fix: ui would take time to display sometimes (see #563)

src/logic/Applications.swift

@@ -81,10 +81,10 @@ class Applications {
 
     static func refreshBadges_(_ items: [(URL?, String?)], _ currentIndex: Int = 0) {
         Windows.list.enumerated().forEach { (i, window) in
+            if !App.app.appIsBeingUsed { return }
             let view = ThumbnailsView.recycledViews[i]
             if let app = (Applications.list.first { window.application.pid == $0.pid }) {
-                if App.app.appIsBeingUsed,
-                   app.runningApplication.activationPolicy == .regular,
+                if app.runningApplication.activationPolicy == .regular,
                    let bundleId = app.runningApplication.bundleIdentifier,
                    let url = NSWorkspace.shared.urlForApplication(withBundleIdentifier: bundleId),
                    let matchingItem = (items.first { $0.0 == url }),

src/logic/BackgroundWork.swift

@@ -30,7 +30,7 @@ class BackgroundWork {
 
 extension DispatchQueue {
     static func globalConcurrent(_ label: String, _ qos: DispatchQoS) -> DispatchQueue {
-        return DispatchQueue(label: label, target: .global(qos: qos.qosClass))
+        return DispatchQueue(label: label, attributes: .concurrent, target: .global(qos: qos.qosClass))
     }
 
     func asyncWithCap(_ deadline: DispatchTime? = nil, _ fn: @escaping () -> Void) {

src/ui/App.swift

@@ -259,8 +259,6 @@ class App: AppCenterApplication, NSApplicationDelegate {
         guard appIsBeingUsed else { return }
         Windows.refreshFirstFewThumbnailsSync()
         guard appIsBeingUsed else { return }
-        Applications.refreshBadges()
-        guard appIsBeingUsed else { return }
         thumbnailsPanel.makeKeyAndOrderFront(nil) // workaround: without this, switching between 2 monitors make thumbnailPanel invisible
         guard appIsBeingUsed else { return }
         refreshOpenUi()