Workaround for UIHostingConfiguration requiring iOS 16

Packages/ComposeUI/Sources/ComposeUI/Views/Attachments/AttachmentCollectionViewCell.swift

@@ -8,34 +8,7 @@
 import UIKit
 import SwiftUI
 
-final class AttachmentCollectionViewCell: UICollectionViewCell {
+struct AttachmentCollectionViewCellView: View {
-    let attachmentView: UIView// & UIContentView
-    
-    override init(frame: CGRect) {
-        attachmentView = UIView()
-        attachmentView.backgroundColor = .red
-//        attachmentView = UIHostingConfiguration(content: {
-//            AttachmentCollectionViewCellView(attachment: nil)
-//        }).makeContentView()
-        
-        super.init(frame: frame)
-        
-        attachmentView.frame = bounds
-        addSubview(attachmentView)
-    }
-    
-    required init?(coder: NSCoder) {
-        fatalError("init(coder:) has not been implemented")
-    }
-    
-    func updateUI(attachment: DraftAttachment) {
-//        attachmentView.configuration = UIHostingConfiguration(content: {
-//            AttachmentCollectionViewCellView(attachment: attachment)
-//        }).margins(.all, .zero)
-    }
-}
-
-private struct AttachmentCollectionViewCellView: View {
     let attachment: DraftAttachment?
     
     var body: some View {
@@ -147,6 +120,21 @@ private struct SquareFrame: Layout {
     }
 }
 
+#if !os(visionOS)
+@available(iOS, obsoleted: 16.0)
+private struct LegacySquareFrame<Content: View>: View {
+    @ViewBuilder let content: Content
+    
+    var body: some View {
+        GeometryReader { proxy in
+            let minDimension = min(proxy.size.width, proxy.size.height)
+            content
+                .frame(width: minDimension, height: minDimension, alignment: .center)
+        }
+    }
+}
+#endif
+
 private extension View {
     @ViewBuilder
     func squareFrame() -> some View {
@@ -160,7 +148,9 @@ private extension View {
                 self
             }
         } else {
-            self
+            LegacySquareFrame {
+                self
+            }
         }
         #endif
     }

Packages/ComposeUI/Sources/ComposeUI/Views/Attachments/AttachmentsSection.swift

@@ -67,7 +67,7 @@ private class WrappedCollectionViewController: UIViewController {
     var draft: Draft!
     private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
     fileprivate var currentInteractiveMoveStartOffsetInCell: CGPoint?
-    fileprivate var currentInteractiveMoveCell: AttachmentCollectionViewCell?
+    fileprivate var currentInteractiveMoveCell: HostingCollectionViewCell?
     fileprivate var addAttachment: ((DraftAttachment) -> Void)? = nil
     
     init(spacing: CGFloat, minItemSize: CGFloat) {
@@ -91,14 +91,11 @@ private class WrappedCollectionViewController: UIViewController {
             section.interGroupSpacing = spacing
             return section
         }
-        let attachmentCell = UICollectionView.CellRegistration<AttachmentCollectionViewCell, DraftAttachment> { cell, indexPath, attachment in
+        let attachmentCell = UICollectionView.CellRegistration<HostingCollectionViewCell, DraftAttachment> { cell, indexPath, attachment in
-            cell.updateUI(attachment: attachment)
+            cell.setView(AttachmentCollectionViewCellView(attachment: attachment))
         }
-        let addButtonCell = UICollectionView.CellRegistration<UICollectionViewCell, Bool> { [unowned self] cell, indexPath, item in
+        let addButtonCell = UICollectionView.CellRegistration<HostingCollectionViewCell, Bool> { [unowned self] cell, indexPath, item in
-            cell.contentView.backgroundColor = .blue
+            cell.setView(AddAttachmentButton(viewController: self, enabled: item))
-//            cell.contentConfiguration = UIHostingConfiguration(content: {
-//                AddAttachmentButton(viewController: self, enabled: item)
-//            }).margins(.all, .zero)
         }
         let collectionView = IntrinsicContentSizeCollectionView(frame: .zero, collectionViewLayout: layout)
         self.view = collectionView
@@ -187,14 +184,14 @@ private class WrappedCollectionViewController: UIViewController {
         case .ended:
             collectionView.endInteractiveMovement()
             UIView.animate(withDuration: 0.2) {
-                self.currentInteractiveMoveCell?.attachmentView.transform = .identity
+                self.currentInteractiveMoveCell?.hostView?.transform = .identity
             }
             currentInteractiveMoveCell = nil
             currentInteractiveMoveStartOffsetInCell = nil
         case .cancelled:
             collectionView.cancelInteractiveMovement()
             UIView.animate(withDuration: 0.2) {
-                self.currentInteractiveMoveCell?.attachmentView.transform = .identity
+                self.currentInteractiveMoveCell?.hostView?.transform = .identity
             }
             currentInteractiveMoveCell = nil
             currentInteractiveMoveStartOffsetInCell = nil
@@ -218,17 +215,20 @@ extension WrappedCollectionViewController: UIGestureRecognizerDelegate {
         let collectionView = gestureRecognizer.view as! UICollectionView
         let location = gestureRecognizer.location(in: collectionView)
         guard let indexPath = collectionView.indexPathForItem(at: location),
-              let cell = collectionView.cellForItem(at: indexPath) as? AttachmentCollectionViewCell else {
+              let cell = collectionView.cellForItem(at: indexPath) as? HostingCollectionViewCell else {
+            return false
+        }
+        guard collectionView.beginInteractiveMovementForItem(at: indexPath) else {
             return false
         }
         UIView.animate(withDuration: 0.2) {
-            cell.attachmentView.transform = CGAffineTransform(scaleX: 1.2, y: 1.2)
+            cell.hostView?.transform = CGAffineTransform(scaleX: 1.2, y: 1.2)
         }
         currentInteractiveMoveCell = cell
         currentInteractiveMoveStartOffsetInCell = gestureRecognizer.location(in: cell)
         currentInteractiveMoveStartOffsetInCell!.x -= cell.bounds.midX
         currentInteractiveMoveStartOffsetInCell!.y -= cell.bounds.midY
-        return collectionView.beginInteractiveMovementForItem(at: indexPath)
+        return true
     }
 }
 
@@ -279,6 +279,62 @@ private final class IntrinsicContentSizeCollectionView: UICollectionView {
     }
 }
 
+#if os(visionOS)
+private class HostingCollectionViewCell: UICollectionViewCell {
+    private(set) var hostView: UIView?
+    
+    func setView<V: View>(_ view: V) {
+        let config = UIHostingConfiguration(content: {
+            view
+        }).margins(.all, 0)
+        
+        if let hostView = hostView as? UIContentView {
+            hostView.configuration = config
+        } else {
+            hostView = config.makeContentView()
+            hostView!.frame = contentView.bounds
+            contentView.addSubview(hostView!)
+        }
+    }
+}
+#else
+@available(iOS, obsoleted: 16.0)
+private class HostingCollectionViewCell: UICollectionViewCell {
+    @available(iOS, obsoleted: 16.0)
+    private var hostController: UIHostingController<AnyView>?
+    private(set) var hostView: UIView?
+    
+    func setView<V: View>(_ view: V) {
+        if #available(iOS 16.0, *) {
+            let config = UIHostingConfiguration(content: {
+                view
+            }).margins(.all, 0)
+            
+            // We don't just use the cell's contentConfiguration property because we need to animate
+            // the size of the host view, and when the host view is the contentView, that doesn't work.
+            if let hostView = hostView as? UIContentView {
+                hostView.configuration = config
+            } else {
+                hostView = config.makeContentView()
+                hostView!.frame = contentView.bounds
+                contentView.addSubview(hostView!)
+            }
+        } else {
+            if let hostController {
+                hostController.rootView = AnyView(view)
+            } else {
+                let host = UIHostingController(rootView: AnyView(view))
+                host.view.frame = contentView.bounds
+                contentView.addSubview(host.view)
+                hostController = host
+                hostView = host.view
+                // drop the hosting controller on the floor and hope nothing bad happens
+            }
+        }
+    }
+}
+#endif
+
 private struct AddAttachmentButton: View {
     unowned let viewController: WrappedCollectionViewController
     let enabled: Bool
@@ -308,7 +364,7 @@ private struct AddAttachmentButton: View {
                 }
             }
         } label: {
-            Image(systemName: "photo.badge.plus")
+            Image(systemName: iconName)
                 .imageScale(.large)
                 .frame(maxWidth: .infinity, maxHeight: .infinity)
                 .background {
@@ -321,6 +377,14 @@ private struct AddAttachmentButton: View {
         }
         .disabled(!enabled)
     }
+    
+    private var iconName: String {
+        if #available(iOS 17.0, *) {
+            "photo.badge.plus"
+        } else {
+            "photo"
+        }
+    }
 }
 
 struct AddAttachmentConditionsModifier: ViewModifier {