GemPuzzle Screensaver for macOS Preview: https://imgur.com/a/s8mRh

GemPuzzleView.swift

//
//  GemPuzzleView.swift
//  GemPuzzle
//
//  Created by Christoph Walcher on 12.01.18.
//  Copyright © 2018 Christoph Walcher. All rights reserved.
//
import ScreenSaver
import Foundation

@objc(GemPuzzleView)
class GemPuzzleView: ScreenSaverView {

    static let COLUMNS = 24
    static let ROWS = 15
    var grid = [[NSImageView]]()
    var prevRow = 0
    var prevColumn = 0

    public override init?(frame: NSRect, isPreview: Bool) {
        super.init(frame: frame, isPreview: isPreview)
        self.animationTimeInterval = 0.1
    }

    required init?(coder decoder: NSCoder) {
        super.init(coder: decoder)
    }

    func screenshot() -> CGImage {
        let windows = CGWindowListCopyWindowInfo(CGWindowListOption.optionOnScreenOnly, kCGNullWindowID) as! [[String: Any]]
        let loginwindow = windows.first(where: { (element) -> Bool in
            return element[kCGWindowOwnerName as String] as! String == "loginwindow"
        })
        let loginwindowID = (loginwindow != nil) ? CGWindowID(loginwindow![kCGWindowNumber as String] as! Int) : kCGNullWindowID
        return CGWindowListCreateImage(CGDisplayBounds(self.window?.screen?.deviceDescription["NSScreenNumber"] as! CGDirectDisplayID),
                                       CGWindowListOption.optionOnScreenBelowWindow, loginwindowID, CGWindowImageOption.nominalResolution)!
    }

    override func startAnimation() {
        var image = screenshot()
        let context = CGContext(data: nil, width: Int(frame.width), height: Int(frame.height), bitsPerComponent: image.bitsPerComponent, bytesPerRow: image.bytesPerRow, space: image.colorSpace!, bitmapInfo: image.alphaInfo.rawValue)!

        context.interpolationQuality = .high
        context.draw(image, in: CGRect(x: 0, y: 0, width: Int(frame.width), height: Int(frame.height)))
        image = context.makeImage()!

        let tilesize = CGSize(width: Double(self.frame.width) / Double(GemPuzzleView.COLUMNS),
                              height: Double(self.frame.height) / Double(GemPuzzleView.ROWS))

        for row in 0..<GemPuzzleView.ROWS {
            var rowgrid = [NSImageView]()
            for column in 0..<GemPuzzleView.COLUMNS {
                let tile = image.cropping(to: CGRect(origin:
                    CGPoint.init(
                        x: tilesize.width.multiplied(by: CGFloat(column)),
                        y: tilesize.height.multiplied(by: CGFloat(row))
                    ), size: tilesize))!
                let imageView = NSImageView(frame: NSRect(origin: CGPoint.init(), size: tilesize))
                imageView.image = NSImage(cgImage: tile, size: tilesize)
                rowgrid.append(imageView)
            }
            grid.append(rowgrid)
        }
        let gridView = NSGridView(views: self.grid)
        gridView.rowSpacing = 0
        gridView.columnSpacing = 0
        gridView.frame = self.frame
        addSubview(gridView)
        super.startAnimation()
    }


    override func hasConfigureSheet() -> Bool {
        return false
    }

    override func animateOneFrame() {
        let row0 = Int(arc4random_uniform(UInt32(GemPuzzleView.ROWS)))
        let row1 = Int(arc4random_uniform(UInt32(GemPuzzleView.ROWS)))
        let column0 = Int(arc4random_uniform(UInt32(GemPuzzleView.COLUMNS)))
        let column1 = Int(arc4random_uniform(UInt32(GemPuzzleView.COLUMNS)))

        let tmp = self.grid[row0][column0].image!
        self.grid[row0][column0].image = self.grid[row1][column1].image!
        self.grid[row1][column1].image = tmp

        super.animateOneFrame()
    }
}