How to reset QLineEdit text by pressing Escape key?

Question

I'm working on a Qt4 project. I have a QLineEdit and I want to re-use behavior that I see when I click the Escape key inside the QLineEdit, but I'm not sure how.

When I press the escape key, I get the field to reset to the value that it was before I started editing. This is useful to me and I want this behavior on-hand.

Ideally, I would like a signal I can fire off that triggers the QLineEdit to reset to the value it was before. I would prefer not to try and fake an escape key event. I can cache the old value of the line edit, but this seems more work if the behavior already exists when I click escape. Thanks.

Answer 1

How can I make QLineEdit widget to respond on Escape key by setting the text programmatically?

Either by overriding QWidget::event virtual function with the child of QLineEdit or a bit more "local", like installing the event filter:

    class MyLineEditEventFilter : public QObject
    {
    public:
        explicit MyLineEditEventFilter(QLineEdit *parent) : QObject(parent)
        {}

        bool eventFilter(QObject *obj, QEvent *e)
        {
            switch (e->type())
            {
                case QEvent::KeyPress:
                {
                    QKeyEvent *keyEvent = static_cast<QKeyEvent *>(e);
                    if (keyEvent->key() == Qt::Key_Escape)
                    {
                        // or set the other text from the variable
                        reinterpret_cast<QLineEdit *>(parent())->setText("Escape!");
                    }
                    break;
                }
            }
            // standard event processing
            return QObject::eventFilter(obj, e);
        }
    };

And the caller is like that:

m_pLineEditSearch = new QLineEdit;
auto* pLineEditEvtFilter = new MyLineEditEventFilter(m_pLineEditSearch);
m_pLineEditSearch->installEventFilter(pLineEditEvtFilter);

For getting the previous text to reset with Escape pressed you may use different methods but you need to obtain the pointer to the object holding the string somehow. That is hard to answer without seeing your code.