Getting volume keys to work in KDE

[Dotan Cohen]

2009/3/12 Shachar Shemesh <shachar at shemesh.biz>:
> Hi all,
>
> I tried to find an answer to this one on the net, and got only things that
> got me in the right direction, but not a complete answer. For the sake of
> documentation, here is how to get KDE to recognize your volume keys (or, for
> that matter, any other special key). The fact that it doesn't happen
> automatically is probably a bug in the keyboard layout code. I might file it
> there. This method works with no special processes running. It works whether
> kmix is running or not. It causes KDE to display visual feedback to the fact
> that the volume is changing.
>
> First order of business is finding out what is the keycode for your
> misfunctioning keys. Run "xev". A new window appears, and any message sent
> to that window appears in the console that ran xev. Be careful not to move
> your mouse or press any key other than the ones you want mapped, as the
> messages form very quickly.
>
> Next, with the xev window active, press the keys you want to map. Your
> output should look something like this:
>
> KeyPress event, serial 34, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 61891190, (-690,-222), root:(785,703),
>     state 0x0, keycode 101 (keysym 0x0, NoSymbol), same_screen YES,
>     XLookupString gives 0 bytes:
>     XmbLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> KeyRelease event, serial 34, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 61891190, (-690,-222), root:(785,703),
>     state 0x0, keycode 101 (keysym 0x0, NoSymbol), same_screen YES,
>     XLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> KeyPress event, serial 34, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 61892564, (-690,-222), root:(785,703),
>     state 0x0, keycode 212 (keysym 0x0, NoSymbol), same_screen YES,
>     XLookupString gives 0 bytes:
>     XmbLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> KeyRelease event, serial 34, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 61892564, (-690,-222), root:(785,703),
>     state 0x0, keycode 212 (keysym 0x0, NoSymbol), same_screen YES,
>     XLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> This tells me that the key for reducing the monitor's brightness has a
> keycode of 101, and for increasing it of 212. Record the keycodes for all
> keys you are interested in. Also, notice that after the keycode you get, in
> brackets, "keysym 0x0, NoSymbol". This indicates that the keyboard mapping
> does not know what this key means. If the key is defined, you output should
> look something like:
>
> KeyRelease event, serial 35, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 62033566, (-65,-284), root:(1410,641),
>     state 0x0, keycode 176 (keysym 0x1008ff13, XF86AudioRaiseVolume),
> same_screen YES,
>     XLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> KeyRelease event, serial 35, synthetic NO, window 0x2a00001,
>     root 0x13b, subw 0x0, time 62035609, (-65,-284), root:(1410,641),
>     state 0x0, keycode 174 (keysym 0x1008ff11, XF86AudioLowerVolume),
> same_screen YES,
>     XLookupString gives 0 bytes:
>     XFilterEvent returns: False
>
> This means that I have already implemented what I'm writing about here, and
> keycodes 174 and 176 are already mapped to the Audio down and up
> respectively. If that is what you get, and the symbol indeed matches the
> key's caption, this guide will not help you (but check out a setting called
> "global shortcuts" in the program that controls the relevant operation).
>
> Also, if you press the key and nothing happens, this guide is also incapable
> of helping you. I would recommend switching to the textual console and
> pressing the key. If you get a message from the kernel saying that an
> unknown scan code was received, the situation is still salvagable. You can
> tell the kernel to map the scan code to the right keycode. If junk is
> displayed then the situation may or may not be salvagable. It might mean
> that the kernel misunderstands the scan code, but it might also mean
> (happened to me with a Microsoft PS/2 keyboard connected through a PS/2->USB
> adapter) that something in the hardware munges the scan code. If nothing at
> all happens, it is possible that the scan code never reaches the kernel, and
> then there is very little anyone can do.
>
> The next order of business is to tell KDE to make a map between the key code
> and the proper key sym. For that, we need a list of valid key symbols. On
> Debian, you can find this list in /usr/share/X11/XKeysymDB. Find there the
> right symbol for the key. For the audio keys, these are XF86AudioLowerVolume
> (volume down), XF86AudioRaiseVolume (volume up) and XF86AudioMute (mute).
> I'm sure the rest are fairly self explanatory as well (well, not all of
> them. For example, XF86Display is the key that switches between monitors -
> not exactly trivial mapping).
>
> Last, we want the KDE startup to make these mappings (which, like I said,
> probably should go into the PC keyboard definition - if anyone has the
> volume keys bound to a different keycode, please shout). Create a file
> called ~/.kde/Autostart/keycodes, which has the following structure:
>
> #!/bin/sh
> xmodmap -e 'keycode 174=XF86AudioLowerVolume'
> xmodmap -e 'keycode 176=XF86AudioRaiseVolume'
> xmodmap -e 'keycode 160=XF86AudioMute'
> xmodmap -e 'keycode 212=XF86MonBrightnessUp'
> xmodmap -e 'keycode 101=XF86MonBrightnessDown'
>
> I'm sure you get the idea from here as far as other undefined keys are
> concerned.
>
> That's it. KDE already has pretty decent default handling of the
> XF86AudioRaiseVolume family of sym codes, so there is nothing further you
> need to do.
>
> Shachar
>

Thank you Shachar. I would like to either post this to the KDE and
Kubuntu lists, or republish it on a webpage so that people can find
it. What say you?

-- 
Dotan Cohen

http://what-is-what.com
http://gibberish.co.il

א-ב-ג-ד-ה-ו-ז-ח-ט-י-ך-כ-ל-ם-מ-ן-נ-ס-ע-ף-פ-ץ-צ-ק-ר-ש-ת
ا-ب-ت-ث-ج-ح-خ-د-ذ-ر-ز-س-ش-ص-ض-ط-ظ-ع-غ-ف-ق-ك-ل-م-ن-ه‍-و-ي
А-Б-В-Г-Д-Е-Ё-Ж-З-И-Й-К-Л-М-Н-О-П-Р-С-Т-У-Ф-Х-Ц-Ч-Ш-Щ-Ъ-Ы-Ь-Э-Ю-Я
а-б-в-г-д-е-ё-ж-з-и-й-к-л-м-н-о-п-р-с-т-у-ф-х-ц-ч-ш-щ-ъ-ы-ь-э-ю-я
ä-ö-ü-ß-Ä-Ö-Ü