How to update two items in an index with use of QStyledItemDelegate and QAbstractItemModel ?

Pauly

I customized a QStyledItemDelegate and QAbstractItemModel for a QTreeView. I have a qwidget that contain a qcolor box and a qlineedit for a given row (index), I'm trying to save color and lineedit text to variables. However I can not update the text into variable... (see code below)

I think the problem is that when the text item is edited, the first "model->setData" for color variable in QStyledItemDelegate "setModelData" function is always executed first, which triggers the "data" function, which returns the original text and QStyledItemDelegate "setEditorData" will overwrite modified text.

I'm thinking I need to tell what is changed in QStyledItemDelegate "setModelData" function so the right setdata can be sent? How can I do that? Or what is the right way to do this?

in QStyledItemDelegate .cpp:

...

void MyDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    MyWidget *widget = static_cast<MyWidget *>(editor);
    widget->blockSignals(true);
    widget->setMyText(index.data(Qt::EditRole).toString());
    widget->setMyColor(index.data(Qt::UserRole).value<QColor>());
    widget->blockSignals(false);
}

void MyDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,
          const QModelIndex &index) const
{
model->setData(index, QVariant(static_cast<MyWidget*>(editor)->getMyColor()), Qt::UserRole);
model->setData(index, QVariant(static_cast<MyWidget*>(editor)->getMyText()), Qt::EditRole);
}

in QAbstractItemModel .cpp:

QVariant MyModel::data(const QModelIndex &index, int role) const
{
if (role == Qt::EditRole){
return myTextVariable;
}

if (role == Qt::UserRole){
return myColorVariable;
}

return QVariant();
}

bool myModel::setData(const QModelIndex& index, const QVariant& value, int role)
{
if (role == Qt::UserRole){
    myColorVariable=value.value<QColor>();
}else if (role == Qt::EditRole){
    myTextVariable=value.toString();
}
}
Q_EMIT dataChanged(index, index);
return true;
}

Christian Ehrlicher

@Pauly said in How to update two items in an index with use of QStyledItemDelegate and QAbstractItemModel ?:

setEditorData

Here you're already using blockSignals() - you can try this for model too. Or remember in a member that you're currently setting the data.

Pauly

Do you mean to block signal for setdata call in MyDelegate::setModelData? Won't that block updating one variable or the other?

I think I would still need to know what got changed in MyDelegate to set such a member? How can I tell? Thanks.

VRonin

Why do you need to block the signals? are you connecting the editor to the delegate? can you show MyDelegate::createEditor?

Also, your myModel::setData and MyModel::data do not use the index supplied at all, is it a 1 row, 1 column model?

Pauly

I do not recall why I block the signal... maybe I just copied this from somewhere...

I did not think the createEditor matters to the question so I skip that code. But here is it:

QWidget *MyDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
        MyWidget *editor = new MyWidget(index, parent);
        editor->setEditorText("text");
        editor->setColor(QColor(Qt::black));
        return editor;
    }

return new QWidget(parent);
}

In reality it is more than one row... I skipped the index here and let's just consider it as one row, it doesn't change the situation, does it? Thank you.

SGaist

Hi,

~~Since you want to modify two elements in one shot, why not pass a QPair to the user role with the two values and let the model put that in the correct places ?~~

As @VRonin suggests below: setItemData is the right tool.

[edit: Fixed suggestions SGaist]

Pauly

Great idea! Along with the same thought, I use QList (just in case if more than two variables to be updated) and it works. This is the new code. Thanks!

in QStyledItemDelegate .cpp:

void MyDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
MyWidget *widget = static_cast<MyWidget *>(editor);
widget->blockSignals(true);
widget->setColor(index.data(Qt::EditRole).toList().at(0).value<QColor>());
widget->setText(index.data(Qt::EditRole).toList().at(1).toString());
widget->blockSignals(false);
}

void MyDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,
      const QModelIndex &index) const
{
listData<<QVariant(static_cast<MyWidget*>(editor)->getColor())<<QVariant(static_cast<MyWidget*>(editor)->getText());
		
model->setData(index, QVariant(listData), Qt::EditRole);
}

in QAbstractItemModel .cpp:

QVariant MyModel::data(const QModelIndex &index, int role) const
{
QList<QVariant> listData;
listData<<QVariant(myColor)<<QVariant(myText);
return listData;
}

bool myModel::setData(const QModelIndex& index, const QVariant& value, int role)
{
myColor=value.toList().at(0).value<QColor>();
myText=value.toList().at(1).toString();
}
Q_EMIT dataChanged(index, index);
return true;
}

VRonin

@SGaist said in How to update two items in an index with use of QStyledItemDelegate and QAbstractItemModel ?:

Since you want to modify two elements in one shot, why not pass a QPair

Are you suggesting a reinvention of https://doc.qt.io/Qt-5/qabstractitemmodel.html#setItemData ?

SGaist

I knew I was forgetting something !