Font hinting and subpixel rendering worked nicely on my Ubutu 12.04 system in Unity, Gnome, twm and e17. Only in Xfce the fonts showed red lines on their borders. I tried to adjust the Xfce-settings for hinting, antialiasing and of course subpixel rendering, without any effect. Then I adjusted the global fontconfig settings in /etc/fonts, of course without success.
Finally I found out that, in the Xfce settings editor, under xsettings/Xft/Lcdfilter the default setting was "lcdnone" (at least I think it's default: I deleted the xfce config files in ~/.local and ~/.config and checked again). This is strange, since the system wide fontconfig settings were configured to use "lcddefault" all the time.
So, steps to reproduce:
Install xfce4 by using the xfce4 package on Ubuntu, log into xfce and check font rendering on an LCD display. Rendering is probably bad. Also check in Xfce settings editor the value of xsettings/Xft/Lcdfilter.
How to fix: Change the defaults for xsettings/Xft/Lcdfilter to lcddefault, or add a checkbox for this to the "normal" setings dialogues of Xfce.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: xfce4 4.8.0.3
ProcVersionSignature: Ubuntu 3.2.0-43.68-generic 3.2.42
Uname: Linux 3.2.0-43-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.2
Architecture: amd64
Date: Fri May 17 10:54:13 2013
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: xfce4
UpgradeStatus: Upgraded to precise on 2012-03-13 (429 days ago)
Status changed to 'Confirmed' because the bug affects multiple users.