qt - Set color to a QTableView row

Question

void MyWindow::initializeModelBySQL(QSqlQueryModel *model,QTableView *table,QString sql){
        model = new QSqlQueryModel(this);
        model->setQuery(sql);
}

With this method i can set a QSQlQueryModels to my QTableviews.

But How i can set color to a row based on a cell value?

Answer 1

The view draws the background based on the Qt::BackgroundRole role of the cell which is the QBrush value returned by QAbstractItemModel::data(index, role) for that role.

You can subclass the QSqlQueryModel to redefine data() to return your calculated color, or if you have Qt > 4.8, you can use a QIdentityProxyModel:

class MyModel : public QIdentityProxyModel
{
    QColor calculateColorForRow(int row) const {
        ...
    }

    QVariant data(const QModelIndex &index, int role)
    {
        if (role == Qt::BackgroundRole) {
           int row = index.row();
           QColor color = calculateColorForRow(row);           
           return QBrush(color);
        }
        return QIdentityProxyModel::data(index, role);
    }
};

And use that model in the view, with the sql model set as source with QIdentityProxyModel::setSourceModel.

OR

You can keep the model unchanged and modify the background with a delegate set on the view with QAbstractItemView::setItemDelegate:

class BackgroundColorDelegate : public QStyledItemDelegate {

public:
    BackgroundColorDelegate(QObject *parent = 0)
        : QStyledItemDelegate(parent)
    {
    }
    QColor calculateColorForRow(int row) const;

    void initStyleOption(QStyleOptionViewItem *option,
                         const QModelIndex &index) const
    {
        QStyledItemDelegate::initStyleOption(option, index);

        QStyleOptionViewItemV4 *optionV4 =
                qstyleoption_cast<QStyleOptionViewItemV4*>(option);

        optionV4->backgroundBrush = QBrush(calculateColorForRow(index.row()));
    }
};

As the last method is not always obvious to translate from C++ code, here is the equivalent in python:

def initStyleOption(self, option, index):
    super(BackgroundColorDelegate,self).initStyleOption(option, index)
    option.backgroundBrush = calculateColorForRow(index.row())