Scrolling behavior

[Yang Zhang]

I'm seeing something weird in GNU screen.  When I use screen on my own
Ubuntu 10.04 box, as I enter a bunch of lines in the shell, I can see
my gnome-terminal window gathering my scrollback, and I can then
scroll back up in gnome-terminal with e.g. mouse wheel, shift-pgup,
etc.
But on my friend's machine with the same Ubuntu 10.04 installed,
screen for some reason doesn't do this.  It never "leaves behind" more
than the current screen in gnome-terminal, so the scrollbar never
changes size, and trying to scroll with the mouse wheel just gets
interpreted as the Up key, causing the shell to go to the previous
line.
We pored over our .screenrc and .inputrc (which barely have any
config), but couldn't find what was causing this.  It doesn't seem to
matter anyway since if I create an entirely new user on my own box,
and an entirely new user on his box, both of which have no custom
.inputrc/.screenrc, we still see this discrepancy.  It's all version
4.00.03jw4 (FAU) 2-May-06.  Any help?  Thanks in advance.
-- 
Yang Zhang
http://yz.mit.edu/