Method retrieve

packages/melonjs/src/physics/broadphase/quadtree.ts:436–481

* Return all objects that could collide with the given object. * * **Re-entrancy contract:** when called with no explicit `result` * argument, this method reuses a single root-level scratch array to * avoid per-frame allocations. The returned reference is therefore * **not safe to retain**

(
		item: QuadTreeItem,
		fn?: QuadTreeSortFn,
		result?: QuadTreeItem[],
	)

	 * @returns array with all detected objects
	 */
	retrieve(
		item: QuadTreeItem,
		fn?: QuadTreeSortFn,
		result?: QuadTreeItem[],
	): QuadTreeItem[] {
		// Reuse the root's scratch array across calls. Pointer events
		// fire on every mouse move and each one used to allocate a
		// fresh `[]`; resetting the existing array's length to 0 is
		// allocation-free. See the JSDoc above for the re-entrancy
		// contract that this optimization implies.
		const isRoot = typeof result === "undefined";
		let out: QuadTreeItem[];
		if (isRoot) {
			out = this._retrieveScratch!;
			out.length = 0;
		} else {
			out = result;
		}

		// add objects at this level
		const objects = this.objects;
		for (let i = 0, len = objects.length; i < len; i++) {
			out.push(objects[i]);
		}

		//if we have subnodes ...
		if (this.nodes.length > 0) {
			const index = this.getIndex(item);

			//if rect fits into a subnode ..
			if (index !== -1) {
				this.nodes[index].retrieve(item, undefined, out);
			} else {
				//if rect does not fit into a subnode, check it against all subnodes
				for (let i = 0; i < this.nodes.length; i++) {
					this.nodes[i].retrieve(item, undefined, out);
				}
			}
		}

		if (isRoot && typeof fn === "function") {
			out.sort(fn);
		}

		return out;
	}

	/**
	 * Remove the given item from the quadtree.