Comment 12 for bug 260589

(In reply to comment #4)
> (In reply to comment #3)
> > (In reply to comment #2)
> > > Let's see if GTK+ is interfering here.
> > >
> > > Can you try
> > >
> > > export GTK_IM_MODULE=xim
> > > gedit
> > >
> > > and check if the Congo layout works now in gedit?
> > >
> >
> > export GTK_IM_MODULE=xim does fix it.
> > So it's a Gtk+ bug?
> >
>
> A change that took place, and I believe it relates to this bug, is at
> http://svn.gnome.org/viewvc/gtk%2B/trunk/gtk/gtkimcontextsimple.c?view=annotate
> lines 928-932.
>
> The order of check_algorithmically() and check_compact_table() changed
> (check_algorithmically() was put first recently), so that issues with the
> compose table mess are silently bypassed.
>

I looked deeper into the issue.

The above information regarding the specific change in the GTK+ code is not correct.

This bug was introduced in GTK+ in March 2008, when the first patch to update gtkimcontextsimple.c was committed.
There was a call at that point for testing,
http://blogs.gnome.org/simos/2008/03/05/testing-the-updated-im-support-in-gtk/
however this issue with the specific use of combining diacritics was missed.

I am planning to close this report as NOTOURBUG and open a report in GNOME Bugzilla.