Cards!

frontend/app/composables/three-scene.ts

@@ -0,0 +1,22 @@
+// Helpers to keep heavy WebGL scene setup off the page's critical path.
+
+// Runs fn once the main thread is idle (falling back to a short timeout),
+// returning a cancel handle so an early unmount never leaks a scheduled init.
+export const scheduleIdle = (fn: () => void, timeout = 1500): (() => void) => {
+  const ric = (window as any).requestIdleCallback as
+    | ((cb: () => void, opts?: { timeout: number }) => number)
+    | undefined
+  if (typeof ric === 'function') {
+    const id = ric(fn, { timeout })
+    return () => (window as any).cancelIdleCallback?.(id)
+  }
+  const id = setTimeout(fn, 200)
+  return () => clearTimeout(id)
+}
+
+// Calls cb whenever tab visibility changes, returning an unsubscribe function.
+export const onVisibility = (cb: (hidden: boolean) => void): (() => void) => {
+  const handler = () => cb(document.hidden)
+  document.addEventListener('visibilitychange', handler)
+  return () => document.removeEventListener('visibilitychange', handler)
+}