add lifecycle listeners

ios/Classes/SwiftPolyvoxFilamentPlugin.swift

@@ -187,6 +187,24 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
             createPixelBuffer(width:Int(args[0]), height:Int(args[1]))
             createDisplayLink()
             result(self.flutterTextureId)
+        case "destroyTexture":
+            if(viewer != nil) {
+                result(FlutterError(code: "INVALID_ARGUMENTS", message: "Destroy the viewer before destroying the texture", details: nil))
+            } else {
+                
+                if(self.flutterTextureId != nil) {
+                    self.registry.unregisterTexture(self.flutterTextureId!)
+                }
+                self.flutterTextureId = nil 
+                self.pixelBuffer = nil
+            }
+        case "destroyViewer":
+            if(viewer != nil) {
+                destroy_swap_chain(viewer)
+                delete_filament_viewer(viewer)
+                viewer = nil
+            }
+            result(true)
         case "resize":
             if(viewer == nil) {
                 print("Error: cannot resize before a viewer has been created")
@@ -203,6 +221,11 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
             print("Resized to \(args[0])x\(args[1])")
             result(self.flutterTextureId);
         case "createFilamentViewer":
+            if(viewer != nil) {
+                destroy_swap_chain(viewer)
+                delete_filament_viewer(viewer)
+                viewer = nil
+            }
             let callback = make_resource_loader(loadResource, freeResource,  Unmanaged.passUnretained(self).toOpaque())
             let args = call.arguments as! [Any]
             let width = args[0] as! Int64
@@ -212,10 +235,6 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
             create_swap_chain(viewer, pixelBufferTextureId, UInt32(width), UInt32(height))
             update_viewport_and_camera_projection(viewer, Int32(args[0] as! Int64), Int32(args[1] as! Int64), 1.0)
             result(unsafeBitCast(viewer, to:Int64.self))
-        case "deleteFilamentViewer":
-            delete_filament_viewer(viewer)
-            viewer = nil
-            result(true)
         case "getAssetManager":
             let assetManager = get_asset_manager(viewer)
             result(unsafeBitCast(assetManager, to:Int64.self))

lib/filament_controller.dart

@@ -23,11 +23,8 @@ class FilamentController {
   final _textureIdController = StreamController<int?>.broadcast();
   Stream<int?> get textureId => _textureIdController.stream;
 
-  final _onInitRequestedController = StreamController.broadcast();
+  // final _viewerAvailableController = StreamController<bool>.broadcast();
-  Stream get onInitializationRequested => _onInitRequestedController.stream;
+  // Stream<bool> get viewerAvailable => _viewerAvailableController.stream;
-
-  final _initialized = Completer();
-  Future get initialized => _initialized.future;
 
   late AssetManager _assetManager;
 
@@ -45,9 +42,24 @@ class FilamentController {
     };
   }
 
+  final _initialSize = Completer<List<int>>();
+  void setInitialSize(int width, int height) {
+    _initialSize.complete([width, height]);
+  }
+
+  ///
+  /// The process for initializing the Filament layer is as follows:
+  /// 1) Create a FilamentController
+  /// 2) Insert a FilamentWidget into the rendering tree
+  /// 3) Initially, this widget will only contain an empty Container. After the first frame is rendered, the widget itself will automatically call [setInitialSize] with the width/height from its constraints
+  /// 4) Call [initialize], which will create a texture/viewer and notify the FilamentWidget that the texture is available
+  /// 5) The FilamentWidget will replace the empty Container with the Texture widget.
+  ///
   Future initialize() async {
-    _onInitRequestedController.add(true);
+    var initialSize = await _initialSize.future;
-    return _initialized.future;
+    var initialWidth = initialSize[0];
+    var initialHeight = initialSize[1];
+    await createViewer(initialWidth, initialHeight);
   }
 
   Future setRendering(bool render) async {
@@ -66,6 +78,17 @@ class FilamentController {
     _pixelRatio = ratio;
   }
 
+  Future destroyViewer() async {
+    await _channel.invokeMethod("destroyViewer");
+  }
+
+  Future destroyTexture() async {
+    await _channel.invokeMethod("destroyTexture");
+    _textureId = null;
+    _assetManager = 0;
+    _textureIdController.add(null);
+  }
+
   Future createViewer(int width, int height) async {
     size = ui.Size(width * _pixelRatio, height * _pixelRatio);
     _textureId =
@@ -90,7 +113,6 @@ class FilamentController {
     await _channel.invokeMethod("updateViewportAndCameraProjection",
         [size.width.toInt(), size.height.toInt(), 1.0]);
 
-    _initialized.complete(true);
     _assetManager = await _channel.invokeMethod("getAssetManager");
     _textureIdController.add(_textureId);
   }
@@ -438,7 +460,7 @@ class FilamentController {
         .invokeMethod("setRotation", [_assetManager, asset, rads, x, y, z]);
   }
 
-  void hide(FilamentEntity asset, String meshName) async {
+  Future hide(FilamentEntity asset, String meshName) async {
     if (await _channel
             .invokeMethod("hideMesh", [_assetManager, asset, meshName]) !=
         1) {
@@ -446,7 +468,7 @@ class FilamentController {
     }
   }
 
-  void reveal(FilamentEntity asset, String meshName) async {
+  Future reveal(FilamentEntity asset, String meshName) async {
     if (await _channel
             .invokeMethod("revealMesh", [_assetManager, asset, meshName]) !=
         1) {

lib/filament_widget.dart

@@ -4,6 +4,8 @@ import 'dart:math';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter/scheduler.dart';
+
 import 'dart:async';
 import 'filament_controller.dart';
 
@@ -56,38 +58,58 @@ class FilamentWidget extends StatefulWidget {
 }
 
 class _FilamentWidgetState extends State<FilamentWidget> {
-  StreamSubscription? _initializationListener;
   StreamSubscription? _textureIdListener;
   int? _textureId;
   bool _resizing = false;
-  bool _hasViewer = false;
+
+  late final AppLifecycleListener _listener;
+  AppLifecycleState? _lastState;
+
+  void _handleStateChange(AppLifecycleState state) async {
+    switch (state) {
+      case AppLifecycleState.detached:
+        print("Detached");
+        await widget.controller.destroyViewer();
+        await widget.controller.destroyTexture();
+        break;
+      case AppLifecycleState.hidden:
+        print("Hidden");
+        _textureId = null;
+        await widget.controller.destroyViewer();
+        await widget.controller.destroyTexture();
+        break;
+      case AppLifecycleState.inactive:
+        print("Inactive");
+        break;
+      case AppLifecycleState.paused:
+        print("Paused");
+        break;
+      case AppLifecycleState.resumed:
+        print("Resumed");
+        if (_textureId == null) {
+          var size = ((context.findRenderObject()) as RenderBox).size;
+          print("Size after resuming : $size");
+          await widget.controller
+              .createViewer(size.width.toInt(), size.height.toInt());
+        }
+        break;
+    }
+    _lastState = state;
+  }
 
   @override
   void initState() {
-    _initializationListener =
+    _listener = AppLifecycleListener(
-        widget.controller.onInitializationRequested.listen((_) {
+      onStateChange: _handleStateChange,
-      WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
+    );
-        var size = ((context.findRenderObject()) as RenderBox).size;
-        print(
-            "Requesting creation of Filament back-end texture/viewer for viewport size $size");
-        await widget.controller
-            .createViewer(size.width.toInt(), size.height.toInt());
-        setState(() {
-          _hasViewer = true;
-        });
 
-        _initializationListener!.cancel();
+    WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
-        _initializationListener = null;
+      var size = ((context.findRenderObject()) as RenderBox).size;
-
+      widget.controller.setInitialSize(size.width.toInt(), size.height.toInt());
-        WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
-          var size = ((context.findRenderObject()) as RenderBox).size;
-          widget.controller.resize(size.width.toInt(), size.height.toInt());
-          print("RESIZED IN POST FRAME CALLBACK TO $size");
-        });
-        setState(() {});
-      });
     });
+
     _textureIdListener = widget.controller.textureId.listen((int? textureId) {
+      print("Set texture ID to $textureId");
       setState(() {
         _textureId = textureId;
       });
@@ -98,15 +120,14 @@ class _FilamentWidgetState extends State<FilamentWidget> {
 
   @override
   void dispose() {
-    _initializationListener?.cancel();
     _textureIdListener?.cancel();
+    _listener.dispose();
     super.dispose();
   }
 
   @override
   Widget build(BuildContext context) {
     return LayoutBuilder(builder: ((context, constraints) {
-      print("constraints $constraints");
       if (_textureId == null) {
         return Container(color: Colors.transparent);
       }
@@ -121,10 +142,6 @@ class _FilamentWidgetState extends State<FilamentWidget> {
           width: constraints.maxWidth,
           child: ResizeObserver(
               onResized: (Size oldSize, Size newSize) async {
-                if (!_hasViewer) {
-                  return;
-                }
-                print("RESIZE OBSERVER $newSize");
                 WidgetsBinding.instance.addPostFrameCallback((_) async {
                   setState(() {
                     _resizing = true;
@@ -139,15 +156,15 @@ class _FilamentWidgetState extends State<FilamentWidget> {
                   });
                 });
               },
-              child: Platform.isLinux
+              child: _resizing
-                  ? _resizing
+                  ? Container()
-                      ? Container()
+                  : Platform.isLinux
-                      : Transform(
+                      ? Transform(
                           alignment: Alignment.center,
                           transform: Matrix4.rotationX(
                               pi), // TODO - this rotation is due to OpenGL texture coordinate working in a different space from Flutter, can we move this to the C++ side somewhere?
                           child: texture)
-                  : texture));
+                      : texture));
     }));
   }
 }