fontconfig corrupted fonts

[CatchesAStar]

Binary package hint: fontconfig

This was initially reported as a KDE bug, but it was later determined to be a fontconfig bug.
See -> https://bugs.kde.org/show_bug.cgi?id=233187 for origional bug report
Fontconfig version :2.8.0

The Antialiasing settings in System Settings-> Appearance -> Fonts
can cause font corruption, depending on the settings.

It occurs randomly, only for that particular character on that screen.
By character, I mean that for example, all "Y"s that are in the application are
corrupted.

This occurs if the antialiasing settings are set to "enbled" and with the
following combinations of settings

SubPixel Rendering: RGB | Hinting Style: None
SubPixel Rendering: RGB | Hinting Style: Slight
SubPixel Rendering: RGB | Hinting Style: Medium
SubPixel Rendering: RGB | Hinting Style: Full
SubPixel Rendering: Disabled | Hinting Style: Medium
SubPixel Rendering: Disabled | Hinting Style: Full

and does not occur with

SubPixel Rendering: Disabled | Hinting Style: None
SubPixel Rendering: Disabled | Hinting Style: Slight

Ive taken a screenshot, so please take a look ->
http://img52.imageshack.us/img52/7463/snapshot1x.png

This occurs only in Lucid

[OlivierS (olivier-olivier)]

some additional information:
- the character that is corrupted might be different in different applications. For example right now the bold o is corrupted in Bluefish, the s in Firefox and the o is corrupted (missing!!) in Thunderbird.
- different font config settings do not seem to have any impact. Not on the issue, but also not on the appearance of the fonts (even if I disable everything the fonts are still anti-aliased?!? I didn't logout/login however). So SubPixel Rendering: Disabled | Hinting Style: None still shows corrupted characters here.

This is on an ATI graphics chip (integrated X1250) with ati driver, on a single display on the DVI port running 1920x1200.

[CatchesAStar (catchesastar)]

This is an issue with the ATI OSS drivers, not fontconfig.
If you change to the propreity drivers, you will find that there is no such corruption that occurs.

[OlivierS (olivier-olivier)]

In bugreport https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers/+bug/568492 similar corruption is reported with the nvidia driver. Is it the same bug or a different one? Setting status back to new.

[OlivierS (olivier-olivier)]

However, on https://bugs.launchpad.net/ubuntu/+bug/475428 a similar issue that is ATI specific is reported.

[john fisher (john-jpfisher)]

I do not agree that this is ATI only.
After upgrading an Intel mobo using on-board Intel graphics from 14.04 to 14.10, I got the same problem. It is not connected with any one font. dpkg-reconfigure fontconfig did not help; neither did removing /etc/fonts/fonts.conf.

What does fix it, but only 95%, is turning off hinting. I used the Unity tweak tool. I can still find a stray example of bad characters here and there.

I am running the classic, not Unity interface. Tested with apps: FireFox, Chrome, Thunderbird, Gimp, Inkspace, Libreoffice all of which had the problem.

The fonts look a lot better with hinting turned on!

[john fisher (john-jpfisher)]

After I posted I found another workaround, maybe worth 98%. I was able to turn hinting back on. There is still an underlying bug.

add or edit xorg.conf as follows
Section "Device"
   Identifier "Intel Graphics"
   Driver "intel"
   Option "AccelMethod" "uxa"
EndSection

http://askubuntu.com/questions/582980/missing-letters-in-menus-and-folder-names/606583#606583

[john fisher (john-jpfisher)]

this bug seems to be related too:
https://bugreports.qt.io/browse/QTBUG-27106

see
http://askubuntu.com/questions/285862/qt5-font-rendering-in-ubuntu-13-04/606964#606964