.isArray(items)) {
+      for (let j = 0; j < items.length; j++) {
+        collected.push(items[j]);
+      }
+    } else {
+      collected.push(items);
+    }
+  });
+  return collected;
+}
+
+const getPropActors = (prop) => prop.getActors();
+const getPropVolumes = (prop) => prop.getVolumes();
+
 // ----------------------------------------------------------------------------
 // vtkRenderer methods
 // ----------------------------------------------------------------------------
@@ -138,10 +158,7 @@ function vtkRenderer(publicAPI, model) {
   };
 
   publicAPI.getActors = () => {
-    model.actors = [];
-    model.props.forEach((prop) => {
-      model.actors = model.actors.concat(prop.getActors());
-    });
+    model.actors = collectFromProps(model.props, getPropActors);
     return model.actors;
   };
   publicAPI.addActor = publicAPI.addViewProp;
@@ -160,10 +177,7 @@ function vtkRenderer(publicAPI, model) {
   };
 
   publicAPI.getVolumes = () => {
-    model.volumes = [];
-    model.props.forEach((prop) => {
-      model.volumes = model.volumes.concat(prop.getVolumes());
-    });
+    model.volumes = collectFromProps(model.props, getPropVolumes);
     return model.volumes;
   };
   publicAPI.addVolume = publicAPI.addViewProp;

Sources/Rendering/Core/Renderer/test/testPropCollection.js

@@ -0,0 +1,35 @@
+import { expect, it } from 'vitest';
+import testUtils from 'vtk.js/Sources/Testing/testUtils';
+
+import vtkActor from 'vtk.js/Sources/Rendering/Core/Actor';
+import vtkImageSlice from 'vtk.js/Sources/Rendering/Core/ImageSlice';
+import vtkRenderer from 'vtk.js/Sources/Rendering/Core/Renderer';
+import vtkVolume from 'vtk.js/Sources/Rendering/Core/Volume';
+
+it.each([
+  ['getActors', vtkActor, vtkImageSlice],
+  ['getVolumes', vtkVolume, vtkVolume],
+])('%s collects props into fresh snapshots', (method, type, singleType) => {
+  const gc = testUtils.createGarbageCollector();
+  const renderer = gc.registerResource(vtkRenderer.newInstance());
+  const first = gc.registerResource(type.newInstance());
+  const second = gc.registerResource(type.newInstance());
+  const single = gc.registerResource(singleType.newInstance());
+  const composite = { [method]: () => [first, second] };
+
+  renderer.addViewProp(composite);
+  renderer.addViewProp({ [method]: () => [] });
+  renderer.addViewProp({ [method]: () => single });
+  const snapshot = renderer[method]();
+  expect(snapshot).toEqual([first, second, single]);
+  expect(renderer[method]()).not.toBe(snapshot);
+
+  renderer.removeViewProp(composite);
+  renderer.addViewProp(first);
+  const current = renderer[method]();
+  expect(current).toEqual([single, first]);
+  expect(renderer[`${method}ByReference`]()).toBe(current);
+  expect(snapshot).toEqual([first, second, single]);
+
+  gc.releaseResources();
+});