louisdh/bezierpath-length

//
//  PathElement.swift
//  BezierPathLength
//
//  Partially based on: https://gist.github.com/zwaldowski/e6aa7f3f81303a688ad4
//
//  Created by Louis D'hauwe on 18/11/2016.
//  Copyright © 2016 Silver Fox. All rights reserved.
//

import Foundation
import CoreGraphics

/// Swifty version of `CGPathElement` & `CGPathElementType`
enum PathElement {

    /// The path element that starts a new subpath. The element holds a single point for the destination.
    case move(to: CGPoint)

    /// The path element that adds a line from the current point to a new point. The element holds a single point for the destination.
    case addLine(to: CGPoint)

    /// The path element that adds a quadratic curve from the current point to the specified point. The element holds a control point and a destination point.
    case addQuadCurve(CGPoint, to: CGPoint)

    /// The path element that adds a cubic curve from the current point to the specified point. The element holds two control points and a destination point.
    case addCurve(CGPoint, CGPoint, to: CGPoint)

    /// The path element that closes and completes a subpath. The element does not contain any points.
    case closeSubpath

    init(element: CGPathElement) {
        switch element.type {
        case .moveToPoint:
            self = .move(to: element.points[0])
        case .addLineToPoint:
            self = .addLine(to: element.points[0])
        case .addQuadCurveToPoint:
            self = .addQuadCurve(element.points[0], to: element.points[1])
        case .addCurveToPoint:
            self = .addCurve(element.points[0], element.points[1], to: element.points[2])
        case .closeSubpath:
            self = .closeSubpath
        }
    }
}

extension CGPath {

    typealias PathApplier = @convention(block) (UnsafePointer<CGPathElement>) -> Void

    func apply(with applier: PathApplier) {

        let callback: @convention(c) (UnsafeMutableRawPointer, UnsafePointer<CGPathElement>) -> Void = { (info, element) in

            let block = unsafeBitCast(info, to: PathApplier.self)
            block(element)

        }

        self.apply(info: unsafeBitCast(applier, to: UnsafeMutableRawPointer.self), function: unsafeBitCast(callback, to: CGPathApplierFunction.self))
    }

    var elements: [PathElement] {
        var pathElements = [PathElement]()

        apply { (element) in

            let pathElement = PathElement(element: element.pointee)
            pathElements.append(pathElement)

        }

        return pathElements
    }

}