Subpixel antialiasing doesn't look very good on my monitor because I get color "ringing". (Subpixel is when red and blue pixels are used on the sides of font dots to try and smooth diagonal/curved lines... you can see this more easily by using "xmag" or "kmag" and zooming into some text on the screen).

I would like to disable subpixel (RGBA) and just use greyscale antialiasing instead. On some systems, I had success by use adding this to my .fonts.conf file:

<match target="font" >
<edit mode="assign" name="rgba" >
<const>off</const>
</edit>
</match>

Normally such a construct would immediately take effect on any new application launched that uses freetype/fontconfig. (I have also used "none" instead of "off"). However, this doesn't appear to work on this Mandriva 2009.1 system! I even tried it in /etc/fonts/conf.d and it doesn't do anything there either.

Documentation for fontconfig is really spotty. I have spent many hours fighting this to no avail. Am I missing something? Thanks!

If you're running KDE3 this can be fixed by running kcontrol from a terminal.
Appearance & Themes -> Fonts -> Configure anti-aliasing
I think you may have to logout and then back in to see the changes.

I am running KDE4 at home. I have verified that when you use systemsettings and go under Appearance->Fonts->Use Anti-Aliasing it is set to Enabled and Use Sub-pixel Rendering is disabled (off/unchecked). I have logged out, even restarted the Xserver. Makes no difference, it is still performing (color) sub-pixel rendering in all applications.

I also verified that KDE4 systemsettings is, indeed, just modifying ~.fonts.conf in exactly the way I was doing manually. I am not sure how this system can ignore ~.fonts.conf and yet use fontconfig.