@panch said:

Would you then restrict the signals/slots to only GUI-related information passing? As a proper way of developing Qt applications, I mean...

QNetworkAccessManager emits signals to tell the world that a download has completed. QSerialPort emits signals to tell the world that some data has been received. QMediaPlayer emits signals to tell the world that its playback status has changed.

These show that signals and slots are "proper" for developing all kinds of things, not just GUIs.

I figured it out. I needed to set my QObject and QCore stuff properly. In the .pro file of the shared library, I added:

QT += core

In the shared library's .h file, I switched this:

class CTSCANSHARED_EXPORT ctScan { public: ...blah blah...

with this:

class CTSCANSHARED_EXPORT ctScan: public QObject { Q_OBJECT public: ...blah blah...

And then ensured the shared library's .h file had this:

#include <QObject>

And then it compiled properly.

@JohanSolo Thanks for the suggestion. I had done some reading about blockSignals() but I went back and looked again. The problem with blockSignals() is that it still leaves me needing to know that I wanted to emit a particular signal but couldn't. I somehow need to know how to re-emit the signal later when the server interaction completes.

An event filter would almost work. I could add a filter for my QState objects. In that case what comes to the eventFilter() method is a QSignalEvent. If I could detect in the filter that my server operation was in progress, then I could save away the event (or the event parameters) then use them to post the event equivalent of the original signal at the correct time. I could dynamic cast the event pointer and even peel off the arguments, but there does not appear to be any public constructor for a QStateMachine::SignalEvent, so I have no way to reconstruct a copy of the original event.

I also looked at using QAbstractTransition or QSignalTransition, but those basically have the same problem. There's no way to store the event to use later.

Thanks! I fix the problem. All works fine, but I have a Rectangle over that hide the window background and that was the problem.