I don't know the syntax for install-properties function... I wound up duplicating the entire gtk-text-tag definition, and including letter-spacing and letter-spacing-set in the correct alphabetical space like this:
(letter-spacing
gtk-text-tag-letter-spacing
"letter-spacing" "gint" t t)
(letter-spacing-set
gtk-text-tag-letter-spacing-set
"letter-spacing-set" "gboolean" t t)
I don't know the syntax for install-properties function... I wound up duplicating the entire gtk-text-tag definition, and including
letter-spacing
andletter-spacing-set
in the correct alphabetical space like this:Tested and works visually.