If you’ve had problems when running the Processing IDE, or indeed any other Java Swing applications, under the xmonad window manager on Linux, here’s the cure – just a simple edit to the ‘processing’ executable (which is really just a shell script). Open it in you favourite text editor, then select the following lines:

# JARs required from JDK (anywhere in/below the JDK home directory) JDKLIBS="rt.jar tools.jar"

And paste the following in their place:

#Make us work with xmonad export AWT_TOOLKIT=MToolkit # JARs required from JDK (anywhere in/below the JDK home directory) JDKLIBS="rt.jar tools.jar"

You should also be able to add the export line to your .xinitrc or your .bash_profile, the former being more sensible if you never use X applications over a remote login. For some reason, however, Processing seems to require the variable to be set every time it is run, hence we export it from the startup script.