[gentoo-user] Xinerama vs TwinView for dual monitor setup

[Alan McKinnon]

Hi,

My notebook has this graphics hardware.

alan@nazgul ~ $ sudo lspci | grep VGA
01:00.0 VGA compatible controller: nVidia Corporation GeForce 8600M GT (rev 
a1)
alan@nazgul ~ $ sudo xdpyinfo | grep -A4 'screen #0'
screen #0:
  print screen:    no
  dimensions:    1920x1200 pixels (332x210 millimeters)
  resolution:    147x145 dots per inch
  depths (7):    24, 1, 4, 8, 15, 16, 32

I also have a second LCD monitor at work, a 1280x1024 that is physically 
slightly larger than the notebook screen, with a corresponding lower dpi.

I've configured it with TwinView to have the second monitor on the right, and 
how I usually use it is to put a user's support mail on that where I can read 
it and fix their issues using the tools on the main monitor. So it's a very 
unsophisticated setup, I have no need for massive 3D accel for eg games, or 
even for placing windows across two monitors. Windows are always on one 
screen or the other (because of the huge dpi difference). There are two 
smallish issues:

The viewports are aligned along the top edge and the 
panel/kicker/plasma/whatever on every desktop environment insists on trying 
to stretch across both monitors, into dead space on the right hand one. I'm 
getting use to right-click on panel, configure, set width to 57% at work, 
100% at home. If I align the viewports on the bottom edges, windows managers 
tend to want to position new windows with their title bars in the dead space 
at the top.

kdm and entrance want to stretch over both monitors. I definitely do not want 
this. Murphy dictates that all useful DM menus will end up in the dead space 
regardless of the theme I use <grrrr>

My research into nvidia's docs leads me to believe that TwinView is designed 
to make the presence of two physical monitors invisible and present one giant 
X screen, with a funky API for dead spaces (which may or may not work). I'm 
thinking Xinerama is the better option, despite the fact that it's old, 
clunky, hopeless at dealing with XRandR and can't be changed on the fly. I'm 
happy to set up two ServerLayouts to deal with this.

I'd appreciate some pros and cons feedback from the list before I embark on a 
huge emerge -e world to include Xinerama support.

-- 
alan dot mckinnon at gmail dot com