Create and use IconImageCache. It centralizes and de-dupes logic for getting feed/article images, and it caches the results, which helps performance.

Mac/Inspector/WebFeedInspectorViewController.swift

@@ -146,18 +146,7 @@ private extension WebFeedInspectorViewController {
 		guard let feed = feed, let iconView = iconView else {
 			return
 		}
-
+		iconView.iconImage = IconImageCache.shared.imageForFeed(feed)
-		if let feedIcon = appDelegate.webFeedIconDownloader.icon(for: feed) {
-			iconView.iconImage = feedIcon
-			return
-		}
-
-		if let favicon = appDelegate.faviconDownloader.favicon(for: feed) {
-			iconView.iconImage = favicon
-			return
-		}
-
-		iconView.iconImage = feed.smallIcon
 	}
 
 	func updateName() {

Mac/MainWindow/Sidebar/SidebarViewController.swift

@@ -763,7 +763,7 @@ private extension SidebarViewController {
 	}
 
 	func imageFor(_ node: Node) -> IconImage? {
-		if let feed = node.representedObject as? WebFeed, let feedIcon = appDelegate.webFeedIconDownloader.icon(for: feed) {
+		if let feed = node.representedObject as? WebFeed, let feedIcon = IconImageCache.shared.imageForFeed(feed) {
 			return feedIcon
 		}
 		if let smallIconProvider = node.representedObject as? SmallIconProvider {

Mac/MainWindow/Timeline/TimelineViewController.swift

@@ -886,28 +886,7 @@ extension TimelineViewController: NSTableViewDelegate {
 		if !showIcons {
 			return nil
 		}
-		
+		return IconImageCache.shared.imageForArticle(article)
-		if let authors = article.authors {
-			for author in authors {
-				if let image = avatarForAuthor(author) {
-					return image
-				}
-			}
-		}
-
-		guard let feed = article.webFeed else {
-			return nil
-		}
-
-		if let feedIcon = appDelegate.webFeedIconDownloader.icon(for: feed) {
-			return feedIcon
-		}
-
-		if let favicon = appDelegate.faviconDownloader.faviconAsIcon(for: feed) {
-			return favicon
-		}
-		
-		return FaviconGenerator.favicon(feed)
 	}
 
 	private func avatarForAuthor(_ author: Author) -> IconImage? {

Multiplatform/Shared/Images/FeedIconImageLoader.swift

@@ -41,20 +41,6 @@ final class FeedIconImageLoader: ObservableObject {
 private extension FeedIconImageLoader {
 	
 	func fetchImage() {
-		if let webFeed = feed as? WebFeed {
+		image = IconImageCache.shared.imageForFeed(feed)
-			if let feedIconImage = appDelegate.webFeedIconDownloader.icon(for: webFeed) {
-				image = feedIconImage
-				return
-			}
-			if let faviconImage = appDelegate.faviconDownloader.faviconAsIcon(for: webFeed) {
-				image = faviconImage
-				return
-			}
-		}
-		
-		if let smallIconProvider = feed as? SmallIconProvider {
-			image = smallIconProvider.smallIcon
-		}
 	}
-	
 }

NetNewsWire.xcodeproj/project.pbxproj

@@ -1011,6 +1011,9 @@
 		844B5B691FEA20DF00C7C76A /* SidebarKeyboardShortcuts.plist in Resources */ = {isa = PBXBuildFile; fileRef = 844B5B681FEA20DF00C7C76A /* SidebarKeyboardShortcuts.plist */; };
 		845213231FCA5B11003B6E93 /* ImageDownloader.swift in Sources */ = {isa = PBXBuildFile; fileRef = 845213221FCA5B10003B6E93 /* ImageDownloader.swift */; };
 		845479881FEB77C000AD8B59 /* TimelineKeyboardShortcuts.plist in Resources */ = {isa = PBXBuildFile; fileRef = 845479871FEB77C000AD8B59 /* TimelineKeyboardShortcuts.plist */; };
+		8454C3F3263F2D8700E3F9C7 /* IconImageCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8454C3F2263F2D8700E3F9C7 /* IconImageCache.swift */; };
+		8454C3F8263F3AD400E3F9C7 /* IconImageCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8454C3F2263F2D8700E3F9C7 /* IconImageCache.swift */; };
+		8454C3FD263F3AD600E3F9C7 /* IconImageCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8454C3F2263F2D8700E3F9C7 /* IconImageCache.swift */; };
 		845A29091FC74B8E007B49E3 /* SingleFaviconDownloader.swift in Sources */ = {isa = PBXBuildFile; fileRef = 845A29081FC74B8E007B49E3 /* SingleFaviconDownloader.swift */; };
 		845A29221FC9251E007B49E3 /* SidebarCellLayout.swift in Sources */ = {isa = PBXBuildFile; fileRef = 845A29211FC9251E007B49E3 /* SidebarCellLayout.swift */; };
 		845A29241FC9255E007B49E3 /* SidebarCellAppearance.swift in Sources */ = {isa = PBXBuildFile; fileRef = 845A29231FC9255E007B49E3 /* SidebarCellAppearance.swift */; };
@@ -1885,6 +1888,7 @@
 		844B5B681FEA20DF00C7C76A /* SidebarKeyboardShortcuts.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = SidebarKeyboardShortcuts.plist; sourceTree = "<group>"; };
 		845213221FCA5B10003B6E93 /* ImageDownloader.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ImageDownloader.swift; sourceTree = "<group>"; };
 		845479871FEB77C000AD8B59 /* TimelineKeyboardShortcuts.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = TimelineKeyboardShortcuts.plist; sourceTree = "<group>"; };
+		8454C3F2263F2D8700E3F9C7 /* IconImageCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IconImageCache.swift; sourceTree = "<group>"; };
 		845A29081FC74B8E007B49E3 /* SingleFaviconDownloader.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SingleFaviconDownloader.swift; sourceTree = "<group>"; };
 		845A29211FC9251E007B49E3 /* SidebarCellLayout.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SidebarCellLayout.swift; sourceTree = "<group>"; };
 		845A29231FC9255E007B49E3 /* SidebarCellAppearance.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SidebarCellAppearance.swift; sourceTree = "<group>"; };
@@ -3418,6 +3422,7 @@
 				842E45CD1ED8C308000A8B52 /* AppNotifications.swift */,
 				51C4CFEF24D37D1F00AF9874 /* Secrets.swift */,
 				511B9805237DCAC90028BCAA /* UserInfoKey.swift */,
+				8454C3F2263F2D8700E3F9C7 /* IconImageCache.swift */,
 				51C452AD2265102800C03939 /* Timeline */,
 				84702AB31FA27AE8006B8943 /* Commands */,
 				51934CCC231078DC006127BE /* Activity */,
@@ -5127,6 +5132,7 @@
 				65ED4007235DEF6C0081F399 /* AddFeedController.swift in Sources */,
 				65ED4008235DEF6C0081F399 /* AccountRefreshTimer.swift in Sources */,
 				65ED4009235DEF6C0081F399 /* SidebarStatusBarView.swift in Sources */,
+				8454C3FD263F3AD600E3F9C7 /* IconImageCache.swift in Sources */,
 				65ED400A235DEF6C0081F399 /* SearchTimelineFeedDelegate.swift in Sources */,
 				65ED400B235DEF6C0081F399 /* TodayFeedDelegate.swift in Sources */,
 				65ED400C235DEF6C0081F399 /* FolderInspectorViewController.swift in Sources */,
@@ -5352,6 +5358,7 @@
 				516AE9B32371C372007DEEAA /* MasterFeedTableViewSectionHeaderLayout.swift in Sources */,
 				51DC370B2405BC9A0095D371 /* PreloadedWebView.swift in Sources */,
 				D3555BF524664566005E48C3 /* ArticleSearchBar.swift in Sources */,
+				8454C3F3263F2D8700E3F9C7 /* IconImageCache.swift in Sources */,
 				B24E9ADE245AB88400DA5718 /* NSAttributedString+NetNewsWire.swift in Sources */,
 				C5A6ED5223C9AF4300AB6BE2 /* TitleActivityItemSource.swift in Sources */,
 				51DC37092402F1470095D371 /* MasterFeedDataSourceOperation.swift in Sources */,
@@ -5522,6 +5529,7 @@
 				849A97771ED9EC04007D329B /* TimelineCellData.swift in Sources */,
 				841ABA6020145EC100980E11 /* BuiltinSmartFeedInspectorViewController.swift in Sources */,
 				D5E4CC54202C1361009B4FFC /* AppDelegate+Scriptability.swift in Sources */,
+				8454C3F8263F3AD400E3F9C7 /* IconImageCache.swift in Sources */,
 				518651B223555EB20078E021 /* NNW3Document.swift in Sources */,
 				D5F4EDB5200744A700B9E363 /* ScriptingObject.swift in Sources */,
 				D5F4EDB920074D7C00B9E363 /* Folder+Scriptability.swift in Sources */,

Shared/Activity/ActivityManager.swift

@@ -248,12 +248,11 @@ private extension ActivityManager {
 		attributeSet.title = feed.nameForDisplay
 		attributeSet.keywords = makeKeywords(feed.nameForDisplay)
 		attributeSet.relatedUniqueIdentifier = ActivityManager.identifer(for: feed)
-		if let iconImage = appDelegate.webFeedIconDownloader.icon(for: feed) {
+
-			attributeSet.thumbnailData = iconImage.image.dataRepresentation()
+		if let iconImage = IconImageCache.shared.imageForFeed(feed) {
-		} else if let iconImage = appDelegate.faviconDownloader.faviconAsIcon(for: feed) {
 			attributeSet.thumbnailData = iconImage.image.dataRepresentation()
 		}
-		
+
 		selectingActivity!.contentAttributeSet = attributeSet
 		selectingActivity!.needsSave = true
 		

Shared/Extensions/ArticleUtilities.swift

@@ -96,32 +96,7 @@ extension Article {
 	}
 
 	func iconImage() -> IconImage? {
-		if let authors = authors, authors.count == 1, let author = authors.first {
+		return IconImageCache.shared.imageForArticle(self)
-			if let image = appDelegate.authorAvatarDownloader.image(for: author) {
-				return image
-			}
-		}
-		
-		if let authors = webFeed?.authors, authors.count == 1, let author = authors.first {
-			if let image = appDelegate.authorAvatarDownloader.image(for: author) {
-				return image
-			}
-		}
-
-		guard let webFeed = webFeed else {
-			return nil
-		}
-		
-		let feedIconImage = appDelegate.webFeedIconDownloader.icon(for: webFeed)
-		if feedIconImage != nil {
-			return feedIconImage
-		}
-		
-		if let faviconImage = appDelegate.faviconDownloader.faviconAsIcon(for: webFeed) {
-			return faviconImage
-		}
-		
-		return FaviconGenerator.favicon(webFeed)
 	}
 	
 	func iconImageUrl(webFeed: WebFeed) -> URL? {

Shared/IconImageCache.swift

@@ -0,0 +1,129 @@
+//
+//  IconImageCache.swift
+//  NetNewsWire-iOS
+//
+//  Created by Brent Simmons on 5/2/21.
+//  Copyright © 2021 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+import Account
+import Articles
+
+class IconImageCache {
+
+	static var shared = IconImageCache()
+
+	private var smartFeedIconImageCache = [FeedIdentifier: IconImage]()
+	private var webFeedIconImageCache = [FeedIdentifier: IconImage]()
+	private var faviconImageCache = [FeedIdentifier: IconImage]()
+	private var smallIconImageCache = [FeedIdentifier: IconImage]()
+	private var authorIconImageCache = [Author: IconImage]()
+
+	func imageFor(_ feedID: FeedIdentifier) -> IconImage? {
+		if let smartFeed = SmartFeedsController.shared.find(by: feedID) {
+			return imageForFeed(smartFeed)
+		}
+		if let feed = AccountManager.shared.existingFeed(with: feedID) {
+			return imageForFeed(feed)
+		}
+		return nil
+	}
+
+	func imageForFeed(_ feed: Feed) -> IconImage? {
+		guard let feedID = feed.feedID else {
+			return nil
+		}
+		
+		if let smartFeed = feed as? PseudoFeed {
+			return imageForSmartFeed(smartFeed, feedID)
+		}
+		if let webFeed = feed as? WebFeed, let iconImage = imageForWebFeed(webFeed, feedID) {
+			return iconImage
+		}
+		if let smallIconProvider = feed as? SmallIconProvider {
+			return imageForSmallIconProvider(smallIconProvider, feedID)
+		}
+
+		return nil
+	}
+
+	func imageForArticle(_ article: Article) -> IconImage? {
+		if let iconImage = imageForAuthors(article.authors) {
+			return iconImage
+		}
+		guard let feed = article.webFeed else {
+			return nil
+		}
+		return imageForFeed(feed)
+	}
+
+	func emptyCache() {
+		smartFeedIconImageCache = [FeedIdentifier: IconImage]()
+		webFeedIconImageCache = [FeedIdentifier: IconImage]()
+		faviconImageCache = [FeedIdentifier: IconImage]()
+		smallIconImageCache = [FeedIdentifier: IconImage]()
+		authorIconImageCache = [Author: IconImage]()
+	}
+}
+
+private extension IconImageCache {
+	
+	func imageForSmartFeed(_ smartFeed: PseudoFeed, _ feedID: FeedIdentifier) -> IconImage? {
+		if let iconImage = smartFeedIconImageCache[feedID] {
+			return iconImage
+		}
+		if let iconImage = smartFeed.smallIcon {
+			smartFeedIconImageCache[feedID] = iconImage
+			return iconImage
+		}
+		return nil
+	}
+
+	func imageForWebFeed(_ webFeed: WebFeed, _ feedID: FeedIdentifier) -> IconImage? {
+		if let iconImage = webFeedIconImageCache[feedID] {
+			return iconImage
+		}
+		if let iconImage = appDelegate.webFeedIconDownloader.icon(for: webFeed) {
+			webFeedIconImageCache[feedID] = iconImage
+			return iconImage
+		}
+		if let faviconImage = faviconImageCache[feedID] {
+			return faviconImage
+		}
+		if let faviconImage = appDelegate.faviconDownloader.faviconAsIcon(for: webFeed) {
+			faviconImageCache[feedID] = faviconImage
+			return faviconImage
+		}
+		return nil
+	}
+
+	func imageForSmallIconProvider(_ provider: SmallIconProvider, _ feedID: FeedIdentifier) -> IconImage? {
+		if let iconImage = smallIconImageCache[feedID] {
+			return iconImage
+		}
+		if let iconImage = provider.smallIcon {
+			smallIconImageCache[feedID] = iconImage
+			return iconImage
+		}
+		return nil
+	}
+
+	func imageForAuthors(_ authors: Set<Author>?) -> IconImage? {
+		guard let authors = authors, authors.count == 1, let author = authors.first else {
+			return nil
+		}
+		return imageForAuthor(author)
+	}
+
+	func imageForAuthor(_ author: Author) -> IconImage? {
+		if let iconImage = authorIconImageCache[author] {
+			return iconImage
+		}
+		if let iconImage = appDelegate.authorAvatarDownloader.image(for: author) {
+			authorIconImageCache[author] = iconImage
+			return iconImage
+		}
+		return nil
+	}
+}

iOS/AppDelegate.swift

@@ -132,6 +132,10 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
 	func applicationWillTerminate(_ application: UIApplication) {
 		shuttingDown = true
 	}
+
+	func applicationDidEnterBackground(_ application: UIApplication) {
+		IconImageCache.shared.emptyCache()
+	}
 	
 	// MARK: Notifications
 	

iOS/Inspector/WebFeedInspectorViewController.swift

@@ -23,14 +23,8 @@ class WebFeedInspectorViewController: UITableViewController {
 	@IBOutlet weak var feedURLLabel: InteractiveLabel!
 	
 	private var headerView: InspectorIconHeaderView?
-	private var iconImage: IconImage {
+	private var iconImage: IconImage? {
-		if let feedIcon = appDelegate.webFeedIconDownloader.icon(for: webFeed) {
+		return IconImageCache.shared.imageForFeed(webFeed)
-			return feedIcon
-		}
-		if let favicon = appDelegate.faviconDownloader.faviconAsIcon(for: webFeed) {
-			return favicon
-		}
-		return FaviconGenerator.favicon(webFeed)
 	}
 	
 	private let homePageIndexPath = IndexPath(row: 0, section: 1)

iOS/MasterFeed/MasterFeedViewController.swift

@@ -42,11 +42,6 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		return true
 	}
 
-	private var smartFeedIconImageCache = [FeedIdentifier: IconImage]()
-	private var webFeedIconImageCache = [FeedIdentifier: IconImage]()
-	private var faviconImageCache = [FeedIdentifier: IconImage]()
-	private var smallIconImageCache = [FeedIdentifier: IconImage]()
-
 	override func viewDidLoad() {
 
 		super.viewDidLoad()
@@ -91,12 +86,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	}
 	
 	override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
-		// Empty IconImage caches
+		IconImageCache.shared.emptyCache()
-		smartFeedIconImageCache = [FeedIdentifier: IconImage]()
-		webFeedIconImageCache = [FeedIdentifier: IconImage]()
-		faviconImageCache = [FeedIdentifier: IconImage]()
-		smallIconImageCache = [FeedIdentifier: IconImage]()
-
 		super.traitCollectionDidChange(previousTraitCollection)
 		reloadAllVisibleCells()
 	}
@@ -858,69 +848,12 @@ private extension MasterFeedViewController {
 	}
 	
 	func configureIcon(_ cell: MasterFeedTableViewCell, _ identifier: MasterFeedTableViewIdentifier) {
-		cell.iconImage = imageFor(identifier)
+		guard let feedID = identifier.feedID else {
+			return
+		}
+		cell.iconImage = IconImageCache.shared.imageFor(feedID)
 	}
 
-	func imageFor(_ identifier: MasterFeedTableViewIdentifier) -> IconImage? {
-		guard let feedID = identifier.feedID else { return nil }
-		
-		if let smartFeed = SmartFeedsController.shared.find(by: feedID) {
-			return imageForSmartFeed(smartFeed, feedID)
-		}
-		
-		guard let feed = AccountManager.shared.existingFeed(with: feedID) else { return nil }
-
-		if let webFeed = feed as? WebFeed, let iconImage = imageForWebFeed(webFeed, feedID) {
-			return iconImage
-		}
-		
-		if let smallIconProvider = feed as? SmallIconProvider, let iconImage = imageForSmallIconProvider(smallIconProvider, feedID) {
-			return iconImage
-		}
-		
-		return nil
-	}
-
-	func imageForSmartFeed(_ smartFeed: PseudoFeed, _ feedID: FeedIdentifier) -> IconImage? {
-		if let iconImage = smartFeedIconImageCache[feedID] {
-			return iconImage
-		}
-		if let iconImage = smartFeed.smallIcon {
-			smartFeedIconImageCache[feedID] = iconImage
-			return iconImage
-		}
-		return nil
-	}
-
-	func imageForWebFeed(_ webFeed: WebFeed, _ feedID: FeedIdentifier) -> IconImage? {
-		if let iconImage = webFeedIconImageCache[feedID] {
-			return iconImage
-		}
-		if let iconImage = appDelegate.webFeedIconDownloader.icon(for: webFeed) {
-			webFeedIconImageCache[feedID] = iconImage
-			return iconImage
-		}
-		if let faviconImage = faviconImageCache[feedID] {
-			return faviconImage
-		}
-		if let faviconImage = appDelegate.faviconDownloader.faviconAsIcon(for: webFeed) {
-			faviconImageCache[feedID] = faviconImage
-			return faviconImage
-		}
-		return nil
-	}
-
-	func imageForSmallIconProvider(_ provider: SmallIconProvider, _ feedID: FeedIdentifier) -> IconImage? {
-		if let iconImage = smallIconImageCache[feedID] {
-			return iconImage
-		}
-		if let iconImage = provider.smallIcon {
-			smallIconImageCache[feedID] = iconImage
-			return iconImage
-		}
-		return nil
-	}
-	
 	func nameFor(_ node: Node) -> String {
 		if let displayNameProvider = node.representedObject as? DisplayNameProvider {
 			return displayNameProvider.nameForDisplay

iOS/SceneCoordinator.swift

@@ -146,22 +146,12 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 	
 	// At some point we should refactor the current Feed IndexPath out and only use the timeline feed
 	private(set) var currentFeedIndexPath: IndexPath?
-	
+
 	var timelineIconImage: IconImage? {
-		if let feed = timelineFeed as? WebFeed {
+		guard let timelineFeed = timelineFeed else {
-			
+			return nil
-			let feedIconImage = appDelegate.webFeedIconDownloader.icon(for: feed)
-			if feedIconImage != nil {
-				return feedIconImage
-			}
-			
-			if let faviconIconImage = appDelegate.faviconDownloader.faviconAsIcon(for: feed) {
-				return faviconIconImage
-			}
-			
 		}
-		
+		return IconImageCache.shared.imageForFeed(timelineFeed)
-		return (timelineFeed as? SmallIconProvider)?.smallIcon
 	}
 	
 	private var exceptionArticleFetcher: ArticleFetcher?