Bug in subpixel hinting configuration?

[Mateusz Łoskot]

Hi,

Yesterday I was tweaking my Xfce desktop on my laptop and I noticed
strange behaviour in subpixel hinting configuration.
May be this is only a problem in incorrectly working User Interface
Settings applet.

My laptop is Dell Latitude D600.
My Linux distribution is Ubuntu 5.10.
My Xfce version is 4.3.90.2 (Xfce 4.4 BETA1), checkouted and compiled a
few days ago.

Here is the story with step-by-step explanation of what I did, and some
screenshots:

First, here is the screen presenting what I mean sayint that my desktop
looks correctly:

http://mateusz.loskot.net/gallery/bugs/xfce_no_subpixel_hinting_and_correct_fonts

As you can see, it's configured to "Use hinting" and to not to "Use
subpixel hinting".

Just for comparison, here is the screen presenting GNOME configuration
overview on the same laptop:

http://mateusz.loskot.net/gallery/bugs/gnome_with_subpixel_hinting_and_correct_fonts

As you can see, on GNOME I use both: hinting + subpixel hinting:


Now, I decided to turn subpixel hinting on Xfce too.
I opened Settings -> User Interface Preferences applet and I checked
"Use subpixel hinting" checkbox. After I rebooted my laptop and logged
to Xfce I noticed that it displays fonts incorrectly. All fonts are very
very small. Note, that I didn't change fonts settings before I reboot.
As you can see on the screens above and the one below, I still have Sans
9 selected:

http://mateusz.loskot.net/gallery/bugs/xfce_with_subpixel_hinting_and_incorrect_fonts


So, I decided to turn subpixel hinting off. I moved to UI Preferences
applet and unchecked appropriate checkbox, rebooted, logged to Xfce
and...no change:

http://mateusz.loskot.net/gallery/bugs/xfce_no_subpixel_hinting_and_fonts_should_be_corrected_back

I researched the problem a bit and I found that changes made using UI
Preferences applet seem to not take any effect.
I noticed that I have hinting turned on in the file
~/.config/xfce4/Xft.xrdb:

http://mateusz.loskot.net/gallery/bugs/xfce_no_subpixel_hinting_and_incorrect_fonts_xft_xrdb

I was not sure if this file is the right one I should look into. It was
just some intuition :-)

So, I decided to delete this file and see what will happen. I deleted
it, rebooted, logged to Xfce and it works!

http://mateusz.loskot.net/gallery/bugs/xfce_no_subpixel_hinting_and_correct_fonts_after_delete_xft_xrdb

I see all my fonts looking correctly back.


I'm not sure if this is a bug, but behaviour of those settings seem to
be quite confusing and unexpected.
I also don't know where is the problem exactly, I just suppose the UI
Preferences applet may not save input settings back.

I found similar bug report but quite different:
http://bugzilla.xfce.org/show_bug.cgi?id=665

May be I should report another one regarding to what I've observed?

Cheers
-- 
Mateusz Łoskot
http://mateusz.loskot.net