Screen used after login

[chris holt <ch...@valco-data.com>]

I am using Jetspeed 1.5 and I have been searching through the code and
can't seem to find where it is decided what screen to show.  I am using
velocity and all I want to know is where does it decide what to replace
$screen_placeholder with.
I have traced through a lot of code and it seems that
$screen_placeholder is replaced with the velocity template that is set
as the screen template.
Am I correct?  If I am where is the screen template set in the code?
 
Thanks,
 
Chris