Font size adjustment

App/Document Controls UI/DocumentControlViewController.swift

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+//
+//  DocumentControlViewController.swift
+//  App
+//
+//  Created by James Magahern on 9/22/20.
+//
+
+import UIKit
+
+class DocumentControlViewController: UIViewController
+{
+    let documentControlView = StackView(dimension: .vertical)
+    let fontSizeAdjustView = FontSizeAdjustView()
+    
+    static public let preferredWidth = CGFloat(200.0)
+    static public let controlHeight = CGFloat(48.0)
+    
+    convenience init() {
+        self.init(nibName: nil, bundle: nil)
+        
+        documentControlView.addArrangedSubview(fontSizeAdjustView)
+    }
+    
+    override func loadView() {
+        self.view = documentControlView
+    }
+    
+    override var preferredContentSize: CGSize {
+        get { documentControlView.sizeThatFits(CGSize(width: Self.preferredWidth, height: -1)) }
+        set {}
+    }
+}

App/Document Controls UI/FontSizeAdjustView.swift

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+//
+//  FontSizeAdjustView.swift
+//  App
+//
+//  Created by James Magahern on 9/22/20.
+//
+
+import UIKit
+
+class FontSizeAdjustView: UIView
+{
+    let decreaseSizeButton = UIButton(frame: .zero)
+    let increaseSizeButton = UIButton(frame: .zero)
+    let labelView = UILabel(frame: .zero)
+    
+    convenience init() {
+        self.init(frame: .zero)
+        
+        labelView.textColor = .secondaryLabel
+        labelView.textAlignment = .center
+        labelView.text = "100%"
+        
+        tintColor = .black
+        
+        decreaseSizeButton.setImage(UIImage(systemName: "minus"), for: .normal)
+        increaseSizeButton.setImage(UIImage(systemName: "plus"), for: .normal)
+        
+        addSubview(increaseSizeButton)
+        addSubview(decreaseSizeButton)
+        addSubview(labelView)
+    }
+    
+    override func sizeThatFits(_ size: CGSize) -> CGSize {
+        CGSize(width: size.width, height: DocumentControlViewController.controlHeight)
+    }
+    
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        
+        decreaseSizeButton.frame = CGRect(
+            x: 0.0, y: 0.0,
+            width: bounds.height,
+            height: bounds.height
+        )
+        
+        increaseSizeButton.frame = CGRect(
+            x: bounds.width - bounds.height, y: 0.0,
+            width: bounds.height,
+            height: bounds.height
+        )
+        
+        labelView.frame = CGRect(
+            x: decreaseSizeButton.frame.maxX, y: 0.0,
+            width: bounds.width - decreaseSizeButton.frame.width - increaseSizeButton.frame.width,
+            height: bounds.height
+        )
+    }
+}