How to change keyboard's key behavior?

[Nouriemm]

Experts,
My question is pretty simple:
I want to press a keyboard's key (on a physical keyboard of-course) and have a custom output.
For example I want to press R on my keyboard and I want to have ® instead.

1. Is it possible to do such thing generally all over a Qt program?
2. If not, is it possible to do it for a widget (something like QLineEdit)?

Thanks in advance

[A Former User]

@Nouriemm Hi, you can use an event filter for this. Look at this: http://doc.qt.io/qt-5/qobject.html and search for "KeyPressEater". That's an example that's already pretty close to what you want to do. Should be easy to adopt it to your needs.

[Nouriemm]

@Wieland
Thanks for the answer.
let us assume that we have done the part of key grabbing like this:

    bool MainWindow::eventFilter(QObject *target, QEvent *event)
   {
        if (event->type() == QEvent::KeyPress) {
            QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
            if (keyEvent->key() == Qt::Key_R) {
                /******what are we suppose to do here ******/
                return true;
            }
        }

    return false; }

But, the question is still remained: How to map Qt::Key_R to ® instantly as a general output of the physical keyboard?

[Devopia53]

You can use a sendEvent() simplify. See my sample code:


bool MainWindow::eventFilter(QObject *o, QEvent *e)
{
    if (o == ui->lineEdit) {
        if (e->type() == QEvent::KeyPress) {
            QKeyEvent   *k = static_cast<QKeyEvent*>(e);

            if (k->key() == Qt::Key_R) {
                if (k->text().compare("®") != 0) {
                    QKeyEvent   ke(k->type(), k->key(), k->modifiers(), QString("®"), k->isAutoRepeat(), k->count());

                    QApplication::sendEvent(ui->lineEdit, &ke);
                    return true;
                }
            }
            return false;
        }
        else {
            return false;
        }
    }
    else {
        return MainWindow::eventFilter(o, e);
    }
}

[Nouriemm]

Thanks to @Devopia53 and @Wieland the problem has solved.
I have polished the @Devopia53 code to something like this to make it more generic:

  bool MainWindow::eventFilter(QObject *o, QEvent *e){

  if (e->type() == QEvent::KeyPress) {
    QKeyEvent   *k = static_cast<QKeyEvent*>(e);

    if (k->key() == Qt::Key_R  &&  k->text() != "®") {
            QKeyEvent   ke(k->type(), k->key(), k->modifiers(), QString("®"), k->isAutoRepeat(), k->count());
            QApplication::sendEvent(o, &ke);
            return true;
        }
}
return false;

}

Just wondering if my code breaks any rule of programming; Specially by not using
** return MainWindow::eventFilter(o, e);**

Cheers

[ValentinMichelet]

@Nouriemm said:

Just wondering if my code breaks any rule of programming; Specially by not using
** return MainWindow::eventFilter(o, e);**

When you override event handling, I think calling the parent's method at the end is a good practice, since Qt works on the event and treats special cases (according to the OS for instance) that you may have forgotten.

[Nouriemm]

Thank you all,
I am going to mark this discussion as solved;
However, Any more comments would be much appreciated;