ui: frost the empty player window background

README.md

@@ -188,6 +188,8 @@ The layout follows [IINA's video-first window](https://iina.io/img/screenshot.pn
 
 The empty player uses the same HUD-glass material, 12-point rounded corners, and muted icon/text palette in a centered welcome card. File and YouTube opening actions share a consistently sized row; the card fits the 400 × 240-point minimum window, and the full window still accepts media-file and YouTube-link drops.
 
+With no media open, the full window uses native behind-window HUD glass to frost the desktop and windows beneath it. The idle Metal surface stays attached but hidden; opening media restores a solid black background and letterboxing, and closing it restores the frosted background. macOS controls the material’s appearance, including Reduce Transparency.
+
 Opening video fits the window to its display aspect ratio, including non-square pixels, and constrains subsequent window resizing. Fullscreen retains the normal letterboxed renderer; audio-only playback and close release the aspect constraint. Extreme ratios that cannot fit both the screen and usable controls keep a freely resizable letterboxed window.
 
 **Compact mode** uses the same window, Metal view, and playback session—not a second window or macOS system PiP. Use the PiP-shaped button in the normal playback controls, **⌃⌘P**, or **Playback Actions → Enter Compact Mode**. The compact-mode button replaces the fullscreen button; fullscreen remains available through its menu, keyboard shortcuts, and double-clicking normal-mode video. Compact mode starts at the current screen's top-right corner with a 16-point inset and a preferred width of 320 points, preserving display aspect where usable screen bounds and the 160 × 90-point minimum allow; extreme ratios retain letterboxing. Compact mode floats above ordinary windows, joins all Spaces, and is configured to join eligible other-app fullscreen spaces and Stage Manager sets. Small hover controls provide play/pause, restore, and Playback Actions; keyboard playback controls remain available.

Sources/App/TerebiApp.swift

@@ -999,17 +999,20 @@ final class PlayerModel: ObservableObject {
 @MainActor
 private struct PlayerGlass: NSViewRepresentable {
     var titlebar = false
+    var blendingMode: NSVisualEffectView.BlendingMode = .withinWindow
 
     func makeNSView(context: Context) -> NSVisualEffectView {
         let view = NSVisualEffectView()
-        view.blendingMode = .withinWindow
+        view.blendingMode = blendingMode
         view.state = .active
         view.appearance = NSAppearance(named: .vibrantDark)
         view.material = titlebar ? .titlebar : .hudWindow
         return view
     }
 
-    func updateNSView(_ view: NSVisualEffectView, context: Context) {}
+    func updateNSView(_ view: NSVisualEffectView, context: Context) {
+        view.blendingMode = blendingMode
+    }
 }
 
 @MainActor
@@ -1389,10 +1392,17 @@ private struct PlayerContent: View {
     var body: some View {
         GeometryReader { geometry in
             ZStack(alignment: .top) {
-                Color.black
+                if model.fileName == nil {
+                    PlayerGlass(blendingMode: .behindWindow)
+                        .allowsHitTesting(false)
+                        .accessibilityHidden(true)
+                } else {
+                    Color.black
+                }
                 if let view = model.videoView {
                     VideoSurface(view: view)
                         .accessibilityLabel("Video")
+                        .opacity(model.fileName == nil ? 0 : 1)
                         .gesture(
                             TapGesture(count: 2).onEnded { model.toggleFullScreen() }
                                 .exclusively(before: TapGesture().onEnded { model.hideControls() })
@@ -1607,7 +1617,8 @@ private struct WindowChrome: NSViewRepresentable {
             window.styleMask.insert(.fullSizeContentView)
             window.titleVisibility = .hidden
             window.titlebarAppearsTransparent = true
-            window.backgroundColor = .black
+            window.isOpaque = false
+            window.backgroundColor = .clear
             window.acceptsMouseMovedEvents = true
             window.collectionBehavior.insert(.fullScreenPrimary)
             window.appearance = NSAppearance(named: .darkAqua)