mirror of https://github.com/lukechilds/damus.git
OlegAba
2 years ago
committed by
William Casarin
William Casarin
4 changed files with 179 additions and 66 deletions
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// |
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// ZoomableScrollView.swift |
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// damus |
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// |
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// Created by Oleg Abalonski on 1/25/23. |
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// |
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import SwiftUI |
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struct ZoomableScrollView<Content: View>: UIViewRepresentable { |
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private var content: Content |
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init(@ViewBuilder content: () -> Content) { |
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self.content = content() |
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} |
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func makeUIView(context: Context) -> UIScrollView { |
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let scrollView = GesturedScrollView() |
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scrollView.delegate = context.coordinator |
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scrollView.maximumZoomScale = 20 |
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scrollView.minimumZoomScale = 1 |
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scrollView.bouncesZoom = true |
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scrollView.showsVerticalScrollIndicator = false |
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scrollView.showsHorizontalScrollIndicator = false |
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let hostedView = context.coordinator.hostingController.view! |
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hostedView.translatesAutoresizingMaskIntoConstraints = true |
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hostedView.autoresizingMask = [.flexibleWidth, .flexibleHeight] |
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hostedView.frame = scrollView.bounds |
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hostedView.backgroundColor = .clear |
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scrollView.addSubview(hostedView) |
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return scrollView |
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} |
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func makeCoordinator() -> Coordinator { |
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return Coordinator(hostingController: UIHostingController(rootView: self.content, ignoreSafeArea: true)) |
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} |
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func updateUIView(_ uiView: UIScrollView, context: Context) { |
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context.coordinator.hostingController.rootView = self.content |
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assert(context.coordinator.hostingController.view.superview == uiView) |
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} |
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class Coordinator: NSObject, UIScrollViewDelegate { |
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var hostingController: UIHostingController<Content> |
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init(hostingController: UIHostingController<Content>) { |
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self.hostingController = hostingController |
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} |
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func viewForZooming(in scrollView: UIScrollView) -> UIView? { |
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return hostingController.view |
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} |
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func scrollViewDidZoom(_ scrollView: UIScrollView) { |
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let viewSize = hostingController.view.frame.size |
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guard let imageSize = scrollView.subviews[0].subviews.last?.frame.size else { return } |
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if scrollView.zoomScale > 1 { |
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let ratioW = viewSize.width / imageSize.width |
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let ratioH = viewSize.height / imageSize.height |
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let ratio = ratioW < ratioH ? ratioW:ratioH |
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let newWidth = imageSize.width * ratio |
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let newHeight = imageSize.height * ratio |
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let left = 0.5 * (newWidth * scrollView.zoomScale > viewSize.width ? (newWidth - viewSize.width) : (scrollView.frame.width - scrollView.contentSize.width)) |
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let top = 0.5 * (newHeight * scrollView.zoomScale > viewSize.height ? (newHeight - viewSize.height) : (scrollView.frame.height - scrollView.contentSize.height)) |
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scrollView.contentInset = UIEdgeInsets(top: top, left: left, bottom: top, right: left) |
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} else { |
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scrollView.contentInset = .zero |
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} |
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} |
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} |
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} |
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fileprivate class GesturedScrollView: UIScrollView, UIGestureRecognizerDelegate { |
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let doubleTapGesture: UITapGestureRecognizer |
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override init(frame: CGRect) { |
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doubleTapGesture = UITapGestureRecognizer() |
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super.init(frame: frame) |
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doubleTapGesture.addTarget(self, action: #selector(handleDoubleTap)) |
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doubleTapGesture.numberOfTapsRequired = 2 |
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addGestureRecognizer(doubleTapGesture) |
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doubleTapGesture.delegate = self |
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} |
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required init?(coder: NSCoder) { |
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fatalError("init(coder:) has not been implemented") |
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} |
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@objc func handleDoubleTap(_ gesture: UITapGestureRecognizer) { |
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if self.zoomScale == 1 { |
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let pointInView = gesture.location(in: self.subviews.first) |
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let newZoomScale = self.maximumZoomScale / 4.0 |
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let scrollViewSize = self.bounds.size |
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let width = scrollViewSize.width / newZoomScale |
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let height = scrollViewSize.height / newZoomScale |
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let originX = pointInView.x - (width / 2.0) |
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let originY = pointInView.y - (height / 2.0) |
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let zoomRect = CGRect(x: originX, y: originY, width: width, height: height) |
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self.zoom(to: zoomRect, animated: true) |
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} else { |
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self.setZoomScale(self.minimumZoomScale, animated: true) |
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} |
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} |
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func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool { |
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return gestureRecognizer == doubleTapGesture |
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} |
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} |
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fileprivate extension UIHostingController { |
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convenience init(rootView: Content, ignoreSafeArea: Bool) { |
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self.init(rootView: rootView) |
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if ignoreSafeArea { |
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disableSafeArea() |
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} |
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} |
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func disableSafeArea() { |
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guard let viewClass = object_getClass(view) else { return } |
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let viewSubclassName = String(cString: class_getName(viewClass)).appending("_IgnoreSafeArea") |
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if let viewSubclass = NSClassFromString(viewSubclassName) { |
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object_setClass(view, viewSubclass) |
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} |
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else { |
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guard let viewClassNameUtf8 = (viewSubclassName as NSString).utf8String else { return } |
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guard let viewSubclass = objc_allocateClassPair(viewClass, viewClassNameUtf8, 0) else { return } |
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if let method = class_getInstanceMethod(UIView.self, #selector(getter: UIView.safeAreaInsets)) { |
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let safeAreaInsets: @convention(block) (AnyObject) -> UIEdgeInsets = { _ in |
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return .zero |
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} |
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class_addMethod(viewSubclass, #selector(getter: UIView.safeAreaInsets), imp_implementationWithBlock(safeAreaInsets), method_getTypeEncoding(method)) |
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} |
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objc_registerClassPair(viewSubclass) |
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object_setClass(view, viewSubclass) |
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} |
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} |
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} |
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