I am going to write program using Qt for some image processing and I want it to be able to run in non-gui mode (daemon mode?). I'm inspired by VLC player, which is "typically" GUI program, where yo...

I have a program where QApplication is created with the new operator. It crashes for unknown reason. I use RedHat Linux, G++ 4.8.2, Qt 4.7.2 which was built with the same compiler. This source con...

I'm porting a Qt desktop application to Linux (Ubuntu 19.10, 64bit desktop, Qt 5.12.5, gcc version 9.2.1), and am seeing some unexpected threads remaining alive after QApplication is finished. Her...

I'm trying to get a simple hello world example running, and already needed some time to figure out what includes to use Now I verified the include paths, the QApplication should actually be there, ...

I have a class that composes a palette and assigns it to the application using QApplication::instance()->setPalette(QPalette palette). And it effectively works. But then I try to use QPalette ...

I am trying to get a reference to the current QApplication object with pyQt5, but couldn't find the function. My search about "pyQt get current QApplication" shows results about how to create an QA...

I'm sending a signal.CTRL_BREAK_EVENT to a QApplication subprocess and the subprocess's handler manages to catch the signal (and perform some magic before exiting). However, when the signal is sent...

In a Qt GUI application, QApplication::style()->objectName() will return the current style, for example "windowsvista". How/where does it choose this default style, and what information does i...

We have a QWidget based application that was previously using a QWindow for OpenGL rendering. To fit that window in our application we had to use QWidget QWidget::createWindowContainer(QWindow); ...

I'd like to know what are the implications (problems) of having multiple QApplication/QCoreApplication instances in the same process, and how to solve some issues regarding it. The scenario is as f...

I currently have a terribly annoying problem while developing programs using Qt and Qt Creator. Whenever I try using qDebug() with a QCoreApplication or QApplication instantiated before using qDebu...

I have understood the following regarding QApplication's exec function: QApplication exec starts the main event loop. It launches the GUI. It processes the signals and calls appropriate slots o...

With PyQt5, both of these return the application object: app = QtWidgets.QApplication.instance() app = QtWidgets.qApp for i in app.arguments()[1:]: ... But why does print(QtWidgets.QApplication...

I have a static class and want it to have static QSettings. But with my initialization I get a warning: QSettings* MySQLConnection::settings = new QSettings(QApplication::applicationDirPath() + "/...

We are using Qt for a visualization engine viewer, and we are having issues with the QApplication::processEvents() method. Since we needed to control the framerate (in a game loop fashion), we over...

I would like to do a rudimentary automation test of my Qt application. It records mouse events and writes them to a file (f.e. mousepress(300, 400)). When starting the automation, it reads the coor...

I try to understand what PyQt does. And one of the first things I didn't, was: QApplication(sys.argv) Why do I have to give QApplication this argument? I know what sys.argv does. But in my Scri...

I'd like to create a library built on top of QTcpServer and QTcpSocket for use in programs that don't have event loops in their main functions (because the Qt event loop is blocking and doesn't pro...

I am trying to handle exception in my Qt application, I went through a couple of posts which indicated of overriding the QApplication::notify method to handle exceptions in a efficient way in Qt. I...