Archive commit

src/ts/client/gameLoop.ts

@@ -0,0 +1,89 @@
+export interface Game {
+	fps: number;
+	load(): any;
+	init(): void;
+	update(delta: number, now: number, last: number): void;
+	draw(): void;
+}
+
+export interface GameLoop {
+	started: Promise<void>;
+	cancel(): void;
+}
+
+let gameLoop: GameLoop | undefined = undefined;
+
+export function startGameLoop(game: Game, onError = (e: Error) => console.error(e)): GameLoop {
+	let handle: any;
+	let backup: any;
+	let cancelled = false;
+
+	let last = Math.round(performance.now());
+	let lastFps = last;
+	let frames = 0;
+	let fps = 0;
+
+	function step(now: number, draw: boolean) {
+		if (draw) {
+			handle = requestAnimationFrame(onFrame);
+		}
+
+		frames++;
+
+		if ((now - lastFps) > 1000) {
+			fps = frames * 1000 / (now - lastFps);
+			frames = 0;
+			lastFps = now;
+		}
+
+		try {
+			game.fps = fps;
+			game.update((now - last) / 1000, now, last);
+
+			if (draw) {
+				game.draw();
+			}
+		} catch (e) {
+			onError(e);
+		}
+
+		last = now;
+	}
+
+	function onTimer() {
+		step(Math.round(performance.now()), false);
+		backup = setTimeout(onTimer, 1000 / 10);
+	}
+
+	function onFrame() {
+		clearTimeout(backup);
+		step(Math.round(performance.now()), true);
+		backup = setTimeout(onTimer, 1000 / 10);
+	}
+
+	function cancel() {
+		cancelAnimationFrame(handle);
+		clearTimeout(backup);
+		cancelled = true;
+	}
+
+	if (gameLoop) {
+		gameLoop.cancel();
+	}
+
+	const started = Promise.resolve()
+		.then(() => game.load())
+		.then(() => {
+			if (cancelled) {
+				throw new Error('Cancelled (loop)');
+			} else {
+				game.init();
+				handle = requestAnimationFrame(onFrame);
+				backup = setTimeout(onTimer, 1000 / 10);
+			}
+		});
+
+	gameLoop = { started, cancel };
+
+	return gameLoop;
+}