Initial implementation of channel overscroll navigation

submodules/ComponentFlow/Source/Components/Text.swift

@@ -0,0 +1,101 @@
+import Foundation
+import UIKit
+
+public final class Text: Component {
+    private final class MeasureState: Equatable {
+        let attributedText: NSAttributedString
+        let availableSize: CGSize
+        let size: CGSize
+        
+        init(attributedText: NSAttributedString, availableSize: CGSize, size: CGSize) {
+            self.attributedText = attributedText
+            self.availableSize = availableSize
+            self.size = size
+        }
+
+        static func ==(lhs: MeasureState, rhs: MeasureState) -> Bool {
+            if !lhs.attributedText.isEqual(rhs.attributedText) {
+                return false
+            }
+            if lhs.availableSize != rhs.availableSize {
+                return false
+            }
+            if lhs.size != rhs.size {
+                return false
+            }
+            return true
+        }
+    }
+    
+    public final class View: UIView {
+        private var measureState: MeasureState?
+
+        func update(component: Text, availableSize: CGSize) -> CGSize {
+            let attributedText = NSAttributedString(string: component.text, attributes: [
+                NSAttributedString.Key.font: component.font,
+                NSAttributedString.Key.foregroundColor: component.color
+            ])
+            
+            if let measureState = self.measureState {
+                if measureState.attributedText.isEqual(to: attributedText) && measureState.availableSize == availableSize {
+                    return measureState.size
+                }
+            }
+            
+            var boundingRect = attributedText.boundingRect(with: availableSize, options: .usesLineFragmentOrigin, context: nil)
+            boundingRect.size.width = ceil(boundingRect.size.width)
+            boundingRect.size.height = ceil(boundingRect.size.height)
+
+            let measureState = MeasureState(attributedText: attributedText, availableSize: availableSize, size: boundingRect.size)
+            if #available(iOS 10.0, *) {
+                let renderer = UIGraphicsImageRenderer(bounds: CGRect(origin: CGPoint(), size: measureState.size))
+                let image = renderer.image { context in
+                    UIGraphicsPushContext(context.cgContext)
+                    measureState.attributedText.draw(at: CGPoint())
+                    UIGraphicsPopContext()
+                }
+                self.layer.contents = image.cgImage
+            } else {
+                UIGraphicsBeginImageContextWithOptions(measureState.size, false, 0.0)
+                measureState.attributedText.draw(at: CGPoint())
+                self.layer.contents = UIGraphicsGetImageFromCurrentImageContext()?.cgImage
+                UIGraphicsEndImageContext()
+            }
+
+            self.measureState = measureState
+            
+            return boundingRect.size
+        }
+    }
+    
+    public let text: String
+    public let font: UIFont
+    public let color: UIColor
+    
+    public init(text: String, font: UIFont, color: UIColor) {
+        self.text = text
+        self.font = font
+        self.color = color
+    }
+
+    public static func ==(lhs: Text, rhs: Text) -> Bool {
+        if lhs.text != rhs.text {
+            return false
+        }
+        if !lhs.font.isEqual(rhs.font) {
+            return false
+        }
+        if !lhs.color.isEqual(rhs.color) {
+            return false
+        }
+        return true
+    }
+    
+    public func makeView() -> View {
+        return View()
+    }
+    
+    public func update(view: View, availableSize: CGSize, transition: Transition) -> CGSize {
+        return view.update(component: self, availableSize: availableSize)
+    }
+}