X11 Input to Robot Operating System

xi2ros allows you to send XInput events (keyboard, mouse) to a ROS system

It is not a real ROS package, nor a library. It is just a piece of code
that you are invited to modify. For instance, the demo tool sends 'pose'
messages on the '/xi2ros/pose' topic when you move your mouse. Most likely,
this is not what you need for your own project. So, feel free to change
this.

Installation

• Tested on Debian Bullseye in June 2020

• Package dependencies

  • xcb: libxcb1-dev libxcb-xkb-dev libxcb-keysyms1-dev libxcb-xinput-dev

  • ros: libroscpp-dev libroscpp-core-dev librosconsole-dev

• Just type 'make'

• Note: This compiles outside of catkin! Yes it is!

Test

• Retrieve the id of your mouse with 'xi2ros -p'

• Start 'roscore' and 'rostopic echo /xi2ros/pose' in others consoles

• Then start './xi2ros -d <your_mouse_id>'</your_mouse_id>

  • Move your mouse, use the wheel: this change the position

  • Do it while pressing the button left, this change the orientation

  • To exit, press button right three times

Explanations

• First of all, play with a standard X11 command: 'xinput' (read the man)

  • This shows you a 'virtual core pointer' and a 'virtual core keyboard'.
    These 'master' devices are the ones that send events to
    applications. But you have to attach some physical devices to
    these virtual devices. By default, all input devices plugged on
    your computer (keyboards, mice, trackpad, touchpad, joysticks,
    etc.) are attached to these two master/virtual devices.

  • A physical input device may be 'attached' or 'floating', 'enabled'
    or 'disabled' (of course, a device can't be attached if it is
    disabled).

  • So, try 'xinput list --long', 'xinput test <id>', 'xinput
    test-xi2 <id>', etc.</id></id>

  • Also note that the concept of 'modifiers' (shift, caps-lock, etc.)
    is managed by these 'virtual core devices', not by physical
    devices which just send press/release events.

• Now, play with 'xi2ros'

  • Try 'xi2ros -p' and 'xi2ros -P'.
    You get almost the same as 'xinput' and 'xinput list --long'

  • Try 'xi2ros -c show -d <id>'. This dummy 'show callback' shows you
    the events sent by your device, like 'xinput test <id>'. To exit,
    press button right or the escape key three times (depending on the
    type of device you have selected)</id></id>

• To sum up, 'xi2ros' do the following:

  1) It detachs the device(s) you have selected from the master(s).
  So your device(s) has no more impact on others applications on
  the screen. You can select several devices in the same time.

  2) It grab each event of this device as reported by the X11 server,
  and passes it to a 'callback' function that you have to code. In
  this demo, there is only the 'show' callback which shows you the
  events on your console, and the 'ros' callback which sends 'pose'
  messages to ROS as described above.

  3) At the end, either by pressing the magic key three times, or at
  the end of a timer that you can configure (type 'xi2ros -h' to
  see the options), it re-attaches your device to its master and
  exits.

  4) Note that if something goes wrong, you may get an uncomfortable
  situation with a device detached from your session. You still
  may reattach it with 'xinput', or just unplug-replug it; or use a
  secondary one.

Coding your own callback

• The main class is the one named 'X11'

  • On initialization, it retrieves the list of connected devices and
    stores the information in 'device' and 'device_class' objects

  • One has to register on it a 'callback' class

  • Its offers several methods to select / deselect desired devices

  • Then it runs the main loop, grab the input events and transmits
    them to the callback

• The class named 'callback' is abstract

  • Each concrete callback class must inherit from it and implements
    the 'Hid ()' method. This method is called by X11 whenever an HID
    event occurs.

  • The class 'callback_show' implements a 'Hid()' method which
    displays the event information on the console. You can get an
    idea of the possibilities.

  • The 'callback_ros' class implements a 'Hid()' method which sends
    'pose' messages to ROS, as described above.

  • You must code your own class 'callback_XXXX', like the two
    examples.

• Good luck. Be happy.

Licence

This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation, either version 3 of the License, or (at your option)
any later version.