John Yates
For reference my environment is Ubuntu Jaunty, Gnome with a single top panel on a 1920x1200 screen. Under Gnome/Metacity I have emacs-snapshot (23.0.93.1) more or less working in the the single mini-buffer for all windows mode. (Here I use the term window to refer to what in the Emacs world would be called a frame.) The mini-buffer window is positioned at the bottom of the screen and is full-screen wide. Alternatively I can position the mini-buffer at the top of the screen just below the Gnome panel.
Now I want to move this Emacs arrangement to xmonad. Because I have arranged for the mini-buffer window to have a distinct resource type I can recognize it in a manage hook. From the xmonad FAQ and some googling I believe that when that window appears I need to set its override-redirect attribute to true and define it as a strut. Though I am working my way through Hal Daumé's "Yet Another Haskell Tutorial" I fear it may be a while before I can code such a doStrut function. Thus my appeal to the readers of this list. My sense is that when the mini-buffer window appears it is properly sized and positioned. Thus there should be no need to compute the strut components, they should be directly liftable from the window.
You might have luck using the XMonad.Layout.Gaps layout in contrib, and by having a managehook that ignores the emacs minibuffer window (using doIgnore). This wouldn't be dynamic (moving the emacs window would require you to reconfigure it), but could work as a kludge until you manage to do it properly.