keyboard_remapper

keyboard_remapper remaps keyboard keys on Windows using the API LowLevelKeyboardProc and LowLevelMouseProc, which are low-level keyboard and mouse hook procedures that intercept key events. It also uses the API SendInput to synthesize keystrokes, mouse motions, and button clicks.

keyboard_remapper does not store any settings permanently on Windows. The key remapping occurs in real time, so if the executable is terminated, the keyboard returns to its default behavior. If a key becomes stuck because keyboard_remapper was closed while the key was pressed, simply pressing and releasing the key will resolve the issue.

The idea for keyboard_remapper is inspired by the excellent work of ililim on his dual-key-remap. The main features of keyboard_remapper are:

1. Dual-role keys with tap timeout and auto-repeat keypress.
2. Hold delay for dual-role keys to prevent accidental activation of the hold functionality during typing.
3. Remapping to multiple keys.
4. Remapping for double-tap and tap&press actions.
5. Remap locking.
6. Layers, incorporating layer lock concepts from Pascal Getreuer.
7. Mouse emulation, inspired by the Orbital Mouse ideas from Pascal Getreuer.

My use case for keyboard_remapper involves creating lower-level keyboard remappings, specifically to remap the spacebar to function as both the space key and the right Ctrl key. Additionally, I set up a layer for Vi-style hjkl movements. On top of keyboard_remapper, I use AutoHotkey for managing hotkeys and hotstrings, as well as for implementing Emacs key bindings universally with ewow.

keyboard_remapper configuration

The remappings for keyboard_remapper are configured through a config.txt file, which is located in the same directory as the keyboard_remapper executable. This allows for easy customization of key behaviors and settings.

Dual-role key

Configuration example:

remap_key=SPACE
when_alone=SPACE
with_other=RIGHT_CTRL

Explanation:

• remap_key: This is the key you want to remap, in this case, the SPACE key.
• when_alone: The action triggered when remap_key is pressed by itself.
• with_other: The action triggered if another key is pressed while remap_key is held down.

Dual-role key timings in keyboard_remapper are managed using two global settings expressed in milliseconds:

• hold_delay: This defines the duration that starts from when the remap_key is pressed. If another key is pressed within this time frame, the action associated with when_alone is triggered instead of the expected hold action.

• tap_timeout: This setting typically defines the maximum time allowed for a tap action before it is considered a hold.

These settings provide fine control over how quickly the system distinguishes between a tap and a hold, allowing for a more customized user experience.

Tap&press

In keyboard_remapper, you can set up a tap&press remapping using the following configuration example:

remap_key=SPACE
when_alone=SPACE
with_other=RIGHT_CTRL
when_doublepress=LEFT_ALT

Explanation:

• when_doublepress: If the remap_key is tapped and then held down within the duration specified by global setting doublepress_timeout (in milliseconds), the action associated with this setting (LEFT_ALT) will be triggered.

This setup allows for versatile key behavior based on how quickly the key is pressed.

If the when_doublepress action is not defined in your keyboard_remapper configuration, the default behavior will be to treat a tap&press as a repetition of the action specified in when_alone. This allows for normal key repetition as defined by the operating system (Windows), meaning that if the key is held down, it will continue to repeat the action until the key is released.

Key lock

In keyboard_remapper, you can implement key locking behavior with the following configuration example:

remap_key=LEFT_SHIFT
when_alone=LEFT_SHIFT
when_tap_lock=LEFT_SHIFT
when_doublepress=LEFT_CTRL
when_double_tap_lock=LEFT_CTRL

Explanation:

• when_tap_lock: If the remap_key is tapped, the assigned key (LEFT_SHIFT) is locked in that state until it is tapped again. This allows users to maintain the shift state without needing to hold the key.
• when_double_tap_lock: If the remap_key is double tapped, the assigned key (LEFT_CTRL) is locked in that state until a subsequent double tap of the remap_key. This provides a way to maintain control functionality without holding the key.

This configuration enhances the flexibility of key usage, allowing for both temporary and persistent key states based on user input patterns.

If both when_tap_lock and when_double_tap_lock are defined, and when_double_tap_lock is triggered, the action associated with when_tap_lock will be reverted.

Layers

In keyboard_remapper, layers allow for more complex key remappings, enabling users to switch between different sets of key configurations easily. This feature is particularly useful for different contexts, such as gaming, programming, or general typing.

Configuration example:

remap_key=KEY_H
layer=layer_vi
when_alone=LEFT

Explanation:

• layer: The remap_key remapping is enabled if the layer specified by layer is active. The name of specified layer has to start with "layer". In this example its name is "layer_vi".

If a key has different remappings associated with different enabling layers, and some of these layers are enabled simultaneously, then priority goes to the last defined remapping in the config.txt file.

Layers can be activated momentarily or permanently:

1. Momentary Activation

   A layer can be activated temporarily by holding down one or more specific keys. While the key is pressed, the remappings associated with that layer will be in effect.

   Configuration example:

   remap_key=LEFT_CTRL
   when_press=layer_vi
   when_doublepress=layer_mouse
   

   Explanation:

   • when_press: While the remap_key is held down, the layer specified by when_press is active.
   • when_doublepress: While the remap_key is tap&pressed, the layer specified by when_doublepress is active.

   It is possible to use a non-modifier key as a dual-role key to enable a layer. Here’s a configuration example:

   remap_key=TAB
   when_alone=TAB
   with_other=
   when_press=layer_tab
   

   Explanation:

   • with_other=: This setting allows the TAB key to function as a dual-role key, where the tap action is registered as TAB and the hold action is set to nothing.
   • when_press=layer_tab: When the TAB key is pressed, it activates the layer_tab without registering the TAB key itself if it is held beyond the tap_timeout.

   To enable a layer with multiple key presses it is possibile to use define_layer as in the following configuration example:

   define_layer=layer_vi
   or_layer=layer_tab
   and_layer=layer_ctrl
   and_layer=layer_win
   and_not_layer=layer_shift
   

   Explanation:

   • define_layer=layer_vi: This line specifies that you are defining the layer_vi. This is the primary layer that will be activated when the conditions are met.
   • or_layer=layer_tab: This indicates that if the layer_tab is active, then the layer_vi is also active.
   • and_layer=layer_ctrl: This indicates that the layer_ctrl must also be active for layer_vi to be enabled if layer_tab is not active. This allows you to combine multiple layers for more complex key remapping.
   • and_layer=layer_win: Similarly, this specifies that layer_win must also be active to enable layer_vi. This means that all specified layers by and_layer= must be active simultaneously for the remappings of layer_vi to take effect.
   • and_not_layer=layer_shift: This setting specifies that layer_shift must not be active to enable layer_vi.

   The logic to enable a layer can be expressed as follows:

   or_layer OR or_layer OR ... OR (and_layer AND and_layer AND NOT and_not_layer AND ...)

   This means that layer_vi will be active if either layer_tab is active, or both layer_ctrl and layer_win are active while layer_shift is not.

   If a layer is defined with define_layer and activated by when_press or when_doublepress, an implicit or_layer is created.

2. Permanent Activation (Lock System)

   A layer can also be activated permanently using a lock mechanism. This means that once the layer is activated, all remappings associated with it remain in effect until the layer is explicitly deactivated.

   Configuration example:

   remap_key=RIGHT_WIN
   when_tap_lock=set_layer_vi
   
   remap_key=RIGHT_WIN
   layer=layer_vi
   when_tap_lock=reset_layer_vi
   when_tap_lock=set_layer_mouse
   
   remap_key=RIGHT_WIN
   layer=layer_mouse
   when_tap_lock=reset_layer_mouse
   

   Explanation:

   • when_tap_lock=set_layer_vi: This setting lock in active state the layer_vi layer.
   • when_tap_lock=reset_layer_vi: This setting release the lock of layer_vi layer.

   Beside set_ and reset_ is available toggle_ to toggle the lock state of specified layer.

   when_double_tap_lock can be used to change lock state of specified layer with remap_key double tap.

   In a key mapping, it is possible to specify multiple when_tap_lock and when_double_tap_lock actions.

   Layers can also be locked using the concept from Pascal Getreuer. In this case, a key is used to lock and unlock the same layer.

   Configuration example:

   remap_key=SPACE
   layer=layer_vi
   when_tap_lock=toggle_layer_vi
   

   Explanation:

   • layer=layer_vi: The lock mechanism is enabled by the layer_vi.
   • when_tap_lock=toggle_layer_vi: When the SPACE key is tapped, it locks the layer_vi. A subsequent tap of the SPACE key unlocks the layer_vi.

Mouse emulation

In keyboard_remapper keyboard keys can be remapped to mouse events.

Configuration example:

remap_key=KEY_I
layer=layer_mouse
when_alone=MOUSE_LBUTTON

Explanation:

• when_alone=MOUSE_LBUTTON: When the layer_mouse is active, the I key is mapped to the mouse left button.

Mappable mouse events:

• Up, Down, Left and Right movements: MOUSE_UP, MOUSE_DOWN, MOUSE_LEFT, MOUSE_RIGHT.
• Orbital mouse movements (from Pascal Getreuer): MOUSE_FORWARD, MOUSE_BACKWARD, MOUSE_STEER_LEFT, MOUSE_STEER_RIGHT.
• Mouse wheel rotations: MOUSE_WHEEL_UP, MOUSE_WHEEL_DOWN, MOUSE_WHEEL_LEFT, MOUSE_WHEEL_RIGHT.
• Mouse buttons: MOUSE_LBUTTON, MOUSE_RBUTTON, MOUSE_MBUTTON, MOUSE_XBUTTON1, MOUSE_XBUTTON2.
• Selection of a mouse button: MOUSE_LBUTTON_SEL, MOUSE_RBUTTON_SEL, MOUSE_MBUTTON_SEL, MOUSE_XBUTTON1_SEL, MOUSE_XBUTTON2_SEL.
• Selected mouse button events: MOUSE_SBUTTON, MOUSE_SHOLD, MOUSE_SRELEASE.

Remapping to multiple keys

In keyboard_remapper, a key can be remapped to multiple keys.

Configuration example:

remap_key=RIGHT_ALT
when_alone=CTRL
when_alone=ALT
when_alone=SHIFT
when_alone=LEFT_WIN

Explanation:

The Right ALT key is mapped to multiple keys: CTRL, ALT, SHIFT, and Left WIN.

The key press sequence follows the order of the when_alone lines. Whereas the key release sequence occurs in reverse order.

It is possible to map multiple keys for when_alone, with_other, when_doublepress, when_tap_lock, and when_double_tap_lock.

Key list

• CTRL LEFT_CTRL RIGHT_CTRL SHIFT LEFT_SHIFT RIGHT_SHIFT ALT LEFT_ALT RIGHT_ALT LEFT_WIN RIGHT_WIN
• BACKSPACE CAPSLOCK ENTER ESCAPE SPACE TAB PLUS COMMA MINUS PERIOD
• UP LEFT RIGHT DOWN
• F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24
• KEY_0 KEY_1 KEY_2 KEY_3 KEY_4 KEY_5 KEY_6 KEY_7 KEY_8 KEY_9
• KEY_A KEY_B KEY_C KEY_D KEY_E KEY_F KEY_G KEY_H KEY_I KEY_J KEY_K KEY_L KEY_M KEY_N KEY_O KEY_P KEY_Q KEY_R KEY_S KEY_T KEY_U KEY_V KEY_W KEY_X KEY_Y KEY_Z
• INSERT DELETE HOME END PAGE_UP PAGE_DOWN PRINT_SCREEN NUMLOCK SCROLLLOCK PAUSE US_SEMI US_SLASH US_TILDE
• MOUSE_UP MOUSE_DOWN MOUSE_LEFT MOUSE_RIGHT
• MOUSE_FORWARD MOUSE_BACKWARD MOUSE_STEER_LEFT MOUSE_STEER_RIGHT
• MOUSE_WHEEL_UP MOUSE_WHEEL_DOWN MOUSE_WHEEL_LEFT MOUSE_WHEEL_RIGHT
• MOUSE_LBUTTON MOUSE_RBUTTON MOUSE_MBUTTON MOUSE_XBUTTON1 MOUSE_XBUTTON2
• MOUSE_SBUTTON MOUSE_SHOLD MOUSE_SRELEASE MOUSE_LBUTTON_SEL MOUSE_RBUTTON_SEL MOUSE_MBUTTON_SEL MOUSE_XBUTTON1_SEL MOUSE_XBUTTON2_SEL

Installation

1. Download and unzip the latest release.
2. Put both keyboard_remapper.exe and config.txt in a permanent directory of your choice. (e.g. C:\Program Files\keyboard_remapper).
3. Create a shortcut to keyboard_remapper.exe in your startup directory (e.g. C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\keyboard_remapper.lnk).
4. Optionally edit config.txt and run keyboard_remapper.exe.

To uninstall, terminate keyboard_remapper.exe from the task manager and remove the startup shortcut.

Building keyboard_remapper.exe

1. Install Build Tools for Visual Studio 2022.
2. Launch the "Native Tools Command Prompt for VS 2022".
3. Run nmake to build keyboard_remapper.exe.