/*

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

See LICENSE.txt for this sample’s licensing information

Abstract:

This view is backed by a CATiledLayer into which the PDF page is rendered into.

*/

import UIKit

class TiledPDFView: UIView {

    var pdfPage: CGPDFPage?

    var myScale: CGFloat!

    // Create a new TiledPDFView with the desired frame and scale.

    init(frame: CGRect, scale: CGFloat)

    {

        super.init(frame: frame)

        let tiledLayer = CATiledLayer(layer: self)

        /*

         levelsOfDetail and levelsOfDetailBias determine how the layer is rendered at different zoom levels. This only matters while the view is zooming, because once the the view is done zooming a new TiledPDFView is created at the correct size and scale.

         */

        tiledLayer.levelsOfDetail = 4

        tiledLayer.levelsOfDetailBias = 3

        tiledLayer.tileSize = CGSize(width: 512.0, height: 512.0)

        myScale = scale

        layer.borderColor = UIColor.lightGray.cgColor

        layer.borderWidth = 5

    }

    // The layer's class should be CATiledLayer.

    override class var layerClass: AnyClass

    {

        get {

            return CATiledLayer.self

        }

    }

    required init?(coder aDecoder: NSCoder)

    {

        print("init(coder:) not implemented")

        abort() /* as per Technical Q&A QA1561: How do I programmatically quit my iOS application?*/

    }

    // Draw the CGPDFPageRef into the layer at the correct scale.

    override func draw(_ layer: CALayer, in ctx: CGContext)

    {

        // Fill the background with white.

        ctx.setFillColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)

        ctx.fill(bounds)

        // Print a blank page and return if our page is nil.

        if ( pdfPage == nil )

        {

            print("page nil")

            return

        }

        // save the cg state

        ctx.saveGState()

        // Flip the context so that the PDF page is rendered right side up.

        ctx.translateBy(x: 0.0, y: bounds.size.height)

        ctx.scaleBy(x: 1.0, y: -1.0)

        // Scale the context so that the PDF page is rendered at the correct size for the zoom level.

        ctx.scaleBy(x: myScale, y: myScale)

        // draw the page, restore and exit

        ctx.drawPDFPage(pdfPage!)

        ctx.restoreGState()

    }

}