From 765991ff72fa329d6c9a7324bb6df35772b09ad4 Mon Sep 17 00:00:00 2001
From: nchopra <naomi.chopra.021@gmail.com>
Date: Mon, 22 Dec 2025 16:27:12 +0530
Subject: [PATCH] fix: handle fn key while consuming shortcut keys

---
 .../Sources/SwiftHelper/ShortcutManager.swift | 30 ++++++++++++++++++-
 .../Sources/SwiftHelper/main.swift            | 12 ++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/packages/native-helpers/swift-helper/Sources/SwiftHelper/ShortcutManager.swift b/packages/native-helpers/swift-helper/Sources/SwiftHelper/ShortcutManager.swift
index d6e9def..794c05a 100644
--- a/packages/native-helpers/swift-helper/Sources/SwiftHelper/ShortcutManager.swift
+++ b/packages/native-helpers/swift-helper/Sources/SwiftHelper/ShortcutManager.swift
@@ -17,6 +17,23 @@ class ShortcutManager {
 
     private var pushToTalkKeys: [String] = []
     private var toggleRecordingKeys: [String] = []
+
+    // ============================================================================
+    // IMPORTANT: Fn Key State Tracking
+    // ============================================================================
+    // We track the Fn key state ourselves via flagsChanged events instead of
+    // trusting event.flags.contains(.maskSecondaryFn) on keyDown/keyUp events.
+    //
+    // WHY: macOS reports UNRELIABLE Fn flag on keyDown events, especially on
+    // MacBooks with the Globe/Fn key. The flag can be true even when Fn is NOT
+    // pressed, causing arrow keys and other keys to be incorrectly consumed.
+    //
+    // FIX: We update fnKeyDown only when we receive flagsChanged events (which
+    // are reliable for modifier state), and use this tracked state for shortcut
+    // matching in shouldConsumeKey().
+    // ============================================================================
+    private var fnKeyDown: Bool = false
+
     private let lock = NSLock()
     private let dateFormatter: DateFormatter
 
@@ -41,6 +58,15 @@ class ShortcutManager {
         logToStderr("[ShortcutManager] Shortcuts updated - PTT: \(pushToTalk), Toggle: \(toggleRecording)")
     }
 
+    /// Update the tracked Fn key state
+    /// Called from event tap callback when flagsChanged event is received
+    /// We track Fn separately because macOS can report unreliable Fn flag on keyDown events
+    func setFnKeyState(_ isDown: Bool) {
+        lock.lock()
+        defer { lock.unlock() }
+        fnKeyDown = isDown
+    }
+
     /// Check if this key event should be consumed (prevent default behavior)
     /// Called from event tap callback for keyDown/keyUp events only
     func shouldConsumeKey(keyCode: Int, modifiers: ModifierState) -> Bool {
@@ -53,8 +79,10 @@ class ShortcutManager {
         }
 
         // Build set of currently active keys (modifiers + this regular key)
+        // Note: We use tracked fnKeyDown instead of modifiers.fn because macOS
+        // can report unreliable Fn flag on keyDown events (especially on MacBooks)
         var activeKeys = Set<String>()
-        if modifiers.fn { activeKeys.insert("Fn") }
+        if fnKeyDown { activeKeys.insert("Fn") }
         if modifiers.cmd { activeKeys.insert("Cmd") }
         if modifiers.ctrl { activeKeys.insert("Ctrl") }
         if modifiers.alt { activeKeys.insert("Alt") }
diff --git a/packages/native-helpers/swift-helper/Sources/SwiftHelper/main.swift b/packages/native-helpers/swift-helper/Sources/SwiftHelper/main.swift
index 3023c59..07c567b 100644
--- a/packages/native-helpers/swift-helper/Sources/SwiftHelper/main.swift
+++ b/packages/native-helpers/swift-helper/Sources/SwiftHelper/main.swift
@@ -81,6 +81,18 @@ func eventTapCallback(
         // Modifier-only events always pass through - they don't cause unwanted behavior on their own
         let keyCode = event.getIntegerValueField(.keyboardEventKeycode)
 
+        // ====================================================================
+        // IMPORTANT: Track Fn key state via flagsChanged (NOT keyDown flags)
+        // ====================================================================
+        // macOS reports UNRELIABLE .maskSecondaryFn on keyDown events,
+        // especially on MacBooks. The flag can be TRUE even when Fn is NOT
+        // pressed! flagsChanged events are reliable, so we track Fn state
+        // here and use it in ShortcutManager.shouldConsumeKey().
+        // See ShortcutManager.swift for more details.
+        // ====================================================================
+        let fnPressed = event.flags.contains(.maskSecondaryFn)
+        ShortcutManager.shared.setFnKeyState(fnPressed)
+
         let payload = KeyEventPayload(
             key: nil,
             code: nil,