In gnome w/ xmonad, how can I call a script when a monitor is plugged in OR when docking my laptop?

Question

Problem:

I have an extra set of top and bottom gnome-panels for a second monitor. When I undock my lenovo Thinkpad (T510), the extra top and bottom panels remain, so I have two on top and two on the bottom. I am currently running a RHEL6/Fedora (x86_64) gnome (2.28.2) instance with xmonad (0.9.1-6.1.el6) set as the window manager, using the xmonad extensions to work within gnome.

Tried:

I've used acpi and found a code for docking and undocking, but when I try to utilize a script I found in this blog post, it gets zero for the call to xrandr. The script works when called on its own from the terminal. I've tried calling a separate looping script in its own thread and it keeps getting zero for the value, long after the screen(s) update(s).

I have figured out how to have a script loop every X seconds and check for a file which is touched into existence in the event of the script getting a zero, then performing the necessary change, but I don't like that approach.

Question:

I'm hoping someone knows a place I can drop a call to the referenced script and have my panels come and go as I would expect without needing to initiate the script manually.

Thanks!

Update: I have added a bounty of 50 (max I can do) for an answer.

Ben

Answer 1

I guess one of the problems listed below occures (or both):

1) looks like your xrandr snippet doesn't return proper values because the $DISPLAY environment variable is not set correctly. Acpi handler script normally runs as a user which is not the user running your current X session. That way xrandr just does not know which $DISPLAY to access.

2) if $DISPLAY is set correctly, the acpid user might still not be able to access your running xsession. You might check whether the script will work over acpi handler, if you execute xhost + as the user who is currently runging the current xsession with $DISPLAY specified in your script. This will disable access control for X. You can reenable it with xhost - again.

Check it, I hope it helps or will at least point you in which direction to dig.