I asked the same question when I used Maverick Meerkat but I can't make that solutions work on Unity. I want to use the keys ´ followed by c and the output should be "ç". It works that way in Windows out of the box, and it did work in Ubuntu 10.10 following the solutions given in the question above. But in 11.04 it outputs "ć". How to change that?
Edit /usr/lib/gtk-2.0/2.10.0/gtk.immodules
Modify the line where you can find "cedilla" add ":en" at the end
"cedilla" "Cedilla" "gtk20" "/usr/share/locale" "az:ca:co:fr:gv:oc:pt:sq:tr:wa:en"
Edit /etc/environment
Add: export GTK_IM_MODULE=cedilla
Edit for Ubuntu 12.10: (according to the other answer by Hoerlle)
the gtk.immodule file is located at:
/usr/lib/x86_64-linux-gnu/gtk-2.0/2.10.0/gtk.immodules
or
/usr/lib/i386-linux-gnu/gtk-2.0/2.10.0/gtk.immodules
For KDE and other applications that are not GTK:
Edit: /usr/share/X11/locale/en_US.UTF-8/Compose
Find all ocorrencies for ć and replace it all for ç, remember to look for the the uppercase matches too Ć and Ç
You may need to restart your gnome.
