fix: Desaturate the selection color when the application looses focus (#16)

Author: jbmorley

Example/Example/Views/Cell.swift

@@ -36,12 +36,13 @@ struct Cell: View {
 
     @Environment(\.isSelected) var isSelected
     @Environment(\.highlightState) var highlightState
+    @Environment(\.selectionColor) var selectionColor
 
     var item: Item
     var isPainted: Bool
 
     var strokeColor: Color {
-        return isSelected || highlightState == .forSelection ? Color.accentColor : Color.clear
+        return isSelected || highlightState == .forSelection ? selectionColor : Color.clear
     }
 
     var body: some View {

Sources/SelectableCollectionView/Views/CollectionViewContainer.swift

@@ -21,6 +21,7 @@
 #if os(macOS)
 
 import Carbon
+import Combine
 import SwiftUI
 
 import SelectableCollectionViewMacResources
@@ -83,6 +84,7 @@ public class CollectionViewContainer<Element: Hashable, Content: View>: NSView,
     private let scrollView: CustomScrollView
     private let collectionView: InteractiveCollectionView
     private var dataSource: DataSource? = nil
+    private var cancellables: Set<AnyCancellable> = []
 
     var provider: ((Element) -> Content?)? = nil
 
@@ -105,7 +107,9 @@ public class CollectionViewContainer<Element: Hashable, Content: View>: NSView,
             else {
                 return ShortcutItemView()
             }
-            view.configure(AnyView(content), parentHasFocus: collectionView.isFirstResponder)
+            view.configure(AnyView(content),
+                           parentHasFocus: collectionView.isFirstResponder,
+                           parentIsKey: collectionView.window?.isKeyWindow ?? false)
             view.element = item
             return view
         }
@@ -129,6 +133,18 @@ public class CollectionViewContainer<Element: Hashable, Content: View>: NSView,
 
         collectionView.isSelectable = true
         collectionView.allowsMultipleSelection = true
+
+        // Observe application activity notifications to allow us to update the selection color.
+        let notificationCenter = NotificationCenter.default
+        notificationCenter
+            .publisher(for: NSApplication.didBecomeActiveNotification)
+            .combineLatest(notificationCenter
+                .publisher(for: NSApplication.didResignActiveNotification))
+            .receive(on: DispatchQueue.main)
+            .sink { [weak self] _ in
+                self?.updateSelection()
+            }
+            .store(in: &cancellables)
     }
 
     required init?(coder: NSCoder) {
@@ -150,7 +166,9 @@ public class CollectionViewContainer<Element: Hashable, Content: View>: NSView,
                 continue
             }
             let content = self.delegate?.collectionViewContainer(self, contentForElement: element)
-            item.configure(AnyView(content), parentHasFocus: collectionView.isFirstResponder)
+            item.configure(AnyView(content),
+                           parentHasFocus: collectionView.isFirstResponder,
+                           parentIsKey: collectionView.window?.isKeyWindow ?? false)
         }
 
         // Update the selection

Sources/SelectableCollectionView/Views/ShortcutItemView.swift

@@ -53,6 +53,7 @@ class ShortcutItemView: NSCollectionViewItem {
     }
 
     private var parentHasFocus: Bool = false
+    private var parentIsKey: Bool = false
 
     override init(nibName nibNameOrNil: NSNib.Name?, bundle nibBundleOrNil: Bundle?) {
         super.init(nibName: nil, bundle: Resources.bundle)
@@ -63,10 +64,11 @@ class ShortcutItemView: NSCollectionViewItem {
     }
 
     private func host(_ content: AnyView) {
+
         let modifiedContent = AnyView(content
             .environment(\.isSelected, isSelected)
             .environment(\.highlightState, .init(highlightState))
-            .environment(\.selectionColor, parentHasFocus ? Color(nsColor: .selectedContentBackgroundColor) : Color(nsColor: .unemphasizedSelectedContentBackgroundColor)))
+            .environment(\.selectionColor, parentHasFocus && parentIsKey ? Color(nsColor: .selectedContentBackgroundColor) : Color(nsColor: .unemphasizedSelectedContentBackgroundColor)))
         if let hostingView = hostingView {
             hostingView.rootView = modifiedContent
         } else {
@@ -81,14 +83,15 @@ class ShortcutItemView: NSCollectionViewItem {
 #warning("TODO: Not sure if this is necessary")
     override func prepareForReuse() {
         super.prepareForReuse()
-        configure(AnyView(EmptyView()), parentHasFocus: false)
+        configure(AnyView(EmptyView()), parentHasFocus: false, parentIsKey: false)
     }
 
 #warning("TODO: Called by the data source")
 #warning("TODO: This should take an item")
-    func configure(_ content: AnyView, parentHasFocus: Bool) {
+    func configure(_ content: AnyView, parentHasFocus: Bool, parentIsKey: Bool) {
         self.content = content
         self.parentHasFocus = parentHasFocus
+        self.parentIsKey = parentIsKey
         host(content)
     }