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")

    # 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.