feat: switcher will show faster (closes #3845)

src/logic/Windows.swift

@@ -4,8 +4,6 @@ class Windows {
     static var list = [Window]()
     static var focusedWindowIndex = Int(0)
     static var hoveredWindowIndex: Int?
-    // the first few thumbnails are the most commonly looked at; we pay special attention to them
-    static let criticalFirstThumbnails = 3
     static var lastWindowActivityType = WindowActivityType.none
 
     /// reordered list based on preferences, keeping the original index
@@ -265,14 +263,7 @@ class Windows {
         Windows.list = sortedTuples.map { $0.1 }
     }
 
-    static func refreshFirstFewThumbnailsSync() {
-        if Appearance.hideThumbnails { return }
-        list.filter { $0.shouldShowTheUser }
-                .prefix(criticalFirstThumbnails)
-                .forEachAsync { window in window.refreshThumbnail() }
-    }
-
-    static func refreshThumbnailsAsync(_ screen: NSScreen, _ currentIndex: Int = criticalFirstThumbnails) {
+    static func refreshThumbnailsAsync(_ screen: NSScreen, _ currentIndex: Int) {
         DispatchQueue.main.async {
             if !App.app.appIsBeingUsed || Appearance.hideThumbnails { return }
             BackgroundWork.mainQueueConcurrentWorkQueue.async {

src/logic/events/KeyboardEvents.swift

@@ -121,6 +121,8 @@ class KeyboardEvents {
 
 fileprivate let cgEventFlagsChangedHandler: CGEventTapCallBack = {_, type, cgEvent, _ in
     if type == .flagsChanged {
+        // TODO: it would be great to shortcut matching and trigger on the background thread
+        // it would enable us to set App.app.isBeingUsed here, and could stop tasks on main when they check the flag
         DispatchQueue.main.async {
             let modifiers = NSEvent.ModifierFlags(rawValue: UInt(cgEvent.flags.rawValue))
             // TODO: ideally, we want to absorb all modifier keys except holdShortcut

src/ui/App.swift

@@ -310,8 +310,6 @@ class App: AppCenterApplication, NSApplicationDelegate {
         guard appIsBeingUsed else { return }
         Appearance.update()
         guard appIsBeingUsed else { return }
-        Windows.refreshFirstFewThumbnailsSync()
-        guard appIsBeingUsed else { return }
         thumbnailsPanel.makeKeyAndOrderFront(nil) // workaround: without this, switching between 2 screens make thumbnailPanel invisible
         guard appIsBeingUsed else { return }
         refreshOpenUi()
@@ -319,7 +317,7 @@ class App: AppCenterApplication, NSApplicationDelegate {
         thumbnailsPanel.show()
         Windows.previewFocusedWindowIfNeeded()
         guard appIsBeingUsed else { return }
-        Windows.refreshThumbnailsAsync(screen)
+        Windows.refreshThumbnailsAsync(screen, 0)
         guard appIsBeingUsed else { return }
         Applications.refreshBadges()
         KeyRepeatTimer.toggleRepeatingKeyNextWindow()