/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 A UIView subclass that is the super class of the other demonstration views in this sample.

 */

import UIKit

extension CGContext {

    func savingGState<Result>(_ body: () throws -> Result) rethrows -> Result {

        self.saveGState()

        defer {

            self.restoreGState()

        }

        return try body()

    }

}

class QuartzView: UIView {

    // center and optionally scale the drawing

    func centerDrawing(inContext: CGContext,  drawingExtent: CGRect, scaleToFit: Bool = false) {

        let xScale = bounds.width / drawingExtent.width

        let yScale = bounds.height / drawingExtent.height

        let doScale = scaleToFit ? min(xScale, yScale) : 1.0

        let xExtra = bounds.width - drawingExtent.width*doScale

        let yExtra = bounds.height - drawingExtent.height*doScale

        inContext.translateBy(x: xExtra/2, y: yExtra/2)

        inContext.scaleBy(x: doScale, y: doScale)

    }

    // As a matter of convinience we'll do all of our drawing here in subclasses of QuartzView.

    func drawInContext(_ ctx: CGContext) {

        // Default is to do nothing.

    }

    override func draw(_ rect: CGRect) {

        drawInContext( UIGraphicsGetCurrentContext()! )

    }

}