Supporting iOS 17 widget environment variables on previous releases

gistfile1.txt

//
//  WidgetEnvironmentBackporting.swift
//  Widget Extension
//
//  Created by Lukas Petr on 06.09.2023.
//  Copyright © 2023 Glimsoft. All rights reserved.
//

//  This solution is heavily inspired by https://developer.apple.com/forums/thread/733780?answerId=759064022#759064022
//  All credit should go to him.

import SwiftUI

struct MyWidgetShowsContainerBackgroundKey: EnvironmentKey {
    static let defaultValue: Bool = true
}

struct MyWidgetRenderingModeIsVibrant: EnvironmentKey {
    static let defaultValue: Bool = false
}

struct MyWidgetContentMargins: EnvironmentKey {
    static let defaultValue = EdgeInsets(top: 0, leading: 0, bottom: 0, trailing: 0)
}

struct MyWidgetContentMarginsAreAvailable: EnvironmentKey {
    static let defaultValue: Bool = false
}

extension EnvironmentValues {
    var myWidgetShowsContainerBackground: Bool {
        set { self[MyWidgetShowsContainerBackgroundKey.self] = newValue }
        get { self[MyWidgetShowsContainerBackgroundKey.self] }
    }
    var myWidgetRenderingModeIsVibrant: Bool {
        set { self[MyWidgetRenderingModeIsVibrant.self] = newValue }
        get { self[MyWidgetRenderingModeIsVibrant.self] }
    }
    var myWidgetContentMargins: EdgeInsets {
        set { self[MyWidgetContentMargins.self] = newValue }
        get { self[MyWidgetContentMargins.self] }
    }
    var myWidgetContentMarginsAreAvailable: Bool {
        set { self[MyWidgetContentMarginsAreAvailable.self] = newValue }
        get { self[MyWidgetContentMarginsAreAvailable.self] }
    }
}

// Magic happens here
struct WidgetEnvironmentReader<Content: View>: View {
    var content: () -> Content
    
    init(@ViewBuilder content: @escaping () -> Content) {
        self.content = content
    }
    
    var body: some View {
        if #available(iOS 17, *) {
            WidgetEnvironmentViewBuilder(content: content)
        } else {
            content()
        }
    }
}

extension WidgetEnvironmentReader {
    @available(iOS 17, *)
    struct WidgetEnvironmentViewBuilder<C: View>: View {
        @Environment(\.showsWidgetContainerBackground) var showsWidgetContainerBackground
        @Environment(\.widgetRenderingMode) var widgetRenderingMode
        @Environment(\.widgetContentMargins) var widgetContentMargins
        
        var content: () -> C
        
        init(@ViewBuilder content: @escaping () -> C) {
            self.content = content
        }
        
        var body: some View {
            content()
                .environment(\.myWidgetShowsContainerBackground, self.showsWidgetContainerBackground)
                .environment(\.myWidgetRenderingModeIsVibrant, self.widgetRenderingMode == .vibrant)
                .environment(\.myWidgetContentMargins, self.widgetContentMargins)
                .environment(\.myWidgetContentMarginsAreAvailable, true)
        }
    }
}

To use it, you can just wrap your widget entry view in the WidgetEnvironmentReader, like this:

struct TrackingWidget: Widget {
    let kind: String = "TrackingWidget"
    
    var body: some WidgetConfiguration {
        StaticConfiguration(kind: self.kind, provider: Provider()) { entry in
            WidgetEnvironmentReader {
                TrackingWidgetEntryView(entry: entry)
            }
        }
        .configurationDisplayName("Tracking Widget")
    }
}