Update the combobox delegate in runtime while the popup is opened

Hi everyone.

I have a QStyleItemDelegate for my QCombobox where I show an icon with a text and two more icons.
The items are displayed well but there is an incorrect behaviour when the user has opened the popup of the combobox. The icons change in runtime and when the popup is opened by the user, in spite of doing a "combobox.update" the icons don't refresh. They only refresh when I close the popup and I open it again. A curious thing too happens when I move the mouse on a combobox item because that item refreshes, but only that one.

¿Any help? Thanks

Post the code of your delegate (or other relevant code) so we can have an idea how to help you.

Thanks for your interest. Here is my delegate:

Code:

---

ComboUpDownDelegate::ComboUpDownDelegate(QObject* parent): AuniaComboDelegate_Base(parent) {
    auto combobox = qobject_cast<QComboBox*>(parent);
    initCombo(combobox);
 
    // Icons
    m_iconClock = Customisation::getImage("time", QSize(16, 16), QColor("#C8C8C8"));
    m_iconWarningNoErrors = Customisation::getImage("warning", QSize(16, 16), QColor("#C8C8C8"));
    ...
    ...more icons
    ...
}
 
ComboUpDownDelegate::~ComboUpDownDelegate() {
}
 
void ComboUpDownDelegate::initCombo(QComboBox* combo) {
    if (combo != nullptr) {
        combo->view()->setEditTriggers(QAbstractItemView::NoEditTriggers);
        combo->installEventFilter(this);
    }
}
 
QSize ComboUpDownDelegate::sizeHint(const QStyleOptionViewItem & option, const QModelIndex & index) const {
    auto combo = static_cast<QComboBox*>(this->parent());
 
    const auto text = index.data(Qt::DisplayRole).toString();
    const auto style = QApplication::style();
 
    QStyleOptionButton opt;
    opt.text = text;
    opt.rect = option.rect;
    opt.icon = index.data(Qt::DecorationRole).value<QIcon>();
    if (combo != nullptr) {
        opt.iconSize = combo->iconSize();
    }
 
    return style->sizeFromContents(QStyle::CT_CheckBox, &opt, QSize());
}
 
QWidget* ComboUpDownDelegate::createEditor(QWidget* parent, const QStyleOptionViewItem& option,
                                           const QModelIndex& index) const {
    return nullptr;
}
 
void ComboUpDownDelegate::paint(QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index) const {
    QComboBox* combo = static_cast<QComboBox*>(this->parent());
 
    // Basic style
    QStyleOptionViewItemV4 modifiedOption(option);
    modifiedOption.text.clear();
    modifiedOption.icon = QIcon();
    QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &modifiedOption, painter);
 
    const auto topLeft = option.rect.topLeft();
    const int margin = 3;
 
    painter->setPen(combo->palette().color(QPalette::Text));
 
    // Icon for the state of the device
    const bool state1 = index.data(ICON1_ROLE).toBool();
    QPixmap icon1(state1 ? m_iconDeviceConnected : m_iconDeviceDisconnected);
    painter->drawPixmap(margin, topLeft.y() + margin + 4, icon1);
 
    // Text to show
    QFont normalFont(painter->font());
    normalFont.setBold(false);
    QFont boldFont(normalFont);
    boldFont.setBold(true);
    QFontMetrics fm(normalFont);
    painter->setPen(QColor("#7C7C7C"));
 
    QPoint p(topLeft + QPoint(icon1.width() + 2.5 * margin, fm.height() + 6));
    const QString deviceText = index.data(Qt::DisplayRole).toString();
    const QString UTText = " - " + index.data(UT_ROLE).toString();
    p = drawText(painter, p, deviceText, boldFont);
    p.setX(p.x() + 2);
    p = drawText(painter, p, UTText, normalFont);
 
    // Icon for the state of the last execution
    const int state3 = index.data(ICON3_ROLE).toInt();
    QPixmap icon3;
    QPixmap noIcon3;
    switch (state3) {
    case 1:
       icon3 = m_iconExecutionNoErrors;
       break;
    case 2:
        icon3 = m_iconExecutionErrors;
        break;
    case 3:
        icon3 = m_iconRunning;
        break;
    default:
        noIcon3 = m_iconExecutionNoErrors;
        break;
    }
    int w;
    if(!icon3.isNull())
    {
       w = option.rect.width() - icon3.width() - margin;
       painter->drawPixmap(w, topLeft.y() + margin + 8, icon3);
    }
    else
    {
        w = option.rect.width() - noIcon3.width() - margin;
    }
 
    // Icon to filter the traces of the devices
    const int state2 = index.data(ICON2_ROLE).toInt();
    QPixmap icon2;
    QPixmap noIcon2;
    switch (state2) {
    case 1:
        icon2 = m_iconEye;
        break;
    case 2:
        icon2 = m_iconStrikethroughEye;
        break;
    default:
       noIcon2 = m_iconEye;
       break;
    }
    if(!icon2.isNull())
    {
        w -= icon2.width();
        w -= 8;
        painter->drawPixmap(w, topLeft.y() + margin + 8, icon2);
    }
}
 
bool ComboUpDownDelegate::eventFilter(QObject *object, QEvent *event) {
    auto combo = qobject_cast<QComboBox*>(object);
 
    if (combo != nullptr && object == this->parent() && event->type() == QEvent::Paint) {
        QStylePainter painter(combo);
 
        painter.setPen(combo->palette().color(QPalette::Text));
 
        QStyleOptionComboBox opt;
        opt.initFrom(combo);
        opt.editable = combo->isEditable();
        opt.frame = combo->hasFrame();
        if (combo->hasFocus() && !opt.editable) {
            opt.state |= QStyle::State_Selected;
        }
        opt.subControls = QStyle::SC_All;
 
        if (m_title.isEmpty()) {
            opt.currentText = combo->currentText();
        } else {
            opt.currentText = m_title.arg(combo->count());
        }
        painter.drawComplexControl(QStyle::CC_ComboBox, opt);
        painter.drawControl(QStyle::CE_ComboBoxLabel, opt);
 
        return true;
    }
    return QStyledItemDelegate::eventFilter(object, event);
}
 
void ComboUpDownDelegate::setTitle(const QString& title) {
    m_title = title;
}
 
QString ComboUpDownDelegate::title() const {
    return m_title;
}

---

And my code where I change the data of the combo:

Code:

---

comboDevices->setItemData(index, 0, ComboUpDownDelegate::ICON2_ROLE);
// Show the running icon
comboDevices->setItemData(index, 3, ComboUpDownDelegate::ICON3_ROLE);
comboDevices->update();

---

This code when the popup of the combobox is opened, the icons don't refresh

I solved the problem.

The thread that changed the value of each role was not the main thread. To solve it I've emitted a queued signal and without changing any line of code, the combo items refresh with the opened popup. I hope my solution will be useful for other developers.

Thanks