Update the "heartbeat" workaround for promise continuations (#81)

Switch to setTimeout, and switch to always running the heartbeat while the engine is alive (the old way doesn't work correctly on Android release builds)

Author: ryantrem

Modules/@babylonjs/react-native/EngineHook.ts

@@ -71,59 +71,26 @@ export function useEngine(): Engine | undefined {
         (async () => {
             if (await BabylonModule.initialize() && !disposed)
             {
-                const engine = new NativeEngine();
-
-                // NOTE: This is a workaround for https://github.com/BabylonJS/BabylonReactNative/issues/60
-                let heartbeat: NodeJS.Timeout | null;
-                const startHeartbeat = () => {
-                    if (!heartbeat) {
-                        heartbeat = setInterval(() => {}, 10);
-                    }
-                };
-                const stopHeartbeat = () => {
-                    if (heartbeat) {
-                        clearInterval(heartbeat);
-                        heartbeat = null;
-                    }
-                }
-                startHeartbeat();
-
-                let renderLoopCount = 0;
-
-                const originalRunRenderLoop: (...args: any[]) => void = engine.runRenderLoop;
-                engine.runRenderLoop = function(...args: any[]): void {
-                    originalRunRenderLoop.apply(this, args);
-                    if (++renderLoopCount == 1) {
-                        stopHeartbeat();
-                    }
-                }
-
-                const originalStopRenderLoop: (...args: any[]) => void = engine.stopRenderLoop;
-                engine.stopRenderLoop = function(...args: any[]): void {
-                    if (--renderLoopCount == 0) {
-                        startHeartbeat();
-                    }
-                    originalStopRenderLoop.apply(this, args);
-                }
-
-                const originalDipose = engine.dispose;
-                engine.dispose = function() {
-                    originalDipose.apply(this);
-                    stopHeartbeat();
-                };
-
-                setEngine(engine);
+                setEngine(new NativeEngine());
             }
         })();
 
+        // NOTE: This is a workaround for https://github.com/BabylonJS/BabylonReactNative/issues/60
+        function heartbeat() {
+            if (!disposed) {
+                setTimeout(heartbeat, 10);
+            }
+        }
+        heartbeat();
+
         return () => {
             disposed = true;
             setEngine(engine => {
                 if (engine) {
                     DisposeEngine(engine);
                 }
                 return undefined;
-            })
+            });
         };
     }, []);