fix: parent cycle problem

.prettierignore

@@ -2,4 +2,5 @@
 node_modules
 packages/react-resizable-panels/dist
 packages/react-resizable-panels-website/.cache
-packages/react-resizable-panels-website/dist
+packages/react-resizable-panels-website/dist
+packages/react-resizable-panels/src/vendor/stacking-order.ts

packages/react-resizable-panels/src/vendor/stacking-order.ts

@@ -1,5 +1,6 @@
 // Forked from NPM stacking-order@2.0.0
 // Background at https://github.com/Rich-Harris/stacking-order/issues/3
+// Background at https://github.com/Rich-Harris/stacking-order/issues/6
 
 import { assert } from "..";
 
@@ -61,7 +62,8 @@ const props =
 
 /** @param {HTMLElement} node */
 function is_flex_item(node: HTMLElement) {
-  const display = getComputedStyle(get_parent(node)).display;
+  // @ts-ignore
+  const display = getComputedStyle(get_parent(node) ?? node).display;
   return display === "flex" || display === "inline-flex";
 }
 
@@ -115,11 +117,12 @@ function get_z_index(node: HTMLElement | null) {
 }
 
 /** @param {HTMLElement} node */
-function get_ancestors(node: HTMLElement) {
+function get_ancestors(node: HTMLElement | null) {
   const ancestors = [];
 
   while (node) {
     ancestors.push(node);
+    // @ts-ignore
     node = get_parent(node);
   }
 
@@ -128,6 +131,9 @@ function get_ancestors(node: HTMLElement) {
 
 /** @param {HTMLElement} node */
 function get_parent(node: HTMLElement) {
-  // @ts-ignore
-  return node.parentNode?.host || node.parentNode;
+  const { parentNode } = node;
+  if (parentNode && parentNode instanceof ShadowRoot) {
+    return parentNode.host
+  }
+  return parentNode;
 }