That is truly odd. How come the XIM code doesn't trigger this
same problem?
I think the XIM code explicitly names the charset it wants.
But our XIM code calls XCreateFontSet, just like Xt code.
And browsing the Xt source, the "Cannot convert string to FontSet"
message
seems to be generated when XCreateFontSet returns NULL, so maybe
we could track it down further by making an appropriate call to
XFontSet and
seeing what it returns. Presumably it will return NULL but with a
non-zero
list of missing charsets.