GtkSpell provides word-processor-style highlighting and replacement
of misspelled words in a GtkTextView widget. Right-clicking a
misspelled word pops up a menu of suggested replacements.

GtkSpell is a library and is mostly of interest to GTK programmers.

This is major version 3 of the library, which is API incompatible
to version 2.

Homepage:
https://gtkspell.sourceforge.net/
