Unlike most other development environments, GLib/Gnome does not provide a platform-wide spell checking system. Users who need spell checking usually use libenchant directly, or something along the lines of SexySpellEntry or GtkSpell. 

This gap in the platform should be addressed, and some sort of easy to use "GSpellChecker" should be available to those who need it. In addition, GTK widgets handling text (i.e. GtkEntry and GtkTextView) should provide optional spell checking support "out of the box".

This has been proposed previously in bug #383706 from 2006. However, the Gnome landscape has changed considerably in the intervening time (in particular with the arrival of GIO), so it's worth kicking things off anew.

Before coming up with a concrete API proposal, it's worth discussing what sort of high-level design we'd like to come up with. I've added some notes to http://wiki.gnome.org/SpellChecking if people would like to have a read.