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QInputMethod * QGuiApplication::inputMethod() [static]

returns the input method.

The input method returns properties about the state and position of the virtual keyboard. It also provides information about the position of the current focused input element.

void MainWindow::on_pushButton_clicked()
{
    XkbStateRec xkbState;
    Display *display = XOpenDisplay(NULL);
    XkbGetState(display, XkbUseCoreKbd, &xkbState);
    qDebug() << xkbState.group;

    Atom real_prop_type; int fmt;
    unsigned long nitems, extra_bytes;
    char *prop_data = NULL;
    Atom rules_atom = XInternAtom(display, "_XKB_RULES_NAMES", False);
    XGetWindowProperty(display, DefaultRootWindow(display), rules_atom, 0L, 1024,
        False, XA_STRING, &real_prop_type, &fmt, &nitems, &extra_bytes, (unsigned char **) (void *) &prop_data);

    QStringList names;
    for(char* p=prop_data; p-prop_data < (long)nitems && p != NULL; p += strlen(p)+1) names.append( p );
    if (names.count() > 3 ) names = names[2].split(",");
    qDebug() << names[xkbState.group];

    XFree(prop_data);
    XCloseDisplay(display);
}