Hrvoje Niksic writes:
IMO `what-cursor-position' should either count the characters or maybe
the pixels. Anything else is bound to be broken in almost every
situation. I know the FSF did differently, and I think they made a
mistake.
I heartily agree. Indeed, I think that for real support of
variable-width fonts, we need two flavors of what-cursor-position, one
which counts the characters, and one which counts the pixels.