use threadpool on C API

lib/filament_controller.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:ffi';
 import 'dart:io';
+import 'dart:isolate';
 import 'dart:ui' as ui;
 
 import 'package:ffi/ffi.dart';
@@ -38,11 +39,17 @@ class FilamentController {
   late FilamentViewer _viewer;
   late AssetManager _assetManager;
 
-  final TickerProvider _tickerProvider;
-  Ticker? _ticker;
   bool _rendering = false;
 
-  FilamentController(this._tickerProvider) {
+  final _port = ReceivePort();
+
+  ///
+  /// This now uses an FFI implementation.
+  /// Platform channels are only used to setup the context/texture (since this is platform-specific) and the render ticker.
+  /// All other methods directly invoke the FFI functions defined in PolyvoxFilamentApi.cpp,
+  /// which itself uses a threadpool so that calls are run on a separate thread.
+  ///
+  FilamentController() {
     _channel.setMethodCallHandler((call) async {
       throw Exception("Unknown method channel invocation ${call.method}");
     });
@@ -63,6 +70,7 @@ class FilamentController {
 
   Future setRendering(bool render) async {
     _rendering = render;
+    _channel.invokeMethod("setRendering", render);
   }
 
   void render() {
@@ -78,7 +86,13 @@ class FilamentController {
     _pixelRatio = ratio;
   }
 
-  Future createTextureViewer(int width, int height) async {
+  Future createViewer(int width, int height) async {
+    // if (_viewer.address == 0) {
+    //   throw Exception("TODO");
+    // }
+    _nativeLibrary.init_dart_api_dl(NativeApi.initializeApiDLData);
+    _nativeLibrary.register_filament_port(_port.sendPort.nativePort);
+
     size = ui.Size(width * _pixelRatio, height * _pixelRatio);
     _textureId =
         await _channel.invokeMethod("createTexture", [size.width, size.height]);
@@ -86,19 +100,15 @@ class FilamentController {
 
     var glContext =
         Pointer<Void>.fromAddress(await _channel.invokeMethod("getContext"));
-
     final loadResource = Pointer<
             NativeFunction<ResourceBuffer Function(Pointer<Char>)>>.fromAddress(
         await _channel.invokeMethod("getLoadResourceFn"));
 
-    print("got $loadResource loadResource");
     var freeResource =
         Pointer<NativeFunction<Void Function(Uint32)>>.fromAddress(
             await _channel.invokeMethod("getFreeResourceFn"));
-
     _viewer = _nativeLibrary.create_filament_viewer(
         glContext, loadResource, freeResource);
-
     // don't pass a surface to the SwapChain as we are effectively creating a headless SwapChain that will render into a RenderTarget associated with a texture
     _nativeLibrary.create_swap_chain(
         _viewer, nullptr, size.width.toInt(), size.height.toInt());
@@ -112,14 +122,8 @@ class FilamentController {
 
     _initialized.complete(true);
     _assetManager = _nativeLibrary.get_asset_manager(_viewer);
-    print("got asset maanger $_assetManager");
 
-    _ticker = _tickerProvider.createTicker((elapsed) {
-      if (_rendering) {
-        render();
-      }
-    });
-    _ticker!.start();
+    await _channel.invokeMethod("setRenderTicker", _viewer.address);
   }
 
   Future resize(int width, int height,
@@ -358,7 +362,6 @@ class FilamentController {
 
   void playAnimation(FilamentEntity asset, int index,
       {bool loop = false, bool reverse = false}) async {
-    print("Playing animation @ $index");
     _nativeLibrary.play_animation(
         _assetManager, asset, index, loop ? 1 : 0, reverse ? 1 : 0);
   }

lib/filament_widget.dart

@@ -67,7 +67,7 @@ class _FilamentWidgetState extends State<FilamentWidget> {
         print(
             "Requesting creation of Filament back-end texture/viewer for viewport size $size");
         await widget.controller
-            .createTextureViewer(size.width.toInt(), size.height.toInt());
+            .createViewer(size.width.toInt(), size.height.toInt());
         print("Filament texture/viewer created.");
         _listener!.cancel();
         _listener = null;

lib/generated_bindings.dart

@@ -19,7 +19,34 @@ class NativeLibrary {
           lookup)
       : _lookup = lookup;
 
-  /// struct to facilitate passing bone animation frame data between Dart/native.
+  int init_dart_api_dl(
+    ffi.Pointer<ffi.Void> data,
+  ) {
+    return _init_dart_api_dl(
+      data,
+    );
+  }
+
+  late final _init_dart_api_dlPtr =
+      _lookup<ffi.NativeFunction<ffi.IntPtr Function(ffi.Pointer<ffi.Void>)>>(
+          'init_dart_api_dl');
+  late final _init_dart_api_dl =
+      _init_dart_api_dlPtr.asFunction<int Function(ffi.Pointer<ffi.Void>)>();
+
+  void register_filament_port(
+    int port,
+  ) {
+    return _register_filament_port(
+      port,
+    );
+  }
+
+  late final _register_filament_portPtr =
+      _lookup<ffi.NativeFunction<ffi.Void Function(ffi.Int)>>(
+          'register_filament_port');
+  late final _register_filament_port =
+      _register_filament_portPtr.asFunction<void Function(int)>();
+
   ffi.Pointer<ffi.Void> create_filament_viewer(
     ffi.Pointer<ffi.Void> context,
     ffi.Pointer<
@@ -52,6 +79,16 @@ class NativeLibrary {
                   ResourceBuffer Function(ffi.Pointer<ffi.Char>)>>,
           ffi.Pointer<ffi.NativeFunction<ffi.Void Function(ffi.Uint32)>>)>();
 
+  renderCallback make_render_callback() {
+    return _make_render_callback();
+  }
+
+  late final _make_render_callbackPtr =
+      _lookup<ffi.NativeFunction<renderCallback Function()>>(
+          'make_render_callback');
+  late final _make_render_callback =
+      _make_render_callbackPtr.asFunction<renderCallback Function()>();
+
   void delete_filament_viewer(
     ffi.Pointer<ffi.Void> viewer,
   ) {
@@ -1122,6 +1159,8 @@ class ResourceBuffer extends ffi.Struct {
   external int id;
 }
 
+typedef renderCallback = ffi.Pointer<
+    ffi.NativeFunction<ffi.Void Function(ffi.Pointer<ffi.Void> viewer)>>;
 typedef EntityId = ffi.Int32;
 
 const int _STDINT_H = 1;