Qt и глобальный перехват событий иксов

XGrabKey(display, XKeysymToKeycode(display, XK_BackSpace), AnyModifier, DefaultRootWindow(display), True, GrabModeAsync, GrabModeAsync);

XGrabKey(display, AnyKey, AnyModifier, DefaultRootWindow(display), True, GrabModeAsync, GrabModeAsync);

#include <X11/Xlib.h>
#include <X11/keysym.h>
#include <stdio.h>

int main() {
    Display *d = XOpenDisplay(0);
    Window root = DefaultRootWindow(d);

    int rv = XGrabKey(d, AnyKey, AnyModifier, root, 1, GrabModeAsync, GrabModeAsync);
    printf("XGrabKey returned %d\n", rv);

    XEvent evt;
    while(1) {
        XNextEvent(d, &evt);
        printf("Got event %d\n", evt.type);
    }
}

XGrabKey returned 1
X Error of failed request:  BadAccess (attempt to access private resource denied)
  Major opcode of failed request:  33 (X_GrabKey)
  Serial number of failed request:  7
  Current serial number in output stream:  7

bool KeyboardWidget::nativeEventFilter(const QByteArray &eventType, void *message, long *) {
	xcb_generic_event_t *ev = static_cast<xcb_generic_event_t*>(message);
	switch (ev->response_type & ~0x80) {
		case XCB_KEY_PRESS: {
			xcb_key_press_event_t *key_press_event = reinterpret_cast<xcb_key_press_event_t*>(ev);
			keyEventReceived(key_press_event->detail, true);
			break;
		}
		case XCB_KEY_RELEASE: {
			xcb_key_release_event_t *key_release_event = reinterpret_cast<xcb_key_release_event_t*>(ev);
			keyEventReceived(key_release_event->detail, false);
			break;
		}
	case XCB_FOCUS_OUT:
		focusChanged();
		break;
	}
	return false;
}

void KeyboardWidget::focusChanged() {
	Display *display = QX11Info::display();
	Window currentWindow;
	int rev;
	XGetInputFocus(display, &currentWindow, &rev);
	if ((currentWindow == PointerRoot) || (currentWindow == None)) {
		currentWindow = DefaultRootWindow(display);
	}
	XSelectInput(display, currentWindow, KeyPressMask | KeyReleaseMask | FocusChangeMask);
}

...

QApplication::instance()->installNativeEventFilter(this);
focusChanged();	

bool KeyboardWidget::nativeEventFilter(const QByteArray &eventType, void *message, long *) {
	xcb_generic_event_t *ev = static_cast<xcb_generic_event_t*>(message);
	XGenericEventCookie *cookie;
	if (m_displayHasXInput && XGetEventData(QX11Info::display(), cookie)) {
		if ((cookie->type == GenericEvent) && (cookie->extension == m_xi_opcode)) {
			XIDeviceEvent *devev = static_cast<XIDeviceEvent*>(cookie->data);
			switch (devev->evtype) {
				case XI_KeyPress:
					keyEventReceived(devev->detail, true);
					break;
				case XI_KeyRelease:
					keyEventReceived(devev->detail, false);
					break;
				case XI_FocusOut:
					focusChanged();
					break;
			}
		}
	} else {
		switch (ev->response_type & ~0x80) {
			case XCB_KEY_PRESS: {
				xcb_key_press_event_t *key_press_event = reinterpret_cast<xcb_key_press_event_t*>(ev);
				keyEventReceived(key_press_event->detail, true);
				break;
			}
			case XCB_KEY_RELEASE: {
				xcb_key_release_event_t *key_release_event = reinterpret_cast<xcb_key_release_event_t*>(ev);
				keyEventReceived(key_release_event->detail, false);
				break;
			}
			case XCB_FOCUS_OUT:
				focusChanged();
				break;
		}
	}
	return false;
}

void KeyboardWidget::focusChanged() {
	Display *display = QX11Info::display();
	Window currentWindow;
	int rev;
	XGetInputFocus(display, &currentWindow, &rev);
	if ((currentWindow == PointerRoot) || (currentWindow == None)) {
		currentWindow = DefaultRootWindow(display);
	}
	if (m_displayHasXInput) {
		XIEventMask evmask;
		evmask.deviceid = XIAllMasterDevices;
		evmask.mask_len = XIMaskLen(XI_LASTEVENT);
		evmask.mask = (unsigned char*)malloc(evmask.mask_len);
		memset(evmask.mask, 0, evmask.mask_len);
		XISetMask(evmask.mask, XI_KeyPress);
		XISetMask(evmask.mask, XI_KeyRelease);
		XISetMask(evmask.mask, XI_FocusOut);
		int prev_evmask_count;
		XIEventMask *prev_evmask = XIGetSelectedEvents(display, currentWindow, &prev_evmask_count);
		if (prev_evmask) {
			for (int i = 0; i < prev_evmask_count; ++i) {
				if (prev_evmask[i].deviceid != XIAllMasterDevices) continue;
				for (int j = 0; j < qMin(evmask.mask_len, prev_evmask[i].mask_len); ++j) {
					evmask.mask[j] |= prev_evmask[i].mask[j];
				}
			}
			XFree(prev_evmask);
		}
		XISelectEvents(display, currentWindow, &evmask, 1);
	}
	XSelectInput(display, currentWindow, KeyPressMask | KeyReleaseMask | FocusChangeMask);
}

...

QApplication::instance()->installNativeEventFilter(this);
{
	int ev, err;
	m_displayHasXInput = XQueryExtension(QX11Info::display(), "XInputExtension", &m_xi_opcode, &ev, &err);
}
focusChanged();

XGenericEventCookie *cookie = &ev.xcookie;