Comment 5 for bug 21637

Some more results:

The compose file in Breezy (probably Dapper) contains "incompatible" (???) compose sequences for polytonic letters that have diacritical marks. Those "incompatible" compose sequences do not produce any characters, so as is, it is not possible to produce daseia, psili and possibly others. Not possible, either in GTK+, QT, old X apps.

If someone fixes the Compose file*, then in QT applications it is possible to type all those characters. In GTK+ applications I was not able to type them, though it is possible that some settings where cached; I did not restart my session.

Due to the upstream GTK+ bug report, for GTK+ applications one needs to set the Input Method to the X Input Method in order to use the fixed Compose file.

To "fix" the compose file, replace the existing Greek polytonic compose sequences in /usr/share/X11/locale/en_US.UTF-8/Compose
with those generated by
http://hal.csd.auth.gr/~vvas/i18n/xkb/polytonic-compose.pl