add createCamera method to FilamentApp

thermion_dart/lib/src/filament/src/implementation/ffi_filament_app.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:thermion_dart/src/filament/src/implementation/ffi_camera.dart';
 import 'package:thermion_dart/src/filament/src/interface/scene.dart';
 import 'package:thermion_dart/src/filament/src/implementation/ffi_asset.dart';
 import 'package:thermion_dart/src/filament/src/implementation/ffi_gizmo.dart';
@@ -194,10 +195,23 @@ class FFIFilamentApp extends FilamentApp<Pointer> {
     return view;
   }
 
+  ///
+  ///
+  ///
   Future<Scene> createScene() async {
     return FFIScene(Engine_createScene(engine));
   }
 
+  ///
+  ///
+  ///
+  Future<Camera> createCamera() async {
+    return FFICamera(
+        await withPointerCallback<TCamera>(
+            (cb) => Engine_createCameraRenderThread(engine, cb)),
+        this);
+  }
+
   ///
   ///
   ///

thermion_dart/lib/src/filament/src/interface/filament_app.dart

@@ -70,6 +70,11 @@ abstract class FilamentApp<T> {
   ///
   Future<Scene> createScene();
 
+  ///
+  ///
+  ///
+  Future<Camera> createCamera();
+
   ///
   ///
   ///

thermion_dart/lib/src/viewer/src/ffi/src/thermion_viewer_ffi.dart

@@ -76,10 +76,8 @@ class ThermionViewerFFI extends ThermionViewer {
     scene = await FilamentApp.instance!.createScene() as FFIScene;
 
     await view.setScene(scene);
-    final camera = FFICamera(
-        await withPointerCallback<TCamera>(
-            (cb) => Engine_createCameraRenderThread(app.engine, cb)),
-        app);
+    final camera = await FilamentApp.instance!.createCamera() as FFICamera;
+
     _cameras.add(camera);
     await camera.setLensProjection();