The option "Highlight Current Line" isn't shown in every color scheme. It works for the color schemes: Kate, Oblivion, Cobalt. It doen't work for the color schemes: Classic, Tango. Steps to repeat: 1. Enable Highlight Current Line (Edit/Settings) 2. Choose color scheme "Classic" or "Tango" (Edit/Settings) -> current line isn't highlighted I tested it with Fedora 27 (Gnome-Desktop).
https://gitlab.gnome.org/GNOME/gtksourceview/commit/c7391cb4f6649cdd872f8fbfe8ca6cd912cb42e0 https://gitlab.gnome.org/GNOME/gtksourceview/commit/94267bde75d65668c19675eeeb2476ad915827b8 This was fixed long ago in gtksourceview. I can confirm that the current line is properly highlighted with both color themes.