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.

If you are targeting macOS 14 then cgPath is already part of the NSBezierPath API - https://developer.apple.com/videos/play/wwdc2023/10054/?time=676

If you are targeting macOS 14 then cgPath is already part of the NSBezierPath API - https://developer.apple.com/videos/play/wwdc2023/10054/?time=676

LOL, do you mean "finally"? It is great that it's been added, but this would have been a logical thing to have had for a long time now. Thanks for pointing that out though, as there are new elements in the case that are not handled by this gist that the new built-in probably does.

If you are targeting macOS 14 then cgPath is already part of the NSBezierPath API - https://developer.apple.com/videos/play/wwdc2023/10054/?time=676

LOL, do you mean "finally"? It is great that it's been added, but this would have been a logical thing to have had for a long time now. Thanks for pointing that out though, as there are new elements in the case that are not handled by this gist that the new built-in probably does.

Even though I did not mean "finally" but I share your view. It's sad to see how appkit is still years behind uikit but on the other hand I'm happy that there is at least some work is going on improving appkit API.

If you are targeting macOS 14 then cgPath is already part of the NSBezierPath API - https://developer.apple.com/videos/play/wwdc2023/10054/?time=676

Nice catch! What a time to be alive 😃