custom qstyleditemdelegate (checkbox) displays number instead of checkbox

andi456

Hi, [set to solved, although the delegate does not work, but concrete question is answered.]

in order to paint the surrounding rectangle of the checkbox in different colours according to some value, I had to subclass QStyledItemDelegate. At first glance, it seems to work, but when I try to check or uncheck the box a number is displayed instead of the box, I've just checked. (Actually there remains a unchanged checkbox in the center of the cell.) [It is integrated in an tableview.]

The number seems to be the Qt::CheckState constant. But how could I debug this strange behaviour?

Kind regards,

Andreas

JonB

@andi456
Sounds like: somewhere in your delegate's paint() you are being asked to show the checkbox with a specified state but you are instead treating it as a number to show as the value?

andi456

@JonB Yes, I'm also suspecting the paint method. I copied some code from an example somewhere....

        auto stateFlag = opt.checkState == Qt::Checked ? QStyle::State_On : QStyle::State_Off;
        opt.state.setFlag(stateFlag, true);

Maybe it's this snippet, which causes the trouble.

JonB

@andi456
I think you should show a minimal example of the paint() override you have defined.

andi456

@JonB Ok, here are the relevant parts of the paint method:

 void CheckBoxZBuchDeckDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
   QStyleOptionViewItem opt = option;
//some code to colorize the background...
   initStyleOption(&opt, index);
   auto * widget = opt.widget;
   auto * style = widget->style();
   int zeile = index.row();
   if ((style) && (zeile < index.model()->rowCount() - 1)) {
        opt.state.setFlag(QStyle::State_HasFocus, false);
        opt.features.setFlag(QStyleOptionViewItem::HasDisplay, false);
        opt.features.setFlag(QStyleOptionViewItem::HasDecoration, false);
        opt.features.setFlag(QStyleOptionViewItem::HasCheckIndicator, false);
        style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);
        qDebug() << "Checkbox delegate paint method called";
        opt.rect = this->getCheckBoxRect(opt);
        auto stateFlag = opt.checkState == Qt::Checked ? QStyle::State_On : QStyle::State_Off;
        opt.state.setFlag(stateFlag, true);
        style->drawPrimitive(QStyle::PE_IndicatorViewItemCheck, &opt, painter, widget);
    } else {
       painter->setPen(Qt::black);
       int spalte = index.column();
       int sum_Flags = this->get_intFromVariant(index.siblingAtColumn(spalte).data(Qt::DisplayRole));
       QString cell_text = QString::number(sum_Flags);
       painter->drawText(opt.rect, Qt::AlignCenter, cell_text);
   }
}

The last line shows the sum of all flags set by the checkbox...

JonB

@andi456 said in custom qstyleditemdelegate (checkbox) displays number instead of checkbox:

if ((style) && (zeile < index.model()->rowCount() - 1)) {

This should be zeile <= index.model()->rowCount() - 1 or zeile < index.model()->rowCount(). With your code whenever the index passed in is the last one (index.model()->rowCount() - 1) you go into the else and paint the number, hence the behaviour you see?

This is why it's always good to show code!

andi456

@JonB No, I don't think so, because I want to have a checkbox in all cells except in the last row. As the rows are indexed based on zero, the index of the last line would be rowCount -1.

JonB

@andi456
My (next) guess: you have

opt.features.setFlag(QStyleOptionViewItem::HasCheckIndicator, false);
...
style->drawPrimitive(QStyle::PE_IndicatorViewItemCheck, &opt, painter, widget);

[BTW, that should be QStyle::PE_IndicatorItemViewItemCheck now.]
So you ask it to show the checkstate value but have no check indicator, maybe that shows it is a number?

Maybe you need to restore that flag before painting the checkbox, or take a look at, say, https://forum.qt.io/topic/4277/solved-painting-in-custom-delegate where the option is copied to a modifiedOption for the checkbox?

andi456

@JonB Yes the HasCheckIndicator flag was wrong. Now the checkbox seems to work, but is being displayed twice, so I guess, I need to center it somehow in the paint method.

andi456

@JonB Tried to implement the hints given in the post you linked. It did center the checkBoxes shown initially, but the checkBox shown, if I try to change the data, is being drawn to the left of the initial checkBox.

Does one need to adjust the createEditor function too?