I'm writing a custom panel for launching applications in PyGTK and want it to occupy a space at the bottom of the screen (single or multiple desktops).

It works fine as far as stickiness goes and always on top using fvwm 2.4.0. However maximised windows still fill the full screen.

The unstable 2.5.x version of fvwm I understand supports the EWMH hints with the insertion of the EwmhBaseStruts option in the configuration file .fvwm2c and I'll be trying this version shortly.

I was just wondering whether there are any other window managers which support this as a configuration file option. I've looked at Blackbox, Windowmaker, so far, but they from what I can tell may only support it if the application itself hints.

I'd rather have the window manager deal with the placement rather than have to specify it in the application I'm writing.

Xfwm has this feature as well (the window manager belonging to the xfce project). You can define "margins" on your desktop that will never be filled when maximizing windows. Openbox has this as well, and it's configurable via obconf. I have no idea how to handle that directly on their respective config files, but they are plain text files so a quick look and some grepping should put you in the right track.