February 19, 2012

Automatically positioning and sizing windows with Devilspie

Filed under: adminstration,blogging,linux — jonEbird @ 1:48 pm

I often talk about my media PC in the living room and how I like to stream music via Pandora in the house. Since I am using Pithos, I can maximize the desktop real estate and enjoy whatever wallpaper suits my mood. In order to best accomplish this, I tend to resize Pithos so that it only shows the current album and song as well as move it off to the corner of the desktop. Although this only takes a moment to accomplish, I’ve grown tired of doing it each and every time I need relaunch Pithos. What I really want to be able to do is automatically resize and position the window immediately when I launch Pithos. Someone has to have solved this before and it’s bugging me enough that I need to solve this once and for all.

I started looking at wmctrl to solve my problem per the recommendation of Patrick Shuff. While familiarizing myself with the utility, I ironically stumbled upon a wmctrl tips page which included a list of other similar tools and the description of devilspie sounded exactly like what I needed:

devilspie is a window-matching utility. It can be configured to detect windows as they are created, and match the window to a set of rules. If the window matches the rules, it can perform a series of actions on that window.

My needs are modest. A resize and a positioning is probably accomplished with a simple declaration to set the window geometry. Let’s install it and start playing.

Fortunately I could install devilspie directly from yum and while the manpage is quite sparse it is packaged with a sufficient README that after a few trial and error iterations, I got a basic configuration working which just ran devilspie in debug mode and could report on the current windows opened and new ones being launched.

sudo yum -y install devilspie
[ ! -d ~/.devilspie ] && { mkdir -m 0755 ~/.devilspie; echo "(debug)" > ~/.devilspie/debug.ds; }

That will continue to run in your terminal, so you may want to open another tab/terminal as we explore.

Since I am a devoted Emacs user, I certainly wasn’t disappointed to learn that devilspie uses s-expressions for it’s configurations. I also found a good unofficial devilspie documentation page written up by Gina Häußge which helps round out the education. Indeed, it looks like I’ll be able to solve my problem with devilspie. After meticulously positioning my Pithos window, I used xwininfo to record my current window geometry. I then created the simplistic config file “~/.devilspie/pithos.ds” as the following:

(if (is (application_name) "Pithos") (begin (geometry "481x163--20-17") (unshade) ))

Some more background on setting up your own configurations. If you notice when you launched devilspie, after the initial install, you can see the information on the current windows and their associated application names. For example, here is what I see for Pithos:

Window Title: 'Pithos - Bankrupt On Selling by Modest Mouse'; Application Name: 'Pithos'; Class: 'Pithos'; Geometry: 483x197+797+523

That should make it easy for coming up with rules to match application names, window names or classes when targeting your applications.

The frustrating thing for me was how each utility was reporting a different geometry value for the windows currently launched. Between xwininfo, devilspie and wmctrl they all had differing opinions on what I should use. You’d think that I could use what devilspie was telling me since that is the utility I’m indented on using but it didn’t work out for me. I’ve used xinwinfo for over a decade and I guess I’m sticking with it.

Finally, I added a final few touches to my desktop configuration before calling it complete. I created a simple shell script to relaunch Pithos indefinitely because occasionally I need to relaunch it but I actually never intend to leave it off: (See installing pithos with virtualenv if you want to see how I installed Pithos)



source ${PITHOS_VENV}/bin/activate
while :; do
    sleep 1

My cheap way of launching apps indefinitely is to run them within my main screen session. I’ll create one for the Pithos restart script and another for devilspie. Here is an excerpt from my ~/.screenrc:

screen -t emacs     0  /usr/bin/emacs -nw
screen -t local     1  /bin/bash
screen -t local     2  /bin/bash
screen -t local     3  /bin/bash
screen -t local     4  /bin/bash
screen -t local     5  /bin/bash
screen -t synergy   10 /usr/bin/synergyc -f
screen -t devilspie 11 /usr/bin/devilspie
screen -t pithos    12 ~/bin/

And all is well in my household again. Should something get borked with Pithos, perhaps due to being paused for too long or whatever, I can simply kill the window which triggers the restart script to launch another copy and devilspie will position and resize it perfectly for me. How will you use devilspie?

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