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:
Qt Code: 
  1. #include <QtGui>
  2.  
  3. class Delegate : public QItemDelegate
  4. {
  5. public:
  6.     Delegate(QObject *parent = 0);
  7.  
  8. protected:
  9.     void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
  10.     {
  11.         QItemDelegate::paint(painter, option, index);
  12.         // highlight the "item" which should be spanned
  13.         painter->setBrush(QColor(200,200,200,50));
  14.         if(index.child(0,0).isValid())
  15.             painter->drawRect(option.rect);
  16.     }
  17. };
  18.  
  19. int main(int argc, char *argv[])
  20. {
  21.     QApplication a(argc, argv);
  22.  
  23.     QStandardItemModel model(2, 2);
  24.     for (int a = 0; a < 2; ++a) {
  25.         QStandardItem *itemA = new QStandardItem(QString("A: %0").arg(a));
  26.         for (int b = 0; b < 2; ++b) {
  27.             QStandardItem *itemB = new QStandardItem(QString("A: %0; B: %1").arg(a).arg(b));
  28.             for (int c = 0; c < 2; ++c) {
  29.                 for (int d = 0; d < 4; ++d) {
  30.                     QStandardItem *itemC = new QStandardItem(QString("(%0;%1) C: %2/%3").arg(a).arg(b).arg(c).arg(d));
  31.                     itemB->setChild(c,d,itemC);
  32.                 }
  33.             }
  34.             itemA->setChild(b,0,itemB);
  35.         }
  36.         model.setItem(a, itemA);
  37.     }
  38.     QTreeView tree;
  39.     tree.setModel(&model);
  40.     tree.setItemDelegate(new Delegate(&a));
  41.  
  42. // this I want to avoid because normally the displayed data is much more...
  43.     tree.setFirstColumnSpanned(0,model.index(-1,0),true);
  44.     tree.setFirstColumnSpanned(1,model.index(-1,0),true);
  45.     tree.setFirstColumnSpanned(0,model.index(0,0),true);
  46.     tree.setFirstColumnSpanned(1,model.index(0,0),true);
  47.     tree.setFirstColumnSpanned(0,model.index(1,0),true);
  48.     tree.setFirstColumnSpanned(1,model.index(1,0),true);
  49.  
  50.     tree.show();
  51.     tree.expandAll();
  52.     return a.exec();
  53. }
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