It seems that when no server arguments are given in /etc/gdm/gdm.conf, the default arguments include -dpi 96 instead of just leaving it up to the xserver to decide the dpi. That means the only way to have the xserver use the values of xorg.conf, or the values read from the monitor, is to specify the arguments to the server and leave out -dpi. The arguments need to be specified with 0=/path/to/X something -dpi 78 -something, and not with command= like earlier.
I think it's a bad thing that the default behaviour when there are no specified arguments is to give a dpi value to the server. If I'm wrong and this is indeed a good thing, then it should at least be more clearly documented. Since this is a gdm problem, I believe this bug report should be moved to gdm. -- Vincent Lönngren <[EMAIL PROTECTED]>
