Fix findUsages/undo/node-lookup bugs, split Viewport and Editor, share command and inspector helpers

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/model/hierarchy.ts

@@ -1,6 +1,7 @@
 import { type Removed, removeWhere } from '../util/list';
 import type { Position } from './Properties';
 import type { SceneObject } from './SceneObject';
+import { descendantsBelow, parentChain, sumAlongChain } from './walk';
 
 /**
  * Parent/child structure of a scene. `scene.objects` stays a flat list (storage order =
@@ -19,21 +20,18 @@ export function findObject(tree: ObjectTree, id: string): SceneObject | undefine
   return tree.objects.find((o) => o.id === id);
 }
 
-export function childrenOf(tree: ObjectTree, parentId: string): SceneObject[] {
+function childrenOf(tree: ObjectTree, parentId: string): SceneObject[] {
   return tree.objects.filter((o) => o.parentId === parentId);
 }
 
+/** The parent of an object, or undefined for a top-level one (and for a dangling link). */
+function parentOf(tree: ObjectTree, object: SceneObject): SceneObject | undefined {
+  return object.parentId ? findObject(tree, object.parentId) : undefined;
+}
+
 /** All objects below `id`, depth-first, parents before children. */
 export function descendantsOf(tree: ObjectTree, id: string): SceneObject[] {
-  const result: SceneObject[] = [];
-  const visit = (parentId: string) => {
-    for (const child of childrenOf(tree, parentId)) {
-      result.push(child);
-      visit(child.id);
-    }
-  };
-  visit(id);
-  return result;
+  return descendantsBelow(id, (parentId) => childrenOf(tree, parentId), (o) => o.id);
 }
 
 /** The ids of `rootIds` and of everything below them – what group operations act on. */
@@ -54,15 +52,7 @@ export function removeSubtrees(tree: ObjectTree, rootIds: readonly string[]): Re
 
 /** An object and every parent above it, nearest first. Stops at a cycle (defensive). */
 export function chainOf(tree: ObjectTree, object: SceneObject): SceneObject[] {
-  const chain = [object];
-  const seen = new Set<string>([object.id]);
-  let parent = object.parentId ? findObject(tree, object.parentId) : undefined;
-  while (parent && !seen.has(parent.id)) {
-    chain.push(parent);
-    seen.add(parent.id);
-    parent = parent.parentId ? findObject(tree, parent.parentId) : undefined;
-  }
-  return chain;
+  return [...parentChain(object, (o) => parentOf(tree, o))];
 }
 
 /** Ids of the ancestors of `id`, nearest parent first. Empty for a top-level object. */
@@ -86,19 +76,17 @@ export function subtreeRoots(tree: ObjectTree, ids: readonly string[]): string[]
   return ids.filter((id) => !ancestorIdsOf(tree, id).some((ancestorId) => set.has(ancestorId)));
 }
 
-function sumAlongChain(tree: ObjectTree, object: SceneObject, withEditorOffset: boolean): Position {
-  const result: Position = { x: 0, y: 0, z: 0 };
-  for (const o of chainOf(tree, object)) {
-    result.x += o.position.x + (withEditorOffset ? o.editorOffset.x : 0);
-    result.y += o.position.y + (withEditorOffset ? o.editorOffset.y : 0);
-    result.z += o.position.z;
-  }
-  return result;
+function positionAlongChain(tree: ObjectTree, object: SceneObject, withEditorOffset: boolean): Position {
+  return sumAlongChain(
+    object,
+    (o) => parentOf(tree, o),
+    (o) => (withEditorOffset ? { x: o.position.x + o.editorOffset.x, y: o.position.y + o.editorOffset.y, z: o.position.z } : o.position),
+  );
 }
 
 /** Position of an object in world units (all local positions along the chain summed up). */
 export function worldPosition(tree: ObjectTree, object: SceneObject): Position {
-  return sumAlongChain(tree, object, false);
+  return positionAlongChain(tree, object, false);
 }
 
 /**
@@ -107,7 +95,7 @@ export function worldPosition(tree: ObjectTree, object: SceneObject): Position {
  * in the game, in collisions or in the graph ever sees it (they all use `worldPosition`).
  */
 export function editorPosition(tree: ObjectTree, object: SceneObject): Position {
-  return sumAlongChain(tree, object, true);
+  return positionAlongChain(tree, object, true);
 }
 
 /** The local position that puts an object at `world` under the given parent ('' = top level). */