There will not be any event loop running in the thread unless you call exec. Qt's widgets have many pre-defined slots, but it is common practice to subclass widgets and add your own slots so that you can handle the signals that you are interested in.
The meta-object contains additional information such as the object's class name.
Note that display is overloaded; Qt will select the appropriate version when you connect a signal to the slot. Documentation contributions included herein are the copyrights of their respective owners. Then you connect the file's QPushButton:: All classes that inherit from QObject or one of its subclasses e. Only the class that defines a signal and its subclasses can emit the signal.
Several of the example programs connect the valueChanged signal of a QScrollBar to the display slot, so the LCD number continuously shows the value of the scroll bar. It is even possible to connect a signal directly to another signal.
You can also define slots to be virtual, which we have found quite useful in practice. Slots A slot is called when a signal connected to it is emitted.
Older toolkits achieve qt wait slot finish kind of communication using callbacks. Signals Signals are emitted by an object when its internal state has changed in some way that might be interesting to the object's client or owner. We want to catch this signal, wherever we might have a dangling reference to the deleted QObjectso we can clean it up.
Qt's widgets have many predefined signals, but we can always subclass widgets to add our own signals to them. You can connect as many signals as you want to a single slot, and a qt wait slot finish can be connected to as many slots as you need. Note that this is currently not available with release builds on Windows.
This means that all of QThread 's queued slots will execute in the old thread. A callback is a pointer to a function, so if you want a processing function to notify you about some event you pass a pointer to another function the callback to the processing function.
All of these would work: Note that other libraries that define variables called signals or slots may cause compiler warnings and errors when compiled alongside a Qt-based application. They must also derive directly or indirectly from QObject.
Another way to champion casino parties code run in a separate thread, is to subclass QThread and reimplement run. Check that it is safe to do so.
We can never be certain that the processing function will call the callback with the correct arguments.