Quote Originally Posted by wysota View Post
"although the difference for real applications is insignificant". That's the important bit. If you spend even one hour of your time trying to work around an insignificant problem (e.g. by posting a question on a number of forums and reading the responses) then that's an hour wasted with no real compensation.

If signals and slots are convinient for you then use them, Qt uses them everywhere anyway so any potential gain in one place will not make any real difference. One silly function call (like calling sleep in your while loop) introduces a delay magnitudes larger than calling a slot.
Yesterday I was not sure yet how often and how fast my callback functions would be called,
that's why my question...

It will be an interval of some milliseconds. So I implemented a QTimer and it is fast enough.

Yes, calling sleep in my while loop is silly, and I found out why today.