Install vim-syntax-gtk by entering the following commands in the terminal:
sudo apt update sudo apt install vim-syntax-gtk
Description:
Syntax files to highlight GTK+ keywords in vim
A collection of C extension syntax files for Xlib, Glib, GObject, GDK, GdkPixBuf, GTK+, ATK, Pango, Cairo, libgimp, libgnome, libgnomecanvas, libgnomeui, libglade, gtkglext, VTE, linc, GConf, ORBit, Evince, GIO libsoup, libunique, GStreamer, GObject-Introspection and Json-Glib.
Homepage: http://www.vim.org/scripts/script.php?script_id=1000
Version: 20110314-1
Section: universe/editors