feat: improve selection background/border color contrast

closes #2352

src/logic/Preferences.swift

@@ -94,7 +94,6 @@ class Preferences {
 
     // constant values
     // not exposed as preferences now but may be in the future, probably through macro preferences
-    static var windowMaterial: NSVisualEffectView.Material { .dark }
     static var fontColor: NSColor { .white }
     static var windowPadding: CGFloat { 18 }
     static var interCellPadding: CGFloat { 5 }

src/ui/main-window/ThumbnailView.swift

@@ -3,7 +3,8 @@ import Cocoa
 class ThumbnailView: NSStackView {
     static let windowsControlSize = CGFloat(16)
     static let windowsControlSpacing = CGFloat(8)
-    static let highlightBackgroundColor = NSColor(red: 0, green: 0, blue: 0, alpha: 0.4)
+    static let highlightBackgroundColor = NSColor(red: 0, green: 0, blue: 0, alpha: 0.5)
+    static let highlightBorderColor = NSColor.white
     var window_: Window?
     var thumbnail = NSImageView()
     var appIcon = NSImageView()
@@ -103,7 +104,7 @@ class ThumbnailView: NSStackView {
         layer!.backgroundColor = (Preferences.theme == .macOs && isFocused) || (Preferences.theme == .windows10 && isHovered)
             ? ThumbnailView.highlightBackgroundColor.cgColor : .clear
         layer!.borderColor = (Preferences.theme == .macOs && isHovered) || (Preferences.theme == .windows10 && isFocused)
-            ? NSColor.controlColor.cgColor : .clear
+            ? ThumbnailView.highlightBorderColor.cgColor : .clear
         let newFrameInset = (isFocused) ? -Preferences.intraCellPadding : Preferences.intraCellPadding
         if newFrameInset != frameInset {
             frameInset = newFrameInset

src/ui/main-window/ThumbnailsView.swift

@@ -7,7 +7,7 @@ class ThumbnailsView: NSVisualEffectView {
 
     convenience init() {
         self.init(frame: .zero)
-        material = Preferences.windowMaterial
+        material = .dark
         state = .active
         wantsLayer = true
         updateRoundedCorners(Preferences.windowCornerRadius)