Making use of Extra Keys under Linux

Introduction

1. Make the keys available to X
2. Bind functionality to the keys
   

Making Extra Keys available to X

1. Start xev from a shell. This is vital as you need to see the log of xev.
2. Now press one of your extra keys. The log will show you output like this:
   
   KeyPress event, serial 27, synthetic NO, window 0x3a00001,
       root 0x36, subw 0x0, time 225375492, (25,175), root:(983,193),
       state 0x0, keycode 229 (keysym 0xffcc), same_screen YES,
       XLookupString gives 0 characters:  ""
   
   KeyRelease event, serial 27, synthetic NO, window 0x3a00001,
       root 0x36, subw 0x0, time 225375577, (25,175), root:(983,193),
       state 0x0, keycode 229 (keysym 0xffcc), same_screen YES,
       XLookupString gives 0 characters:  ""
   
   xev will log literally every event, hence the first section corresponds to pressing the key, the second section to key release. The essential part here is the keycode, highlighted in blue. For this key, the respective keycode is 229.
   Repeat this process for all your extra keys and make notes of those keycodes.
   Note that not all extra keys can be put to use. Some keyboards and also keyboards of laptops have extra keys that need dedicated drivers to be able to make use of them. You will realize this when you press one of those keys and see no output in the xev log.
   
3. Now we have to tell X that these keys exits and how to use them. To do so, we have to set up a modmap for X. In most cases, there will already exist some files, usually .Xmodmap in you home directory and/or /etc/X11/Xmodmap. These are simple text files that can be loaded with a program called xmodmap. For each of your extra keys, you have to make an entry in one of these files that looks like this:
   
   keycode 229 = F13
   
   229 is the keycode that we found out in the previous step. F13 is an internal label that we assign to the key. It could be rzlpfrpf or anything else, but in most cases it will make sense to continue enumerating the extra keys as function keys.
   Depending upon whether you want to make these keys available to all users or just an individual user, /etc/X11/Xmodmap or .Xmodmap in the home directory is the right place for these keycode entries.
   
4. Now it is time to test you new modmap. Load it via xmodmap <filename>. If there are any syntax errors, you will know by now. To doublecheck your new modmap, issue xmodmap -pk. That will print all keycodes and their assgnments side by side. For our example, you would have to look for the line corresponding to keycode 229. It should look like this:
   
       229         0xffcc (F13)
   
   The hex code  0xffcc may vary, the essential part is that F13 has been assigned to keycode 229.
5. Do not forget to make sure that you modmap file is really loaded when X starts! Simply restart X, log in and use xmodmap -pk to verify that your modmap was loaded.
   

Binding typical Functionalities under KDE 3

• To bind a program to start to a certain key, start the menu editor. There you can bind a key to any application that is in your start menu. If you want to start an application that is not yet included in your start menu when pressing a certain extra key, you will have to create a respective entry first.
• If you want to trigger certain actions within specific programs, things are not so easy. If it is not a KDE application, chances are very bad. If it is a KDE application, look if there is a menu entry to redefine key bindings. It may be rather hidden at times, see the kmix sample below.
• If you still could not bind a key to your desired action, edit .kde/share/config/khotkeysrc in your home directory. For example, if you want to open a certain file /tmp/foo using nedit by pressing F13, create a new entry that looks like this:
  
  [Section2]
  MenuEntry=false
  Name=whatever
  Run=/usr/X11R6/bin/nedit /tmp/foo
  Shortcut=F13
  
  Note that the section number (here: 2) is an enumeration. MenuEntry is false since there is not a respective menu entry for this action, or you could have used the menu editor to bind the key, Name can be whatever you want. Run is the command to execute (note that you should use absolute path names when referencing non-KDE applications or files) and Shortcut is the key symbol to assign the action to.
  

• To lock the screen, use the command
  dcop kdesktop KScreensaverIface lock
• To shut the machine down (logging you off first), use the command
  dcop ksmserver ksmserver logout 0 2 0
• CD player control
  play: dcop kscd default play
  stop: dcop kscd default stop
  next track: dcop kscd default next
  previous track: dcop kscd default previous
• volume control
  mute: dcop kmix Mixer0 setMute 0 1
  decrease volume: dcop kmix Mixer0 decreaseVolume 0
  increase volume: dcop kmix Mixer0 increaseVolume 0
  Note: the latter two assume that you are using sound device 0. That should be fine for most users unless you have multiple sound cards in your system.
• Another way to bind increasing or decreasing volume or muting: Start kmix, right-click on the volume symbol (or any other of the controls) and choose key bindings. The following dialogue offers the possibility to bind keys to the respective actions.

Sample: Logitech iTouch Keyboard

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