Translations:FAQ/47/en

For more detailed explanation, xmodmap is a very low level tool, that doesn't aware keyboard layout. For X11, keyboard layout is built on a set of profile, when such profile is loaded, anything you changed with xmodmap will be overwritten, this isn't specific to fcitx, but all tool that support keyboard layout configuration. Xkb option is a set of profile that can do some pre-defined change over keyboard layout, including many thing that people usually do with xmodmap, for example, defining where dead key is, switching Caps Lock and Esc, and so on. Unless you have special requirements, xkb layout and xkb option is recommended.