qt-everywhere-src-5.14.1/qtbase/src/corelib/doc/snippets/events/events.cpp

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#include <QCheckBox>
#include <QMouseEvent>

class MyCheckBox : public QCheckBox
{
public:
    void mousePressEvent(QMouseEvent *event) override;
};

//! [0]
void MyCheckBox::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        // handle left mouse button here
    } else {
        // pass on other buttons to base class
        QCheckBox::mousePressEvent(event);
    }
}
//! [0]

class MyWidget : public QWidget
{
public:
    bool event(QEvent *event) override;
};

static const int MyCustomEventType = 1099;

class MyCustomEvent : public QEvent
{
public:
    MyCustomEvent() : QEvent((QEvent::Type)MyCustomEventType) {}
};

//! [1]
bool MyWidget::event(QEvent *event)
{
    if (event->type() == QEvent::KeyPress) {
        QKeyEvent *ke = static_cast<QKeyEvent *>(event);
        if (ke->key() == Qt::Key_Tab) {
            // special tab handling here
            return true;
        }
    } else if (event->type() == MyCustomEventType) {
        MyCustomEvent *myEvent = static_cast<MyCustomEvent *>(event);
        // custom event handling here
        return true;
    }

    return QWidget::event(event);
}
//! [1]

int main()
{
}