Convert NSBezierPath to CGPath (Swift 5.1, Xcode 11.3 (11C29))

NSBezierPath+cgPath.swift

extension NSBezierPath {
    
    /// A `CGPath` object representing the current `NSBezierPath`.
    var cgPath: CGPath {
        let path = CGMutablePath()
        let points = UnsafeMutablePointer<NSPoint>.allocate(capacity: 3)

        if elementCount > 0 {
            var didClosePath = true

            for index in 0..<elementCount {
                let pathType = element(at: index, associatedPoints: points)

                switch pathType {
                case .moveTo:
                    path.move(to: points[0])
                case .lineTo:
                    path.addLine(to: points[0])
                    didClosePath = false
                case .curveTo:
                    path.addCurve(to: points[2], control1: points[0], control2: points[1])
                    didClosePath = false
                case .closePath:
                    path.closeSubpath()
                    didClosePath = true
                @unknown default:
                    break
                }
            }

            if !didClosePath { path.closeSubpath() }
        }

        points.deallocate()
        return path
    }
}

Pure awesomeness. Thank you.

👍

Alert, This code has a bug at line 24.

path.addCurve(to: CGPoint(x: points[0].x, y: points[0].y), control1: control1, control2: control2)

It should be

path.addCurve(to: points[2], control1: points[0], control2: points[1])

@keefo Do you have an example of a non-working path so I can check?

Thanks for this!

@juliensagot I was curious about @keefo's comment and found that Apple's docs say it is indeed (and confusingly) ordered 2, 0, 1 instead of 0, 1, 2. Check this docs page - the relevant part is the last sentence in the Discussion section:

For curve operations, the order of the points is controlPoint1 (points[0]), controlPoint2 (points[1]), endPoint (points[2]).

Hi @juliensagot

@keefo Do you have an example of a non-working path so I can check?

I use this original code to draw a circle in my project.
it gives me weird results. So, I checked the Apple doc and updated line 24. It works now in my project.

https://github.com/keefo/NeewerLite/blob/main/NeewerLite/NeewerLite/Common/ColorWheel.swift#L112
https://github.com/keefo/NeewerLite/blob/main/NeewerLite/NeewerLite/Common/NSBezierPathExtensions.swift#L28

@keefo @dceddia Thank you guys! I've updated the gist 🙏

Why do you call closeSubPath() at line 31? If you want a path that is not closed, then this causes issues.