keymapper

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A cross-platform context-aware key remapper. It allows to:

• Redefine your keyboard layout and shortcuts systemwide or per application.
• Manage all your keyboard shortcuts in a single configuration file.
• Change shortcuts for similar actions in different applications at once.
• Share configuration files between multiple systems (GNU/Linux, Windows, MacOS, FreeBSD).
• Specify input and output as characters instead of the keys required to type them.
• Bind keyboard shortcuts to launch applications.
• Control the state from external applications using keymapperctl.
• Use mouse buttons and wheel in your mappings.

Configuration

Configuration files are easily written by hand and mostly consist of lines with input expressions and corresponding output expressions separated by >>:

# comments start with # and continue until the end of a line
CapsLock >> Backspace
Z >> Y
Y >> Z
Control{Q} >> Alt{F4}

Unless overridden using the command line argument -c, the configuration is read from keymapper.conf, which is looked for in the common places:

• on all systems in $XDG_CONFIG_HOME and $HOME/.config,
• on Linux, MacOS and FreeBSD also in /etc,
• on Windows also in the user's profile, AppData\Local and AppData\Roaming folders,

each with an optional keymapper subdirectory and finally in the working directory.

The command line argument -u causes the configuration to be automatically reloaded whenever the configuration file changes.

:warning: In case of emergency: You can always press the special key combination Shift+Escape+K to terminate keymapperd.

Key names

The keys are named after their scan codes and are not affected by the present keyboard layout. The names have been chosen to match on what the web browsers have agreed upon, so this handy website can be used to get a key's name. For convenience the letter and digits keys are also named A to Z and 0 to 9. The logical keys Shift, Control, Alt and Meta are also defined (each matches the left and right modifier keys). There are also virtual keys for state switching and an Any key.

The mouse buttons are named ButtonLeft, ButtonRight, ButtonMiddle, ButtonBack and ButtonForward, the wheel is named WheelUp, WheelDown, WheelLeft and WheelRight.

It is also possible to directly provide the scan code instead of the key name in decimal or hex notation (e.g. 159, 0x9F).

:warning: Beware that the configuration file is case sensitive.

Input expressions

Input expressions consist of one or more key names separated by spaces or parenthesis, which give them different meaning:

• A B means that keys have to be pressed successively (released in any order).
• (A B) means that keys have to be pressed simultaneously in any order.
• A{B} means that a key has to be held while another is pressed.
• Groups and modifiers can also be nested like A{B{C}} or (A B){C}.
• !A means that a key must not be pressed. When an expression ends with !A, it triggers when the key is released.
• "..." string literals match when the enclosed characters are typed.
• With an initial ? the mapping gets skipped as long as it only partially matches.

Output expressions

The output expression format is analogous to the input expression format:

• A B means that keys are pressed successively.
• (A B) means that both keys are pressed simultaneously.
• A{B} means that a key is held while another is pressed.
• !A means that the (potentially pressed) key should be released before the rest of the expression is applied.
• ^ splits the output in two parts, one which is applied when the input key is pressed and one when the key is released.
• "..." string literals allow to specify characters to type.
• $() can be used for launching applications.
• An empty expression can be used to suppress any output.

Order of mappings

Mappings are applied in consecutive order until a match is found, therefore their order is of importance. While the following outputs A as soon as Meta is pressed:

Meta    >> A
Meta{X} >> B

The other way round, nothing is output when Meta is pressed alone because depending on whether an X follows, either B or A is output:

Meta{X} >> B
Meta    >> A

:warning: You may want to add a @forward-modifiers directive to your configuration, which ensures that the common mouse-modifiers are never held back:

@forward-modifiers Shift Control Alt

For a detailed description of how the mapping is applied, see the Functional principle section.

Context awareness

Context blocks allow to enable mappings only in specific contexts. A context can be defined by system, the focused window title, window class, process path or the input device/device-id an event originates from.\ A block continues until the next block (respectively the end of the file). The block which applies in all contexts can be reopened using default. e.g.:

[default]

[title = "Visual Studio"]

[system = "Linux", class != "qtcreator"] # '!=' inverses a condition

[device = "Some Device Name"] # consecutive blocks share mappings
[device = "Some Other Device"]

[system = "Windows" path = "notepad.exe"] # comma separator is optional

:warning: The device/device-id filters on Windows require the installation of a virtual device driver. The process path may not be available on Wayland and for processes with higher privileges. The window title is not available on MacOS.

The values of a context can be easily obtained using the Next Key Info function of the tray icon or keymapperctl.

Class and device filters match contexts with the exact same string, others match contexts containing the string. For finer control regular expressions can be used. These have to be delimited with slashes. Optionally i can be appended to make the comparison case insensitive:

[title = /Visual Studio Code|Code OSS/i]

Additionally a modifier filter allows to activate blocks depending on the state of one or more keys:

# active when Virtual1 is down and Virtual2 is not
[modifier = "Virtual1 !Virtual2"]

Finally blocks can be activated depending on whether two strings match. Macros may be used for generating the strings. e.g.:

# active when environment variable has some specific value
[getenv["HOSTNAME"] = "LaptopMum"]

Abstract commands

To simplify mapping of one input expression to different output expressions, it can be mapped to an abstract command first. The command name can be chosen arbitrarily but must not be a key name. The configuration is case sensitive and all key names start with a capital letter, so it is advisable to begin command names with a lowercase letter:

Control{B} >> build

Subsequently this command can be mapped to one output expression per context. The last active mapping overrides the previous ones:

build >> Control{B}

[title="Visual Studio"]
build >> (Shift Control){B}

Multiple stages

By inserting [stage] a configuration can be split into stages, which are evaluated separately. The output of a stage is the input of the following stage, where it can be mapped further:

# adjust keyboard layout
Z >> Y
Y >> Z

# map keys output by previous stage
[stage]
Control{Z} >> undo

Output on key release

When an output expression contains ^, it is only applied up to this point, when the input key is pressed. The part after the ^ is not applied until the input is released. Both parts can be empty:

# type "cmd" after the Windows run dialog appeared
Meta{C} >> Meta{R} ^ "cmd" Enter

# prevent key repeat
A >> B^

# output B when A is released
A >> ^B

Virtual keys

Virtual0 to Virtual255 are virtual keys, which can be used as state switches. They are toggled when used in output expressions:

# toggle Virtual1 whenever ScrollLock is pressed
ScrollLock >> Virtual1

# release Virtual1 when Escape is pressed
Escape >> !Virtual1

They can be used as modifiers in input expressions:

# map A to B when Virtual1 is down
Virtual1{A} >> B

# map E to F when Virtual1 is NOT down
!Virtual1 E >> F

# keep G held as long as Virtual1 is down
Virtual1 >> G

# output H when Virtual1 is released
!Virtual1 >> H

Toggling virtual keys can also have immediate effects. Using them as modifiers is toggling them twice:

# toggle Virtual1 before and after pressing B
# this effectively maps D to A B C
Virtual1 >> A ^ C
D >> Virtual1{B}

# {} may also be empty. This maps C to A B
Virtual2 >> B
Virtual1 >> A Virtual2{}
C >> Virtual1{}

ContextActive exists separately for each context and is toggled when the context becomes active/inactive:

# toggle Virtual1 when entering and when leaving context
[title="Firefox"]
ContextActive >> Virtual1 ^ !Virtual1

Any key

Any can be used in input and output expressions. In input expressions it matches any key and in output expressions it outputs the matched input.

# swap Control and Shift
Control{Any} >> Shift{Any}
Shift{Any} >> Control{Any}

To exclude an application from any mapping this can be added to the top of the configuration:

[title="Remote Desktop"]
Any >> Any

[default]

On the output side it can also be used to release previously pressed modifiers first:

A >> !Any A

Timeouts

Input expressions can contain timeouts in milliseconds e.g. 500ms to specify the minimum duration a key needs to be held, or the minimum duration between two events. This can also be negated like !500ms to specify maximum durations:

# output Escape when CapsLock is held for a while
CapsLock{500ms} >> Escape

# output Escape when Control is pressed and released quickly
Control{!250ms} >> Escape

# output C when B quickly follows an A
A !250ms B >> C

# output D when A is tapped twice quickly
A{!200ms} !200ms A{!200ms} >> D

In output expressions it can be used to delay output or keep a key held for a while. e.g.:

A >> B 500ms C{1000ms}

:warning: Delaying output also stops the processing of input for the given duration. For pressing and releasing keys asynchronously one has to resort to keymapperctl. e.g.:

# keep mouse button held for 5 seconds
Meta{Space} >> $(keymapperctl --press ButtonLeft --wait 5000 --release ButtonLeft)

Character typing

Output expressions can contain string literals with characters to type. The typeable characters depend on your keyboard layout. e.g.:

AltRight{A} >> '@'

# long lines can be split using '\'
Meta{A} K >> \
  "Kind regards,\n" \
  "Douglas Quaid"

They can also be used in input expressions to match when the character are typed. e.g.:

? 'Abc' >> Backspace Backspace "Matched!"

:warning: The keyboard layout is evaluated when the configuration is loaded, switching is not yet supported.

Key aliases / Macros

For convenience aliases for keys and even sequences can be defined. e.g.:

Win = Meta
Boss = Virtual            # assigns an unused virtual key
Alt = AltLeft | AltRight  # defines a logical key
proceed = Tab Tab Enter

In strings, regular expressions and terminal commands aliases can be inserted using ${Var} or $Var. e.g.:

greet = "Hello"
F1 >> "${greet} World"

An alias can also be parameterized to create a macro. The arguments are provided in square brackets and referenced by $0, $1... e.g.:

print = $(echo $0 $1 >> ~/keymapper.txt)
F1 >> print["pressed the key", F1]

# multiple mappings on one line can be separated using ;
swap = $0 >> $1; \ 
       $1 >> $0
swap[Y, Z]

There are a few builtin macros repeat[EXPR, N], length[STR], default[A, B], apply[EXPR, ARGS...], add/sub/mul/div/mod/min/max[A, B], getenv["VAR"] which allow to generate mappings and define some more advanced macros. e.g.:

# when last character of string is typed, undo using backspace and output new string
substitute = ? "$0" >> repeat[Backspace, sub[length["$0"], 1]] "$1"
substitute["Cat", "Dog"]

# generate the string to output with an external program
substituteExec = ? "$0" >> repeat[Backspace, sub[length["$0"], 1]] \
  $(keymapperctl --type "$($1)")
substituteExec[":whoami", "whoami"]

# add a `FN >> Meta{N}` mapping for each function key
apply[F$0 >> Meta{$0}, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

$$ is substituted with the actual parameter count, which allows to add overloads:

log1 = $(echo "$0" >> $LOG_FILE)
log2 = $(echo "[$1]" "$0" >> $LOG_FILE)

# switch builds log1 or log2, which is then called with the second argument list
switch = $0$1
log = switch["log", $$][$0, $1]

F1 >> log["info message"]
F2 >> log["error message", "state"]

Application launching

$() can be used to embed terminal commands in output expressions, which should be executed when triggered. e.g.:

Meta{C} >> $(C:\windows\system32\calc.exe) ^
Meta{W} >> $(exo-open --launch WebBrowser) ^

# on Windows console applications are revealed by prepending 'start'
Meta{C} >> $(start powershell) ^

:warning: You may want to append ^ to ensure that the command is not executed repeatedly as long as the input is kept held.

Directives

The following directives, which are lines starting with an @, can be inserted in the configuration file:

• forward-modifiers allows to set a list of keys which should never be held back. e.g.:

  @forward-modifiers Shift Control Alt

  It effectively forwards these keys in each stage immediately, like:

  
  Shift   >> Shift