Fix using Control+C keyboard shortcut

It was incorrectly triggering the dialog for it being taken by the system. This is because we were not storing the `.function` modifier in the shortcut. The system shortcut is Fn+Control+C.

Sources/KeyboardShortcuts/RecorderCocoa.swift

@@ -264,7 +264,7 @@ extension KeyboardShortcuts {
 
 				// The “shift” key is not allowed without other modifiers or a function key, since it doesn't actually work.
 				guard
-					!event.modifiers.subtracting(.shift).isEmpty
+					!event.modifiers.subtracting([.shift, .function]).isEmpty
 						|| event.specialKey?.isFunctionKey == true,
 					let shortcut = Shortcut(event: event)
 				else {

Sources/KeyboardShortcuts/Shortcut.swift

@@ -61,7 +61,8 @@ extension KeyboardShortcuts {
 
 			self.init(
 				carbonKeyCode: Int(event.keyCode),
-				carbonModifiers: event.modifierFlags.carbon
+				// Note: We could potentially support users specifying shortcuts with the Fn key, but I haven't found a reliable way to differentate when to display the Fn key and not. For example, with Fn+F1 we only want to display F1, but with Fn+V, we want to display both. I cannot just specialize it for F keys as it applies to other keys too, like Fn+arrowup.
+				carbonModifiers: event.modifierFlags.subtracting(.function).carbon
 			)
 		}
 

Sources/KeyboardShortcuts/Utilities.swift

@@ -152,8 +152,8 @@ extension NSEvent {
 		modifierFlags
 			.intersection(.deviceIndependentFlagsMask)
 			// We remove `capsLock` as it shouldn't affect the modifiers.
-			// We remove `numericPad`/`function` as arrow keys trigger it, use `event.specialKeys` instead.
-			.subtracting([.capsLock, .numericPad, .function])
+			// We remove `numericPad` as arrow keys trigger it, use `event.specialKeys` instead.
+			.subtracting([.capsLock, .numericPad])
 	}
 
 	/**
@@ -262,6 +262,9 @@ enum UnicodeSymbols {
 
 
 extension NSEvent.ModifierFlags {
+	// Not documented anywhere, but reverse-engineered by me.
+	private static let functionKey = 1 << 17 // 131072 (0x20000)
+
 	var carbon: Int {
 		var modifierFlags = 0
 
@@ -281,6 +284,10 @@ extension NSEvent.ModifierFlags {
 			modifierFlags |= cmdKey
 		}
 
+		if contains(.function) {
+			modifierFlags |= Self.functionKey
+		}
+
 		return modifierFlags
 	}
 
@@ -302,6 +309,10 @@ extension NSEvent.ModifierFlags {
 		if carbon & cmdKey == cmdKey {
 			insert(.command)
 		}
+
+		if carbon & Self.functionKey == Self.functionKey {
+			insert(.function)
+		}
 	}
 }