How to change the font of the qcombobox label/header only? - qt

Question

When I change the font of my QComboBox comboBox->setFont(whateverQFont); it is applied on the dropdown menu as well (all the items), and it overrides the Qt::FontRole data I have set on my items with comboBox->setItemData(index, itemSpecificFont, Qt::FontRole);
I'd like to set a font on the QComboBox label only and leave the dropdown displayed as it was. Or even better : to have directly the same font as the selected item.
Is there an easy way to do that ?
Edit: Solution of Jasonhan works fine for an editable QComboBox (-> setting the font on the QLineEdit) but is not applicable for a regular QComboBox, as the QLabel is private.

Answer 1

Before starting implement a custom model you could try with QListView.
It just applies to the drop-down menu and you can change its font with the usual setFont function; the you have to apply it to your QComboBox thorugh routine setView.
Something like this (it's not Qt C++ code, I've skipped all arguments in function calls):
QComboBox *combobox = new QComboBox();
combobox->setFont();
...
QListView *listview = new QListView();
listview->setFont();
combobox->setView(listview);

Answer 2

After 2 years, I saw this question. I don't know whether you have found a better method or not. If not, following code may give you a hint.
QComboBox label as you said is actually a QLineEdit, so you just need to set this component's font, and it will solve your problem.
QComboBox *box = new QComboBox();
//add some list items to box
if (box->lineEdit())
box->lineEdit()->setFont(font);//font is your desirable font

Answer 3

Something that works for a non-editable QComboBox is to install a QProxyStyle that sets the font when a CE_ComboBoxLabel control element is drawn.
Here's an example that sets the label font to italic:
#include <QApplication>
#include <QProxyStyle>
#include <QPainter>
#include <QComboBox>
class MyProxyStyle : public QProxyStyle
{
public:
void drawControl(QStyle::ControlElement element, const QStyleOption *option,
QPainter *painter, const QWidget *widget = nullptr) const override
{
if (element == QStyle::CE_ComboBoxLabel)
{
auto fnt = painter->font();
fnt.setItalic(true);
painter->setFont(fnt);
}
QProxyStyle::drawControl(element, option, painter, widget);
}
};
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
app.setStyle(new MyProxyStyle);
QComboBox cb;
cb.addItem("Option 1");
cb.addItem("Option 2");
cb.addItem("Option 3");
cb.show();
app.exec();
}