Version: unspecified (using KDE 4.4.4)
Have system with the following displays:
Screen 0: minimum 320 x 200, current 2944 x 1080, maximum 4096 x 4096
VGA-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
1280x1024 75.0 60.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
LVDS connected 1024x768+1920+0 (normal left inverted right x axis y axis) 0mm x 0mm
1024x768 60.4*+ 60.0
800x600 60.3 59.9 56.2
640x480 59.9 59.4
S-video disconnected (normal left inverted right x axis y axis)
kdm_greet puts the login screen on the LVDS even though it is not primary (and in fact is closed).
According to https://bugs.freedesktop.org/show_bug.cgi?id=28936, it is kdm that should disable the LVDS display if the lid is closed.
After some more research, this may be a Qt issue. Apparently for this system, screen 0 is the right side screen and screen 1 is on the left. kdm_greet places the login panel on screen 0 by default. Setting GreeterScreen to -1 in /etc/kde/kdm/kdmrc gets it to appear on the left screen.
in a broader sense ...
*** This bug has been marked as a duplicate of bug 48602 ***