Add a DeviceInputSystem factory function (#8225)

* Add a DeviceInputSystem factory function that creates either a native DeviceInputSystem or js DeviceInputSystem

src/DeviceInput/InputDevices/deviceSourceManager.ts

@@ -81,7 +81,7 @@ export class DeviceSourceManager implements IDisposable {
         const numberOfDeviceTypes = Object.keys(DeviceType).length / 2;
         this._devices = new Array<Array<DeviceSource<DeviceType>>>(numberOfDeviceTypes);
         this._firstDevice = new Array<number>(numberOfDeviceTypes);
-        this._deviceInputSystem = new DeviceInputSystem(engine);
+        this._deviceInputSystem = DeviceInputSystem.Create(engine);
 
         this._deviceInputSystem.onDeviceConnected = (deviceType, deviceSlot) => {
             this.onBeforeDeviceConnectedObservable.notifyObservers({ deviceType, deviceSlot });

src/DeviceInput/deviceInputSystem.ts

@@ -3,6 +3,9 @@ import { IDisposable } from '../scene';
 import { Nullable } from '../types';
 import { DeviceType } from './InputDevices/deviceEnums';
 
+/** @hidden */
+declare const _native: any;
+
 /**
  * This class will take all inputs from Keyboard, Pointer, and
  * any Gamepads and provide a polling system that all devices
@@ -45,11 +48,7 @@ export class DeviceInputSystem implements IDisposable {
     private static _MAX_KEYCODES: number = 255;
     private static _MAX_POINTER_INPUTS: number = 7;
 
-    /**
-     * Default Constructor
-     * @param engine - engine to pull input element from
-     */
-    constructor(engine: Engine) {
+    private constructor(engine: Engine) {
         const inputElement = engine.getInputElement();
         if (inputElement) {
             this._elementToAttachTo = inputElement;
@@ -59,6 +58,20 @@ export class DeviceInputSystem implements IDisposable {
         }
     }
 
+    /**
+     * Creates a new DeviceInputSystem instance
+     * @param engine Engine to pull input element from
+     * @returns The new instance
+     */
+    public static Create(engine: Engine): DeviceInputSystem {
+        // If running in Babylon Native, then defer to the native input system, which has the same public contract
+        if (typeof _native.DeviceInputSystem !== 'undefined') {
+            return new _native.DeviceInputSystem(engine);
+        }
+
+        return new DeviceInputSystem(engine);
+    }
+
     // Public functions
     /**
      * Checks for current device input value, given an id and input index