Key remapping on Windows and Linux

99-keyremap.hwdb

# /etc/udev/hwdb.d/99-keyremap.hwdb

# Remap a key or swap keys for a keyboard using udev

# To remap a key, replace the bus, vendor, product, scancode, keycode in:
#evdev:input:b<bus>v<vendor>p<product>*
#  KEYBOARD_KEY_<scancode>=<keycode>

# Apply your changes to this file with:
# #> systemd-hwdb update && udevadm trigger

# To find device bus, vendor, product:
#
# $> cat /proc/bus/input/devices 
#I: Bus=0011 Vendor=0001 Product=0001 Version=ab54
#N: Name="AT Translated Set 2 keyboard"
#H: Handlers=sysrq kbd event3 leds

# The previous command allows us to find the scancode and keycode.
# The handlers line of the previous command gives us `event3` from which we can
#
# #> evtest /dev/input/event3
#Event: time 1611518997.616241, type 4 (EV_MSC), code 4 (MSC_SCAN), value 3a
#Event: time 1611518997.616241, type 1 (EV_KEY), code 58 (KEY_CAPSLOCK), value 1
#Event: time 1611518997.616241, -------------- SYN_REPORT ------------
#Event: time 1611518997.616793, type 17 (EV_LED), code 1 (LED_CAPSL), value 1
#Event: time 1611518997.616793, -------------- SYN_REPORT ------------
#Event: time 1611518997.656002, type 4 (EV_MSC), code 4 (MSC_SCAN), value 3a
#Event: time 1611518997.656002, type 1 (EV_KEY), code 58 (KEY_CAPSLOCK), value 0
#Event: time 1611518997.656002, -------------- SYN_REPORT ------------
#Event: time 1611519000.174220, type 4 (EV_MSC), code 4 (MSC_SCAN), value 1d
#Event: time 1611519000.174220, type 1 (EV_KEY), code 29 (KEY_LEFTCTRL), value 1
#Event: time 1611519000.174220, -------------- SYN_REPORT ------------
#Event: time 1611519000.213325, type 4 (EV_MSC), code 4 (MSC_SCAN), value 1d
#Event: time 1611519000.213325, type 1 (EV_KEY), code 29 (KEY_LEFTCTRL), value 0
#Event: time 1611519000.213325, -------------- SYN_REPORT ------------
#
# The line with MSC_SCAN value 3a gives us the scancode, 3a
# The line directly bellow gives its keycode in lower case from KEY_*, capslock

# Swap capslock with ctrl:
evdev:input:b0011v0001p0001*
  KEYBOARD_KEY_3a=leftctrl
  KEYBOARD_KEY_1d=capslock

# To debug:
# #> udevadm test $(udevadm info --query=path --name=/dev/input/event3) 2>&1 | less

capslock_remap.reg

Windows Registry Editor Version 5.00

; DIK Keycodes can be found here:
; https://github.com/glfw/glfw/blob/d203ccbf5ec4442809a0696a704b2b3a7041559d/deps/mingw/dinput.h#L509

; The hex data is in five groups of four bytes:
;   00,00,00,00,\    header version (always 00000000)
;   00,00,00,00,\    header flags (always 00000000)
;   04,00,00,00,\    # of entries (3 in this case) plus a NULL terminator line.
;                    Entries are in 2-byte pairs: Key code to send & keyboard key to send it.
;                    Each entry is in LSB, MSB order.
;   1d,00,3a,00,\    Send LEFT CTRL (0x001d) code when user presses the CAPS LOCK key (0x003a) 
;   38,00,1d,00,\    Send LEFT ALT (0x0038) code when user presses the LEFT CTRL key (0x001d) 
;   3a,00,38,00,\    Send CAPS LOCK (0x003a) code when user presses the LEFT ALT key (0x0038) 
;   00,00,00,00      NULL terminator

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,\
                   00,00,00,00,\
                   03,00,00,00,\
                   1d,00,3a,00,\
                   3a,00,1d,00,\
                   00,00,00,00