Using a less suspicious way to customize window buttons suggested by @jnadeau

Author: insidegui

EventsUI/EventsUI/EVTWindow.swift

@@ -36,12 +36,7 @@ open class EVTWindow: NSWindow {
         return NSAppearance(named: NSAppearanceNameVibrantDark)!
     }
 
-    fileprivate var titlebarWidgets: [NSButton]? {
-        return titlebarView?.subviews.flatMap { subview in
-            guard subview.isKind(of: NSClassFromString("_NSThemeWidget")!) else { return nil }
-            return subview as? NSButton
-        }
-    }
+    fileprivate var titlebarWidgets = Set<NSButton>()
 
     fileprivate func appearanceForWidgets() -> NSAppearance? {
         if allowsPiPMode {
@@ -53,7 +48,7 @@ open class EVTWindow: NSWindow {
 
     fileprivate func applyAppearanceToWidgets() {
         let appearance = appearanceForWidgets()
-        titlebarWidgets?.forEach { $0.appearance = appearance }
+        titlebarWidgets.forEach { $0.appearance = appearance }
     }
 
     fileprivate var _storedTitlebarView: NSVisualEffectView?
@@ -192,6 +187,14 @@ open class EVTWindow: NSWindow {
             }, completionHandler: nil)
     }
 
+    open override func standardWindowButton(_ b: NSWindowButton) -> NSButton? {
+        guard let button = super.standardWindowButton(b) else { return nil }
+        
+        titlebarWidgets.insert(button)
+        
+        return button
+    }
+    
     // MARK: - Content management
 
     open override var title: String {