Cleanup ReactNativeAppBuilder and ReactNativeWin32App

This PR simplifies and scopes down the API for ReactNativeAppBuilder and
ReactNativeWin32App.

Closes microsoft#13946

packages/sample-app-fabric/windows/SampleAppFabric/SampleAppFabric.cpp

@@ -8,6 +8,7 @@
 
 #include "NativeModules.h"
 
+// A PackageProvider containing any turbo modules you define within this app project
 struct CompReactPackageProvider
     : winrt::implements<CompReactPackageProvider, winrt::Microsoft::ReactNative::IReactPackageProvider> {
  public: // IReactPackageProvider
@@ -16,65 +17,66 @@ struct CompReactPackageProvider
   }
 };
 
-// Global Variables:
-constexpr PCWSTR windowTitle = L"sample_app_fabric";
-constexpr PCWSTR mainComponentName = L"sample_app_fabric";
-
+// The entry point of the Win32 application
 _Use_decl_annotations_ int CALLBACK WinMain(HINSTANCE instance, HINSTANCE, PSTR /* commandLine */, int showCmd) {
-  // Initialize WinRT.
+  // Initialize WinRT
   winrt::init_apartment(winrt::apartment_type::single_threaded);
 
   // Enable per monitor DPI scaling
   SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
 
-  // Create a top-level window.
-  auto window = winrt::Microsoft::UI::Windowing::AppWindow::Create();
-  window.Title(windowTitle);
-  window.Resize({1000, 1000});
-  window.Show();
-
+  // Find the path hosting the app exe file
   WCHAR appDirectory[MAX_PATH];
   GetModuleFileNameW(NULL, appDirectory, MAX_PATH);
   PathCchRemoveFileSpec(appDirectory, MAX_PATH);
 
-  // DebugBundlePath is used when loading from a bundle server such as metro. If this parameter
-  // is not provided fallback to a combination of JavaScriptBundleFile and BundleRootPath
-  auto reactInstanceSettingsBuilder {
-    winrt::Microsoft::ReactNative::ReactInstanceSettingsBuilder()
-        .DebugBundlePath(L"index")
-        .JavaScriptBundleFile(L"index.windows")
-        .BundleRootPath(std::wstring(L"file://").append(appDirectory).append(L"\\Bundle\\").c_str())
+  // Create a ReactNativeWin32App with the ReactNativeAppBuilder
+  auto reactNativeWin32App{winrt::Microsoft::ReactNative::ReactNativeAppBuilder().Build()};
+
+  // Configure the initial InstanceSettings for the app's ReactNativeHost
+  auto settings{reactNativeWin32App.ReactNativeHost().InstanceSettings()};
+  // Register any autolinked native modules
+  RegisterAutolinkedNativeModulePackages(settings.PackageProviders());
+  // Register any native modules defined within this app project
+  settings.PackageProviders().Append(winrt::make<CompReactPackageProvider>());
+
 #if BUNDLE
-        .UseFastRefresh(false)
+  // Load the JS bundle from a file (not Metro):
+  // Set the path (on disk) where the .bundle file is located
+  settings.BundleRootPath(std::wstring(L"file://").append(appDirectory).append(L"\\Bundle\\").c_str());
+  // Set the name of the bundle file (without the .bundle extension)
+  settings.JavaScriptBundleFile(L"index.windows");
+  // Disable hot reload
+  settings.UseFastRefresh(false);
 #else
-        .UseFastRefresh(true)
+  // Load the JS bundle from Metro
+  settings.JavaScriptBundleFile(L"index");
+  // Enable hot reload
+  settings.UseFastRefresh(true);
 #endif
 #if _DEBUG
-        .UseDirectDebugger(true)
-        .UseDeveloperSupport(true)
+  // For Debug builds
+  // Enable Direct Debugging of JS
+  settings.UseDirectDebugger(true);
+  // Enable the Developer Menu
+  settings.UseDeveloperSupport(true);
 #else
-        .UseDirectDebugger(false)
-        .UseDeveloperSupport(false)
+  // For Release builds:
+  // Disable Direct Debugging of JS
+  settings.UseDirectDebugger(false);
+  // Disable the Developer Menu
+  settings.UseDeveloperSupport(false);
 #endif
-  };
-
-  auto packageProviders{winrt::single_threaded_vector<winrt::Microsoft::ReactNative::IReactPackageProvider>()};
-
-  RegisterAutolinkedNativeModulePackages(packageProviders);
-  packageProviders.Append(winrt::make<CompReactPackageProvider>());
-
-  winrt::Microsoft::ReactNative::ReactViewOptions viewOptions;
-  viewOptions.ComponentName(mainComponentName);
 
-  // Initialize and Manage the ReactNativeHost
-  auto reactNativeAppBuilder{winrt::Microsoft::ReactNative::ReactNativeAppBuilder()
-                                 .AddPackageProviders(packageProviders)
-                                 .SetReactInstanceSettings(reactInstanceSettingsBuilder.ReactInstanceSettings())
-                                 .SetAppWindow(window)
-                                 .SetReactViewOptions(viewOptions)};
+  // Get the AppWindow so we can configure its initial title and size
+  auto appWindow{reactNativeWin32App.AppWindow()};
+  appWindow.Title(L"sample_app_fabric");
+  appWindow.Resize({1000, 1000});
 
-  // Start the react-native instance by creating a javascript runtime and load the bundle.
-  auto reactNativeWin32App{reactNativeAppBuilder.Build()};
+  // Get the ReactViewOptions so we can set the initial RN component to load
+  auto viewOptions{reactNativeWin32App.ReactViewOptions()};
+  viewOptions.ComponentName(L"sample_app_fabric");
 
+  // Start the app
   reactNativeWin32App.Start();
 }