This has been documented for eons. https://doc.qt.io/qt-5/signalsandslots.html https://doc.qt.io/qt-5/signalsandslots.html "Compared to callbacks, signals and

This has been documented for eons. https://doc.qt.io/qt-5/signalsandslots.html https://doc.qt.io/qt-5/signalsandslots.html "Compared to callbacks, signals and slots are slightly slower because of the increased flexibility they provide, although the difference for real applications is insignificant. In general, emitting a signal that is connected to some slots, is approximately ten times slower than calling the receivers directly, with non-virtual function calls."