element-ios/RiotSwiftUI/Modules/Common/Util/WaitOverlay.swift

// 
// Copyright 2021 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

/// `WaitOverlay` allows to easily add an overlay that covers the entire with an `ActivityIndicator` at the center
@available(iOS 14.0, *)
struct WaitOverlay: ViewModifier {
    // MARK: - Properties
    
    var alignment: Alignment = .center
    @Binding var isLoading: Bool
    
    // MARK: - Private
    
    @Environment(\.theme) private var theme: ThemeSwiftUI

    // MARK: - Public
    
    public func body(content: Content) -> some View
    {
        ZStack(alignment: alignment) {
            content
            if isLoading {
                ZStack {
                    Color.clear
                    ActivityIndicator()
                }
                .frame(width: .infinity, height: .infinity)
                .transition(.opacity)
                .allowsHitTesting(true)
            }
        }
        .animation(.easeIn(duration: 0.2))
    }
}

@available(iOS 14.0, *)
struct WaitView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            VStack {
                ThemableNavigationBar(title: nil, showBackButton: true, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: "Some Title", showBackButton: true, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: nil, showBackButton: false, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: "Some Title", showBackButton: false, backAction: {}, closeAction: {})
            }
            .modifier(WaitOverlay(isLoading: .constant(true)))
            VStack {
                ThemableNavigationBar(title: nil, showBackButton: true, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: "Some Title", showBackButton: true, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: nil, showBackButton: false, backAction: {}, closeAction: {})
                ThemableNavigationBar(title: "Some Title", showBackButton: false, backAction: {}, closeAction: {})
            }
            .modifier(WaitOverlay(alignment:.topLeading, isLoading:  .constant(true)))
            VStack {
                ThemableNavigationBar(title: nil, showBackButton: true, backAction: {}, closeAction: {}).theme(.dark)
                ThemableNavigationBar(title: "Some Title", showBackButton: true, backAction: {}, closeAction: {}).theme(.dark)
                ThemableNavigationBar(title: nil, showBackButton: false, backAction: {}, closeAction: {}).theme(.dark)
                ThemableNavigationBar(title: "Some Title", showBackButton: false, backAction: {}, closeAction: {}).theme(.dark)
            }
            
            .modifier(WaitOverlay(isLoading:  .constant(true))).theme(.dark)
            .preferredColorScheme(.dark)
        }
        .padding()
    }
}