Don't bgfx::shutdown for debug builds since it doesn't work with fast refresh (#126)

* Don't bgfx::shutdown for debug builds since it doesn't work with fast refresh
* Update docs to include a test step for fast refresh

Author: ryantrem

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

@@ -83,7 +83,12 @@ export function useEngine(): Engine | undefined {
             if (engine) {
                 DisposeEngine(engine);
             }
-            BabylonModule.reset();
+            // Ideally we would always do a reset here as we don't want different behavior between debug and release. Unfortunately, fast refresh has some strange behavior that
+            // makes it quite difficult to get this to work correctly (e.g. it re-runs previous useEffect instances, which means it can try to use Babylon Native in a de-initialized state).
+            // TODO: https://github.com/BabylonJS/BabylonReactNative/issues/125
+            if (!__DEV__) {
+                BabylonModule.reset();
+            }
             setEngine(undefined);
         };
     }, []);

README.md

@@ -152,7 +152,8 @@ When making local changes, the following manual test steps should be performed w
 1. **View replacement** - tap the *Toggle EngineView* button twice to replace the render target view.
 1. **Engine dispose** - tap the *Toggle EngineScreen* button twice to dispose and re-instantiate the Babylon engine.
 1. **Suspend/resume** - switch to a different app and then back to the Playground and make sure it is still rendering correctly.
-1. **Dev mode reload** - in the Metro server console window, press the `R` key on the keyboard to reload the JS engine and make sure rendering restarts successfully.
+1. **Fast refresh** (debug only) - save the App.tsx file to trigger a fast refresh.
+1. **Dev mode reload** (debug only) - in the Metro server console window, press the `R` key on the keyboard to reload the JS engine and make sure rendering restarts successfully.
 1. **XR mode** - tap the *Start XR* button and make sure XR mode is working.
 1. **XR display rotation** - rotate the device 90 degrees and make sure the view rotates and renders correctly.
 1. **XR view replacement** - tap the *Toggle EngineView* button twice to replace the render target view.