TranslucentTitleBarApp.swift

//
//  TranslucentTitleBarApp.swift
//  TranslucentTitleBar
//
//  Created by Alexander Sandberg on 20.10.22.
//

import SwiftUI

@main
struct TranslucentTitleBarApp: App {

	@NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate

	var body: some Scene {
		WindowGroup {
			ContentView()
				.toolbar {
					// Force expanded title bar
					ToolbarItem(placement: .automatic) {
						Spacer()
					}
				}
		}
		// Set title bar styles
		.windowStyle(.titleBar)
		.windowToolbarStyle(.unified(showsTitle: true))
	}
}

class AppDelegate: NSObject, NSApplicationDelegate {
	func applicationDidFinishLaunching(_ notification: Notification) {
		for window in NSApp.windows {
			// Set title bar to transparent, because can't be done in SwiftUI
			window.titlebarAppearsTransparent = true
		}
	}
}

struct ContentView: View {
	var body: some View {
		ZStack(alignment: .top) {
			ScrollView {
				VStack(spacing: 16) {
					// Add some scrollable content
					ForEach(1...10, id: \.self) { _ in
						RoundedRectangle(cornerRadius: 16, style: .continuous)
							.fill(.foreground)
							.opacity(0.9)
							.frame(width: 300, height: 100)
					}
				}
				.padding()
				.frame(maxWidth: .infinity)
			}

			// Add custom title bar view
			VisualEffectView(blendingMode: .withinWindow, material: .hudWindow)
			// Make it appear below the actual title bar
				.edgesIgnoringSafeArea(.top)
			// Restrict the size to 0 points inside the safe area
			// i.e. make it the size of the title bar safe area
				.frame(height: 0)
		}
		.background(
			// Add translucent background to window
			VisualEffectView(blendingMode: .behindWindow, material: .underWindowBackground)
				.edgesIgnoringSafeArea(.top)
		)
		.frame(minWidth: 400, maxWidth: .infinity, minHeight: 300, maxHeight: .infinity)
	}
}

struct ContentView_Previews: PreviewProvider {
	static var previews: some View {
		ContentView()
	}
}

struct VisualEffectView: NSViewRepresentable {

	var blendingMode: NSVisualEffectView.BlendingMode
	var material: NSVisualEffectView.Material

	func makeNSView(context: Context) -> NSVisualEffectView {
		let view = NSVisualEffectView()

		view.blendingMode = blendingMode
		view.isEmphasized = true
		view.material = material
		return view
	}

	func updateNSView(_ nsView: NSVisualEffectView, context: Context) {}
}