Comment 42 for bug 107320

Matthew Nuzum schreef:
> The Option "DDC" "no" workaround fixes the problem for me, but I'm
> curious if anyone can explain what this does?

(quote from http://en.wikipedia.org/wiki/Display_Data_Channel)

"The Display Data Channel or DDC is a digital connection between a
computer display and a graphics adapter that allows the display to
communicate its specifications to the adapter. The standard was created
by the Video Electronics Standards Association (VESA)."

What in my opinion happens is that either:
- your monitor reports the wrong physical dimensions
- your graphics driver doens't interpret the DDC information correctly.

My guess it is the latter happens as switching to another driver also
fixes the problem for me (i810, although I think that driver has no 3D
hardware capabilities). But maybe the i810 driver is simply incapable of
reading DDC and therefor the error doesn't occur (ergo: it's your
monitor hardware's fault)?

Anyway, by telling xorg not to use the DDC information it probably
assumes some default dimensions of your hardware which are more accurate
than what DDC reports.

//puccha

BTW: This workaround not only fixed problems with the login screen, gdm
for me but also:

mythtv (video and live tv where squized)
compiz-fusion (would boot up with HUGE titlebars)
teamspeak (menu scaling was incorrect to the point it was unuseable.)