How to get the background color returned by the model takes precedence over the style

I have a QTreeView

render QAbstractItemModel

where I would like to set the background of certain cells based on data in a model. I am returning QBrush

from model::data(Qt::BackgroundColorRole)

and working until I apply the style to the element.

Setting any style on the element (even something that has nothing to do with the background color, like styling the border) overrides the color I return from the model (calls to the model asking for the background color). That is, the view behaves as if the model never returned any color.

I am using Qt 4.8 and I cannot upgrade to a later version.

Is there a way to make the color returned from the model take precedence over the style? Why Qt behaves in such a weird way: The model has a narrower granularity and knows a way more than style can know why style takes precedence. After all, the model shouldn't return a color for each cell - just a few specific ones?

I guess this is a bug in Qt, I opened a bug report that reproduces with this code:

#include <QtCore/qabstractitemmodel.h>
#include <QtGui/qtreeview.h>
#include <QtGui/qtableview.h>
#include <QtGui/qapplication.h>

class MyModel : public QAbstractItemModel
{
public:
    MyModel(QObject *parent) :QAbstractItemModel(parent){}

    int rowCount(const QModelIndex &parent = QModelIndex()) const
    { return 2; }
    int columnCount(const QModelIndex &parent = QModelIndex()) const
    { return parent.isValid() ? 0 : 2; }
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const
    {
        if(index.row() >= 0 && index.column() >= 0)
        {
            switch(role)
            {
            case Qt::DisplayRole:
                return QString("a");
            case Qt::BackgroundRole:
                return QBrush(QColor(255 * index.row(), 255 * index.column(), 0));
            default:
                break;
            }
        }
        return QVariant();
    }
    virtual QModelIndex index(int pos, int column, const QModelIndex &parent = QModelIndex()) const
    { return createIndex(pos, column, 0); }
    virtual QModelIndex parent(const QModelIndex &child) const
    { return QModelIndex(); }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QTreeView view;
    MyModel myModel(0);
    view.setModel(&myModel);
    view.show();

    //a.setStyleSheet("QTreeView::item { border: 1px solid black; }");
    return a.exec();
}

      

        
        
        
      

    

If you uncomment the line before returning, all backgrounds are gone.