Convert old themes to the new format

This is now invalid, old theme support has been removed and will be part of a separate tool.

Rofi 1.4 can still read in and convert the old theme format. To read the old format, convert it, and dump it into a new file run:

rofi -config {old theme} -dump-theme > new_theme.rasi

This gives a very basic theme, with the colors from the old theme. You can preview the theme using:

rofi -theme new_theme.rasi -show run