HotSwitch-HS

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macOS window switcher with window-assigned hotkeys and AltTab cycling.

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# HotSwitch-HS

![top](https://raw.githubusercontent.com/oniatsu/HotSwitch-HS/main/doc/img/top.png)

HotSwitch-HS is a [Hammerspoon](https://www.hammerspoon.org/) module for macOS that gives you fast, predictable window switching.

It supports two main modes:

- **Window-assigned key mode** — Register a window-assigned key to each window once. Then open the panel and press that key to jump to the window instantly. The key never changes, so you can switch without thinking.
- **AltTab mode** — Hold a modifier (e.g. `option`) and press `tab` repeatedly to cycle through windows. Release the modifier to focus.

---

# Installation

## 1. Install [Hammerspoon](https://www.hammerspoon.org/)

Hammerspoon is a macOS automation tool that lets you write Lua scripts to control windows, hotkeys, and system events. HotSwitch-HS runs as a Hammerspoon module — Hammerspoon must be installed and running for it to work.

## 2. Download HotSwitch-HS

```bash
git clone https://github.com/oniatsu/HotSwitch-HS.git ~/.hammerspoon/hotswitch-hs
```

---

# Mode 1: Window-assigned key switching

Register a window-assigned key to each window. Use it (e.g. `command + .` → `s`) to focus it instantly. The key is always the same — no searching, no thinking.

## Setup

Add to `~/.hammerspoon/init.lua`:

```lua
local hotswitchHs = require("hotswitch-hs/hotswitch-hs")
hotswitchHs.enableAutoUpdate() -- optional: auto-update via git pull
hs.hotkey.bind({"command"}, ".", hotswitchHs.togglePanel)
```

Any keybind works for the trigger:

```lua
hs.hotkey.bind({"command"}, ".", hotswitchHs.togglePanel)     -- command + .
hs.hotkey.bind({"command"}, ";", hotswitchHs.togglePanel)     -- command + ;
hs.hotkey.bind({"control"}, "space", hotswitchHs.togglePanel) -- control + space
hs.hotkey.bind({"command", "shift"}, "a", hotswitchHs.togglePanel) -- command + shift + a

-- These are NOT valid — macOS reserves them:
-- hs.hotkey.bind({"command"}, "tab", hotswitchHs.togglePanel)
-- hs.hotkey.bind({"command"}, "space", hotswitchHs.togglePanel)
```

See [hs.hotkey.bind() reference](https://www.hammerspoon.org/docs/hs.hotkey.html#bind) for details.

### command + tab (requires [Karabiner-Elements](https://karabiner-elements.pqrs.org/))

macOS reserves `command + tab`, so Hammerspoon cannot intercept it directly. Use Karabiner-Elements to remap it to a free key:

`~/.config/karabiner/karabiner.json`:

```json
{
    "from": {
        "key_code": "tab",
        "modifiers": { "mandatory": [ "command" ] }
    },
    "to": [ { "key_code": "f13" } ],
    "type": "basic"
}
```

`~/.hammerspoon/init.lua`:

```lua
hs.hotkey.bind({}, "f13", hotswitchHs.togglePanel)
```

Press `command + tab` to open/close the panel, then use `Tab` and `Return` to navigate.

## Panel key bindings

| Key | Action |
| --- | ------ |
| Your trigger key | Open / close the panel |
| `Space` | Toggle registration mode |
| `Tab` or `Down` | Select next window |
| `Shift+Tab` or `Up` | Select previous window |
| `Return` | Focus the selected window |
| `Delete` | Remove the window-assigned key from the selected window |
| `Escape` | Close the panel |
| `[a-zA-Z0-9]`, `-`, `[`, `]`, `.`, `/` | Focus the window (or register the key in registration mode) |

## How to register a key to a window

1. Open the panel (press your trigger key).
2. Select a window with `Tab` or arrow keys.
3. Press `Space` to enter registration mode.
4. Press any character key — that key is now assigned to this window.

Once registered, a key is reserved and will not appear as an auto-generated key for other windows. To remove a registration, select the window and press `Delete`.

## How to switch windows

1. Open the panel (press your trigger key, e.g. `command + .`).
2. Press the window-assigned key for the target window.

The window-assigned key is always the same. That is what makes this mode the fastest.

> **Auto-generated keys:** Before you register any keys, HotSwitch-HS assigns keys automatically so you can start using it right away. Registering your own window-assigned keys is recommended for maximum speed.

---

# Mode 2: AltTab cycling

Hold a modifier key and press a key repeatedly to cycle through windows. Release the modifier to focus the selected window. Windows are ordered by most-recently-focused.

## Setup

`cycleWithModifier` handles key repeat and modifier-release detection entirely within Hammerspoon. Any non-reserved modifier+key combination works — for example:

```lua
local hotswitchHs = require("hotswitch-hs/hotswitch-hs")

-- option + tab / option + shift + tab
hs.hotkey.bind({"option"}, "tab", function() hotswitchHs.cycleWithModifier({"option"}, "tab") end)
hs.hotkey.bind({"option", "shift"}, "tab", function() hotswitchHs.cycleWithModifier({"option", "shift"}, "tab") end)

-- command + . / command + shift + .
hs.hotkey.bind({"command"}, ".", function() hotswitchHs.cycleWithModifier({"command"}, ".") end)
hs.hotkey.bind({"command", "shift"}, ".", function() hotswitchHs.cycleWithModifier({"command", "shift"}, ".") end)
```

- Forward key (`tab` / `.`) — cycle forward
- Backward key with `shift` — cycle backward
- Release the modifier — focus the selected window

### command + tab cycling (requires [Karabiner-Elements](https://karabiner-elements.pqrs.org/))

macOS reserves `command + tab`, so Hammerspoon cannot intercept it directly. Use Karabiner-Elements to remap it, then bind in Hammerspoon for full AltTab-style cycling.

`~/.config/karabiner/karabiner.json`:

```json
[
    {
        "description": "command key release → commitCycle (f14)",
        "from": { "key_code": "left_command" },
        "to": [ { "key_code": "left_command" } ],
        "to_after_key_up": [ { "key_code": "f14" } ],
        "type": "basic"
    },
    {
        "description": "cmd+tab → cycleNext (f15)",
        "from": {
            "key_code": "tab",
            "modifiers": { "mandatory": [ "command" ] }
        },
        "to": [ { "key_code": "f15" } ],
        "type": "basic"
    },
    {
        "description": "cmd+shift+tab → cyclePrevious (f16)",
        "from": {
            "key_code": "tab",
            "modifiers": { "mandatory": [ "command", "shift" ] }
        },
        "to": [ { "key_code": "f16" } ],
        "type": "basic"
    }
]
```

`~/.hammerspoon/init.lua`:

```lua
hs.hotkey.bind({}, "f14", hotswitchHs.commitCycle)
hs.hotkey.bind({}, "f15", hotswitchHs.cycleNext, nil, hotswitchHs.cycleNext)
hs.hotkey.bind({}, "f16", hotswitchHs.cyclePrevious, nil, hotswitchHs.cyclePrevious)
```

- `command + tab` — cycle forward
- `command + shift + tab` — cycle backward
- Release `command` — focus the selected window

> **Note:** The `to_after_key_up` on `left_command` fires on every command key release, not only after cmd+tab. `commitCycle` is a no-op unless `cycleNext` or `cyclePrevious` was called first, so spurious firings (e.g. after cmd+c) are harmless.

---

# Direct window switch (no panel)

Switch to the next or previous window immediately, without opening the panel. Windows are ordered by most-recently-focused.

```lua
hs.hotkey.bind({"option"}, "n", hotswitchHs.switchToNextWindow)
hs.hotkey.bind({"option"}, "p", hotswitchHs.switchToPreviousWindow)
```

- `switchToNextWindow()` — focus the second most-recently-used window
- `switchToPreviousWindow()` — focus the least-recently-used window (cycles in reverse)

---

# Preferences

Add any of these to `~/.hammerspoon/init.lua`.

## Auto update

```lua
hotswitchHs.enableAutoUpdate()
```

Updates HotSwitch-HS via `git pull` automatically when needed.

## Auto-generated keys

```lua
hotswitchHs.setAutoGeneratedKeys({"1", "2", "3", "4", "5", "6", "7", "8", "9", "0"})
```

Defines which keys are auto-assigned to windows before you register your own. Default keys are [here](https://github.com/oniatsu/HotSwitch-HS/blob/main/lib/common/KeyConstants.lua#L25-L27).

## Show windows from all spaces

```lua
hotswitchHs.enableAllSpaceWindows()
```

By default, only windows in the current space are shown. This shows windows from all spaces.

## Additional symbol keys

```lua
hotswitchHs.addJapaneseKeyboardLayoutSymbolKeys()
```

Adds [Japanese keyboard layout symbols](https://github.com/oniatsu/HotSwitch-HS/blob/main/lib/common/KeyConstants.lua#L31) as registerable keys.

## Always show panel on primary screen

```lua
hotswitchHs.setPanelToAlwaysShowOnPrimaryScreen()
```

By default the panel appears on the screen containing the currently focused window. This forces it to the primary screen instead.

## Always show app name (compact panel)

```lua
hotswitchHs.setPanelToAlwaysShowAppName()
```

By default the panel shows the window title (or app name when an app has only one window). This always shows the app name instead, and narrows the panel width accordingly.

## Custom title for a specific app

```lua
hotswitchHs.setCustomAppTitle("com.apple.finder", "My Finder")
```

Overrides the displayed title for windows belonging to the given bundle ID. Call multiple times to set titles for multiple apps. Takes priority over `setPanelToAlwaysShowAppName()` and the default window title/app name logic for that bundle ID.

## Log level

```lua
hotswitchHs.setLogLevel("nothing") -- default
-- can be 'nothing', 'error', 'warning', 'info', 'debug', or 'verbose'
```

On macOS Ventura 13.x, printing many logs in Hammerspoon console causes slowness ([Hammerspoon bug](https://github.com/Hammerspoon/hammerspoon/issues/3306)). The default is `nothing`.

---

# Troubleshooting

- **Keybind not working?** Open Hammerspoon Console (menubar icon → `Console...`) and check for error messages.
- **Still broken?** Update HotSwitch-HS: `cd ~/.hammerspoon/hotswitch-hs && git pull`

## Known issue: windows not showing after wake from sleep

Reload Hammerspoon config to fix it. This is likely a Hammerspoon bug.

Tip: add a reload keybind for quick recovery:

```lua
hs.hotkey.bind({"command", "option", "control"}, "r", hs.reload)
hs.alert.show("Hammerspoon is reloaded")
```

## Known issue: only one Finder window is shown in the panel

When Finder has multiple windows open, HotSwitch-HS shows only the most recently focused one. Selecting it focuses Finder via `hs.application.launchOrFocusByBundleID`, which brings whatever window Finder considers frontmost.

**Root cause — stale subscription cache:** HotSwitch-HS uses `hs.window.filter` with a `windowVisible` event subscription for performance. When Finder windows are merged into a tab group, Finder does not fire the proper accessibility notification (`AXUIElement` hidden/destroyed event). As a result, the filter's internal cache retains the now-phantom window objects from before the merge, and they continue to appear as real entries. There is no reliable way from within Hammerspoon to tell a phantom cache entry apart from a real window without a fresh accessibility query, and fresh queries defeat the subscription-cache performance benefit.

**Focusing quirk:** Even if phantom entries could be filtered, `window:focus()` internally calls `becomeMain()` (sets `AXMain = true`), which causes Finder to jump to the first tab instead of the tab that was active before switching away. Alternative APIs (`raise()` + `application:activate()`) avoid the tab reset but did not reliably resolve the phantom-entry problem.

Until a clean solution exists within Hammerspoon's window filter API, the panel is limited to showing one Finder window.

**Recommended workaround:** Use Finder's tab feature to keep all folders in a single window. With all folders open as tabs, HotSwitch-HS can reach Finder in one keystroke, and you can switch folders within Finder using its own tab bar or `command + {` / `command + }`.

---

# Update manually

```
cd ~/.hammerspoon/hotswitch-hs
git pull
```

# Uninstallation

```
rm -rf ~/.hammerspoon/hotswitch-hs
```

---

# Development

## Requirements

- Hammerspoon

## Steps

1. Edit `.lua` files.
2. Reload Hammerspoon config and verify behavior.

### Owner's steps

3. Check latest git tag: `git describe --tags --abbrev=0`
4. Add a new git tag and push it.

## Note

- Pay attention to Lua's garbage collection.

---

# ChangeLogs

- v2.5.13: Fix focus failing for windows with no AXMain window
  - `WindowModel.focusWindow()` returned early without focusing anything when `application:mainWindow()` was nil. Some windows never become AXMain, so they appeared in the panel but could not be focused. Now falls back to `raise()` + `activate(true)` in that case
- v2.5.12: Fix preferences/settings dialogs (e.g. iTerm2 Settings) being hidden and unfocusable
  - The floating-tool-palette filter relied on `window:isStandard()`, which is always `false` for `AXDialog` windows by definition — this silently excluded every settings/preferences dialog in every app, not just tool palettes. Now uses an empty title to detect floating tool palettes instead
  - Focusing a non-standard window (`AXDialog`/`AXFloatingWindow`) directly from a different app didn't work — the `raise()` + `activate(true)` workaround only ran when switching within the same app. It's now applied regardless of which app currently has focus
- v2.5.11: Fix crash when a window's app has no bundle ID
  - `BaseCanvasView:showWindowInfo` crashed with `table index is nil` when `application:bundleID()` returned nil for a window; now falls back to an `"unknown:<appName>"` key that can't collide with a real bundle ID
- v2.5.10: Fix Finder window handling to show real windows instead of tabs
  - Finder tabs merged into one window were being listed as separate panel entries due to a stale `hs.window.filter` cache; now queries Finder's windows fresh via the accessibility API instead
  - Multiple real Finder windows are now shown individually (previously only the most recently focused one was shown)
  - Focusing a Finder window now uses `raise()` + `activate(true)` instead of `launchOrFocusByBundleID`, so it targets the correct window instead of just bringing Finder forward
- v2.5.9: Add option to set a custom display title per bundle ID
  - `hotswitchHs.setCustomAppTitle(bundleID, title)` — overrides the displayed title for windows of a specific app, matched by bundle ID
- v2.5.8: Filter out floating tool palettes (e.g. Clip Studio Paint panels) from window list
  - Windows with subrole `AXDialog` and `isStandard=false` are now excluded; preferences/settings dialogs (`AXDialog` + `isStandard=true`) are still shown
- v2.5.7: Fix selected row background width when using setPanelToAlwaysShowAppName()
  - The selection highlight was always drawn at full panel width (`PANEL_W = 520`) instead of the narrowed width (`PANEL_W_APP_NAME_ONLY = 300`)
- v2.5.6: Add option to always show app name in panel
  - `hotswitchHs.setPanelToAlwaysShowAppName()` — always displays the app name instead of the window title, and narrows the panel width
- v2.5.5: Show app name for single-window apps
  - Display the app name instead of the window title when the app has only one window in the panel
  - Remove Slack-specific hardcoded app name handling (now covered by the general single-window logic)
- v2.5.3: Updater fixes
  - Fix false update notifications when local version is ahead of the latest GitHub tag (add semver comparison)
- v2.5.2: Reduce cycle panel show delay
  - Reduce panel show delay from 0.1s to 0.05s for snappier response
- v2.5.1: CycleMode improvements
  - Support focusing a window-assigned key during cycling (pressing an assigned key while cycling now focuses that window directly)
- v2.5.0: Rename public API for consistency
  - `openOrClose()` → `togglePanel()`
  - `openOrSelectWithModifier()` → `cycleWithModifier()`
  - `openOrSelectNext()` / `openOrSelectPrevious()` → `cycleNext()` / `cyclePrevious()`
  - `focusOpenOrSelectNextWindow()` → `commitCycle()`
  - `openOrClose()` is kept as a backward-compatible alias
  - Fix focusing non-standard windows (AXDialog / AXFloating, e.g. iTerm2 Settings)
  - Show fixed "Finder" label instead of window title for Finder entries in the panel
  - Updater: switch to tags API and include CHANGELOG in update notification
  - Revert showing all Finder windows (only the most recently focused Finder window is shown)
- v2.4.2: Add `switchToPreviousWindow()`
  - `hotswitchHs.switchToPreviousWindow()` — focus the least-recently-used window (reverse of `switchToNextWindow`)
- v2.4.1: Bug fixes
  - Show all Finder windows in the switcher panel (previously only one was shown)
  - Fix AltTab-style cycling: handle key input during deferred panel open, reset selection position on new cycle, prevent timer leaks, guard canvas before panel is shown
- v2.4.0: Add AltTab-style cycling API
  - `cycleNext()` / `cyclePrevious()` — cycle forward/backward through windows
  - `commitCycle()` — focus selected window on modifier release
  - `cycleWithModifier(modifiers, key)` — all-in-one cycling with automatic modifier release detection
- v2.3.4: Modify focusing a Finder window
- v2.2.6: Add a utility method
  - `hotswitchHs.switchToNextWindow()` — focus the next most-recently-used window without opening the panel
- v2.2.5: Add option to always show the panel on primary screen
  - `hotswitchHs.setPanelToAlwaysShowOnPrimaryScreen()`
- v2.1.5: Change saving keys to use bundleID instead of app name
  - If you used this app before this version, you need to register keys again.
- v2.1.0: Add auto updater
  - `hotswitchHs.enableAutoUpdate()`
- v2.0.0: Connect Git tag with GitHub Release
- v1.17: Add auto generated keys
- v1.4: Change app info text to app icon on panel
- v1.0: First release

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