Grabbing a key in X11

I'm trying to grab a key to use it as a global shortcut in X11. I reduced my code to a simple test:

Code:

---

#include <QtGui>
#include <QX11Info>
 
#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/keysym.h>
 
#ifdef KeyPress
const int XKeyPress   = KeyPress;
const int XKeyRelease = KeyRelease;
#undef KeyPress
#undef KeyRelease
#endif
 
class GrabWidget : public QTextBrowser
{
	Q_OBJECT
 
public:
	GrabWidget(QWidget *parent)
	 : QTextBrowser(parent)
	{
		qApp->installEventFilter(this);
 
		m_keyCode = XKeysymToKeycode(QX11Info::display(), XK_F11);
		XGrabKey(QX11Info::display(), m_keyCode, ControlMask|ShiftMask, QX11Info::appRootWindow(), False, GrabModeAsync, GrabModeAsync);
		XFlush(QX11Info::display());
	}
 
	~GrabWidget()
	{
		XUngrabKey(QX11Info::display(), m_keyCode, ControlMask|ShiftMask, QX11Info::appRootWindow());
	}
 
	bool GrabWidget::eventFilter(QObject */*watched*/, QEvent *event)
	{
		if(event->type() == QEvent::KeyPress) {
			QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
			int qtKey = keyEvent->key();
			if(keyEvent->modifiers() == (Qt::ControlModifier|Qt::ShiftModifier) && qtKey == Qt::Key_F11) {
				insertPlainText("Ctrl+Shift+F11 pressed!\n");
				return false;
			}
		}
		return true;
	}
 
private:
	int m_keyCode;
};

---

Grabbing the key seems to be working since I don't get any error message from Xlib (whereas I get BadAccess if I try to grab a different key which is already grabbed by another application) but I don't get any key press events, nor even if I press that key combination when my own widget has focus. So, what's wrong? How should I receive KeyPress events when I grab a key? I also tried with x11Event() but I get events only when my widget has focus not when another has it.

Thanks.

PS: I know it's not portable but I already made an implementation for Windows using RegisterHotKey() and now I'm just trying to implement it for X11.

Try QxtGlobalShortcut.

I already tried subclassing QApplication to reimplement x11EventFilter(), which is what QxtGlobalShortcut does. In fact I've tried it and it doesn't work. It has the same problem: XGrabKey seems to work but no key press notifications are received when the application doesn't have focus. Even when the application has it, QxtGlobalShortcut doesn't emit the activated() signal!

Code:

---

int main(int argc, char **argv)
{
	QxtApplication app(argc, argv);
	TestWidget t;
	t.show();
	return app.exec();
}

---

Code:

---

class TestWidget : public QTextBrowser
{
    Q_OBJECT
 
public:
    TestWidget(QWidget *parent = 0) : QTextBrowser(parent)
    {
        m_globalShortcut.setShortcut(QKeySequence("Ctrl+Shift+F11"));
        m_globalShortcut.setEnabled(true);
        connect(&m_globalShortcut, SIGNAL(activated()),
                this, SLOT(logActivation()));
    }
 
public slots:
    void logActivation()
    {
        insertPlainText("+ Ctrl+Shift+F11 pressed!\n");
    }
 
private:
    QxtGlobalShortcut m_globalShortcut;
};

---

What does setShortcut() return? "Ctrl+Shift+F11" is probably reserved, thus registering the shortcut fails.

It always returns true, no matter which key combination I use. I tried with other key combinations, such as Ctrl+Shift+J, Ctrl+Alt+J or Ctrl+Alt+R, for instance. The only difference is that with the last one the following message is printed in the console:

Code:

---

X Error: BadAccess (attempt to access private resource denied) 10
  Major opcode: 33 (X_GrabKey)
  Resource id:  0x5d

---

So Ctrl+Alt+R is already grabbed by another application but the former key combinations aren't and they still don't work. :-( I have openSUSE 10.3 with X.org 7.2 here but I've also tried in openSUSE 11.0 with X.org 7.3 and got the same results. Key grabbing works in my system, as I have Yakuake here and whenever I press F12 it opens as expected.

Sorry, I almost forgot this thread. Anyway, I can confirm that the test application above works as it is just fine on my system (Kubuntu 8.04.1, X.org 7.3, Qt 4.4.0, Qxt 0.4.0).