feat: added hooks to engine step loop

Author: ColinEspinas

src/core/Engine.ts

@@ -63,6 +63,10 @@ export class Engine {
       fullscreen: true,
       container: 'body',
       framerate: null,
+      hooks: {
+        beforeStep: () => { },
+        afterStep: () => { },
+      },
       ...options,
     }
     this._container = document.querySelector(this._options.container as string) as HTMLElement
@@ -98,6 +102,18 @@ export class Engine {
    * to fix the timestep for fixed update loops (useful for physics and user interactions).
    */
   protected step(now: number): void {
+    // Call beforeStep hook
+    try {
+      if (!this.options.hooks || !this.options.hooks.beforeStep) {
+        throw new EngineError(this, 'ENGINE:FAILURE', 'No beforeStep hook given to engine.')
+      }
+      this.options.hooks.beforeStep()
+    }
+    // eslint-disable-next-line unused-imports/no-unused-vars
+    catch (_) {
+      throw new EngineError(this, 'ENGINE:FAILURE', 'Error in beforeStep hook')
+    }
+
     if (!this.rootNode) {
       throw new EngineError(this, 'ENGINE:FAILURE', 'No root node given to engine, cannot run.')
     }
@@ -118,6 +134,18 @@ export class Engine {
       system.step(this.time.delta)
     })
     this.rootNode.step(this.time.delta)
+    // Call afterStep hook
+    try {
+      if (!this.options.hooks || !this.options.hooks.afterStep) {
+        throw new EngineError(this, 'ENGINE:FAILURE', 'No afterStep hook given to engine.')
+      }
+      this.options.hooks.afterStep()
+    }
+    // eslint-disable-next-line unused-imports/no-unused-vars
+    catch (_) {
+      throw new EngineError(this, 'ENGINE:FAILURE', 'Error in afterStep hook')
+    }
+
     // Request next step
     requestAnimationFrame(this.step.bind(this))
   }

src/types/options.d.ts

@@ -32,4 +32,20 @@ export interface EngineOptions {
    * @default null
    */
   framerate?: number | null
+
+  /**
+   * Hooks are functions that are called at specific points in the engine's runtime.
+   */
+  hooks?: {
+    /**
+     * Called before the engine's step loop.
+     * @default () => { }
+     */
+    beforeStep: () => void
+    /**
+     * Called after the engine's step loop.
+     * @default () => { }
+     */
+    afterStep: () => void
+  }
 }