Author: Nilo Dantas - n1lo
Based on: https://bugs.launchpad.net/ubuntu/+source/ibus/+bug/518056 - helio-valente post

How to use Cedilha on US Keyboard on ArchLinux

1) Put: English(US, internacional with dead Keys) on your system keyboard layout.

2) Editing the files:

sudo vim /usr/lib/gtk-3.0/3.0.0/immodules.cache
sudo vim /usr/lib/gtk-2.0/2.10.0/immodules.cache

changing the line

"cedilla" "Cedilla" "gtk20" "/usr/share/locale" "az:ca:co:fr:gv:oc:pt:sq:tr:wa"

to

"cedilla" "Cedilla" "gtk20" "/usr/share/locale" "az:ca:co:fr:gv:oc:pt:sq:tr:wa:en"

3) replacing "ć" to "ç" and "Ć" to "Ç" on /usr/share/X11/locale/en_US.UTF-8/Compose

sudo cp /usr/share/X11/locale/en_US.UTF-8/Compose /usr/share/X11/locale/en_US.UTF-8/Compose.bak
sed 's/ć/ç/g' < /usr/share/X11/locale/en_US.UTF-8/Compose | sed 's/Ć/Ç/g' > Compose
sudo mv Compose /usr/share/X11/locale/en_US.UTF-8/Compose

4) add two lines on /etc/environment

GTK_IM_MODULE=cedilla
QT_IM_MODULE=cedilla

5)restart your computer