ConicGradientAnimation.swift

import SwiftUI


extension UnitPoint {
    /// Compute the unit circle coordinates rotating at the center of UnitPoint fitted inside the bounding box
    /// - Parameters:
    ///   - angle: angle of rotation vector of the coordinate
    ///   - factor: scaling factor of the unit circle
    init(angle: Angle, scaling factor: Double = 1) {
        self.init(x: (1 + factor * sin(angle.radians)) / 2, y: (1 + factor * cos(angle.radians)) / 2)
    }
}

struct ConicGradientAngleAnimatableModifier: AnimatableModifier {
    var animatableData: Double

    init(angle degrees: Double) {
        animatableData = degrees
    }

    func body(content: Content) -> some View {
        let angle = Angle.degrees(animatableData)
        content
            .foregroundStyle(
                .conicGradient(colors: [.red, .yellow, .green, .blue, .purple, .red],
                               center: .init(angle: angle, scaling: 0.7),
                               angle: angle)
            )
    }
}

struct GradientText: View {
    @State private var animationAngle = 360.0
    let text: String

    var body: some View {
        Text(text)
            .modifier(ConicGradientAngleAnimatableModifier(angle: animationAngle))
            .animation(.linear(duration: 3).repeatForever(autoreverses: false), value: animationAngle)
            .onAppear { animationAngle = 0 }
    }

    init(_ text: String) {
        self.text = text
    }
}