Well, here's my latest tooltip stuff ... I fixed the displayed formula
problem, but I still have a problem: the formula gets typeset three
times (see the number?). How can this be avoided?

Now I'd like to make the tooltip fixable. That is, if the user clicks
while the tooltip is displayed, the tooltip remains fixed, and does
not disappear when the user moves the mouse away. A second click would
make it "disappearable" again. Is this possible?