tablemodel row, set / reset background color

Hi everybody,
I'm struggling around with a propably simple problem. I use a QSqlQueryModel to display some data. When a cell is double-clicked, the whole row should be marked by changing the background color. This is done by reimplementing the model and overload the data function.
But: when another row is double-clicked the previous coloured row stays marked (but should not). When a button is clicked, or the window is resized, the marking vanishes.
Can I emit some signal to redraw the table view? What happens, when a button is clicked - can I do the same?
I also tried to emit dataChanged and layoutChanged signals from within the data function, but because it's const this seems not to work (compiler complains: passing 'const MyModel' as 'this' argument of 'void QAbstractItemModel::layoutChanged()' discards qualifiers [-fpermissive])

Also I tried repaint(), it had no effect.

Code:

---

QVariant MyModel::data(const QModelIndex &item, int role) const
{
  QVariant result = QSqlQueryModel::data(item, role);
 
  int row = item.row();
  int col = item.column();
 
  // generate a log message when this method gets called
  qDebug() << QString("row %1, col%2, role %3").arg(row).arg(col).arg(role);
 
  switch(role){
    case Qt::BackgroundRole:
      if (row == active_row) // member active_row is set by a funciton call
        {
          QBrush redBackground(Qt::red);
          return redBackground;
        }
      break;
    }
 
  return result;
}

---

If you set active_role in a function call, shouldn't that function emit the signals?
After all that function changes what data() will return afterwards.

Cheers,
_

I wasn't clear enough in my description. The QSqlQueryModel is derived to MyModel:

Code:

---

MyModel::MyModel(QObject *parent)
     :QSqlQueryModel(parent)
 {
  active_row = -1; // no row will be colored
 }

---

So, I have nothing to do with setting the color in the application code. All that must be done is to set the active row.

Code:

---

void MyModel::setActiveRow(int row) // called from slot doubleClick
{
  active_row = row;
}

---

The workaround I found meanwhile, is to implement a function, that emits the protected signal "layoutChanged":

Code:

---

void MyModel::__layoutChanged()
{
  emit layoutChanged();
}

---

I have to call it after calling setActiveRow. That's no clean interface, further on there must be a reason, why the signal is protected.
It works so far, but is there any better solution?

Quote:

---

Originally Posted by linoprit

So, I have nothing to do with setting the color in the application code. All that must be done is to set the active row.

Code:

---

void MyModel::setActiveRow(int row) // called from slot doubleClick
{
  active_row = row;
}

---

---

This method changes the model's data, i.e. MyModel::data() returns different values after that call changed active_row.
So naturally it is the place to emit change signals.

Code:

---

void MyModel::setActiveRow(int row)
{
    if (active_row == row)
        return; // no change
 
    int oldRow = active_row;
    active_row = row;
 
    // de-highlight previously active row
    if (oldRow > -1) {
        QModelIndex rowBegin = index(oldRow, 0);
        QModelIndex rowEnd = index(oldRow, columnCount() - 1);
        emit dataChanged(rowBegin, rowEnd);
    }
 
    // highlight newly active row
    if (row > -1) {
        QModelIndex rowBegin = index(row, 0);
        QModelIndex rowEnd = index(row, columnCount() - 1);
        emit dataChanged(rowBegin, rowEnd);
    }
}

---

Cheers,
_

Thank you very much! That was what I didn't understand.
The set-function has to control which parts need to be redrawn, not the data-function.

Code is working. Great!

Cheers,
Harald