jockej / pwld

Per window layout daemon

pwld

====

The Per Window Layout Daemon

pwld is a very simple X daemon which keeps track of the keyboard layout per window. It does this by listening to events on the root window. It attempts to be as simple as possible. Unix signals and files are used to communicate with the daemon.

It is a simple little program, written by a simple little man. The error handling is practically non existent, the interface is brittle (for example the layouts specified on the command line need to be in the same order as when they were given to setxkbmap(1)), the communication is done via files and signals instead of for example dbus. But it seems to work for my simple needs.

How it works

pwld relies on keyboard layouts having been set already. A good way to do that is with setxkbmap(1). For example:

setxkbmap -layout "us,se"

You would the start pwld like so:

pwld -l us,se -d

When started pwld will write its pid to the file /tmp/pwld.pid.

There are two ways to change the layout for a window. To set the next layout, send SIGUSR1 to the daemon, like so:

kill -s SIGUSR1 `cat /tmp/pwld.pid`

The other way is to set a named layout by writing it to the file /tmp/pwld.in and sending SIGUSR2, like so:

echo se > /tmp/pwld.in
kill -s SIGUSR2 `cat /tmp/pwld.pid`

This feature is mainly made to be used by other programs, for example Emacs.

To make pwld exit cleanly and remove all its files, send a SIGTERM.

Example

In my ~/.xprofile I have the following:

setxkbmap -option "" -layout "us,se" -option ctrl:swapcaps
pwld -l us,se -d

And in my ~/.i3/config I have this:

bindsym $mod+m exec kill -s USR1 `cat /tmp/pwld.pid`

Lastly, in my ~/.conkyrc I have this:

${execp cat /tmp/pwld.out}

Building and installing

This program uses the autotools, so the build/install procedure is pretty much the usual ./configure, make, make install. Details follow.

Arch Linux

On Arch Linux you can use the PKGBUILD file to make the package. If you don't know how, read all about it on the Arch Wiki.

This program depends on the libbsd package, for the pidfile handling, so you need to have that installed. The PKGBUILD file mentioned above will take care of that for you.

If you already have it installed the usual:

$./configure --prefix=/usr
$make
\#make install

will do.

OpenBSD

On OpenBSD you need to configure the package like this in order to find the X libraries:

CPPFLAGS=-I/usr/X11R6/include LDFLAGS=-L/usr/X11R6/lib ./configure --prefix=/usr/local

Then it's just make and make install as usual.

On OpenBSD pwld will use my own implementation of the pidfilef functions form FreeBSD, these are probably not very good, but they seem to work. (The reason for this is that OpenBSD instead provides the pidfile(3) function. This however puts the pidfile in /var/run, which is only writeable by root, so that means it can't be used in a user program, which kinda sucks.)

FreeBSD

I haven't actually tried to build this on FreeBSD, so I can't in good conscience say it works. But I think it should work. YMMV.