Dead keys for accents (like â, è, ç) stopped working in LibreOffice and Pidgin after I upgraded to Ubuntu 16.04.
This issue is better solved by the next input:
$ ibus-daemon --xim
And, also activating this Keyboard input method system in the System preferences - Language Support:
Keyboard input method system => XIM
The reason is that, when a language has complex characters like "à", the "Ibus" always generates problems, even to the "very known" non Gnome applications like Skype and Microsoft Office-PlayOnLinux. The typical error is that appears "`a" instead of "à".
My recommendation is that you add the "ibus-daemon --xim" as Startup Application in order to forget this issue forever.
The fix provided by
ibus-setup may not work after startup. To start it with the session, add to startup the command
ibus-daemon --xim, as stated here.
UPDATE ON A DIFFERENT CAUSE THAN iBUS:
In Kubuntu 18.04 all worked fine. Trying LXQt on top of that and no dead keys in Libreoffice. It seems in this case it was not an ibus problem, but one with the libreoffice UI backend - as suggested here. Solved it as indicated here: edit/create the file
/etc/profile.d/libreoffice-fresh.sh ( or
/etc/profile.d/libreoffice-still.sh, as said here) and uncomment/add the line
export SAL_USE_VCLPLUGIN=gtk3, then reboot.