Tick source

lib/tick.ts

@@ -0,0 +1,36 @@
+import { Cancel, Source } from "./source";
+
+export type PhysicsTick = ["physics"];
+export type RenderTick = ["render", number];
+
+export function tick(fps: number): Source<PhysicsTick | RenderTick> {
+  function tickSource(): PhysicsTick;
+  function tickSource(
+    callback: (tick: PhysicsTick | RenderTick) => void
+  ): Cancel;
+  function tickSource(callback?: (tick: PhysicsTick | RenderTick) => void) {
+    if (callback) {
+      let lastPhysicsTick: number = new Date().getTime();
+
+      const physicsInterval = setInterval(() => {
+        lastPhysicsTick = new Date().getTime();
+        callback(["physics"]);
+      }, 1000 / fps);
+
+      let animationFrame = requestAnimationFrame(function animationTick() {
+        const now = new Date().getTime();
+        callback(["render", now - lastPhysicsTick]);
+        animationFrame = requestAnimationFrame(animationTick);
+      });
+
+      return () => {
+        clearInterval(physicsInterval);
+        cancelAnimationFrame(animationFrame);
+      };
+    } else {
+      return ["physics"];
+    }
+  }
+
+  return tickSource;
+}