Reorganize existing app files into macOS folder

- Add an iOS target

Metaballs-macOS/ViewController.swift

@@ -0,0 +1,108 @@
+//
+//  ViewController.swift
+//  Metaballs
+//
+//  Created by Eryn Wells on 7/30/17.
+//  Copyright © 2017 Eryn Wells. All rights reserved.
+//
+
+import Cocoa
+import MetalKit
+
+class ViewController: NSViewController, RendererDelegate {
+    private static func defaultParameters() -> Parameters {
+        var p = Parameters()
+        let defaults = UserDefaults.standard
+        let style = defaults.colorStyle ?? .gradient2Horizontal
+        p.colorStyle = style
+        let color0 = defaults.color0 ?? Float4(0.50, 0.79, 1, 1)
+        p.color0 = color0
+        let color1 = defaults.color1 ?? Float4(0.88, 0.50, 1, 1)
+        p.color1 = color1
+        return p
+    }
+
+    internal var field: Field {
+        didSet {
+            field.size = Size(size: metalView.drawableSize)
+        }
+    }
+
+    private var renderer: Renderer!
+
+    internal var metalView: MTKView {
+        return self.view as! MTKView
+    }
+
+    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
+        let params = ViewController.defaultParameters()
+        field = Field(parameters: params)
+        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
+    }
+
+    required init?(coder: NSCoder) {
+        let params = ViewController.defaultParameters()
+        field = Field(parameters: params)
+        super.init(coder: coder)
+    }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        do {
+            renderer = try Renderer(delegate: self)
+        } catch let e {
+            print("\(e)")
+            view = newErrorView()
+            return
+        }
+
+        metalView.delegate = renderer
+    }
+
+    override func viewWillAppear() {
+        super.viewWillAppear()
+        renderer.mtkView(metalView, drawableSizeWillChange: metalView.drawableSize)
+        for _ in 1...10 {
+            addBallWithRandomRadius()
+        }
+    }
+
+    override func mouseDown(with event: NSEvent) {
+        addBallWithRandomRadius()
+    }
+
+    override func rightMouseDown(with event: NSEvent) {
+        field.clear()
+        for _ in 1...10 {
+            addBallWithRandomRadius()
+        }
+    }
+
+    // MARK: - Private
+
+    private func newErrorView() -> NSView {
+        let view = NSView()
+        view.layer?.backgroundColor = NSColor.red.cgColor
+        return view
+    }
+
+    private func addBallWithRandomRadius() {
+        let base = UInt32(view.bounds.width * 0.05)
+        let variance = UInt32(base * 2)
+        let r = Float(base + arc4random_uniform(variance))
+        field.add(ballWithRadius: r)
+    }
+
+    // MARK: - RendererDelegate
+
+    var renderSize: Size {
+        get {
+            return field.size
+        }
+        set {
+            field.size = newValue
+        }
+    }
+}
+