GTK+, or the GIMP Toolkit, is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK+ is suitable for projects ranging from small one-off tools to complete application suites.
nvim ~/.gtkrc-2.0
gtk-theme-name='theme'
gtk-icon-theme-name='icon'
nvim ~/.config/gtk-3.0/settings.ini
[Settings]
gtk-theme-name=theme
gtk-icon-theme-name=icon