desktop-packages team mailing list archive

[Ingo Ruhnke <grumbel@xxxxxx>]

Did another test to confirm that the problem is in cairo. The attached
program will generate a /tmp/out.png with text in RGB, BGR, VRGB and
VBGR ordering, the vertical ordering will show up correctly, while the
horizontal ones are identical. Furthermore on option of the type:

    cairo_font_options_set_antialias(fopts, CAIRO_ANTIALIAS_GRAY);

will still produce subpixel anti-aliasing, not grayscale, i.e. all the
same problems that can be seen in the Ubunte Font Rendering Details
dialog.

** Attachment added: "text.cpp"
   https://bugs.launchpad.net/ubuntu/+source/gtk+2.0/+bug/703191/+attachment/2324109/+files/text.cpp

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https://bugs.launchpad.net/bugs/703191

Title:
  BGR-ordered subpixel font rendering appears broken/nonfunctional in
  Gnome/GTK+

Status in GTK+ GUI Toolkit:
  Unknown
Status in “gtk+2.0” package in Ubuntu:
  Confirmed

Bug description:
  I'm filing this bug against gtk+, but frankly I don't know exactly
  what package is the culprit.  It's occurring somewhere between the
  Gnome "Appearance" preference panel and freetype, I suppose.


  In summary, subpixel-antialiased font rendering to a Blue-Green-Red
  (BGR) ordered display panel is broken in Maverick (10.10, Gnome).
  There is NO DIFFERENCE between text rendered using the "RGB" setting
  and the "BGR" setting.  It is blurry and fringy on my BGR panel in
  both cases, contrary to my experiences over the last few years with
  previous releases, under which I always had sharp results.


  I'm running Ubuntu 10.10, 64-bit, on a generic PC with an Nvidia
  7900GS card, using the latest proprietary Nvidia driver.  The monitor
  is a Dell 1800FP, one of the few BGR panels out there, unfortunately,
  and it is connected via DVI.


  There is no change whatsoever when toggling between the two horizontal
  subpixel options in the "Appearance" settings panel
  (System->Preferences->Appearance->Fonts->Details).  No matter how
  closely I look, not a single pixel changes. I can see small changes
  (as expected) when I go back and forth between "RGB" and "VRGB," for
  example, but "RGB"<->"BGR" appears to do absolutely nothing.


  I can verify that what I'm seeing (with either "RGB" or "BGR"
  selected) is, in fact, RGB-ordered subpixel rendering.  If I take a
  screenshot and mirror it horizontally, which essentially turns RGB
  into BGR, what I see is very nice, clear text on my screen.
  Unmirrored, it's ugly and fringy.


  I have tried various versions of the Nvidia driver, and it doesn't
  help.  Nor does using an unaccelerated driver.  Nor does the status of
  compiz desktop effects, on vs. off.


  I have had excellent font rendering in the past, up through and
  including Lucid (10.04).


  In Firefox, for some reason, the systemwide RGB/BGR setting *does*
  work. If I select "BGR" in the Gnome appearance preferences and
  refresh a web page, it looks GREAT! Re-select "RGB," refresh, and it's
  ugly again.  All other text on the screen in Gnome/GTK applications
  remains unchanged.


  And Qt-based applications also work correctly, according to the
  settings I have in ~/.fonts.conf.  Those applications have great-
  looking text.


  So there's something weird going on. This preference isn't being
  respected by my desktop or the Gnome/GTK applications I use, and it
  has worked perfectly in the past.  My Google searches for others
  experiencing this problem have come up empty.


  In attempting to troubleshoot this problem, I tried numerous different
  LiveCD images to see whether they worked.  (I booted them in a kvm
  virtual machine, and carefully inspected their on-screen output.)
  Here's the summary:


  Ubuntu 10.10: BROKEN - no BGR font rendering (both 32-bit and 64-bit
  versions tested)


  Xubuntu 10.10: BROKEN - no BGR font rendering


  Ubuntu 11.04 alpha: BROKEN - no BGR font rendering


  Ubuntu 10.04.1: WORKS FINE!


  Kubuntu 10.10: WORKS FINE!


  Obviously, in each case, I had to change the default rendering options
  through settings.


  So apparently BGR font rendering is OK in KDE/Qt, and broken in GTK-
  based releases, both Gnome and XFCE.  And the bug seems to be carrying
  over into Natty, at least early in its cycle.


  I look forward to seeing this regression corrected.

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: libgtk2.0-0 2.22.0-0ubuntu1
  ProcVersionSignature: Ubuntu 2.6.35-24.42-generic 2.6.35.8
  Uname: Linux 2.6.35-24-generic x86_64
  NonfreeKernelModules: nvidia
  Architecture: amd64
  Date: Fri Jan 14 22:14:58 2011
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: gtk+2.0

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