c++ - How to detect global key sequence press in Qt?

Question

I want to detect whether a key sequence is pressed and want to perform certain task on that event in Qt. Currently I can detect keypresses for certain widgets but how to detect global keypresses. By global I mean that even if the application is minimized or hidden , it should detect key press.

I tried making an eventFilter for the application, by first overloading QObject::eventFilter like this:

bool GlobalEventFilter::eventFilter(QObject *Object, QEvent *Event)
{
  if (Event->type() == QEvent::KeyPress)
  {
    QKeyEvent *KeyEvent = (QKeyEvent*)Event;

    switch(KeyEvent->key())
    {
      case Qt::Key_F1:
        cout<<"F1 press detected"<<endl;
        return true;
      default:
        break;
    }
  }
  return QObject::eventFilter(Object,Event);
}

and then installing that object as the eventFilter for my application:

QApplication a(argc,argv);
a.installEventFilter(new GlobalEventFilter());

and I also tried the doing this:

QCoreApplication::instance()->installEventFilter(new GlobalEventFilter());

In both the cases I am able to detect key presses when my application window is open but it fails when window is minimized or hidden. How to solve this?

Answer 1

This feature is not implemented in Qt. You can use Qxt. Qxt is an extension library for Qt providing a suite of cross-platform utility classes to add functionality not readily available in Qt. It has Global Shortcut (hot keys) which detects key presses even if the application is minimized.

After compiling and linking your application to Qxt, you can include QxtGlobalShortcut:

#include <QxtGlobalShortcut>

Example usage:

QxtGlobalShortcut* shortcut = new QxtGlobalShortcut(window);
connect(shortcut, SIGNAL(activated()), window, SLOT(toggleVisibility()));
shortcut->setShortcut(QKeySequence("Ctrl+Shift+F12"));