Refine header caching

Sources/ASCollectionView/Cells/ASCollectionViewDecoration.swift

@@ -17,7 +17,7 @@ class ASCollectionViewDecoration<Content: Decoration>: ASCollectionViewSupplemen
 	{
 		super.init(frame: frame)
 		let view = Content()
-		setupFor(view: view)
+		hostingController = ASHostingController(view)
 		willAppear(in: nil)
 	}
 

Sources/ASCollectionView/Cells/ASCollectionViewSupplementaryView.swift

@@ -12,18 +12,6 @@ class ASCollectionViewSupplementaryView: UICollectionReusableView
 	var selfSizingConfig: ASSelfSizingConfig = .init(selfSizeHorizontally: true, selfSizeVertically: true)
 	var maxSizeForSelfSizing: ASOptionalSize = .none
 
-	func setupFor<Content: View>(view: Content)
-	{
-		if let hc = hostingController as? ASHostingController<Content>
-		{
-			hc.setView(view)
-		}
-		else
-		{
-			hostingController = ASHostingController<Content>(view)
-		}
-	}
-
 	func setupForEmpty()
 	{
 		hostingController = nil

Sources/ASCollectionView/Cells/ASTableViewSupplementaryView.swift

@@ -7,7 +7,11 @@ import UIKit
 @available(iOS 13.0, *)
 class ASTableViewSupplementaryView: UITableViewHeaderFooterView
 {
-	var hostingController: ASHostingControllerProtocol?
+	var hostingController: ASHostingControllerProtocol? {
+		didSet {
+			setNeedsLayout()
+		}
+	}
 	var sectionIDHash: Int?
 
 	override init(reuseIdentifier: String?)

Sources/ASCollectionView/Implementation/ASCollectionView.swift

@@ -326,9 +326,8 @@ public struct ASCollectionView<SectionID: Hashable>: UIViewControllerRepresentab
 			{ kind in
 				cv.indexPathsForVisibleSupplementaryElements(ofKind: kind).forEach
 				{
-					guard let supplementaryView = parent.sections[safe: $0.section]?.supplementary(ofKind: kind) else { return }
-					(cv.supplementaryView(forElementKind: kind, at: $0) as? ASCollectionViewSupplementaryView)?
-						.setupFor(view: supplementaryView)
+					guard let view = (cv.supplementaryView(forElementKind: kind, at: $0) as? ASCollectionViewSupplementaryView) else { return }
+					view.hostingController = parent.sections[safe: $0.section]?.dataSource.updateOrCreateHostController(forSupplementaryKind: kind, existingHC: view.hostingController)
 				}
 			}
 		}

Sources/ASCollectionView/Implementation/ASTableView.swift

@@ -108,6 +108,8 @@ public struct ASTableView<SectionID: Hashable>: UIViewControllerRepresentable, C
 
 		private var hasDoneInitialSetup = false
 		private var hasSkippedFirstUpdate = false
+		
+		private var visibleSupplementaries: [ASSupplementaryCellID<SectionID>: ASTableViewSupplementaryView] = [:]
 
 		// MARK: Caching
 
@@ -254,23 +256,10 @@ public struct ASTableView<SectionID: Hashable>: UIViewControllerRepresentable, C
 				else { return }
 				self.section(forItemID: itemID)?.dataSource.update(hc, forItemID: itemID)
 			}
-
-			tv.visibleHeaderViews.forEach { view in
-				guard
-					let view = view as? ASTableViewSupplementaryView,
-					let sectionIDHash = view.sectionIDHash,
-					let hc = view.hostingController
-				else { return }
-				self.parent.sections.first(where: { $0.id.hashValue == sectionIDHash })?.dataSource.update(hc, forSupplementaryKind: UICollectionView.elementKindSectionHeader)
-			}
-
-			tv.visibleFooterViews.forEach { view in
-				guard
-					let view = view as? ASTableViewSupplementaryView,
-					let sectionIDHash = view.sectionIDHash,
-					let hc = view.hostingController
-				else { return }
-				self.parent.sections.first(where: { $0.id.hashValue == sectionIDHash })?.dataSource.update(hc, forSupplementaryKind: UICollectionView.elementKindSectionFooter)
+			
+			visibleSupplementaries.forEach { (key, view) in
+				guard let section = self.parent.sections.first(where: { $0.id.hashValue == key.sectionID.hashValue }) else { return }
+				view.hostingController = section.dataSource.updateOrCreateHostController(forSupplementaryKind: key.supplementaryKind, existingHC: view.hostingController)
 			}
 		}
 
@@ -306,7 +295,7 @@ public struct ASTableView<SectionID: Hashable>: UIViewControllerRepresentable, C
 		var lastContentSize: CGSize = .zero
 		func didUpdateContentSize(_ size: CGSize)
 		{
-			guard let tv = tableViewController?.tableView, tv.contentSize != lastContentSize else { return }
+			guard let tv = tableViewController?.tableView, tv.contentSize != lastContentSize, tv.contentSize.height != 0 else { return }
 			let firstSize = lastContentSize == .zero
 			lastContentSize = tv.contentSize
 			parent.contentSizeTracker?.contentSize = size
@@ -357,22 +346,42 @@ public struct ASTableView<SectionID: Hashable>: UIViewControllerRepresentable, C
 
 		public func tableView(_ tableView: UITableView, willDisplayHeaderView view: UIView, forSection section: Int)
 		{
-			tableViewController.map { (view as? ASTableViewSupplementaryView)?.willAppear(in: $0) }
+			guard let view = (view as? ASTableViewSupplementaryView) else { return }
+			if let section = parent.sections[safe: section] {
+				let supplementaryID = ASSupplementaryCellID(sectionID: section.id, supplementaryKind: UICollectionView.elementKindSectionHeader)
+				visibleSupplementaries[supplementaryID] = view
+			}
+			tableViewController.map { view.willAppear(in: $0) }
 		}
 
 		public func tableView(_ tableView: UITableView, didEndDisplayingHeaderView view: UIView, forSection section: Int)
 		{
-			(view as? ASTableViewSupplementaryView)?.didDisappear()
+			guard let view = (view as? ASTableViewSupplementaryView) else { return }
+			if let section = parent.sections[safe: section] {
+				let supplementaryID = ASSupplementaryCellID(sectionID: section.id, supplementaryKind: UICollectionView.elementKindSectionHeader)
+				visibleSupplementaries.removeValue(forKey: supplementaryID)
+			}
+			view.didDisappear()
 		}
 
 		public func tableView(_ tableView: UITableView, willDisplayFooterView view: UIView, forSection section: Int)
 		{
-			tableViewController.map { (view as? ASTableViewSupplementaryView)?.willAppear(in: $0) }
+			guard let view = (view as? ASTableViewSupplementaryView) else { return }
+			if let section = parent.sections[safe: section] {
+				let supplementaryID = ASSupplementaryCellID(sectionID: section.id, supplementaryKind: UICollectionView.elementKindSectionFooter)
+				visibleSupplementaries[supplementaryID] = view
+			}
+			tableViewController.map { view.willAppear(in: $0) }
 		}
 
 		public func tableView(_ tableView: UITableView, didEndDisplayingFooterView view: UIView, forSection section: Int)
 		{
-			(view as? ASTableViewSupplementaryView)?.didDisappear()
+			guard let view = (view as? ASTableViewSupplementaryView) else { return }
+			if let section = parent.sections[safe: section] {
+				let supplementaryID = ASSupplementaryCellID(sectionID: section.id, supplementaryKind: UICollectionView.elementKindSectionFooter)
+				visibleSupplementaries.removeValue(forKey: supplementaryID)
+			}
+			view.didDisappear()
 		}
 
 		public func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath])