how can I know which object caused a specific event ?

[yeye_olive]

For the record, although the sender()-based solution works, it is considered bad pratice because it breaks modularity.

You can use the QSignalMapper class to "forward" a signal without parameters to a signal with a parameter identifying the sender. In your case this means that you lose the int parameter of the sliderMoved(int) signal, but you can recover it with QAbstractSlider::sliderPosition().

Another solution consists in defining a distinct tiny slot for each slider that just calls a common handler with a pointer to the slider as argument.