vncviewer crashes on startup when using xmonad

[Brian Amberg]

When using xmonad (with gnome in my case), vncviewer crashes with the failed assertion:

vncviewer: TXScrollbar.cxx:47: void TXScrollbar::set(int, int, int, bool): Assertion `limit_ > 0 && len_ >= 0 && len_ <= limit_' failed.

This can be fixed by replacing the assertion in TXScrollbar::set with

if (len_ > limit_) len_ = limit_;

such that TXScrollbar::set looks like this

void TXScrollbar::set(int limit_, int start_, int len_, bool vert)
{
  // This assertion fails under certain window managers.
  // assert(limit_ > 0 && len_ >= 0 && len_ <= limit_);

  if (len_ > limit_) len_ = limit_;
  if (start_ < 0) start_ = 0;
  if (start_ > limit_ - len_) start_ = limit_ - len_;

  if (limit[vert] != limit_ || start[vert] != start_ || len[vert] != len_) {
    limit[vert] = limit_;
    start[vert] = start_;
    len[vert] = len_;
    paint();
  }
}

I hope this patch is helpful.

best regards,

Brian Amberg

bamberg@shuttle:~/ lsb_release -rd
Description: Ubuntu 8.04
Release: 8.04

[penalvch (penalvch)]

Brian Amberg, thank you for reporting this and helping make Ubuntu better. However, Hardy Desktop is EOL, and your crash report is missing. If this is reproducible in a supported release, please follow these instructions to have apport report a new bug about your crash that can be dealt with by the automatic retracer. First, execute at a terminal:
cd /var/crash && sudo rm * ; sudo apt-get update && sudo apt-get -y upgrade && sudo service apport start force_start=1

If you are running the Ubuntu Stable Release you might need to enable apport in /etc/default/apport and restart.

Now reproduce the crash, then open your file manager, navigate to your /var/crash directory and open the crash report you wish to submit.
If this fails you will have to open a terminal and file your report with 'ubuntu-bug /var/crash/_my_crash_report.crash' where _my_crash_report.crash is the crash you would like to report. If you get an error that you aren't allowed to access this report you will have to file it with 'sudo ubuntu-bug /var/crash/_my_crash_report.crash'. If you run the command against the crash report and a window pops up asking you to report this, but then never opens a new report, you would be affected by https://bugs.launchpad.net/ubuntu/+source/apport/+bug/994921 . In order to WORKAROUND this, one would need to open the following file via a command line:
sudo nano /etc/apport/crashdb.conf

and comment out the line:
'problem_types': ['Bug', 'Package'],

by changing it to:
# 'problem_types': ['Bug', 'Package'],

Save, close, and try to file the crash report again via:
ubuntu-bug /var/crash/_my_crash_report.crash

I'm closing this bug report since the process outlined above will automatically open a new bug report which can then dealt with more efficiently.

Please feel free to subscribe me to this new report.

Also, please do not attach your crash report manually to this report and reopen it.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs