The stock XCompose file which ships with most distros isn't exhaustive
and uses a number of layout specific keysyms intended to be easy to
memorize (rather than globally accessible). To circumvent this problem
we ship our own set of simplified compose definitions.
If we encounter a utf8 sequence corresponding to a glyph for which a
known XKB compose sequence exists, we replace the glyph with the
corresponding sequence. This allows non-english users to easilly specify
alternate glyphs without having to memorize the appropriate macros.