I installed FC6T3 under Parallells on a MacBook. It automatically chose the display size of 1600x1200 when the MacBook monitor is only 1280x1024. FC5 required configuring the display size. In combination with bug #206900 where s-c-d won't change the display size, I had to manually edit xorg.conf to get the right size. I am not sure if Parallels supports EDID and correctly reports the resolution to the guest OS. I put in a support ticket to find that out.
Created attachment 136498 [details] Xorg log
There does not appear to be any DDC information available, and the faked VBIOS is reporting a maximum resolution of 1600x1200, so that's what we end up using. As it stands, this isn't a bug we can fix. If Parallels gains the ability to report native screen size somehow this will get fixed. The options are: - set the maximum resolution available through VBIOS to native screen size - add DDC emulation to Parallels (and wire up our vesa driver to use it better) - add VBE Panel extensions support to their VBIOS (and wire up our vesa driver to use that info at all)