[Qt-interest] Slow QTreeWidget

[Kenneth Beck]

Can someone tell me why my performance is so slow with this code? I am 
filling a tree widget that has about 40+ columns, but only 14 rows. As 
the table is filled with all 14 rows initially, the first row is added 
quickly, but each subsequent row appears more and more slowly, as if the 
code is updating previous rows for each new row. Here is the code for 
adding a row:

void
ModMaxTestDlg::addResultRow(double elaps_mins, int rnr, int ct, double 
*data)
   {
   QList<QTreeWidgetItem *> lvitems=moduleRsltList->findItems
	(QString::number(rnr), Qt::MatchExactly,0);
   QTreeWidgetItem *lvitem=0;
   if (lvitems.count()>0)
     lvitem= lvitems[0];
   if (!lvitem)
     {
     lvitem= new QTreeWidgetItem(moduleRsltList);
     lvitem->setData(0,Qt::DisplayRole,QString::number(rnr));
     lvitem->setData(1,Qt::DisplayRole,
	QString::number(elaps_mins,'f',2));
     }
   if (ct && (lvitem!=0))
     {
     int i;
     for (i=1;i<=ct;i++)
       lvitem->setText(i+1,QString::number(data[i-1],'f',6));
     }
   }

The addResultRow() gets called in a simple for-loop. I know the time 
constraint is here, in the last for loop that calls lvitem->setText ct 
times.

Qt 4.5.0, Windows XP, using Visual C++ 2003.