Restore the article scroll position when restarting NetNewsWire

Mac/MainWindow/Detail/DetailViewController.swift

@@ -16,8 +16,8 @@ enum DetailState: Equatable {
 	case noSelection
 	case multipleSelection
 	case loading
-	case article(Article)
-	case extracted(Article, ExtractedArticle)
+	case article(Article, CGFloat?)
+	case extracted(Article, ExtractedArticle, CGFloat?)
 }
 
 final class DetailViewController: NSViewController, WKUIDelegate {
@@ -81,13 +81,18 @@ final class DetailViewController: NSViewController, WKUIDelegate {
 	// MARK: - Navigation
 	
 	func focus() {
-		
 		guard let window = currentWebViewController.webView.window else {
 			return
 		}
 		window.makeFirstResponderUnlessDescendantIsFirstResponder(currentWebViewController.webView)
 	}
 	
+	// MARK: State Restoration
+	
+	func saveState(to state: inout [AnyHashable : Any]) {
+		currentWebViewController.saveState(to: &state)
+	}
+	
 }
 
 // MARK: - DetailWebViewControllerDelegate

Mac/MainWindow/Detail/DetailWebView.swift

@@ -10,8 +10,13 @@ import AppKit
 import WebKit
 import RSCore
 
+protocol DetailWebViewDelegate: AnyObject {
+	func didScroll(_ : DetailWebView)
+}
+
 final class DetailWebView: WKWebView {
 
+	weak var detailDelegate: DetailWebViewDelegate?
 	weak var keyboardDelegate: KeyboardDelegate?
 	
 	override func accessibilityLabel() -> String? {
@@ -62,6 +67,11 @@ final class DetailWebView: WKWebView {
 			bigSurOffsetFix()
 		}
 	}
+	
+	override func scrollWheel(with event: NSEvent) {
+		super.scrollWheel(with: event)
+		detailDelegate?.didScroll(self)
+	}
 		
 	private var inBigSurOffsetFix = false
 	

Mac/MainWindow/Detail/DetailWebViewController.swift

@@ -24,6 +24,12 @@ final class DetailWebViewController: NSViewController {
 	var state: DetailState = .noSelection {
 		didSet {
 			if state != oldValue {
+				switch state {
+				case .article(_, let scrollY), .extracted(_, _, let scrollY):
+					windowScrollY = scrollY
+				default:
+					break
+				}
 				reloadHTML()
 			}
 		}
@@ -31,9 +37,9 @@ final class DetailWebViewController: NSViewController {
 	
 	var article: Article? {
 		switch state {
-		case .article(let article):
+		case .article(let article, _):
 			return article
-		case .extracted(let article, _):
+		case .extracted(let article, _, _):
 			return article
 		default:
 			return nil
@@ -55,9 +61,19 @@ final class DetailWebViewController: NSViewController {
 	
 	private let detailIconSchemeHandler = DetailIconSchemeHandler()
 	private var waitingForFirstReload = false
-	private var windowScrollY: CGFloat?
 	private let keyboardDelegate = DetailKeyboardDelegate()
-	
+	private let scrollPositionQueue = CoalescingQueue(name: "Article Scroll Position", interval: 0.3, maxInterval: 0.3)
+	private var windowScrollY: CGFloat?
+
+	private var isShowingExtractedArticle: Bool {
+		switch state {
+		case .extracted(_, _, _):
+			return true
+		default:
+			return false
+		}
+	}
+
 	private struct MessageName {
 		static let mouseDidEnter = "mouseDidEnter"
 		static let mouseDidExit = "mouseDidExit"
@@ -81,6 +97,7 @@ final class DetailWebViewController: NSViewController {
 		webView = DetailWebView(frame: NSRect.zero, configuration: configuration)
 		webView.uiDelegate = self
 		webView.navigationDelegate = self
+		webView.detailDelegate = self
 		webView.keyboardDelegate = keyboardDelegate
 		webView.translatesAutoresizingMaskIntoConstraints = false
 		if let userAgent = UserAgent.fromInfoPlist() {
@@ -177,6 +194,31 @@ final class DetailWebViewController: NSViewController {
 	override func scrollPageUp(_ sender: Any?) {
 		webView.scrollPageUp(sender)
 	}
+
+	// MARK: State Restoration
+	
+	func saveState(to state: inout [AnyHashable : Any]) {
+		state[UserInfoKey.isShowingExtractedArticle] = isShowingExtractedArticle
+		state[UserInfoKey.articleWindowScrollY] = windowScrollY
+	}
+	
+}
+
+// MARK: DetailWebViewDelegate
+
+extension DetailWebViewController: DetailWebViewDelegate {
+
+	func didScroll(_: DetailWebView) {
+		
+		scrollPositionQueue.add(self, #selector(scrollPositionDidChange))
+	}
+	
+	@objc func scrollPositionDidChange() {
+		fetchScrollInfo() { scrollInfo in
+			self.windowScrollY = scrollInfo?.offsetY
+		}
+	}
+	
 }
 
 // MARK: - WKScriptMessageHandler
@@ -229,11 +271,11 @@ extension DetailWebViewController: WKNavigationDelegate, WKUIDelegate {
 			DispatchQueue.main.asyncAfter(deadline: .now() + 0.05) {
 				webView.isHidden = false
 			}
-		}
-		
-		if let windowScrollY = windowScrollY {
-			webView.evaluateJavaScript("window.scrollTo(0, \(windowScrollY));")
-			self.windowScrollY = nil
+		} else {
+			if let windowScrollY = windowScrollY {
+				webView.evaluateJavaScript("window.scrollTo(0, \(windowScrollY));")
+				self.windowScrollY = nil
+			}
 		}
 	}
 
@@ -281,10 +323,10 @@ private extension DetailWebViewController {
 			rendering = ArticleRenderer.multipleSelectionHTML(theme: theme)
 		case .loading:
 			rendering = ArticleRenderer.loadingHTML(theme: theme)
-		case .article(let article):
+		case .article(let article, _):
 			detailIconSchemeHandler.currentArticle = article
 			rendering = ArticleRenderer.articleHTML(article: article, theme: theme)
-		case .extracted(let article, let extractedArticle):
+		case .extracted(let article, let extractedArticle, _):
 			detailIconSchemeHandler.currentArticle = article
 			rendering = ArticleRenderer.articleHTML(article: article, extractedArticle: extractedArticle, theme: theme)
 		}

Mac/MainWindow/MainWindowController.swift

@@ -56,6 +56,7 @@ class MainWindowController : NSWindowController, NSUserInterfaceValidations {
 		}
 	}
 	private var searchSmartFeed: SmartFeed? = nil
+	private var restoreArticleWindowScrollY: CGFloat?
 
 	// MARK: - NSWindowController
 
@@ -410,20 +411,20 @@ class MainWindowController : NSWindowController, NSUserInterfaceValidations {
 			articleExtractor?.cancel()
 			articleExtractor = nil
 			isShowingExtractedArticle = false
-			detailViewController?.setState(DetailState.article(article), mode: timelineSourceMode)
+			detailViewController?.setState(DetailState.article(article, nil), mode: timelineSourceMode)
 			return
 		}
 		
 		guard !isShowingExtractedArticle else {
 			isShowingExtractedArticle = false
-			detailViewController?.setState(DetailState.article(article), mode: timelineSourceMode)
+			detailViewController?.setState(DetailState.article(article, nil), mode: timelineSourceMode)
 			return
 		}
 		
 		if let articleExtractor = articleExtractor, let extractedArticle = articleExtractor.article {
 			if currentLink == articleExtractor.articleLink {
 				isShowingExtractedArticle = true
-				let detailState = DetailState.extracted(article, extractedArticle)
+				let detailState = DetailState.extracted(article, extractedArticle, nil)
 				detailViewController?.setState(detailState, mode: timelineSourceMode)
 			}
 		} else {
@@ -619,7 +620,8 @@ extension MainWindowController: TimelineContainerViewControllerDelegate {
 					detailState = .loading
 					startArticleExtractorForCurrentLink()
 				} else {
-					detailState = .article(articles.first!)
+					detailState = .article(articles.first!, restoreArticleWindowScrollY)
+					restoreArticleWindowScrollY = nil
 				}
 			} else {
 				detailState = .multipleSelection
@@ -719,7 +721,8 @@ extension MainWindowController: ArticleExtractorDelegate {
 	func articleExtractionDidComplete(extractedArticle: ExtractedArticle) {
 		if let article = oneSelectedArticle, articleExtractor?.state != .cancelled {
 			isShowingExtractedArticle = true
-			let detailState = DetailState.extracted(article, extractedArticle)
+			let detailState = DetailState.extracted(article, extractedArticle, restoreArticleWindowScrollY)
+			restoreArticleWindowScrollY = nil
 			detailViewController?.setState(detailState, mode: timelineSourceMode)
 			makeToolbarValidate()
 		}
@@ -1043,6 +1046,7 @@ private extension MainWindowController {
 		saveSplitViewState(to: &state)
 		sidebarViewController?.saveState(to: &state)
 		timelineContainerViewController?.saveState(to: &state)
+		detailViewController?.saveState(to: &state)
 		return state
 	}
 
@@ -1051,8 +1055,19 @@ private extension MainWindowController {
 			window?.toggleFullScreen(self)
 		}
 		restoreSplitViewState(from: state)
+		
 		sidebarViewController?.restoreState(from: state)
+		
+		let articleWindowScrollY = state[UserInfoKey.articleWindowScrollY] as? CGFloat
+		restoreArticleWindowScrollY = articleWindowScrollY
 		timelineContainerViewController?.restoreState(from: state)
+		
+		let isShowingExtractedArticle = state[UserInfoKey.isShowingExtractedArticle] as? Bool ?? false
+		if isShowingExtractedArticle {
+			restoreArticleWindowScrollY = articleWindowScrollY
+			startArticleExtractorForCurrentLink()
+		}
+		
 	}
 
 	// MARK: - Command Validation