Tools for awaiting ready -- still can't make focus() work

ts/elemwrapper.ts

@@ -1,3 +1,5 @@
+import { waitForAnimationFrame } from "./event";
+
 export class ElemWrapper {
     public elem: HTMLElement;
 
@@ -51,4 +53,10 @@ export class ElemWrapper {
     setID(id: string) {
         this.elem.id = id;
     }
-}
+
+    async waitForShadowQuerySelector(selector: string) {
+        while (this.elem.shadowRoot?.querySelector(selector) === undefined) {
+            await waitForAnimationFrame();
+        }
+    }
+}