Coalesce background Root notifications without delaying input updates

src/lib/canvas-bindings/frame-queue.ts

@@ -1,3 +1,4 @@
+import type {ExternalSource} from './selectors.ts';
 /** Presentation invalidations only. Commands, history and network work never wait here. */
 export type FrameClock={request(callback:()=>void):unknown;cancel(handle:unknown):void};
 export function createFrameQueue<K>(clock:FrameClock,publish:(dirty:ReadonlySet<K>)=>void){
@@ -9,3 +10,13 @@ export function createFrameQueue<K>(clock:FrameClock,publish:(dirty:ReadonlySet<
   dispose(){if(disposed)return;disposed=true;if(scheduled)clock.cancel(scheduled.handle);scheduled=undefined;dirty.clear();},
  });
 }
+
+/** Coalesce presentation notifications; immediate invalidations flush pending work synchronously. */
+export function createFrameSource<S>(source:{getSnapshot():S;subscribe(notify:(immediate?:boolean)=>void):()=>void},clock:FrameClock):ExternalSource<S>{
+ return Object.freeze({getSnapshot:()=>source.getSnapshot(),subscribe(notify:()=>void){
+  const queue=createFrameQueue<number>(clock,()=>notify());
+  let stop:()=>void;
+  try{stop=source.subscribe(immediate=>{queue.invalidate([0]);if(immediate)queue.flush();});}catch(error){queue.dispose();throw error;}
+  return()=>{try{stop();}finally{queue.dispose();}};
+ }});
+}