Update window border.

src/Helpers.swift

@@ -86,14 +86,6 @@ func systemImage(_ name: String, _ size: NSFont.TextStyle, _ scale: NSImage.Symb
         .withSymbolConfiguration(NSImage.SymbolConfiguration(textStyle: size, scale: scale).applying(configuration))
 }
 
-func isDirectory(atPath path: String) -> Bool {
-    var isDir: ObjCBool = false
-    if FileManager.default.fileExists(atPath: path, isDirectory: &isDir) {
-        return isDir.boolValue
-    }
-    return false
-}
-
 extension String {
     // This converts string to UInt as a fourCharCode
     public var fourCharCodeValue: Int {

src/SearchViewController.swift

@@ -44,7 +44,6 @@ class SearchViewController: NSViewController, NSTextFieldDelegate, NSPopoverDele
         effect.wantsLayer = true
         effect.layer?.masksToBounds = true
 
-        effect.layer?.borderColor = NSColor.labelColor.withAlphaComponent(0.2).cgColor
         effect.layer?.borderWidth = 1
         effect.layer?.cornerRadius = windowCornerRadius
 
@@ -167,11 +166,16 @@ class SearchViewController: NSViewController, NSTextFieldDelegate, NSPopoverDele
     override func viewDidLoad() {
         super.viewDidLoad()
 
+        // NOTE: This needs removeObserver on deinit?
+        DistributedNotificationCenter.default.addObserver(self, selector: #selector(osThemeChanged(sender:)), name: NSNotification.Name(rawValue: "AppleInterfaceThemeChangedNotification"), object: nil)
+
         // Initialize an array of reusable cells.
         for _ in 0..<maxItems {
             programsListCells.append(ProgramsTableViewCell())
         }
 
+        updateViewsBasedOnTheme()
+
         view.wantsLayer = true
         view.layer?.backgroundColor = NSColor.clear.cgColor
 
@@ -362,4 +366,16 @@ class SearchViewController: NSViewController, NSTextFieldDelegate, NSPopoverDele
             programsTableViewSelection = programsTableView.selectedRow
         }
     }
+
+    @objc func osThemeChanged(sender: NSNotification) {
+        updateViewsBasedOnTheme()
+    }
+
+    @objc func updateViewsBasedOnTheme() {
+        if NSApp.windows.first?.effectiveAppearance.bestMatch(from: [.darkAqua, .vibrantDark]) == .darkAqua { // dark
+            backgroundView.layer?.borderColor = NSColor.white.withAlphaComponent(0.2).cgColor
+        } else { // light
+            backgroundView.layer?.borderColor = NSColor.black.withAlphaComponent(0.2).cgColor
+        }
+    }
 }