QComboBox doesn't show its item list

Question

I have problem with QComboBox as item delegeate editor for QTableWidget. QTableWidget uses SqlTypeDelegate as item delegate.

When I draw QTableWidget inside QGraphicsScene(through QGraphicsProxyWidget) then QComboBox popup list of available items is not shown. But if I'm using QTableWidget as a normal widget(drawn not through QGraphicsScene\View) then QComboBox behavior is normal - it shows item list.

What should I do to force QComboBox to show its item list?

below sample code:

main.cpp:

#include <QtGui/QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QTableWidget>
#include "sqltypedelegate.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QGraphicsScene scene;
    QTableWidget *table = new QTableWidget(4,2);
    table->setItemDelegate(new SqlTypeDelegate(table));
    QGraphicsProxyWidget *proxy = scene.addWidget(table);
    QGraphicsView view(&scene);
    view.show();
    return app.exec();
}

sqltypedelegate.h:

#include <QItemDelegate>
#include <QStyledItemDelegate>
#include <QModelIndex>
#include <QObject>
#include <QSize>
#include <QComboBox>

class SqlTypeDelegate : public QItemDelegate
{
    Q_OBJECT
public:
    SqlTypeDelegate(QObject *parent = 0);
    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option,
                          const QModelIndex &index) const;
    void setEditorData(QWidget *editor, const QModelIndex &index) const;
    void setModelData(QWidget *editor, QAbstractItemModel *model,
                      const QModelIndex &index) const;
    void updateEditorGeometry(QWidget *editor,
        const QStyleOptionViewItem &option, const QModelIndex &index) const;
};

sqltypedelegate.cpp:

#include <QtGui>
#include "sqltypedelegate.h"

SqlTypeDelegate::SqlTypeDelegate(QObject *parent)
    : QItemDelegate(parent)
{}

QWidget *SqlTypeDelegate::createEditor(QWidget *parent,
    const QStyleOptionViewItem &/* option */,
    const QModelIndex &/* index */) const
{
    QComboBox *editor = new QComboBox(parent);
    editor->addItem(QString("decimal(50)"));
    editor->addItem(QString("integer"));
    editor->addItem(QString("varchar(50)"));
    editor->addItem(QString("char"));

    editor->setEditable(true);
    return editor;
}

void SqlTypeDelegate::setEditorData(QWidget *editor,
                                    const QModelIndex &index) const
{
    QString value = index.model()->data(index, Qt::EditRole).toString();
    QComboBox *comboBox = static_cast<QComboBox*>(editor);
    comboBox->setEditText(value);
}

void SqlTypeDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,
                                   const QModelIndex &index) const
{
    QComboBox *comboBox = static_cast<QComboBox*>(editor);
    model->setData(index, comboBox->currentText(), Qt::EditRole);
}

void SqlTypeDelegate::updateEditorGeometry(QWidget *editor,
    const QStyleOptionViewItem &option, const QModelIndex &/* index */) const
{
    QComboBox *comboBox = static_cast<QComboBox*>(editor);
    comboBox->setGeometry(option.rect);
}

Answer 1

Finaly I've found solution: event filters! Just lurk for QEvent::MouseButtonRelease and then call showPopup.

bool SqlTypeDelegate::eventFilter(QObject *object, QEvent *event)
{
    QComboBox * comboBox = dynamic_cast<QComboBox*>(object);
    if (comboBox)
    {
        if (event->type() == QEvent::MouseButtonRelease)
        {
            comboBox->showPopup();
            return true;
        }
    }
    else
    {
        return QItemDelegate::eventFilter( object, event );
    }
    return false;
}