gradient layer with angle in swift

gradient_layer_with_angle_in_swift.swift

// how to create a gradient view
let gradientLayer = CAGradientLayer()
gradientLayer.frame = view.bounds
gradientLayer.colors = [UIColor.orange.cgColor, UIColor.white.cgColor,UIColor.green.cgColor]
gradientLayer.locations = [0.0, 0.5, 1.0]
gradientLayer.apply(angle: 45.0)
view.layer.insertSublayer(gradientLayer, at: 0)


//helper extention to CAGradientLayer
extension CAGradientLayer {
    func apply(angle : Double) {
        let x: Double! = angle / 360.0
        let a = pow(sinf(Float(2.0 * Double.pi * ((x + 0.75) / 2.0))),2.0);
        let b = pow(sinf(Float(2*Double.pi*((x+0.0)/2))),2);
        let c = pow(sinf(Float(2*Double.pi*((x+0.25)/2))),2);
        let d = pow(sinf(Float(2*Double.pi*((x+0.5)/2))),2);
        
        endPoint = CGPoint(x: CGFloat(c),y: CGFloat(d))
        startPoint = CGPoint(x: CGFloat(a),y:CGFloat(b))
    }
}

Hi it would be really great if you could please share the logic behind the calculations, I am unable to understand why you did what you did, so if could you guide on the calculation bit it would be really really appreciated

The code above causes Xcode 13.4 to take around a minute to build for some reason, possibly due to the type inference / type conversion. The following simplified code instead takes around 2 seconds to build:

func apply(angle: CGFloat) {
    let x = angle / 360

    let a = pow(sin(.pi * (x + 0.75)), 2)
    let b = pow(sin(.pi * (x + 0.0)), 2)
    let c = pow(sin(.pi * (x + 0.25)), 2)
    let d = pow(sin(.pi * (x + 0.5)), 2)

    endPoint = CGPoint(x: c, y: d)
    startPoint = CGPoint(x: a, y: b)
}

@thezonie Yeah, that's great. Thanks for the update. 💕

func getPoints(from degrees: Double) -> (UnitPoint, UnitPoint) {
let x = (180 - degrees) / 360

let x0 = pow(sin(.pi * (x + 0.75)), 2)
let y0 = pow(sin(.pi * (x + 0.0)), 2)
let x1 = pow(sin(.pi * (x + 0.25)), 2)
let y1 = pow(sin(.pi * (x + 0.5)), 2)

return (.init(x: x0, y: y0), .init(x: x1, y: y1))

}

works for me when copy angle from figma