Install xfwm4-dbg by entering the following commands in the terminal:
sudo apt update sudo apt install xfwm4-dbg
Description:
window manager of the Xfce project (debugging symbols)
This package contains debugging symbols for xfwm4, the Xfce window manager. Install it if you need to debug issues in xfwm4.
Homepage: http://www.xfce.org/
Version: 4.12.4-0ubuntu1
Section: universe/debug