Change to stop recycling the article view controller when switching panel modes on the iPad. Issue #1570

iOS/Article/ArticleViewController.swift

@@ -53,6 +53,7 @@ class ArticleViewController: UIViewController {
 			updateUI()
 		}
 	}
+	var restoreWindowScrollY = 0
 	
 	private let keyboardManager = KeyboardManager(type: .detail)
 	override var keyCommands: [UIKeyCommand]? {
@@ -92,6 +93,7 @@ class ArticleViewController: UIViewController {
 		])
 				
 		let controller = createWebViewController(article)
+		controller.restoreWindowScrollY = restoreWindowScrollY
 		articleExtractorButton.buttonState = controller.articleExtractorButtonState
 		pageViewController.setViewControllers([controller], direction: .forward, animated: false, completion: nil)
 		
@@ -246,6 +248,13 @@ class ArticleViewController: UIViewController {
 // MARK: WebViewControllerDelegate
 
 extension ArticleViewController: WebViewControllerDelegate {
+	
+	func webViewController(_ webViewController: WebViewController, restoreWindowScrollYDidUpdate restoreWindowScrollY: Int) {
+		if webViewController === currentWebViewController {
+			self.restoreWindowScrollY = restoreWindowScrollY
+		}
+	}
+	
 	func webViewController(_ webViewController: WebViewController, articleExtractorButtonStateDidUpdate buttonState: ArticleExtractorButtonState) {
 		if webViewController === currentWebViewController {
 			articleExtractorButton.buttonState = buttonState

iOS/Article/WebViewController.swift

@@ -8,11 +8,13 @@
 
 import UIKit
 import WebKit
+import RSCore
 import Account
 import Articles
 import SafariServices
 
 protocol WebViewControllerDelegate: class {
+	func webViewController(_: WebViewController, restoreWindowScrollYDidUpdate: Int)
 	func webViewController(_: WebViewController, articleExtractorButtonStateDidUpdate: ArticleExtractorButtonState)
 }
 
@@ -68,7 +70,12 @@ class WebViewController: UIViewController {
 		}
 	}
 	
-	var restoreOffset = 0
+	let scrollPositionQueue = CoalescingQueue(name: "Article Scroll Position", interval: 0.3, maxInterval: 1.0)
+	var restoreWindowScrollY = 0 {
+		didSet {
+			delegate?.webViewController(self, restoreWindowScrollYDidUpdate: restoreWindowScrollY)
+		}
+	}
 	
 	deinit {
 		if webView != nil  {
@@ -109,6 +116,7 @@ class WebViewController: UIViewController {
 			// Configure the webview
 			webView.navigationDelegate = self
 			webView.uiDelegate = self
+			webView.scrollView.delegate = self
 			self.configureContextMenuInteraction()
 
 			webView.configuration.userContentController.add(WrapperScriptMessageHandler(self), name: MessageName.imageWasClicked)
@@ -186,11 +194,8 @@ class WebViewController: UIViewController {
 	}
 	
 	func fullReload() {
-		webView?.evaluateJavaScript("window.scrollY") { (scrollY, _) in
-			self.restoreOffset = scrollY as! Int
 		self.reloadHTML()
 	}
-	}
 
 	func showBars() {
 		AppDefaults.articleFullscreenEnabled = false
@@ -408,6 +413,22 @@ extension WebViewController: UIViewControllerTransitioningDelegate {
 	}
 }
 
+// MARK:
+
+extension WebViewController: UIScrollViewDelegate {
+	
+	func scrollViewDidScroll(_ scrollView: UIScrollView) {
+		scrollPositionQueue.add(self, #selector(scrollPositionDidChange))
+	}
+	
+	@objc func scrollPositionDidChange() {
+		webView?.evaluateJavaScript("window.scrollY") { (scrollY, _) in
+			self.restoreWindowScrollY = scrollY as! Int
+		}
+	}
+	
+}
+
 // MARK: JSON
 
 private struct TemplateData: Codable {
@@ -472,10 +493,10 @@ private extension WebViewController {
 		var render = "error();"
 		if let data = try? encoder.encode(templateData) {
 			let json = String(data: data, encoding: .utf8)!
-			render = "render(\(json), \(restoreOffset));"
+			render = "render(\(json), \(restoreWindowScrollY));"
 		}
 
-		restoreOffset = 0
+		restoreWindowScrollY = 0
 		
 		WebViewProvider.shared.articleIconSchemeHandler.currentArticle = article
 		webView.scrollView.setZoomScale(1.0, animated: false)

iOS/MasterTimeline/MasterTimelineViewController.swift

@@ -28,7 +28,7 @@ class MasterTimelineViewController: UITableViewController, UndoableCommandRunner
 	
 	weak var coordinator: SceneCoordinator!
 	var undoableCommands = [UndoableCommand]()
-	let scrollPositionQueue = CoalescingQueue(name: "Scroll Position", interval: 0.3, maxInterval: 1.0)
+	let scrollPositionQueue = CoalescingQueue(name: "Timeline Scroll Position", interval: 0.3, maxInterval: 1.0)
 
 	private let keyboardManager = KeyboardManager(type: .timeline)
 	override var keyCommands: [UIKeyCommand]? {

iOS/SceneCoordinator.swift

@@ -1677,19 +1677,14 @@ private extension SceneCoordinator {
 	}
 	
 	@discardableResult
-	func installArticleController(_ recycledArticleController: ArticleViewController? = nil, animated: Bool) -> ArticleViewController {
+	func installArticleController(restoreWindowScrollY: Int = 0, animated: Bool) -> ArticleViewController {
 
 		isArticleViewControllerPending = true
 
-		let articleController: ArticleViewController = {
+		let articleController = UIStoryboard.main.instantiateController(ofType: ArticleViewController.self)
-			if let controller = recycledArticleController {
+		articleController.coordinator = self
-				return controller
+		articleController.article = currentArticle
-			} else {
+		articleController.restoreWindowScrollY = restoreWindowScrollY
-				let controller = UIStoryboard.main.instantiateController(ofType: ArticleViewController.self)
-				controller.coordinator = self
-				return controller
-			}
-		}()
 				
 		if let subSplit = subSplitViewController {
 			let controller = addNavControllerIfNecessary(articleController, showButton: false)
@@ -1701,12 +1696,6 @@ private extension SceneCoordinator {
 			rootSplitViewController.showDetailViewController(controller, sender: self)
   	 	}
 		
-		// We have to do a full reload when installing an article controller.  We may have changed color contexts
-		// and need to update the article colors.  An example is in dark mode.  Split screen doesn't use true black
-		// like darkmode usually does.
-		
-		// TODO: This should probably only happen to recycled article controllers
-		articleController.fullReload()
 		return articleController
 		
 	}
@@ -1758,7 +1747,7 @@ private extension SceneCoordinator {
 	}
 	
 	func configureThreePanelMode() {
-		let recycledArticleController = articleViewController
+		let articleRestoreWindowScrollY = articleViewController?.restoreWindowScrollY ?? 0
 		defer {
 			masterNavigationController.viewControllers = [masterFeedViewController]
 		}
@@ -1773,14 +1762,14 @@ private extension SceneCoordinator {
 		masterTimelineViewController?.navigationItem.leftBarButtonItem = rootSplitViewController.displayModeButtonItem
 		masterTimelineViewController?.navigationItem.leftItemsSupplementBackButton = true
 
-		installArticleController(recycledArticleController, animated: false)
+		installArticleController(restoreWindowScrollY: articleRestoreWindowScrollY, animated: false)
 		
 		masterFeedViewController.restoreSelectionIfNecessary(adjustScroll: true)
 		masterTimelineViewController!.restoreSelectionIfNecessary(adjustScroll: false)
 	}
 	
 	func configureStandardPanelMode() {
-		let recycledArticleController = articleViewController
+		let articleRestoreWindowScrollY = articleViewController?.restoreWindowScrollY ?? 0
 		rootSplitViewController.preferredPrimaryColumnWidthFraction = UISplitViewController.automaticDimension
 		
 		// Set the is Pending flags early to prevent the navigation controller delegate from thinking that we
@@ -1800,7 +1789,7 @@ private extension SceneCoordinator {
 			masterNavigationController.pushViewController(masterTimelineViewController!, animated: false)
 		}
 
-		installArticleController(recycledArticleController, animated: false)
+		installArticleController(restoreWindowScrollY: articleRestoreWindowScrollY, animated: false)
 	}
 	
 	// MARK: NSUserActivity