Boring.swift

//
//  ContentView.swift
//  Boring
//
//  Created by Ivan Cantarino on 26/02/2025.
//

import SwiftUI

struct ContentView: View {
    var body: some View {
        ZStack {
            Text("! Boring")
                .font(.system(size: 100, weight: .heavy, design: .default))
                .foregroundColor(.white)
                .stroke(color: .black, width: 3)

            Text("! Boring")
                .font(.system(size: 100, weight: .heavy, design: .default))
                .foregroundColor(.white)
                .stroke(color: .black, width: 3)
                .offset(y: -6)
        }

    }
}

extension View {
    func stroke(color: Color, width: CGFloat = 1) -> some View {
        modifier(StrokeModifier(strokeSize: width, strokeColor: color))
    }
}

struct StrokeModifier: ViewModifier {
    private let id = UUID()
    var strokeSize: CGFloat = 1
    var strokeColor: Color = .blue

    func body(content: Content) -> some View {
        if strokeSize > 0 {
            appliedStrokeBackground(content: content)
        } else {
            content
        }
    }

    private func appliedStrokeBackground(content: Content) -> some View {
        content
            .padding(strokeSize*2)
            .background(
                Rectangle()
                    .foregroundColor(strokeColor)
                    .mask(alignment: .center) {
                        mask(content: content)
                    }
            )
    }

    func mask(content: Content) -> some View {
        Canvas { context, size in
            context.addFilter(.alphaThreshold(min: 0.01))
            if let resolvedView = context.resolveSymbol(id: id) {
                context.draw(resolvedView, at: .init(x: size.width/2, y: size.height/2))
            }
        } symbols: {
            content
                .tag(id)
                .blur(radius: strokeSize)
        }
    }
}