Allow adjusting window background blur

Sources/Luminare/Components/Auxiliary/LuminareBackgroundTintOverlay.swift

@@ -0,0 +1,20 @@
+//
+//  LuminareBackgroundTintOverlay.swift
+//  Luminare
+//
+//  Created by Adon Omeri on 2025-03-24.
+//
+
+import SwiftUI
+
+/// The tint overlay applied on top of any `VisualEffectView` inside Luminare backgrounds.
+struct LuminareBackgroundTintOverlay: View {
+    @Environment(\.colorScheme) private var colorScheme
+
+    var body: some View {
+        Rectangle()
+            .foregroundStyle(.tint)
+            .opacity(colorScheme == .light ? 0.025 : 0.1)
+            .blendMode(.multiply)
+    }
+}

Sources/Luminare/Components/Auxiliary/Modifiers/LuminareBackgroundEffectModifier.swift

@@ -10,20 +10,20 @@ import SwiftUI
 /// A background effect that matches ``Luminare``.
 public struct LuminareBackgroundEffectModifier: ViewModifier {
     @Environment(\.colorScheme) private var colorscheme
+    @Environment(\.luminareBackgroundBlurStyle) private var blurStyle
 
     public func body(content: Content) -> some View {
         content
             .background {
                 ZStack {
-                    VisualEffectView(
-                        material: .menu,
-                        blendingMode: .behindWindow
-                    )
+                    if blurStyle == .regular {
+                        VisualEffectView(
+                            material: .menu,
+                            blendingMode: .behindWindow
+                        )
 
-                    Rectangle()
-                        .foregroundStyle(.tint)
-                        .opacity(colorscheme == .light ? 0.025 : 0.1)
-                        .blendMode(.multiply)
+                        LuminareBackgroundTintOverlay()
+                    }
                 }
                 .compositingGroup()
                 .ignoresSafeArea()

Sources/Luminare/Components/Auxiliary/VisualEffectView.swift

@@ -7,17 +7,82 @@
 
 import SwiftUI
 
+/// Source: https://oskargroth.com/blog/reverse-engineering-nsvisualeffectview
 struct VisualEffectView: NSViewRepresentable {
     let material: NSVisualEffectView.Material
     let blendingMode: NSVisualEffectView.BlendingMode
+    let blurStyle: LuminareBackgroundBlurStyle
+
+    init(
+        material: NSVisualEffectView.Material,
+        blendingMode: NSVisualEffectView.BlendingMode,
+        blurStyle: LuminareBackgroundBlurStyle = .regular
+    ) {
+        self.material = material
+        self.blendingMode = blendingMode
+        self.blurStyle = blurStyle
+    }
 
     func makeNSView(context _: Context) -> NSVisualEffectView {
         let visualEffectView = NSVisualEffectView()
         visualEffectView.material = material
         visualEffectView.blendingMode = blendingMode
         visualEffectView.isEmphasized = true
+        applyCustomBlurIfNeeded(to: visualEffectView)
         return visualEffectView
     }
 
-    func updateNSView(_: NSVisualEffectView, context _: Context) {}
+    func updateNSView(_ view: NSVisualEffectView, context _: Context) {
+        view.material = material
+        view.blendingMode = blendingMode
+        applyCustomBlurIfNeeded(to: view)
+    }
+
+    private func applyCustomBlurIfNeeded(to view: NSVisualEffectView) {
+        guard case let .custom(radius) = blurStyle else {
+            return
+        }
+
+        view.wantsLayer = true
+
+        DispatchQueue.main.async {
+            guard let backdropLayer = backdropLayer(in: view) else {
+                return
+            }
+
+            backdropLayer.setValue(radius, forKeyPath: "filters.gaussianBlur.inputRadius")
+        }
+    }
+
+    private func backdropLayer(in view: NSView) -> CALayer? {
+        if let layer = backdropLayer(in: view.layer) {
+            return layer
+        }
+
+        for subview in view.subviews {
+            if let layer = backdropLayer(in: subview) {
+                return layer
+            }
+        }
+
+        return nil
+    }
+
+    private func backdropLayer(in layer: CALayer?) -> CALayer? {
+        guard let layer else {
+            return nil
+        }
+
+        if String(describing: type(of: layer)).contains("Backdrop") {
+            return layer
+        }
+
+        for sublayer in layer.sublayers ?? [] {
+            if let backdropLayer = backdropLayer(in: sublayer) {
+                return backdropLayer
+            }
+        }
+
+        return nil
+    }
 }

Sources/Luminare/Main Window/LuminareView.swift

@@ -16,6 +16,7 @@ public struct LuminareView<Content>: View where Content: View {
     // MARK: Environments
 
     @Environment(\.luminareTintColor) private var tintColor
+    @Environment(\.luminareBackgroundBlurStyle) private var backgroundBlurStyle
 
     // MARK: Fields
 
@@ -32,5 +33,19 @@ public struct LuminareView<Content>: View where Content: View {
             .focusable(false)
             .buttonStyle(.luminare)
             .luminareTint(overridingWith: tintColor)
+            .background {
+                if case .custom = backgroundBlurStyle {
+                    ZStack {
+                        VisualEffectView(
+                            material: .menu,
+                            blendingMode: .behindWindow,
+                            blurStyle: backgroundBlurStyle
+                        )
+                        LuminareBackgroundTintOverlay()
+                    }
+                    .ignoresSafeArea()
+                    .allowsHitTesting(false)
+                }
+            }
     }
 }

Sources/Luminare/Main Window/LuminareWindow.swift

@@ -22,8 +22,12 @@ public class LuminareWindow: NSWindow {
     /// Initializes a ``LuminareWindow``.
     ///
     /// - Parameters:
+    ///   - backgroundBlurStyle: the default blur style used by ``luminareBackground()`` within the window.
     ///   - content: the content view of the window, wrapped in a ``LuminareView``.
-    public init(content: @escaping () -> some View) {
+    public init(
+        backgroundBlurStyle: LuminareBackgroundBlurStyle = .regular,
+        content: @escaping () -> some View
+    ) {
         super.init(
             contentRect: .zero,
             styleMask: [.titled, .fullSizeContentView, .closable],
@@ -33,7 +37,10 @@ public class LuminareWindow: NSWindow {
 
         // Wrapping the NSHostingView in a parent NSView allows us to reposition the traffic lights, since NSHostingViews cannot have subviews directly.
         let view = NSView()
-        let luminareView = NSHostingView(rootView: LuminareView(content: content))
+        let luminareView = NSHostingView(
+            rootView: LuminareView(content: content)
+                .environment(\.luminareBackgroundBlurStyle, backgroundBlurStyle)
+        )
         view.addSubview(luminareView)
 
         luminareView.translatesAutoresizingMaskIntoConstraints = false
@@ -66,7 +73,7 @@ public class LuminareWindow: NSWindow {
     }
 
     func relocateTrafficLights() {
-        guard let contentView, let trafficLightsOrigin else {
+        guard contentView != nil, let trafficLightsOrigin else {
             return
         }
 

Sources/Luminare/Utilities/Extensions/EnvironmentValues+Extensions.swift

@@ -11,6 +11,7 @@ import SwiftUI
 
 extension EnvironmentValues {
     @Entry var luminareClickedOutside: Bool = false
+    @Entry var luminareBackgroundBlurStyle: LuminareBackgroundBlurStyle = .regular
 }
 
 // MARK: - Common

Sources/Luminare/Utilities/Extensions/View+Extensions.swift

@@ -189,6 +189,7 @@ public extension View {
         )
     }
 
+    /// Applies the standard Luminare background effect using the blur style from the environment.
     func luminareBackground() -> some View {
         modifier(
             LuminareBackgroundEffectModifier()

Sources/Luminare/Utilities/LuminareBackgroundBlurStyle.swift

@@ -0,0 +1,18 @@
+//
+//  LuminareBackgroundBlurStyle.swift
+//  Luminare
+//
+//  Created by Adon Omeri on 2025-03-23.
+//
+
+import SwiftUI
+
+/// Controls how `luminareBackground` and the window’s root view render their blur.
+public enum LuminareBackgroundBlurStyle: Equatable, Sendable {
+    /// Applies a regular window material to the window.
+    ///  - Note: This type does not use private APIs and is stable.
+    case regular
+    /// Set a custom blur level for the window.
+    /// - Warning: This type uses private APIs and may break in a future OS. Test on all macOS versions you are targeting.
+    case custom(radius: CGFloat)
+}