Hi. Please help me, this is my last attempt before reinstalling Arch on my system. I made a new user for my sister, and the font rendering (font is oxygen) is terrible. If I use any other font, it works flawlessly, but Oxygen doesn't. I have no idea what to do. Also, if I use the Gnome-Breeze theme, fonts don't render, but for any other theme, they do. Can you please help me? Thank you all soo much!

Reinstalling the system won't get you anywhere.

Either the font is installed per-user (ie. in the home directory of your user) and your sister gets a failsafe font or she has a different fontconfig setup (which can operate per font), "breaking" hinting, antialiasing etc.
That's hard to tell w/o seeing the issue.

> fonts don't render
Hummm?
Do you maybe use the breeze-dark theme?
Maybe "black cat in the dark" issue? (ie. could the foreground color match the background? gtk+ sucks terribly on notably "bright on dark" setups, it basically does not work)

The oxygen font is universally installed, here is a snapshot of how GNOME apps look:

http://postimg.org/image/arbr4dsvf/

And here is my system settings for GNOME apps:

http://postimg.org/image/c2k88hkdl/

Also, thank you so much for helping

So?
That's the oxygen font in the first shot and something different (with blurry subpixel rendering, the oxygen font has a bigger upper bow in "B") in the second.

I'd rather say you configured the oxygen font for gtk+ applications and something different for Qt/KDE applications?

If I'm understanding you right, you are saying that I have a different font for KDE apps, and a different font for GTK apps? Um, I don't. Here is my KDE font settings. also, correct me if I'm wrong.

Snapshot: http://postimg.org/image/ye1zpedc3/

If you want my .gtkrc-2.0 file, here:
http://pastebin.com/Nd6a9iUZ

Again, thanks for your support

Ah, the oxygen font has no characteristic "B", it's matter of size and hinting settings.

Ok, so what's your problem then? The blurry rendering in Qt applications?
You should be able to get rid of that in the antialiasing settings (hintslight and rather the autohinter)

Look at the screenshot from pulseaudio Volume Control, and look at it now, when I changed the font to Liberation Sans:
http://postimg.org/image/4bls5z9ip/

In the first picture, the fonts don't look good. They don't look like they should. Here, in my account, the oxygen font on gtk looks like this:
With Oxygen Font in my account: http://postimg.org/image/bcybxvdrj/
With Oxygen Font in my sister's account: http://postimg.org/image/arbr4dsvf/

can you see the difference?

That is a hinting difference, controlled by fontconfig.
Since it seems related to tze user, it will be a local config.

-> copy over ~/.config/fontconfig from your account to your sisters (and lookup ~/.config/fontconfig/fonts.conf to spot the relevant settings)
Older installations might have deprecated (but still interpreted) settings in ~/.fonts.conf/ and ~/.fonts.conf.d/

Thanks for the reply. I copied the font config file over to my sister's account, but I noticed that it didn't have a fonts.conf file. So, to test, I made a new account, and that account didn't have one either. Also, copying the fontconfig/ folder didn't do anything. It's still the same

I copied the font config file over to my sister's account, but I noticed that it didn't have a fonts.conf file

I frankly fail to read sense into this. You mean she (like the new account) had no user font config? That's "normal".

Also, copying the fontconfig/ folder didn't do anything.

Did you watch permissions/ownership? (her account needs read access to that file)

I'm pretty sure that you're rendering fonts on hintslight while she's on hintfull - but why that's the case (except for the above), I've no idea either.

Thank you soo much! You are the best! All I had to do was open up the font settings in the KDE control center and turn on anti-alising! It's fixed now! Thank you So!! Much!!!! I just hate ugly fonts.

I use infinality patchset and spent 2 days on this issue related to this bug :
https://bugs.kde.org/show_bug.cgi?id=350039

Now, fonts are beautiful and the rendering is identical on qt4/5 and gtk2/3.

The workaround is to force rendering options like you did it.