Another problem with QWhatsThis::showText() method: word wrapping. If you want to turn it off, you’d probably face with some problems: it’s not as easy as it supposed to be.
I’ve found the solution that satisfied me: instead of calling
QWhatsThis::showText(myPoint, "blah blah...", ...);
I frame “blah blah …” text into table with <nobr> tags and use this call:
QWhatsThis::showText(myPoint, "<table><tr><td><nobr>blah blah...</nobr></td></tr></table>", ...);
This solved my problems.