Hit send before I had checked the headers, and it only went to Daniel. Sorry for the extra mail, Daniel.

---------- Forwarded message ----------
From: Mike Meyer <mwm@mired.org>
Date: Wed, Oct 1, 2014 at 5:06 PM
Subject: Re: [xmonad] Patch to add new Layout message
To: Daniel Wagner <dmwit@dmwit.com>

On Sat, Sep 27, 2014 at 8:27 PM, Daniel Wagner <dmwit@dmwit.com> wrote:

Excerpts from Mike Meyer's message of 2014-09-23 07:31:08 -0700:
> The Message is called "SplitMaster", and has no arguments. It sets the
> client count of the master pane to 1 if it's not currently 1, thus
> providing a quick way to get back to that setting. It setgs the client
> count for the master pane to 2 if it's currently 1, effectively making it a
> toggle between the two modes of a split master pane and an full size master
> pane.

Can this be done entirely from the configuration? For example, a
low-tech solution would be to simply have two Tall layouts in your
layout hook (one with one master pane and one with two master panes) and
a keybinding that toggles between them, e.g. using
X.A.CycleSelectedLayouts [1].

I recognize that this is not *identical*, but perhaps it's close to your
needs and doesn't require changes xmonad's corej

After thinking about it some, I would say using multiple Layouts won't work - but I'm not an expert. The problem for me is that I actually use multiple Layouts, and switching between them is a conceptually different thing from switching between one and two clients in the master pane. So using an extra layout for this would create extra steps when I wanted to change the number of clients in the master pane AND when I wanted to change layouts. I think I'd rather have the current behavior. If someone wants o

Is there some way to have a configuration with two sets of layouts to toggle between? that would certainly do the trick. While I can see how to do that, I'm not sure it's in general a good idea and so suspect it's not there.