[vox-tech] dual head / xrandr help

[Charles McLaughlin]

Hi,

I have a laptop that I occasionally dock and would like to mirror the 
built-in screen to an external monitor connected to the dock.  I tried 
Xinerama, but it froze X.  It seems like the xrandr command is a good 
workaround - I can use it to enable the external monitor when I dock the 
laptop.  However, I have one little problem.... xrandr doesn't know 
about my external monitor's widescreen resolution:

cmclaugh at ubuntu:~$ xrandr
Screen 0: minimum 320 x 200, current 1440 x 900, maximum 1440 x 1440
VGA disconnected (normal left inverted right)
LVDS connected 1440x900+0+0 (normal left inverted right) 303mm x 190mm
    1440x900       60.0*+
    1280x800       60.0
    1280x768       60.0
    1024x768       60.0
    800x600        60.3
    640x480        59.9
TMDS-1 connected 1280x800+0+0 (normal left inverted right) 0mm x 0mm
    1280x800       60.0*
    1280x768       60.0
    1024x768       60.0
    800x600        60.3
    640x480        59.9
TV disconnected (normal left inverted right)

I read the xrandr man page and found the --newmode switch.  But I'm not 
sure how to use it.  In particular, I don't know the <clock Mhz> <hdisp> 
<vdisp> and other values for my external monitor.

After a little googling, I found the gtf command.  I suppose it will 
tell me how to find the values I need... But I don't know what to make 
of it's output:

cmclaugh at ubuntu:~$ gtf 1650 1050 60

   # 1648x1050 @ 60.00 Hz (GTF) hsync: 65.22 kHz; pclk: 144.01 MHz
   Modeline "1648x1050_60.00"  144.01  1648 1752 1928 2208  1050 1051 
1054 1087  -HSync +Vsync

Help?

Thanks,
Charles