How to align QComboBox dropdown menu

[MasterBlade]

I used QLineEdit to align QCombobox texts to center, but the dropdown menu is still aligned to the left. How can I align it to center?

2nd question. After using QLineEdit, clicking on the text will not popup dropdown menu. I have to click that down-arrow to call the dropdown. Is there a way to pop it up by just clicking the text?

[eyllanesc]

If you want to align the texts of a QComboBox to the center, it is not necessary to use a QLineEdit since a QProxyStyle is enough. In the case of the popup, a custom delegate is sufficient:

#include <QtWidgets>


class AlignDelegate: public QStyledItemDelegate{
public:
    AlignDelegate(Qt::Alignment alignment, QObject *parent = nullptr):
        QStyledItemDelegate(parent), m_alignment(alignment)
    {

    }
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const
    {
        QStyledItemDelegate::initStyleOption(option, index);
        option->displayAlignment = m_alignment;
    }
    Qt::Alignment m_alignment;
};

class AlignComboBoxProxy: public QProxyStyle{
public:
    using QProxyStyle::QProxyStyle;
    void drawItemText(QPainter *painter,
                      const QRect &rect,
                      int /*flags*/,
                      const QPalette &pal,
                      bool enabled,
                      const QString &text,
                      QPalette::ColorRole textRole) const
    {

        QProxyStyle::drawItemText(painter, rect, Qt::AlignCenter, pal, enabled, text, textRole);
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QComboBox w;
    w.setStyle(new AlignComboBoxProxy(w.style()));
    for(int i=0; i < 10; ++i){
        w.addItem(QString("item-%1").arg(i));
    }
    w.setItemDelegate(new AlignDelegate(Qt::AlignCenter, &w));
    w.show();
    return a.exec();
}

[MasterBlade]

@eyllanesc said in How to align QComboBox dropdown menu:

If you want to align the texts of a QComboBox to the center, it is not necessary to use a QLineEdit since a QProxyStyle is enough. In the case of the popup, a custom delegate is sufficient:

#include <QtWidgets>


class AlignDelegate: public QStyledItemDelegate{
public:
    AlignDelegate(Qt::Alignment alignment, QObject *parent = nullptr):
        QStyledItemDelegate(parent), m_alignment(alignment)
    {

    }
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const
    {
        QStyledItemDelegate::initStyleOption(option, index);
        option->displayAlignment = m_alignment;
    }
    Qt::Alignment m_alignment;
};

class AlignComboBoxProxy: public QProxyStyle{
public:
    using QProxyStyle::QProxyStyle;
    void drawItemText(QPainter *painter,
                      const QRect &rect,
                      int /*flags*/,
                      const QPalette &pal,
                      bool enabled,
                      const QString &text,
                      QPalette::ColorRole textRole) const
    {

        QProxyStyle::drawItemText(painter, rect, Qt::AlignCenter, pal, enabled, text, textRole);
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QComboBox w;
    w.setStyle(new AlignComboBoxProxy(w.style()));
    for(int i=0; i < 10; ++i){
        w.addItem(QString("item-%1").arg(i));
    }
    w.setItemDelegate(new AlignDelegate(Qt::AlignCenter, &w));
    w.show();
    return a.exec();
}

This is perfect! Thank you so much!