This document seeks to serve as a central repository for information regarding debugging, i.e. to see what's going on under the hood of various programs.
lxqt-session
There's a log file at $HOME/.config/lxqt/debug.log that will populate with information using QLoggingCategory.
There's a few ways to turn this logging on, but the easiest way is to add the following before exec lxqt-session in /usr/bin/startlxqt:
export QT_LOGGING_RULES="*.debug=false;lxqt-session.debug=true"
which turns off all debugging except for those messages with the lxqt-session category.
lxqt-globalkeysd
The log level can be controlled from command line options. The following will print all types of messages to /var/log/syslog:
lxqt-globalkeysd --use-syslog --log-level=debug
You can choose different levels (see lxqt-globalkeysd --help) and you can eschew the syslog switch and debug information will be printed to stderr.
other LXQt applications
At time of writing, other LXQt applications use qDebug, which just prints to stderr. Running with 2>/path/to/some/file will get that output. Since startlxqt runs all the applications in /etc/xdg/autostart, any of these files can be edited so that their Exec key includes this addition.
Example:
Exec=lxqt-panel "2>/tmp/lxqt-panel.log"
Calamares
See $HOME/.cache/Calamares/session.log.
See also /var/log/installer/debug which is created by our calamares-logs-helper script upon a successful install.
To start Calamares in debug mode sudo calamares -d. Debug mode will give information regarding the modules that are loaded and the associated settings.