Add effects to the congratulations screen when personalisation is disabled.

Improve the API of the EffectsView to make it more swifty.

RiotSwiftUI/Modules/Common/EffectsScene/EffectsView.swift

@@ -0,0 +1,62 @@
+// 
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import SwiftUI
+import SceneKit
+
+@available(iOS 14.0, *)
+/// A SwiftUI wrapper around `SCNView`, that unlike `SceneView` allows the
+/// scene to have a transparent background and be rendered on top of other views.
+struct EffectsView: UIViewRepresentable {
+    
+    // MARK: - Private
+    
+    @Environment(\.theme) private var theme
+    
+    // MARK: - Public
+    
+    enum EffectsType {
+        /// A confetti drop effect from the top centre of the screen.
+        case confetti
+        /// No effect will be shown.
+        case none
+    }
+    
+    /// The type of effects to be shown in the view.
+    var effectsType: EffectsType = .none
+    
+    // MARK: - Lifecycle
+    
+    func makeUIView(context: Context) -> SCNView {
+        SCNView(frame: .zero)
+    }
+    
+    func updateUIView(_ sceneView: SCNView, context: Context) {
+        sceneView.scene = makeScene()
+        sceneView.backgroundColor = .clear
+    }
+    
+    // MARK: - Private
+    
+    private func makeScene() -> EffectsScene? {
+        switch effectsType {
+        case .confetti:
+            return EffectsScene.confetti(with: theme)
+        case .none:
+            return nil
+        }
+    }
+}