/usr/share/fcitx/configdesc/fcitx-unicode.desc is in fcitx-modules 1:4.2.9.1-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | [Unicode/Key]
Type=Hotkey
Description=Key
DefaultValue=CTRL_ALT_SHIFT_U
[DescriptionFile]
LocaleDomain=fcitx
|