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c++qtqt5qcombobox

How to know when down-arrow of Combo box is clicked?

I have a ComboBox and set it to be edited. 

QComboBox *myCombo = new QComboBox(this);
myCombo->setEditable(true);
myCombo->setStyleSheet("QComboBox::down-arrow{image: url(:/bulb.png);}");
myCombo->setCursor( QCursor( Qt::PointingHandCursor ) );

enter image description here

So now when i click onto the editing field, nothing happen. But what I need is, when I click onto the bulb (which is the down-arrow), something (like a table or a dialog....) should be appeared. How can I recognize this click event in this case? I looked at the list of signals for combo box but could not find any signal for that.

Solution

  • By overwriting the mousePressEvent() method you must use hitTestComplexControl() method to know that QStyle::SubControl has been pressed by issuing a signal if it is QStyle::SC_ComboBoxArrow.

    #include <QtWidgets>

class ComboBox: public QComboBox
{
    Q_OBJECT
public:
    using QComboBox::QComboBox;
signals:
    void clicked();
protected:
    void mousePressEvent(QMouseEvent *event) override{
        QComboBox::mousePressEvent(event);
        QStyleOptionComboBox opt;
        initStyleOption(&opt);
        QStyle::SubControl sc = style()->hitTestComplexControl(QStyle::CC_ComboBox, &opt, event->pos(), this);
        if(sc == QStyle::SC_ComboBoxArrow)
            emit clicked();
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    ComboBox w;
    w.setEditable(true);
    w.setStyleSheet("QComboBox::down-arrow{image: url(:/bulb.png);}");
    QObject::connect(&w, &ComboBox::clicked, [](){
        qDebug()<<"clicked";
    });
    w.show();
    return a.exec();
}
#include "main.moc"

    Although showPopup() is a possible option this can be called directly without the down-arrow being pressed, for example by calling it directly: myCombo->showPopup() so it is not the correct option.