In Qt, signals and slots require matching argument types:
QObject::connect: Incompatible sender/receiver arguments QLabel::linkActivated(QString) --> Butt
From the signals slots documentation:
The signature of a signal must match the signature of the receiving slot. (In fact a slot may have a shorter signature than the signal it receives because it can ignore extra arguments.)
This means that a signal of the form
signal(int, int, QString)
can only be connected with slots with the following signatures
slot1(int, int, QString)
slot2(int, int)
slot3(int)
slot4()
As koan suggests the best approach is to use another slot with a QString argument and then call the slot you actually want.