add oddbird polyfill - not quite working

Not quite working yet.  polyfill is loaded, but positioned elements are spanning whole viewport.  Parking this for now.

client/components/Anchored.jsx

@@ -71,10 +71,14 @@ const Anchored = ({ children })=>{
 // forward ref for AnchoredTrigger
 const AnchoredTrigger = forwardRef(({ toggleVisibility, visible, children, className, ...props }, ref)=>(
 	<button
-		ref={ref}
+		ref={(el)=>{
+			// setAttribute bypasses React's style sanitization so the anchor polyfill can read it
+			el?.setAttribute('style', `anchor-name: --${props.id}`);
+			if(typeof ref === 'function') ref(el);
+			else if(ref) ref.current = el;
+		}}
 		className={`anchored-trigger${visible ? ' active' : ''} ${className}`}
 		onClick={toggleVisibility}
-		style={{ anchorName: `--${props.id}` }}   // setting anchor properties here allows greater recyclability.
 		{...props}
 	>
 		{children}
@@ -84,9 +88,12 @@ const AnchoredTrigger = forwardRef(({ toggleVisibility, visible, children, class
 // forward ref for AnchoredBox
 const AnchoredBox = forwardRef(({ visible, children, className, anchorId, ...props }, ref)=>(
 	<div
-		ref={ref}
+		ref={(el)=>{
+			el?.setAttribute('style', `position-anchor: --${anchorId}`);
+			if(typeof ref === 'function') ref(el);
+			else if(ref) ref.current = el;
+		}}
 		className={`anchored-box${visible ? ' active' : ''} ${className}`}
-		style={{ positionAnchor: `--${anchorId}` }}   // setting anchor properties here allows greater recyclability.
 		{...props}
 	>
 		{children}

client/components/anchorPositioningPolyfill.js

@@ -0,0 +1,29 @@
+import './anchorPositioningPolyfill.less';
+
+let polyfillPromise;
+
+const supportsAnchorPositioning = ()=>'anchorName' in document.documentElement.style;
+
+const afterInitialRender = ()=>new Promise((resolve)=>{
+	requestAnimationFrame(()=>{
+		requestAnimationFrame(resolve);
+	});
+});
+
+export const bootstrapAnchorPositioningPolyfill = ()=>{
+	if(supportsAnchorPositioning()) return Promise.resolve(false);
+	if(polyfillPromise) return polyfillPromise;
+
+	polyfillPromise = afterInitialRender()
+		.then(async ()=>{
+			const { default: polyfill } = await import('@oddbird/css-anchor-positioning/fn');
+			await polyfill();
+			return true;
+		})
+		.catch((error)=>{
+			polyfillPromise = undefined;
+			throw error;
+		});
+
+	return polyfillPromise;
+};

client/components/anchorPositioningPolyfill.less

@@ -0,0 +1,15 @@
+.hb-anchor-source {
+	anchor-name: var(--hb-anchor-name);
+}
+
+.hb-anchor-target {
+	position-anchor: var(--hb-position-anchor);
+}
+
+.hb-position-area {
+	position-area: var(--hb-position-area);
+}
+
+.hb-position-try-fallbacks {
+	position-try-fallbacks: var(--hb-position-try-fallbacks);
+}

client/components/dropdown/dropdown.jsx

@@ -13,7 +13,7 @@
  */
 
 import './dropdown.less';
-import React, { useEffect } from 'react';
+import React, { useEffect, useRef } from 'react';
 import _ from 'lodash';
 
 // use react context to keep track of the menu depth (menus in menus)
@@ -27,6 +27,16 @@ const Dropdown = ({ groupName, className = null, icon, children, color = null, c
 	// A menu is a submenu if depth > 0
 	const isSubMenu = depth > 0;
 
+	const wrapperRef = useRef(null);
+	const menuRef = useRef(null);
+
+	// Use setAttribute instead of the React style prop because React silently strips unknown CSS
+	// properties (like anchor-name) from inline styles in browsers that don't support them.
+	// setAttribute writes raw CSS text that the anchor positioning polyfill can read.
+	useEffect(()=>{
+		wrapperRef.current?.setAttribute('style', `anchor-name: ${anchorName}`);
+		menuRef.current?.setAttribute('style', `position-anchor: ${anchorName}`);
+	}, [anchorName]);
 
 	// hide popover with click inside iframe (not supported by light dismiss)
 	useEffect(()=>{
@@ -59,7 +69,7 @@ const Dropdown = ({ groupName, className = null, icon, children, color = null, c
 	};
 
 	return (
-		<div className={['menu-wrapper', className].join(' ')} style={{ anchorName }} role='none' >
+		<div ref={wrapperRef} className={['menu-wrapper', className].join(' ')} role='none' >
 			<button
 				id={groupName.replace(' ', '-')}
 				className={['menu-item', color].join(' ')}
@@ -73,10 +83,10 @@ const Dropdown = ({ groupName, className = null, icon, children, color = null, c
 			</button>
 			<MenuDepthContext.Provider value={depth + 1}>
 				<div
+					ref={menuRef}
 					id={menuId}
 					className='menu-list'
 					popover='auto'
-					style={{ positionAnchor: anchorName }}
 					role='menu'
 				>
 					{children}