refactor(frontend): scripts -> utility

packages/frontend/src/utility/idle-render.ts

@@ -0,0 +1,60 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+const requestIdleCallback: typeof globalThis.requestIdleCallback = globalThis.requestIdleCallback ?? ((callback) => {
+	const start = performance.now();
+	const timeoutId = setTimeout(() => {
+		callback({
+			didTimeout: false, // polyfill でタイムアウト発火することはない
+			timeRemaining() {
+				const diff = performance.now() - start;
+				return Math.max(0, 50 - diff); // <https://www.w3.org/TR/requestidlecallback/#idle-periods>
+			},
+		});
+	});
+	return timeoutId;
+});
+const cancelIdleCallback: typeof globalThis.cancelIdleCallback = globalThis.cancelIdleCallback ?? ((timeoutId) => {
+	clearTimeout(timeoutId);
+});
+
+class IdlingRenderScheduler {
+	#renderers: Set<FrameRequestCallback>;
+	#rafId: number;
+	#ricId: number;
+
+	constructor() {
+		this.#renderers = new Set();
+		this.#rafId = 0;
+		this.#ricId = requestIdleCallback((deadline) => this.#schedule(deadline));
+	}
+
+	#schedule(deadline: IdleDeadline): void {
+		if (deadline.timeRemaining()) {
+			this.#rafId = requestAnimationFrame((time) => {
+				for (const renderer of this.#renderers) {
+					renderer(time);
+				}
+			});
+		}
+		this.#ricId = requestIdleCallback((arg) => this.#schedule(arg));
+	}
+
+	add(renderer: FrameRequestCallback): void {
+		this.#renderers.add(renderer);
+	}
+
+	delete(renderer: FrameRequestCallback): void {
+		this.#renderers.delete(renderer);
+	}
+
+	dispose(): void {
+		this.#renderers.clear();
+		cancelAnimationFrame(this.#rafId);
+		cancelIdleCallback(this.#ricId);
+	}
+}
+
+export const defaultIdlingRenderScheduler = new IdlingRenderScheduler();