Fix #547 by implementing state restoration in the sidebar and timeline view controllers.

NetNewsWire/MainWindow/MainWindowController.swift

@@ -78,11 +78,17 @@ class MainWindowController : NSWindowController, NSUserInterfaceValidations, NSW
 	// MARK: - Notifications
 
 	func window(_ window: NSWindow, willEncodeRestorableState state: NSCoder) {
+
 		saveSplitViewState(to: state)
 	}
 
 	func window(_ window: NSWindow, didDecodeRestorableState state: NSCoder) {
+		
 		restoreSplitViewState(from: state)
+
+		// Make sure the timeline view is first responder if possible, to start out viewing
+		// whatever preserved selection might have been restored
+		makeTimelineViewFirstResponder()
 	}
 
 	@objc func refreshProgressDidChange(_ note: Notification) {

NetNewsWire/MainWindow/Sidebar/SidebarViewController.swift

@@ -70,6 +70,26 @@ import RSCore
 		}
 	}
 
+	// MARK: State Restoration
+
+	private static let stateRestorationSelectedRowIndexes = "selectedRowIndexes"
+
+	override func encodeRestorableState(with coder: NSCoder) {
+
+		super.encodeRestorableState(with: coder)
+
+		coder.encode(outlineView.selectedRowIndexes, forKey: SidebarViewController.stateRestorationSelectedRowIndexes)
+	}
+
+	override func restoreState(with coder: NSCoder) {
+
+		super.restoreState(with: coder)
+
+		if let restoredRowIndexes = coder.decodeObject(of: [NSIndexSet.self], forKey: SidebarViewController.stateRestorationSelectedRowIndexes) as? IndexSet {
+			outlineView.selectRowIndexes(restoredRowIndexes, byExtendingSelection: false)
+		}
+	}
+
 	// MARK: - Notifications
 
 	@objc func unreadCountDidChange(_ note: Notification) {
@@ -278,6 +298,8 @@ import RSCore
     func outlineViewSelectionDidChange(_ notification: Notification) {
 
 		postSidebarSelectionDidChangeNotification(selectedObjects.isEmpty ? nil : selectedObjects)
+
+		self.invalidateRestorableState()
     }
 
 	//MARK: - Node Manipulation

NetNewsWire/MainWindow/Timeline/TimelineViewController.swift

@@ -143,6 +143,26 @@ class TimelineViewController: NSViewController, UndoableCommandRunner {
 		sharingServiceDelegate = SharingServiceDelegate(self.view.window)
 	}
 
+	// MARK: State Restoration
+
+	private static let stateRestorationSelectedArticles = "selectedArticles"
+
+	override func encodeRestorableState(with coder: NSCoder) {
+
+		super.encodeRestorableState(with: coder)
+
+		coder.encode(self.selectedArticleIDs(), forKey: TimelineViewController.stateRestorationSelectedArticles)
+	}
+
+	override func restoreState(with coder: NSCoder) {
+
+		super.restoreState(with: coder)
+
+		if let restoredArticleIDs = (try? coder.decodeTopLevelObject(forKey: TimelineViewController.stateRestorationSelectedArticles)) as? [String] {
+			self.restoreSelection(restoredArticleIDs)
+		}
+	}
+
 	// MARK: Appearance Change
 
 	private func fontSizeDidChange() {
@@ -618,6 +638,8 @@ extension TimelineViewController: NSTableViewDelegate {
 		}
 
 		postTimelineSelectionDidChangeNotification(selectedArticles)
+
+		self.invalidateRestorableState()
 	}
 
 	private func postTimelineSelectionDidChangeNotification(_ selectedArticles: ArticleArray?) {