Adds back/forward buttons to page menu

App/Common UI/StackView.swift

@@ -0,0 +1,139 @@
+//
+//  StackView.swift
+//  App
+//
+//  Created by James Magahern on 9/22/20.
+//
+
+import UIKit
+
+class StackView<T: UIView>: UIView
+{
+    public enum LayoutType {
+        case intrinsicSize
+        case equalSize
+    }
+    
+    var arrangedSubviews: [T] = []
+        { didSet { setNeedsLayout() } }
+    
+    var layoutDimension: UIAxis = .vertical
+    var layoutType: LayoutType = .intrinsicSize
+    
+    convenience init(dimension: UIAxis = .vertical, layoutType: LayoutType = .intrinsicSize) {
+        self.init(frame: .zero)
+        self.layoutDimension = dimension
+        self.layoutType = layoutType
+    }
+    
+    // Convenience
+    public func addArrangedSubview(_ view: T) {
+        addSubview(view)
+        arrangedSubviews.append(view)
+        setNeedsLayout()
+    }
+    
+    public func removeArrangedSubview(_ view: T) {
+        if view.superview == self {
+            view.removeFromSuperview()
+        }
+        
+        arrangedSubviews.removeAll { $0 == view }
+        setNeedsLayout()
+    }
+    
+    public func removeAllArrangedSubviews() {
+        arrangedSubviews.forEach { $0.removeFromSuperview() }
+        arrangedSubviews.removeAll()
+        setNeedsLayout()
+    }
+    
+    override func sizeThatFits(_ containerSize: CGSize) -> CGSize {
+        var size: CGSize = .zero
+        
+        if layoutDimension == .horizontal {
+            size.height = containerSize.height
+        } else {
+            size.width = containerSize.width
+        }
+        
+        var spaceRemaining = containerSize
+        for view in arrangedSubviews {
+            let viewSize = view.sizeThatFits(spaceRemaining)
+            if layoutDimension == .horizontal {
+                size.width += viewSize.width
+                spaceRemaining.width -= viewSize.width
+            } else {
+                size.height += viewSize.height
+                spaceRemaining.height -= viewSize.height
+            }
+        }
+        
+        return size
+    }
+    
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        
+        if layoutType == .intrinsicSize {
+            layoutWithIntrinsicSize()
+        } else if layoutType == .equalSize {
+            layoutWithEqualSize()
+        } else {
+            fatalError("StackView: I don't know how to lay out this type")
+        }
+    }
+    
+    fileprivate func layoutWithIntrinsicSize() {
+        var origin: CGPoint = CGPoint(x: safeAreaInsets.left, y: safeAreaInsets.top)
+        var spaceRemaining = bounds.size
+        for view in arrangedSubviews {
+            var viewSize = view.sizeThatFits(spaceRemaining)
+            
+            var offset: CGPoint = .zero
+            if layoutDimension == .horizontal {
+                offset.x = viewSize.width
+                viewSize.height = bounds.height
+                spaceRemaining.width -= viewSize.width
+            } else {
+                offset.y = viewSize.height
+                viewSize.width = bounds.width
+                spaceRemaining.height -= viewSize.height
+            }
+            
+            view.frame = CGRect(origin: origin, size: viewSize)
+            origin.x += offset.x
+            origin.y += offset.y
+        }
+
+    }
+    
+    fileprivate func layoutWithEqualSize() {
+        let numberOfItems = arrangedSubviews.count
+        
+        let structureDimension: CGFloat = (
+            (layoutDimension == .horizontal) ? bounds.height : bounds.width
+        )
+        
+        let itemDimension: CGFloat = (
+            (layoutDimension == .horizontal) ? (bounds.width / CGFloat(numberOfItems)) : (bounds.height / CGFloat(numberOfItems))
+        )
+        
+        var origin: CGPoint = CGPoint(x: safeAreaInsets.left, y: safeAreaInsets.top)
+        for view in arrangedSubviews {
+            let size: CGSize = (
+                (layoutDimension == .horizontal)
+                    ? CGSize(width: itemDimension, height: structureDimension)
+                    : CGSize(width: structureDimension, height: itemDimension)
+            )
+            
+            view.frame = CGRect(origin: origin, size: size)
+            
+            origin = (
+                (layoutDimension == .horizontal)
+                    ? CGPoint(x: origin.x + size.width, y: origin.y)
+                    : CGPoint(x: origin.x, y: origin.y + size.height)
+            )
+        }
+    }
+}