Improve cached startup state and keep directory scans responsive

Latest/Interface/Main Window/Update Table View/Controller/UpdateTableView+Search.swift

@@ -24,7 +24,7 @@ extension UpdateTableViewController {
 		if sender.stringValue.isEmpty {
 			searchQuery = nil
 		}
-		self.scheduleTableViewUpdate(with: self.snapshot.updated(with: searchQuery), animated: false)
+		self.scheduleSnapshotUpdate(withApps: self.snapshot.apps, filterQuery: searchQuery, animated: false)
 
 		// Reload all visible lists
 		self.scrubber?.reloadData()

Latest/Interface/Main Window/Update Table View/Controller/UpdateTableViewController.swift

@@ -13,8 +13,19 @@ import Cocoa
  */
 class UpdateTableViewController: NSViewController, NSMenuItemValidation, NSTableViewDataSource, NSTableViewDelegate, NSMenuDelegate, Observer {
 
+	private struct SnapshotUpdateRequest {
+		let apps: [App]
+		let configuration: AppListSnapshot.Configuration
+		let animated: Bool
+	}
+
 	var id = UUID()
 
+	/// Background queue used to prepare expensive snapshots without blocking the main thread.
+	private let snapshotQueue = DispatchQueue(label: "UpdateTableViewController.snapshot", qos: .userInitiated)
+	private var pendingSnapshotUpdate: SnapshotUpdateRequest?
+	private var snapshotUpdateInProgress = false
+
     /// The array holding the apps that have an update available.
 	var snapshot: AppListSnapshot = AppListSnapshot(withApps: [], filterQuery: nil) {
 		didSet {
@@ -73,8 +84,7 @@ class UpdateTableViewController: NSViewController, NSMenuItemValidation, NSTable
 		AppListSettings.shared.add(self, handler: self.updateSnapshot)
 
 		UpdateCheckCoordinator.shared.appProvider.addObserver(self) { newValue in
-			self.scheduleTableViewUpdate(with: AppListSnapshot(withApps: newValue, filterQuery: self.snapshot.filterQuery), animated: true)
-			self.updateTitleAndBatch()
+			self.scheduleSnapshotUpdate(withApps: newValue, filterQuery: self.snapshot.filterQuery, animated: true)
 		}
 
 		if #available(macOS 11, *) {
@@ -104,8 +114,7 @@ class UpdateTableViewController: NSViewController, NSMenuItemValidation, NSTable
     @IBOutlet weak var tableView: NSTableView!
 
 	func updateSnapshot() {
-		self.scheduleTableViewUpdate(with: self.snapshot.updated(), animated: true)
-		self.updateTitleAndBatch()
+		self.scheduleSnapshotUpdate(withApps: self.snapshot.apps, filterQuery: self.snapshot.filterQuery, animated: true)
 	}
 
 
@@ -251,6 +260,40 @@ class UpdateTableViewController: NSViewController, NSMenuItemValidation, NSTable
 	/// Whether a table view update is currently ongoing.
 	private var tableViewUpdateInProgress = false
 
+	func scheduleSnapshotUpdate(withApps apps: [App], filterQuery: String?, animated: Bool) {
+		let request = SnapshotUpdateRequest(
+			apps: apps,
+			configuration: AppListSnapshot.Configuration(filterQuery: filterQuery),
+			animated: animated
+		)
+		pendingSnapshotUpdate = request
+		startNextSnapshotUpdateIfNeeded()
+	}
+
+	private func startNextSnapshotUpdateIfNeeded() {
+		guard !snapshotUpdateInProgress, let request = pendingSnapshotUpdate else { return }
+		pendingSnapshotUpdate = nil
+		snapshotUpdateInProgress = true
+
+		snapshotQueue.async {
+			let snapshot = AppListSnapshot(withApps: request.apps, configuration: request.configuration)
+
+			DispatchQueue.main.async {
+				let shouldAnimate = request.animated && self.shouldAnimateTransition(from: self.snapshot, to: snapshot)
+				self.scheduleTableViewUpdate(with: snapshot, animated: shouldAnimate)
+				self.updateTitleAndBatch()
+				self.snapshotUpdateInProgress = false
+				self.startNextSnapshotUpdateIfNeeded()
+			}
+		}
+	}
+
+	private func shouldAnimateTransition(from oldSnapshot: AppListSnapshot, to newSnapshot: AppListSnapshot) -> Bool {
+		let maxEntryCount = max(oldSnapshot.entries.count, newSnapshot.entries.count)
+		let delta = abs(oldSnapshot.entries.count - newSnapshot.entries.count)
+		return maxEntryCount <= 150 && delta <= 30
+	}
+
 	/// Schedules a table view update with the given snapshot.
 	func scheduleTableViewUpdate(with snapshot: AppListSnapshot, animated: Bool) {
 		self.newSnapshot = snapshot

Latest/Interface/Main Window/Views/UpdateButton.swift

@@ -126,7 +126,7 @@ class UpdateButton: NSButton {
 		switch state {
 		case .none:
 			if let app = self.app, self.showActionButton {
-				self.updateInterfaceVisibility(with: app.updateAvailable ? .update : .open)
+				self.updateInterfaceVisibility(with: app.updateAvailable ? (app.canPerformUpdate ? .update : .open) : .open)
 			} else {
 				self.updateInterfaceVisibility(with: .none)
 			}