[WIP] Folder tags

submodules/TelegramUI/Components/BackButtonComponent/BUILD

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+load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
+
+swift_library(
+    name = "BackButtonComponent",
+    module_name = "BackButtonComponent",
+    srcs = glob([
+        "Sources/**/*.swift",
+    ]),
+    copts = [
+        "-warnings-as-errors",
+    ],
+    deps = [
+        "//submodules/ComponentFlow",
+        "//submodules/Components/BundleIconComponent",
+        "//submodules/Display",
+    ],
+    visibility = [
+        "//visibility:public",
+    ],
+)

submodules/TelegramUI/Components/BackButtonComponent/Sources/BackButtonComponent.swift

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+import Foundation
+import UIKit
+import ComponentFlow
+import BundleIconComponent
+import Display
+
+public final class BackButtonComponent: Component {
+    public let title: String
+    public let color: UIColor
+    public let action: () -> Void
+    
+    public init(
+        title: String,
+        color: UIColor,
+        action: @escaping () -> Void
+    ) {
+        self.title = title
+        self.color = color
+        self.action = action
+    }
+    
+    public static func ==(lhs: BackButtonComponent, rhs: BackButtonComponent) -> Bool {
+        if lhs.title != rhs.title {
+            return false
+        }
+        if lhs.color != rhs.color {
+            return false
+        }
+        return true
+    }
+    
+    public final class View: HighlightTrackingButton {
+        private let arrow = ComponentView<Empty>()
+        private let title = ComponentView<Empty>()
+        
+        private var component: BackButtonComponent?
+        
+        public override init(frame: CGRect) {
+            super.init(frame: frame)
+            
+            self.highligthedChanged = { [weak self] highlighted in
+                if let self {
+                    if highlighted {
+                        self.layer.removeAnimation(forKey: "opacity")
+                        self.alpha = 0.65
+                    } else {
+                        self.alpha = 1.0
+                        self.layer.animateAlpha(from: 0.65, to: 1.0, duration: 0.2)
+                    }
+                }
+            }
+            self.addTarget(self, action: #selector(self.pressed), for: .touchUpInside)
+        }
+        
+        required public init?(coder: NSCoder) {
+            fatalError("init(coder:) has not been implemented")
+        }
+        
+        @objc private func pressed() {
+            guard let component = self.component else {
+                return
+            }
+            component.action()
+        }
+        
+        override public func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
+            return super.hitTest(point, with: event)
+        }
+        
+        func update(component: BackButtonComponent, availableSize: CGSize, state: EmptyComponentState, environment: Environment<Empty>, transition: Transition) -> CGSize {
+            let sideInset: CGFloat = 4.0
+            
+            let titleSize = self.title.update(
+                transition: .immediate,
+                component: AnyComponent(Text(text: component.title, font: Font.regular(17.0), color: component.color)),
+                environment: {},
+                containerSize: CGSize(width: availableSize.width - 4.0, height: availableSize.height)
+            )
+
+            let size = CGSize(width: sideInset * 2.0 + titleSize.width, height: availableSize.height)
+
+            let titleFrame = titleSize.centered(in: CGRect(origin: CGPoint(), size: size))
+            if let titleView = self.title.view {
+                if titleView.superview == nil {
+                    titleView.layer.anchorPoint = CGPoint()
+                    self.addSubview(titleView)
+                }
+                transition.setPosition(view: titleView, position: titleFrame.origin)
+                titleView.bounds = CGRect(origin: CGPoint(), size: titleFrame.size)
+            }
+            
+            return size
+        }
+    }
+    
+    public func makeView() -> View {
+        return View(frame: CGRect())
+    }
+    
+    public func update(view: View, availableSize: CGSize, state: EmptyComponentState, environment: Environment<Empty>, transition: Transition) -> CGSize {
+        return view.update(component: self, availableSize: availableSize, state: state, environment: environment, transition: transition)
+    }
+}