Troubleshooting

So something has gone wrong... what do you do?

When Qtile is running, it logs error messages (and other messages) to its log file. This is found at ~/.local/share/qtile/qtile.log. This is the first place to check to see what is going on. If you are getting unexpected errors from normal usage or your configuration (and you're not doing something wacky) and believe you have found a bug, then please report a bug.

If you are hacking on Qtile and you want to debug your changes, this log is your best friend. You can send messages to the log from within libqtile by using the logger:

from libqtile.log_utils import logger

logger.warning("Your message here")
logger.warning(variable_you_want_to_print)

try:
    # some changes here that might error
except Exception:
    logger.exception("Uh oh!")

logger.warning is convenient because its messages will always be visibile in the log. logger.exception is helpful because it will print the full traceback of an error to the log. By sticking these amongst your changes you can look more closely at the effects of any changes you made to Qtile's internals.

X11: Capturing an xtrace

Occasionally, a bug will be low level enough to require an xtrace of Qtile's conversations with the X server. To capture one of these, create an xinitrc or similar file with:

exec xtrace qtile >> ~/qtile.log

This will put the xtrace output in Qtile's logfile as well. You can then demonstrate the bug, and paste the contents of this file into the bug report.

Note that xtrace may be named x11trace on some platforms, for example, on Fedora.

Debugging in Wayland

To get incredibly verbose output of communications between clients and the server, you can set WAYLAND_DEBUG=1 in the environment before starting the process. This applies to the server itself, so be aware that running qtile with this set will generate lots of output for Qtile and all clients that it launches. If you're including this output with a bug report please try to cut out just the relevant portions.

If you're hacking on Qtile and would like this debug log output for it rather than any clients, it can be helpful to run the helper script at scripts/wephyr in the source from an existing session. You can then run clients from another terminal using the WAYLAND_DISPLAY value printed by Qtile, so that the debug logs printed by Qtile are only the server's.

If you suspect a client may be responsible for a bug, it can be helpful to look at the issue trackers for other compositors, such as sway. Similarly if you're hacking on Qtile's internals and think you've found an unexpected quirk it may be helpful to search the issue tracker for wlroots.

Common Issues

Cairo errors

When running the Xephyr script (./scripts/xephyr), you might see tracebacks with attribute errors like the following or similar:

AttributeError: cffi library 'libcairo.so.2' has no function, constant or global variable named 'cairo_xcb_surface_create'

If it happens, it might be because the cairocffi and xcffib dependencies were installed in the wrong order.

To fix this:

1. uninstall them from your environment: with pip uninstall cairocffi xcffib if using a virtualenv, or with your system package-manager if you installed the development version of Qtile system-wide.

2. re-install them sequentially (again, with pip or with your package-manager):

   pip install xcffib
   pip install --no-cache-dir cairocffi
   

See this issue comment for more information.

If you are using your system package-manager and the issue still happens, the packaging of cairocffi might be broken for your distribution. Try to contact the persons responsible for cairocffi's packaging on your distribution, or to install it from the sources with xcffib available.

Fonts errors

When running the test suite or the Xephyr script (./scripts/xephyr), you might see errors in the output like the following or similar:

• Xephyr script:

  xterm: cannot load font "-Misc-Fixed-medium-R-*-*-13-120-75-75-C-120-ISO10646-1"
  xterm: cannot load font "-misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso10646-1"
  

• pytest:

  ---------- Captured stderr call ----------
  Warning: Cannot convert string "8x13" to type FontStruct
  Warning: Unable to load any usable ISO8859 font
  Warning: Unable to load any usable ISO8859 font
  Error: Aborting: no font found
  
  -------- Captured stderr teardown --------
  Qtile exited with exitcode: -9
  

If it happens, it might be because you're missing fonts on your system.

On ArchLinux, you can fix this by installing xorg-fonts-misc:

sudo pacman -S xorg-fonts-misc

Try to search for "xorg fonts misc" with your distribution name on the internet to find how to install them.