SwitchFix

macOS menu bar utility that auto-corrects keyboard layout mistakes. Type in the wrong layout (English instead of Ukrainian/Russian) and SwitchFix detects it, deletes the mistyped word, switches the layout, and retypes the correct text — like PuntoSwitcher, but native and lightweight.

Features

• Automatic correction — detects wrong-layout words on space/enter and corrects them instantly
• Hotkey mode — correct only when you press Ctrl+Shift+Space (configurable)
• Selection correction — select text and press the hotkey to convert it
• Undo — Cmd+Z within 5 seconds reverts the last correction
• Revert hotkey — CapsLock reverts the last correction (configurable)
• Three layouts — English (US/ABC/British/Dvorak/Colemak), Ukrainian, Russian
• Ukrainian variants — auto-detects and supports both Ukrainian and Ukrainian Legacy keymaps
• Smart filtering — skips password fields, URLs, emails, camelCase, mixed scripts
• App blacklist — disabled in terminals, IDEs, and code editors by default (toggle per app)
• Launch at Login — optional auto-start via SMAppService
• Confidence-based switching — delays layout switch for ambiguous short words
• Compact bundle — ~11MB .app bundle with expanded dictionaries, no external dependencies

Requirements

• macOS 13.0+
• Accessibility permission (prompted on first launch)
• Swift 5.9+ and Command Line Tools (for building)

Installation

Download the latest release from the Releases page.

1. Open the downloaded .dmg file.
2. Drag SwitchFix.app to your Applications folder.
3. Launch the app. You will need to grant Accessibility permissions for it to work.

Note: Since the app is not notarized by Apple, you might see a warning. Right-click the app and choose "Open" to bypass it, or go to System Settings > Privacy & Security to allow it.

Build

# Debug build
swift build

# Run tests (54 tests, standalone runner — no Xcode required)
swift run TestRunner

# Build .app bundle (ad-hoc signed)
scripts/build-app.sh

# Create DMG for distribution
scripts/create-dmg.sh

The built app is at dist/SwitchFix.app.

How It Works

1. KeyboardMonitor installs a CGEventTap (listen-only) to capture keystrokes
2. Characters accumulate in LayoutDetector's word buffer
3. On word boundary (space, enter, tab), the buffer is checked:
   • Convert the word to alternative layouts via LayoutMapper character tables
   • Validate each conversion against BloomFilter dictionaries (EN: 48k, UK: 320k, RU: 146k words)
4. If a valid word is found in another layout, TextCorrector:
   • Deletes the mistyped characters (+ boundary char) via CGEvent backspaces
   • Switches the input source via TIS API
   • Retypes the correct text via keyboardSetUnicodeString
   • Retypes the boundary character (space/enter)

Architecture

Sources/
├── SwitchFixApp/     # Entry point, AppDelegate (wires the pipeline)
├── Core/             # KeyboardMonitor, LayoutDetector, LayoutMapper,
│                     #   TextCorrector, InputSourceManager
├── Dictionary/       # BloomFilter, DictionaryLoader, WordValidator
│   └── Resources/    #   en_US.txt, uk_UA.txt, ru_RU.txt
├── UI/               # StatusBarController, PreferencesManager
└── Utils/            # Permissions (AXUIElement), AppFilter, KeyCodeMapping,
                      #   SystemHotkeyConflicts

Menu Bar

SwitchFix lives in the menu bar with an Ab icon. The menu provides:

• Enable/Disable toggle
• Correction Mode — Automatic or Hotkey Only
• Conflict warning — shows when CapsLock is also used by macOS for input source switching
• Installed Layouts — shows all detected system layouts
• Launch at Login
• Quit

Hotkey Configuration

SwitchFix stores hotkeys in UserDefaults:

• SwitchFix_hotkeyKeyCode + SwitchFix_hotkeyModifiers for correction hotkey (default: Ctrl+Shift+Space)
• SwitchFix_revertHotkeyKeyCode + SwitchFix_revertHotkeyModifiers for revert hotkey (default: CapsLock)

Examples:

# Set revert hotkey to CapsLock (no modifiers)
defaults write com.switchfix.app SwitchFix_revertHotkeyKeyCode -int 57
defaults write com.switchfix.app SwitchFix_revertHotkeyModifiers -int 0

# Set correction hotkey to Ctrl+Shift+Space
defaults write com.switchfix.app SwitchFix_hotkeyKeyCode -int 49
defaults write com.switchfix.app SwitchFix_hotkeyModifiers -int $((262144+131072))

If SwitchFix observes that pressing CapsLock also triggers a macOS input-source switch, it shows a conflict warning in the menu.

Diagnostics

SwitchFix logs key decisions via NSLog. Open Console.app and filter for [SwitchFix] to see:

• Discovered input sources at startup
• Dictionary loading (word counts, paths)
• Detection decisions (buffer contents, conversion results)
• Correction actions (deletion count, layout switch, typed text)
• App switching (allowed/blocked)

License

MIT