Dear Maintainer,

Browsing iceweasel gives sometimes partly unreadable text.
Text looks scrambled, pixelized or bulky.
Not only he content of the web pages, but also the tab header and sometimes
iceweasel's  menue.

In 2009 there has been a problem with libcairo (Debian bug #666468) but now restoring the old
libcairo does not help anymore. So i believ it's a new bug. (But the output is the same,
for comparison)

Switching off hardware acceleration in iceweasel does not help, either.

But i could solve the issue by enabling shadow framebuffer in nouveau's xorg.conf:
  Section "Device"
    Option "ShadowFB" "true"

The error is only visible in iceweasel. All other programs behave normally, that means: look good.


   * What led up to the situation?
       Browsing web-pages. At first they look normal. Suddenly, after some seconds
       parts of text become unreadable.
       It looks scrambeled, pixelized, as a block.
       Hoover with the mouse or moving the iceweasel window out of the screen and back
       restores readability for some time.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?
       Start iceweasel, load (any) web page. Scroll.

   * What was the outcome of this action?
       Partly unreadable text.

   * What outcome did you expect instead?
       Normally rendered readable text

Additional information:

The behaviour is the same (bad text readability) if i install iceweasel
from experimental (instead of sid's):
  # apt-cache policy iceweasel
  iceweasel: 15.0.1-1

My X:
  # apt-cache policy xorg
  xorg:  1:7.7+1 0
  xserver-xorg-video-nouveau:  1:1.0.1-3

My hardware:
  # lspci
  VGA compatible controller:
         NVIDIA Corporation GF108 [Quadro 1000M] (rev a1)

could you provide a screenshot of the poorly-rendered text?  that might
help other users and developers to see what you're talking about.

thanks for your report, i hope someone more knowledgable than me can
help sort out what the problem is.

regards,

Hi Daniel,

in the hope it will be helpfull, i found a screenshot by somebody else
which looks exactly like my experience:
http://img844.imageshack.us/img844/7517/bildschirmfoto120520122.png

Thanks and good luck!
Uli

You should check out libcairo2 bugs →
http://bugs.debian.org/cgi-bin/pkgreport.cgi?pkg=libcairo2;dist=unstable
Several people (me included) had this problem with libcairo2 (version
1.12). I "solved" it by downgrading to 1.10

Jérémie

I got an answer on this from outside Debian.
And yes, it sounds like the very same issue.

---
It isn't a bug in iceweasel, actual it is a bug in xorg-server, first
reported on 31 Mar 2012:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=666468

The bug is triggered by libcairo, and first come visible on ATI Cards.
Unfortunately the fix for ATI move the bug to the nouveau driver.

Other Distros (manly ubuntu) aren’t bitten by this bug, because they
ship a patched version of libcairo, were they switch of the related
functions in cairo. I didn't believe that this is the right workaround,
because cairo didn't do it wrong, it is xorg related, so the workaround
to use a nouveau.conf and switch off acceleration in the "Xorg-driver"
is closer to the real Bug. Well it isn't a solution to use a
nouveau.conf, but it is somewhat clearer, then to patch a library for
disable a function, which do it right, but trigger a bug in a other
"library".
---

src:iceweasel has been superseded by src:firefox-esr in version
45.0esr-1 in March 2016. Transitional packages to ease upgrades were
provided in the wheezy, jessie, stretch and buster releases. The
transitional packages have been removed finally before the bullseye
release in August 2021.
After regular security support for buster ended in August 2022 and LTS
support ended in June 2024, I'm closing the remaining bug reports now.

Andreas