In a dual monitor system, what determines which monitor has the KDE taskbar? I use xrandr. My monitors are LVDS and VGA-0. Whenever both monitors are active the taskbar is on LVDS, the latop's LCD panel. How can I get the taskbar to be on VGA-0 while both monitors are active? I've already tried using the --primary option of xrandr and shown below but it didn't seem to do anything.

xrandr --output VGA-0 --primary
(DOESN'T WORK)

The primary monitor usually has the panel. Why the --primary option is not working for you I do not know unfortunately.

Is there a configuration file for KDE4 that I could edit, to tell KDE to always make a certain monitor the primary one?

In KDE Trunk, it is possible to select the main monitor from a drop down menu in the Display configuration panel. Prior to that, it is not possible to have KDE set the main monitor.

It is possible however, by running "xrandr --output <output> --primary" with "krandrtray" running.

Can I assume 'Trunk' means the latest development version? When might we expect that version to be adopted by the major Linux distros?

Correct, trunk is latest development. Trunk will be relased as KDE 4.6 according to the KDE 4.6 Release Schedule which is posted on Techbase.

See http://techbase.kde.org/Schedules/KDE4/ ... e_Schedule

Major distributions usually pick it up when making their next release after the release date. Note that many distributions have "package freezes" meaning no new versions after that date, so it may take longer.

I noticed on my notebook that VGA0 is always primary with NO option to change it whatsoever. VGA0 unfortunately is the external beamer. LVDS1 which is the internal notebook LCD is always secondary device. I can mirror them but when having extended desktop, the panel is always on the beamer screen, not the notebook.

Which video card / drivere are you using? This is likely a XRandR bug somewhere.

According to lspci:
VGA compatible controller: ATI Technologies Inc Radeon Mobility M7 LW [Radeon Mobility 7500]

from my xorg.conf file:
Driver "ati"

Is the command xrandr --output VGA-0 --primary supposed to take effect immediately or after a following xrandr command?

It should take effect immediately, once the command is run.