Quartz Inner Shadow (playground)

QuartzInnerShadow.swift

import Cocoa
import XCPlayground
import XCTest
/*
shadow.shadowColor = NSColor.blackColor().colorWithAlphaComponent(1.0)
shadow.shadowOffset = NSMakeSize(0.1, 0.1)
shadow.shadowBlurRadius = 15
*/

extension NSShadow{
    convenience init(_ color:NSColor,_ offsetX:CGFloat,_ offsetY:CGFloat,_ blurRadius:CGFloat){
        self.init()
        self.shadowColor = color
        self.shadowOffset = NSMakeSize(offsetX,offsetY)
        self.shadowBlurRadius = blurRadius
    }
}
extension NSColor{
    /**
     * EXAMPLE: :NSColor(NSColor.blackColor(),0.5)//outputs a black color with 50% transparancy
     */
    convenience init(_ color:NSColor,_ alpha:CGFloat/*0.0 - 1.0*/){
        let ciColor:CIColor = CIColor(color: color)!
        self.init(red: ciColor.red, green: ciColor.green, blue: ciColor.blue, alpha: alpha)
    }
    /**
     * EXAMPLE: NSColor.redColor().alpha(0.5)
     */
    func alpha(alpha:CGFloat)->NSColor{
        return NSColor(self,alpha)
    }
}
class FlippedView:NSView {//Organizes your view from top to bottom
    override var flipped:Bool {return true}
}
class Container:FlippedView{
    var color:NSColor = NSColor.blueColor()
    
    override var wantsDefaultClipping:Bool{return false}//avoids clipping the view
    override var wantsUpdateLayer:Bool {return true}
    init(_ width:Int = 400, _ height:Int = 400, _ color:NSColor = NSColor.blueColor() ) {
        Swift.print("Container.init()")
        self.color = color
        let frame = NSRect(x: 0, y: 0, width: width, height: height)
        super.init(frame: frame)
        self.wantsLayer = false
    }
    /**
     * NOTE: One can also use NSShadow(shadow.shadowColor!.colorWithAlphaComponent(1.0),shadow.shadowOffset.width,shadow.shadowOffset.height,shadow.shadowBlurRadius).set() instead of CGContextSetShadowWithColor
     */
    override func drawRect(dirtyRect: NSRect) {
        
        //Swift.print("drawRect()")
        //// General Declarations
        let context = NSGraphicsContext.currentContext()!.CGContext
        
        /*Draw first shapes:*/
        let path:CGMutablePathRef  = CGPathCreateMutable();
        let rectangle:CGRect = CGRectMake(10.0, 10.0,200.0, 200.0);
        let roundRectPath:CGMutablePathRef = CGPathCreateWithRoundedRect(rectangle, 20, 20, nil) as! CGMutablePathRef/* Add the roundRectangle to the roundRectPath*/
        CGPathAddPath(path, nil, roundRectPath)/*Adds the roundRectPath to the path*/
        /*draw second shape*/
        let rect:CGRect = CGRectMake(210.0, 210.0,100.0, 100.0)
        let rectPath:CGMutablePathRef = CGPathCreateWithRect(rect, nil) as! CGMutablePathRef
        CGPathAddPath(path, nil, rectPath)/*Adds the rectPath to the path*/
        /*Add,fill and draw path to the context*/
        CGContextAddPath(context,path)/* Add the path to the context*/
        CGContextSetFillColorWithColor(context,NSColor.cyanColor().CGColor)
        //CGContextDrawPath(context, CGPathDrawingMode.Fill)/*draw the path with a fill*/ //
        CGContextDrawPath(context, CGPathDrawingMode.Fill)
        /*Init the inset dropshadow scheme*/
        CGContextSaveGState(context);/*init the gState*/
        CGContextAddPath(context, path);/*add The clipping path to the context*/
        CGContextClip(context);/*The clipping ensures that the shadow is within its shape that it tries to cast an inset shadow on*/
        /*Stores data about the Shadow*/
        let shadow = NSShadow(NSColor.blackColor().alpha(1.0),0.1,0.1,15)
        let opaqueShadowColor:CGColorRef = CGColorCreateCopyWithAlpha(shadow.shadowColor!.CGColor, 1.0)!/*We need a copy of the shadow color as CGColor with alpha set to 1*/
        CGContextSetAlpha(context, CGColorGetAlpha(shadow.shadowColor!.CGColor));
        CGContextBeginTransparencyLayer(context, nil);
        CGContextSetShadowWithColor(context, shadow.shadowOffset, shadow.shadowBlurRadius, opaqueShadowColor);/*This is where the setting of the shadow happens*/
        
        CGContextSetBlendMode(context, CGBlendMode.SourceOut);/*The blend mode creates the hole in the shadow so that it appears like an inner shadow*/
        CGContextSetFillColorWithColor(context, opaqueShadowColor);
        CGContextAddPath(context, path);
        CGContextFillPath(context);
        CGContextEndTransparencyLayer(context);
        
        CGContextRestoreGState(context);/*end the gState*/
        /*end the inset dropshadow scheme*/
        /*Continue drawing regular stuff here, like stroke*/
        CGContextAddPath(context, path);/*The clipping path*/
        CGContextSetStrokeColorWithColor(context, NSColor.magentaColor().CGColor)
        CGContextSetLineWidth(context, 10)//set the stroke width!
        CGContextDrawPath(context, CGPathDrawingMode.Stroke)

    }
    /**
     * Required by super class
     */
    required init?(coder: NSCoder) {fatalError("init(coder:) has not been implemented")}
}


let container = Container()

XCPlaygroundPage.currentPage.liveView = container

Example: