fix resizing on iOS

ios/Classes/SwiftPolyvoxFilamentPlugin.swift

@@ -1,6 +1,5 @@
 import Flutter
 import UIKit
-import OpenGLES.ES3
 import GLKit
 
 public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture {
@@ -12,12 +11,12 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
     var width: Double = 0
     var height: Double = 0
   
-    var context: EAGLContext?;
-    var targetPixelBuffer: CVPixelBuffer?;
-    var textureCache: CVOpenGLESTextureCache?;
-    var texture: CVOpenGLESTexture? = nil;
-    var frameBuffer: GLuint = 0;
     
+    var targetPixelBuffer: CVPixelBuffer?;
+    // var context: EAGLContext?;
+    // var textureCache: CVOpenGLESTextureCache?;
+    // var texture: CVOpenGLESTexture? = nil;
+    // var frameBuffer: GLuint = 0;
     
     var pixelBufferAttrs = [
         kCVPixelBufferPixelFormatTypeKey: NSNumber(value: kCVPixelFormatType_32BGRA),
@@ -83,10 +82,11 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
     }
   
     @objc func doRender() {
-      if(viewer != nil && _rendering) {
+        guard _rendering == true, let textureId = self.textureId, let viewer = viewer else {
-        render(viewer, 0)
+          return
-        self.registry.textureFrameAvailable(self.textureId!)
         }
+        render(viewer, 0)
+        self.registry.textureFrameAvailable(textureId)
     }
   
     public func copyPixelBuffer() -> Unmanaged<CVPixelBuffer>? {
@@ -97,6 +97,10 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
         return Unmanaged.passRetained(targetPixelBuffer!);
     }
   
+    public func onTextureUnregistered(texture:FlutterTexture) {
+        print("Texture unregistered")
+    }
+    
     public static func register(with registrar: FlutterPluginRegistrar) {
         let _messenger = registrar.messenger();
         messenger = _messenger;
@@ -124,6 +128,8 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
   
     private func initialize(width:Int32, height:Int32) {
 
+      print("Initializing with size \(width)x\(height)")
+
       createPixelBuffer(width:Int(width), height:Int(height))
       self.textureId = self.registry.register(self)
 
@@ -142,12 +148,29 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
         unsafeBitCast(targetPixelBuffer!, to: UnsafeMutableRawPointer.self),
         UInt32(width), UInt32(height))
 
-      update_viewport_and_camera_projection(self.viewer!, Int32(width), Int32(height), 1.0);
+      update_viewport_and_camera_projection(self.viewer!, width, height, 1.0);
       
       createDisplayLink()
 
     }
   
+  private func resize(width:Int32, height:Int32) {
+    print("Resizing to size \(width)x\(height)")
+    if(self.textureId != nil) {
+      self.registry.unregisterTexture(self.textureId!)
+    }
+    createPixelBuffer(width: Int(width), height:Int(height))
+
+    create_swap_chain(
+      self.viewer,
+      unsafeBitCast(targetPixelBuffer!, to: UnsafeMutableRawPointer.self),
+      UInt32(width), UInt32(height))
+
+    update_viewport_and_camera_projection(self.viewer!, width, height, 1.0);
+
+    self.textureId = self.registry.register(self)
+  }
+  
     public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
       let methodName = call.method;
 
@@ -180,7 +203,7 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
             let numBoneAnimations = boneAnimations.count
             
             var boneAnimStructs = UnsafeMutableBufferPointer<BoneAnimation>.allocate(capacity: numBoneAnimations)
-            
+            if numBoneAnimations > 0 {
               for i in 0...numBoneAnimations - 1 {
                 let boneNames = boneAnimations[i][0] as! Array<String>
                 let meshNames = boneAnimations[i][1] as! Array<String>
@@ -212,6 +235,8 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
                   numMeshTargets: meshNames.count
                 )
               }
+            }
+            
                   
             let numFrames = args[4] as! Int
             let frameLenInMs = args[5] as! Double
@@ -345,14 +370,10 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
           result("OK")
         case "resize":
           let args = call.arguments as! Array<Double>
-            let width = Int(args[0])
+          let width = Int32(args[0])
-            let height = Int(args[1])
+          let height = Int32(args[1])
-            createPixelBuffer(width: width, height:height)
+        resize(width:width, height:height)
-            create_swap_chain(
+          result(self.textureId)
-              self.viewer, 
-              unsafeBitCast(targetPixelBuffer!, to: UnsafeMutableRawPointer.self),
-              UInt32(width), UInt32(height))
-            result("OK")
         case "rotateStart":
           let args = call.arguments as! Array<Any>
           grab_begin(self.viewer, Float(args[0] as! Double), Float(args[1] as! Double), false)