possibly scrambled qt4 apps in Ubuntu Jaunty Jackalope while using VRGB and LCD

In less than 48 hours Ubuntu Jaunty Jackalope will be released officially! While using Jaunty for more than a month I am pleased to see this great new release getting it’s way to a huge usership. While preparing my small „new features in Ubuntu Jaunty Jackalope“ talk for the „Ubuntu Berlin“ release party at c-base, I’d like to point out one open bug, that will make it into the release and might get some users into strange trouble:

When you have – for whatever reason (either by chance, clicking around or due to having a rotated display) – changed the display mode of Ubuntu to VRGB or VBGR (you can easily do this in the „System>Preferences>Appearance>Fonts“ menu) and additionaly turned on the lcd/subpixel mode, probably all of your qt4 applications – even qtconfig – will be totatlly scrambled and unreadable. The bug might hit you under Ubuntu (without a blue „K“ in the beginning) as you probably run something like VirtualBox, Skype or even Amarok in your Gnome environment. It will probably look like this:

Screenshot showing the scrambled qt application
Screenshot showing the scrambled qt application

But: Don’t panic! This bug only occurs when you changed some defaults in the Appearance/Fonts settings to rather uncommon or often maybe useless settings and switching back is fairly easy. But as I ran into this and put some effort into the corresponding bug on launchpad Subpixel/Lcd mode with VRGB/VBGR makes qt4 applications on Jaunty unreadable, I noticed, that a remarkable bunch of users posted duplicate bug reports or commented the report.

So if you are running into this error, all you have to do, is:

  1. exit all qt applications,
  2. go into „System>Preferences>Appearance>Fonts“,
  3. change VRGB/BGR to RGB/BGR.

That’s all. If you want to examine the bug, do the following (don’t do this at home):

  1. exit all qt applications,
  2. go into „System>Preferences>Appearance>Fonts“,
  3. change RGB/BGR to VRGB/BGR,
  4. switch to lcd/subpixel mode.

Afterwards your qt applications will look scrambled. If you don’t know, which one to run for a test, you probably have „qtconfig“ installed.

(I had a little chat with some developers about the severity of this bug. Though I think it’d would be definitely better not having it in a release, I understand the point, that the environment must be set up in a rather special way to run into this and it popped up quite late. Therefore it did not make it into the release critical bugs, but I am quite sure, it will be fixed soon.)

That’s all about this. I wish you a smooth upgrade to Jaunty – see you there :)

[update 2009-04-03]

As you can read on https://bugs.launchpad.net/ubuntu/+source/qt4-x11/+bug/334657, a patch has been committed to the Ubuntu repositories, that has been found here:

http://cvs.fedoraproject.org/viewvc/rpms/qt/devel/qt-x11-opensource-src-4.5.0-disable_ft_lcdfilter.patch?revision=1.1&view=markup

So the fix as an update is coming closer…

Ein Gedanke zu “possibly scrambled qt4 apps in Ubuntu Jaunty Jackalope while using VRGB and LCD

  1. It is sad to see that this bug isn’t release critical. After a long term hassle (5 yrs) with Gentoo, a short term flirt (1/4yr) with Arch, I finally arrived at Ubuntu in the hope of more stability on my workspace. VRGB mode is critical to anyone using a rotated display (try xrandr -o left).

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