gistfile1.swift

//
//  UIBezierPath+Ring.swift
//  WheelBase
//
//  Created by Oliver Drobnik on 13.07.15.
//  Copyright (c) 2015 Cocoanetics. All rights reserved.
//

import Foundation
import UIKit
import Darwin

extension UIBezierPath
{
	convenience init(ringSegmentWithCenter center: CGPoint, innerRadius: CGFloat, outerRadius: CGFloat, startAngle: CGFloat, endAngle: CGFloat)
	{
		// helper function to determine a location
		func _positionAtAngle(center: CGPoint, angle: CGFloat, radius: CGFloat) -> CGPoint
		{
			var dx = radius * sin(angle)
			var dy = radius * cos(angle)
			
			return CGPoint(x: center.x + dx, y: center.y - dy)
		}

		self.init()
		
		let ringWidth = outerRadius - innerRadius;
		
		// addArc has angles rotated 90 degrees CCW
		let startArcAngle = startAngle - CGFloat(M_PI_2)
		let endArcAngle = endAngle - CGFloat(M_PI_2)
		
		// start cap
		let middleRadius = (outerRadius + innerRadius)/2.0;
		let middleStartPoint = _positionAtAngle(center, startAngle, middleRadius)
		self.addArcWithCenter(middleStartPoint, radius: ringWidth/2.0, startAngle: startArcAngle + CGFloat(M_PI), endAngle: startArcAngle, clockwise: true)
		
		// outer arc
		self.addArcWithCenter(center, radius: outerRadius, startAngle: startArcAngle, endAngle: endArcAngle, clockwise: true)
		
		// end cap
		let middleEndPoint = _positionAtAngle(center, endAngle, middleRadius)
		self.addArcWithCenter(middleEndPoint, radius: ringWidth/2.0, startAngle: endArcAngle, endAngle: endAngle+CGFloat(M_PI_2), clockwise: true)
		
		// inner arc
		self.addArcWithCenter(center, radius: innerRadius, startAngle: endArcAngle, endAngle: startArcAngle, clockwise: false)
		
		closePath()
	}
}