QTreeView and spanning columns

[Lykurg]

Hi,

I'll have a model represented in a tree view with three levels of which the last level has n columns. I want that the first two levels are spanning over the n columns. Right now I am using QTreeView::setFirstColumnSpanned(). The "problem" is only that the model/view will chance very often and therefor I have to call setFirstColumnSpanned every time the view's data gets updated. Is there maybe an option - I have missed - in a custom model which does that automatically or is setFirstColumnSpanned the only way for it.

Sample code:

#include <QtGui>
 
class Delegate : public QItemDelegate
{
public:
    Delegate(QObject *parent = 0);
 
protected:
    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
    {
        QItemDelegate::paint(painter, option, index);
        // highlight the "item" which should be spanned
        painter->setBrush(QColor(200,200,200,50));
        if(index.child(0,0).isValid())
            painter->drawRect(option.rect);
    }
};
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    QStandardItemModel model(2, 2);
    for (int a = 0; a < 2; ++a) {
        QStandardItem *itemA = new QStandardItem(QString("A: %0").arg(a));
        for (int b = 0; b < 2; ++b) {
            QStandardItem *itemB = new QStandardItem(QString("A: %0; B: %1").arg(a).arg(b));
            for (int c = 0; c < 2; ++c) {
                for (int d = 0; d < 4; ++d) {
                    QStandardItem *itemC = new QStandardItem(QString("(%0;%1) C: %2/%3").arg(a).arg(b).arg(c).arg(d));
                    itemB->setChild(c,d,itemC);
                }
            }
            itemA->setChild(b,0,itemB);
        }
        model.setItem(a, itemA);
    }
    QTreeView tree;
    tree.setModel(&model);
    tree.setItemDelegate(new Delegate(&a));
 
// this I want to avoid because normally the displayed data is much more...
    tree.setFirstColumnSpanned(0,model.index(-1,0),true);
    tree.setFirstColumnSpanned(1,model.index(-1,0),true);
    tree.setFirstColumnSpanned(0,model.index(0,0),true);
    tree.setFirstColumnSpanned(1,model.index(0,0),true);
    tree.setFirstColumnSpanned(0,model.index(1,0),true);
    tree.setFirstColumnSpanned(1,model.index(1,0),true);
 
    tree.show();
    tree.expandAll();
    return a.exec();
}

#include <QtGui>

class Delegate : public QItemDelegate
{
public:
    Delegate(QObject *parent = 0);

protected:
    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
    {
        QItemDelegate::paint(painter, option, index);
        // highlight the "item" which should be spanned
        painter->setBrush(QColor(200,200,200,50));
        if(index.child(0,0).isValid())
            painter->drawRect(option.rect);
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QStandardItemModel model(2, 2);
    for (int a = 0; a < 2; ++a) {
        QStandardItem *itemA = new QStandardItem(QString("A: %0").arg(a));
        for (int b = 0; b < 2; ++b) {
            QStandardItem *itemB = new QStandardItem(QString("A: %0; B: %1").arg(a).arg(b));
            for (int c = 0; c < 2; ++c) {
                for (int d = 0; d < 4; ++d) {
                    QStandardItem *itemC = new QStandardItem(QString("(%0;%1) C: %2/%3").arg(a).arg(b).arg(c).arg(d));
                    itemB->setChild(c,d,itemC);
                }
            }
            itemA->setChild(b,0,itemB);
        }
        model.setItem(a, itemA);
    }
    QTreeView tree;
    tree.setModel(&model);
    tree.setItemDelegate(new Delegate(&a));

// this I want to avoid because normally the displayed data is much more...
    tree.setFirstColumnSpanned(0,model.index(-1,0),true);
    tree.setFirstColumnSpanned(1,model.index(-1,0),true);
    tree.setFirstColumnSpanned(0,model.index(0,0),true);
    tree.setFirstColumnSpanned(1,model.index(0,0),true);
    tree.setFirstColumnSpanned(0,model.index(1,0),true);
    tree.setFirstColumnSpanned(1,model.index(1,0),true);

    tree.show();
    tree.expandAll();
    return a.exec();
}

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[Lykurg]

almost two years later. BUMP and HELP!

[wysota]

Maybe you're approaching the problem from the wrong end? How about subclassing QTreeView and doing the spanning there? As a last resort you can connect to the signals from the model emitted when the model changes and enable spanning based on some properties (e.g. custom role) of the model.

[TorstenG]

Well, I haven't found a good solution, but a way to to it.

I call setFirstColumnSpanned() directly from my model from the data() method when this item is accessed.
Of course, the model needs to know its view ... and this causes a bit headache but it works for me.

[Shikha]

Hi, can you please post here how did you call the function setFirstColumnSpanned from the data() function. I am having similar problem but didn't find any solution to this.