Add tick marks to timeline layout sliders

iOS/UIKit Extensions/TickMarkSlider.swift

@@ -0,0 +1,61 @@
+//
+//  TickMarkSlider.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 11/8/19.
+//  Copyright © 2019 Ranchero Software. All rights reserved.
+//
+
+import UIKit
+
+class TickMarkSlider: UISlider {
+
+	func addTickMarks() {
+
+		let numberOfGaps = Int(maximumValue) - Int(minimumValue)
+		
+		var gapLayoutGuides = [UILayoutGuide]()
+		
+		for i in 0...numberOfGaps {
+			
+			let tick = UIView()
+			tick.translatesAutoresizingMaskIntoConstraints = false
+			tick.backgroundColor = AppAssets.tickMarkColor
+			insertSubview(tick, belowSubview: self)
+
+			tick.widthAnchor.constraint(equalToConstant: 3).isActive = true
+			tick.heightAnchor.constraint(equalToConstant: 10).isActive = true
+			tick.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
+
+			if i == 0 {
+				tick.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
+			}
+			
+			if let lastGapLayoutGuild = gapLayoutGuides.last {
+				lastGapLayoutGuild.trailingAnchor.constraint(equalTo: tick.leadingAnchor).isActive = true
+			}
+			
+			if i != numberOfGaps {
+				let gapLayoutGuild = UILayoutGuide()
+				gapLayoutGuides.append(gapLayoutGuild)
+				addLayoutGuide(gapLayoutGuild)
+				tick.trailingAnchor.constraint(equalTo: gapLayoutGuild.leadingAnchor).isActive = true
+			} else {
+				tick.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
+			}
+			
+		}
+		
+		if let firstGapLayoutGuild = gapLayoutGuides.first {
+			for i in 1..<gapLayoutGuides.count {
+				gapLayoutGuides[i].widthAnchor.constraint(equalTo: firstGapLayoutGuild.widthAnchor).isActive = true
+			}
+		}
+				
+	}
+
+	override func endTracking(_ touch: UITouch?, with event: UIEvent?) {
+		value = value.rounded()
+	}
+	
+}