Centering window over window with current focus

["Neal H. Walfield" <neal walfield org>]

(Resending since my message was held for moderation, because I was not
subscribed, and the message has apparently not been released yet.)

Hi,

I work on GnuPG.  We have a helper program call pinentry that asks for
the user's passphrase.  This means that a program like Enigmail
doesn't need to handle the user's passphrase and accidentally leak it
due to a bug like heart bleed.

I have a dual-monitor setup and I've observed the following issue:
when pinentry is started, it appears on the monitor that currently has
the mouse cursor rather the the monitor that has the window with the
focus.  This is a bit annoying and occurs quite often for me due to my
limited use of the mouse.  Is there a way to change this
programatically or is this perhaps a theme or window manager policy
that I can't override (I'm using XFCE from Debian Stable on this
system)?  If I can change it, I'd appreciate any pointers to get me
started.

Thanks!

:) Neal