Set the setDefault(true) key to spacebar - eventFilter()?

[fhammer]

Hi,

i need to change the key which is set for the setDefault(true) behaviour of an QPushButton. On my system (ubuntu Linux 19.04) with Qt 5.12.3 it is the ENTER key. But i need to have the SPACEBAR for it. I cannot find a function like setDefaultKey(Qt::Key_Space) so i guessed i have to do it via eventFilter().

Unfortunately it seems to be impossible to fetch a Qt::Key_Space keypress Event e.g. if a spinbox in the same dialog have focus.

This is the dialog:

This is the eventFilter() code:

bool MetronomDialogImpl::eventFilter(QObject *object, QEvent *event)
{
    qDebug() << event->type();
    if (event->type() == QEvent::KeyPress ) {
        QKeyEvent *ke = static_cast<QKeyEvent *>(event);
        qDebug() << ke->key();
        if (ke->key() == Qt::Key_Space) {
            qDebug() << "Space";
            pushButton_play->click();
            return true;
         }
     }

    return QDialog::eventFilter(object, event);
}

If any childwidget like QSlider of QSpinbox have focus i currently cannot grab the keypress event.

What can i do to fetch the spacebar press event globally for the QDialog?

[SamurayH]

Hi @fhammer,
You can try QPushButton::setShortcut or QAction:

    pushButton_play->setShortcut(QKeySequence(Qt::Key_Space));

or

    QAction *playAction = new QAction(this);
    playAction->setShortcut(QKeySequence(Qt::Key_Space));
    addAction(playAction);

    connect(playAction, &QAction::triggered, pushButton_play, &QPushButton::click);

But you may still have a problem when one of the QSpinboxs is focused, because they handle the space key press first (and it's a very normal behavior, think of it as a lineedit !). So I recommend, if you want a one key shortcut, using a different key (e.g Qt::Key_F5) , if you insist to be the space key, then try combining it with a modifier (Qt::SHIFT, Qt::CTRL, Qt::ALT, or Qt::META).

[fhammer]

Hi SamurayH,

thanks for the hint with setShortcut(QKeySequence(Qt::Key_Space));
That helped a lot. Concerning the spinboxes you also were right. I need to build a MyMetronomeSpinbox class give it the pushButton_play object and filter the spacebar there via:

void MyMetronomeSpinBox::keyPressEvent(QKeyEvent *event) {
    if (event->key() == Qt::Key_Space) {
        myPlayButton->click();
        QSpinBox::keyPressEvent(event);
    } else {
        QSpinBox::keyPressEvent(event);
    }
}

Now it works like a charme ;-)
Thanks you!