How to detect that my application lost focus in Qt?

c++ qt qt4 qt5 qevent
Michal picture Michal · Jan 3, 2013 · Viewed 7.5k times · Source

I'm displaying a popup window when the mouse cursor is over a certain widget and I'd like to hide this popup when the mouse leaves the widget.

To do it, I reimplemented leaveEvent(). This seems to work in all cases except when switching to another application by Alt+Tab. I figured out that I probably need to catch another event, but somehow I can't find the proper one. Can you suggest one?

Answer

Daniel Hedberg picture Daniel Hedberg · Jan 3, 2013

The event you are looking for is QEvent::ApplicationDeactivate: "The application has been suspended, and is unavailable to the user".

You can install an event filter on your QApplication instance to catch this event. See the documentation for QObject::installEventFilter(QObject*) for more details how this works.

Since Qt 5.2 the QEvent::ApplicationDeactivate event is deprecated. The correct way to identify when an application is deactivated in Qt 5.2 (or later) is to use the QGuiApplication::applicationStateChanged(Qt::ApplicationState state) signal.

Related questions

How to rotate text for drawText?

I would like to rotate the text 45 degrees? QFont font; font.setPixelSize(12); //grid for(int i = 0; i < 10; i++){ painter->drawLine(100, 100 + i * 800/9, 900, 100 + i * 800/9); str = QString::number((double)9 - i, 'd', 1); painter->setFont(font); painter->drawText(75, 100 + i * 800/9 - 6, 40, 40, 1, …

Read More
Difference in opengl speed between Qt 4/5 and Opengl API

I have read all the questions on SO that i could find about qt 4 and 5 opengl. This one came the closest OpenGL vs QOpenGL/QtOpenGL in Qt 5: differences and limitations? , I have no idea why it was closed because its …

Read More
Console output in a Qt GUI app?

I have a Qt GUI application running on Windows that allows command-line options to be passed and under some circumstances I want to output a message to the console and then quit, for example: int main(int argc, char *argv[]) { …

Read More