Initialization of applications GTK vs. Qt

[H]

I am running the Mate desktop on CentOS 7 and trying to get fcitx working so I can switch between two western keyboards and typing pinyin.

Unfortunately the instructions on the net are lacking and the graphical configuration tool for fcitx is missing from EPEL.

At this stage, I have, with the support of one person on the CentOS mailing list who types Japanese, got it working in:
- terminal windows and
- an application using Qt, KeePassX.

I have not been able to get three applications using GTK working: Firefox, Thunderbird and LibreOffice. I can get them working when I have the three environment variables preceding the name of the application but not when launched from the desktop.

I suspect GTK and Qt applications are initialized differently - perhaps by X - but I do not know how to resolve this.

Any pointers or ideas for further research are appreciated!

Thank you.
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