[ltp] T420s volume controls

[Ole Langbehn]

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Hi David,

On 13.03.2013 02:32, David Woodfall wrote:
> I notice that when I upgraded from my T42 to a T420s the volume and
> mute keys generate Xorg key events. This would be great but I prefer
> it to do hardware mixing, same as my old T42.

on my t520, my mute key is still wired in hardware, i guess. Only the
up/down keys are software.

I've set it up so that while in X, the keys control alsa. Here's a page
that describes how to map keys to commands in different DEs:

https://wiki.archlinux.org/index.php/Extra_Keyboard_Keys_in_Xorg

I've written a small script that I've mapped to the keys:


#!/usr/bin/env bash

function getCurrentVolume {
  amixer -- sget Master playback|egrep -e "^  (Mono|Front)"|sed
's/^[^]]*\[\([^]]*\)%\].*$/\1/g'|sort -u
}

function getStepForVolume {
  DIFF=3D$((100-$1))
  echo "define min(x,y){if(y>x){return y} else{return
x}};min(1,l(${DIFF})/l(2)*2)+0.51" | bc -l| xargs printf "%1.0f\n"
}

fold -w1 <<< $1 | while read token; do
    echo $token
    case $token in
      "-"|"+" )
        CUR=3D$(getCurrentVolume)
        STEP=3D$(getStepForVolume $CUR)
        amixer -- sset Master playback ${STEP}%${1}
        notify-send "Changed volume" "from $CUR to $(getCurrentVolume)"
        ;;
      * )
        notify-send Error "wrong argument: \"$1\""
        ;;
    esac
done


the math in getStepForVolume can be adjusted to your liking for
bigger/smaller increments.

can be called with any number of +/- chars as arguments, e.g.

~/bin/volume "---"

to turn down the volume three steps

And now I can do wonderful stuff like mapping single
increments/decrements to the volume keys without modifier, and mapping
bigger steps to the volume keys with shift/ctrl as modifier.

hth,

Ole


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