Xubuntu 20.04 clean install in a virtual machine. All dependencies installed. _Show the plugin on desktop_ (**show_on_desktop = 1**) and _Control active windows_ (**only_maximized = 0**) should be set. ``` Thread 1 "panel-1-windowc" received signal SIGSEGV, Segmentation fault. 0x00007ffff7fbd1ee in is_window_on_active_workspace_and_no_other_maximized_windows_above (window=0x555555974220) at windowck-title.c:113 ``` I suspect it has to do with how Xfwm4 stacks windows. At least, that's what I have observed in my debugging process. When the root window (0x0) becomes active for a split second, the plug-in segfaults. The following two files show the correlation between the two events: [The output of a shell script that monitors active window](/uploads/8aa1cb8256ac974dfae84f2a5b321992/tmp.lzjzxQS39c) [The output of **gdb** when `PANEL_DEBUG` is set](/uploads/6a6ae42d14811b8ee09d39d416f095e1/tmp.nfA2DicUnK) _windowck-plugin-1_ is added and initialized at 17:20:46.852583081. Opening a new window (of _Thunar_, in this case) at 17:21:43.964363209 causes the root window to become active and the plug-in crashes at 17:21:44.200072155. ``` [ 17:21:39.687335343 ] _NET_ACTIVE_WINDOW(WINDOW): window id # 0x1a00013, 0x0 [ 17:21:43.906980647 ] _NET_ACTIVE_WINDOW(WINDOW): window id # 0x0, 0x0 [ 17:21:43.964363209 ] _NET_ACTIVE_WINDOW(WINDOW): window id # 0x1c00007, 0x0 [ 17:21:44.200072155 ] Thread 1 "panel-1-windowc" received signal SIGSEGV, Segmentation fault. ``` The _gdb_ log can be fixed with `awk 'NR==2 || NR%3==2' tmp.nfA2DicUnK` [This issue](https://github.com/takinoy/xfce4-windowck-plugin/issues/63) might be related. See [this](https://forum.xfce.org/viewtopic.php?id=15393) topic for more details.