[xmonad] zaphod mode

[Brandon Allbery]

On Tue, Dec 20, 2011 at 14:00, Martin Carroll <
martin.carroll at alcatel-lucent.com> wrote:

>        DISPLAY=:0.1 xmonad &   # Managing screen 1
>        DISPLAY=:0.0 xmonad     # Managing screen 0, exit to exit X.
>
> Unfortunately, that doesn't work.  Mike points out that some finagling
> might be necessary to get this to work, but after several hours I was
> unable to find the right finagling.  I *conjecture* that xmonad does not
> support zaphod.
>

The problem here is xmonad uses the Xinerama/XRandR multiscreen information
to find out what to manage.  If you want to run legacy dual-head, you need
to get the second screen out of the Xinerama config, which means having an
xorg.conf with the right incantations.

Problem here is that Googling has been suggesting to me that the
x.orgfolks have been systematically disabling legacy mode.  You can
test this by
seeing if xdpyinfo reports multiple screens or not (xdpyinfo | grep 'number
of screens'); if it says 1, you have Xinerama or XRandR combining the
physical displays with a single server root window, and xmonad will use it
as such.  You will need to separate them (separate X11 "screen"s with
separate root windows).

You cannot fake it, btw; everything involved pretty much requires distinct
root windows on each screen.  If xmonad is seeing multiple monitors, it's
because the screens have been assigned to different ranges of the same root
window, and even if you block xmonad from paying attention to Xinerama
various other window management operations would fail in exactly the same
way that you see if you try to run a second window manager on the same
screen (specifically, both the WM_S0 property is "owned" — as X11 reports
it, both screens are X11 screen 0 — and the SubstructureRedirectMask is
already being selected by another client).

-- 
brandon s allbery                                      allbery.b at gmail.com
wandering unix systems administrator (available)     (412) 475-9364 vm/sms
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