input-remapper/readme/development.md

Development

Contributions are very welcome, I will gladly review and discuss any merge requests. If you have questions about the code and architecture, feel free to open an issue. This file should give an overview about some internals of key-mapper.

Roadmap

• show a dropdown to select valid devices
• creating presets per device
• renaming presets
• show a mapping table
• make that list extend itself automatically
• read keycodes with evdev
• inject the mapping
• keep the system defaults for unmapped buttons
• button to stop mapping and using system defaults
• highlight changes and alert before discarding unsaved changes
• automatically load presets on login for plugged in devices
• make sure it works on wayland
• support timed macros, maybe using some sort of syntax
• add to the AUR, provide .deb file
• basic support for gamepads as keyboard and mouse combi
• executing a macro forever while holding down the key using h
• mapping D-Pad directions as buttons
• configure joystick purpose and speed via the GUI
• support for non-GUI TTY environments with a command to stop and start
• start the daemon in such a way to not require usermod
• mapping a combined button press to a key
• add "disable" as mapping option
• mapping joystick directions as buttons, making it act like a D-Pad
• mapping mouse wheel events to buttons
• automatically load presets when devices get plugged in after login (udev)
• map keys using a modifier + modifier + ... + key syntax
• inject in an additional device instead to avoid clashing capabilities
• don't run any GUI code as root for improved wayland compatibility
• injecting keys that aren't available in the systems keyboard layout
• getting it into the official debian repo

Tests

sudo pip install coverage
pylint keymapper --extension-pkg-whitelist=evdev
sudo pip install . && coverage run tests/test.py
coverage combine && coverage report -m

To read events, evtest is very helpful. Add -d to key-mapper-gtk to get debug output.

Single tests can be executed via

python3 tests/test.py test_paths.TestPaths.test_mkdir

Releasing

ssh/login into a debian/ubuntu environment

./scripts/build.sh

This will generate key-mapper/deb/key-mapper-0.7.1.deb

Badges

sudo pip install git+https://github.com/jongracecox/anybadge
./scripts/badges.sh

New badges, if needed, will be created in readme/ and they just need to be commited.

Files

gui

• bin/key-mapper-gtk the executable that starts the gui. It also sends messages to the service via dbus if certain buttons are clicked.
• bin/key-mapper-helper provides information to the gui that requires root rights. Is stopped when the gui closes.
• data/key-mapper.policy configures pkexec. By using auth_admin_keep the user is not asked multiple times for each task that needs elevated rights. This is done instead of granting the whole application root rights because it is considered problematic.
• data/key-mapper.desktop is the entry in the start menu

cli

• bin/key-mapper-control is an executable to send messages to the service via dbus. It can be used to start and stop injection without a GUI. The gui also uses it to run the service (if not already running) and helper, because by using one single command for both the polkit rules file remembers not to ask for a password again.

service

• bin/key-mapper-service executable that starts listening for commands via dbus and runs the injector when needed. It shouldn't matter how it is started as long as it manages to start without throwing errors. It usually needs root rights.
• data/key-mapper.service starts key-mapper-service automatically on boot on distros using systemd.
• data/keymapper.Control.conf is needed to connect to dbus services started by systemd from other applications.

autoload

• data/key-mapper-autoload.desktop executes on login and tells the systemd service to stop injecting (possibly the presets of another user) and to inject the users autoloaded presets instead (if any are configured)
• data/key-mapper.rules udev rule that sends a message to the service to start injecting for new devices when they are seen for the first time.

Example system startup

1. systemd loads key-mapper.service on boot
2. on login, key-mapper-autoload.desktop is executed, which has knowledge of the current user und doesn't run as root
   2.1 it sends the users config directory to the service
   2.2 it makes the service stop all ongoing injectings
   2.3 it tells the service to start loading all of the configured presets
3. a bluetooth device gets connected, so udev runs key-mapper.rules which tells the service to start injecting for that device if it has a preset assigned. Works because step 2 told the service about the current users config.

Communication to the service always happens via key-mapper-control

Permissions

gui

The gui process starts without root rights. It makes sure the daemon and helper are running via pkexec.

daemon

The daemon exists to keep injections alive beyond the lifetime of the user interface. Runs via root. Communicates via dbus. Either started via systemd or pkexec.

helper

The helper provides information to the user interface like events and devices. Communicates via pipes. It should not exceed the lifetime of the user interface because it exposes all the input events. Starts via pkexec.

Unsupported Devices

Either open up an issue or debug it yourself and make a pull request.

You will need to work with the devices capabilities. You can get those using

sudo evtest

It tries or doesn't try to map ABS_X/ABS_Y

Is the device a gamepad? Does the GUI show joystick configurations?

• if yes, no: adjust is_gamepad to loosen up the constraints
• if no, yes: adjust is_gamepad to tighten up the constraints

Try to do it in such a way that other devices won't break. Also see readme/capabilities.md

It won't offer mapping a button

If sudo evtest shows an event for the button, try to modify should_map_as_btn. If not, the button cannot be mapped.

How it works

It uses evdev. The links below point to older code in 0.7.0 so that their line numbers remain valid.

1. It grabs a device (e.g. /dev/input/event3), so that the key events won't reach X11/Wayland anymore source
2. Reads the events from it (evtest can do it, you can also do cat /dev/input/event3 which yields binary stuff) source
3. Looks up the mapping if that event maps to anything source
4. Injects the output event in a new device that key-mapper created (another new path in /dev/input, device name is suffixed by "mapped") source, new device
5. Forwards any events that should not be mapped to anything in another new device (device name is suffixed by "forwarded") source, new device

This stuff is going on as a daemon in the background

Resources

• Guidelines for device capabilities
• PyGObject API Reference
• python-evdev
• Python Unix Domain Sockets