LazyFillComboBox.h

#ifndef LAZY_FILL_COMBO_BOX_HPP__
#define LAZY_FILL_COMBO_BOX_HPP__
 
#include <QComboBox>
 
class QWidget;
 
//
// Class LazyFillComboBox
//
// QComboBox derivative that signals show and hide of the pop up list.
//
class LazyFillComboBox : public QComboBox {
    Q_OBJECT
 
  public:
    Q_SIGNAL void about_to_show_popup();
    Q_SIGNAL void popup_hidden();
 
    explicit LazyFillComboBox(QWidget *parent = nullptr) : QComboBox{parent} {}
 
#if QT_VERSION >= QT_VERSION_CHECK(5, 12, 0)
    void showPopup() override {
        Q_EMIT about_to_show_popup();
        QComboBox::showPopup();
    }
 
    void hidePopup() override {
        QComboBox::hidePopup();
        Q_EMIT popup_hidden();
    }
#else
    void mousePressEvent(QMouseEvent *e) override {
        Q_EMIT about_to_show_popup();
        QComboBox::mousePressEvent(e);
    }
 
    void mouseReleaseEvent(QMouseEvent *e) override {
        QComboBox::mouseReleaseEvent(e);
        Q_EMIT popup_hidden();
    }
#endif
};
 
#endif