Hide Icon from the label of QComboBox - c++

Question

I am trying to implement a QComboBox, which holds QIcon and QString, like this:
QComboBox.addItem(icon, label);
I want the icons to be visible in the drop-down list, but not in the toolbar. Only the string should be visible after item selection.
Is there an easy way to do this?

Answer 1

To solve this problem, it is enough to override the paintEvent method, taking the default implementation from the sources. Before drawing control QStyle::CE_ComboBoxLabel, it is necessary to set an invalid value of the QStyleOptionComboBox.currentIcon
This works well if the combobox is not editable, otherwise there is an empty space on the left side intended for drawing the icon. Looking at the source, I found out that the combobox changes the geometry of the QLineEdit. If the current element has an icon then geometrically QLineEdit will shift to the right. In order to prevent this in the same paintEvent, it is necessary to force the geometry of QLineEdit without taking into account the icon.
The following code takes this into account and works well in both modes:
class ComboBox : public QComboBox {
public:
ComboBox(QWidget *parent = nullptr)
: QComboBox(parent) { }
protected:
void paintEvent(QPaintEvent *) override {
QStylePainter painter(this);
painter.setPen(palette().color(QPalette::Text));
// draw the combobox frame, focusrect and selected etc.
QStyleOptionComboBox opt;
initStyleOption(&opt);
painter.drawComplexControl(QStyle::CC_ComboBox, opt);
// draw the icon and text
opt.currentIcon = QIcon();
if (auto le = lineEdit()) {
le->setGeometry(style()->subControlRect(QStyle::CC_ComboBox, &opt, QStyle::SC_ComboBoxEditField, this));
} else {
painter.drawControl(QStyle::CE_ComboBoxLabel, opt);
}
}
};

Answer 2

The best way is to set a delegate and to draw the items yourself.
Then you can choose when or not to draw the icon ( decorationRole ), you can choose not to draw the icon for the index which is the current index.
I could find a quick example on how to use a delegate on combobox:
http://programmingexamples.net/wiki/Qt/Delegates/ComboBoxDelegate
But I am afraid it is not the most easist of the ways.
Good luck!