when shortcut taken by system, allow user to use anyway

Sources/KeyboardShortcuts/Localization/en.lproj/Localizable.strings

@@ -3,3 +3,4 @@
 "keyboard_shortcut_used_by_menu_item" = "This keyboard shortcut cannot be used as it’s already used by the “%@” menu item.";
 "keyboard_shortcut_used_by_system" = "This keyboard shortcut cannot be used as it’s already a system-wide keyboard shortcut.";
 "keyboard_shortcuts_can_be_changed" = "Most system-wide keyboard shortcuts can be changed in “System Settings › Keyboard › Keyboard Shortcuts”.";
+"force_use_shortcut" = "Use Anyway";

Sources/KeyboardShortcuts/RecorderCocoa.swift

@@ -248,19 +248,27 @@ extension KeyboardShortcuts {
 					return nil
 				}
 
-				guard !shortcut.isTakenBySystem else {
+				if shortcut.isTakenBySystem {
 					self.blur()
 
-					NSAlert.showModal(
+					let modalResponse = NSAlert.showModal(
 						for: self.window,
 						title: "keyboard_shortcut_used_by_system".localized,
 						// TODO: Add button to offer to open the relevant system settings pane for the user.
-						message: "keyboard_shortcuts_can_be_changed".localized
+						message: "keyboard_shortcuts_can_be_changed".localized,
+						buttonTitles: [
+							"force_use_shortcut".localized,
+							"Cancel"
+						]
 					)
 
 					self.focus()
 
-					return nil
+					// first button returned from alert means user wants to continue setting this 
+					// shortcut despite it being used by system.
+					guard modalResponse == .alertFirstButtonReturn else {
+						return nil
+					}
 				}
 
 				self.stringValue = "\(shortcut)"

Sources/KeyboardShortcuts/Utilities.swift

@@ -138,13 +138,15 @@ extension NSAlert {
 		title: String,
 		message: String? = nil,
 		style: Style = .warning,
-		icon: NSImage? = nil
+		icon: NSImage? = nil,
+		buttonTitles: [String] = []
 	) -> NSApplication.ModalResponse {
 		NSAlert(
 			title: title,
 			message: message,
 			style: style,
-			icon: icon
+			icon: icon,
+			buttonTitles: buttonTitles
 		).runModal(for: window)
 	}
 
@@ -152,12 +154,17 @@ extension NSAlert {
 		title: String,
 		message: String? = nil,
 		style: Style = .warning,
-		icon: NSImage? = nil
+		icon: NSImage? = nil,
+		buttonTitles: [String] = []
 	) {
 		self.init()
 		self.messageText = title
 		self.alertStyle = style
 		self.icon = icon
+		
+		for buttonTitle in buttonTitles {
+			self.addButton(withTitle: buttonTitle)
+		}
 
 		if let message {
 			self.informativeText = message