Take a look at Signals and slots across threads. If you always use signals and slots to communicate with the worker thread, Qt handles the moveToThread for you if it’s needed and you used the correct connection. Edit: I would guess the article’s author was seeing his problem since he was calling start in the … Read more
Slots are a Qt-specific extension of C++. It only compiles after sending the code through Qt’s preprocessor, the Meta-Object Compiler (moc). See http://doc.qt.io/qt-5/moc.html for documentation. Edit: As Frank points out, moc is only required for linking. The extra keywords are #defined away with the standard preprocessor.
Create a custom signal, and emit it from your reimplemented event handler: class MyWidget(QtGui.QWidget): keyPressed = QtCore.pyqtSignal(int) def keyPressEvent(self, event): super(MyWidget, self).keyPressEvent(event) self.keyPressed.emit(event.key()) … def on_key(key): # test for a specific key if key == QtCore.Qt.Key_Return: print(‘return key pressed’) else: print(‘key pressed: %i’ % key) self.widget.keyPressed.connect(on_key) (NB: calling the base-class implementation is required in order … Read more
Qt checks a normalized signature, meaning Normalization reduces whitespace to a minimum, moves ‘const’ to the front where appropriate, removes ‘const’ from value types and replaces const references with values.
OK. So, I did a little more investigating. Seems this is possible. I was able to emit a signal, and receive value from the slot the signal was connected to. But, the problem was that it only returned the last return value from the multiple connected slots: Here’s a simple class definition (main.cpp): #include <QObject> … Read more
The main purpose of pyqtSlot is to allow several different overloads of a slot to be defined, each with a different signature. It may also be needed sometimes when making cross-thread connections (see this answer for one such scenario). However, these use-cases are relatively rare, and in most PyQt applications it is not necessary to … Read more
Update for QT5: Yes you can static void someFunction() { qDebug() << “pressed”; } // … somewhere else QObject::connect(button, &QPushButton::clicked, someFunction); In QT4 you can’t: No it is not allowed. Rather, it is allowed to use a slot which is a static function, but to be able to connect it you need an instance. In … Read more
It is not possible to mix template and Q_OBJECT but if you have a subset of types you can list the slots and signals like this: class SignalsSlots : public QObject { Q_OBJECT public: explicit SignalsSlots(QObject *parent = 0) : QObject(parent) {} public slots: virtual void writeAsync(int value) {} virtual void writeAsync(float value) {} virtual … Read more
How to pass arguments to callback functions in PyQt You can use functools.partial from standart Python library. Example with QAction: some_action.triggered.connect(functools.partial(some_callback, param1, param2))
First, try with boost::signal anyway. Don’t assume it will not be fast enough until you try in your specific case that is your application If it’s not efficient enough, maybe something like FastDelegate will suit your needs? (i did’nt try it but heard it was a nice solution in some cases where boost::signal don’t seem … Read more