I recently upgraded to Ubuntu 15.04 and ibus-unikey just didn’t function correctly. Whenever I switched to Vietnamese input from English input, only the first Vietnamese character was rendered correctly. From then on, I couldn’t type in Telex anymore.
The solution I found was to switch to fcitx-unikey. There is another one, called fcitx-bogo. I installed both of them but only the unikey one showed up. I can type in Vietnamese now so I am satisfied!
Once you have installed everything above. Go to the terminal and type “im-config”, follow the instructions and set fcitx as your default input method.
Then you should see a keyboard appear in the top right status bar in the screen.
Click on the that keyboard and choose “Configure”.
In the “Input method” tab, click on the plus sign to add a new input method.
Untick “Only show current language”, then find “Unikey” and add it.
Go back to the keyboard again, click on it and choose input method (with a arrow “>” like this), then choose “Unikey”.
Now you should be able to type in Vietnamese!
Note that if you don’t any effect of your changes, you have to log out then log in Ubuntu to enable them.