Copying a selection in a QTableView properly (model index issues)

Question

I have a QTableView that displays parsed data from a file. I open the file, parse it into different columns based on its delimiter for each line in the file, and then output it to the view. I am using a QStandardItemModel for this.

Relevant code that sets up the model:

QStandardItemModel* model = new QStandardItemModel(this);

int lineIndex = 0;
QStringList headers;
headers << "Col1" << "Col2";
model->setHorizontalHeaderLabels(headers);
file.seek(0);
QTextStream inData(&file);
while (!inData.atEnd()){
  QString line = inData.readLine();
  QStringList lineToken = line.split(":"/*, QString::SkipEmptyParts*/);
  for (int j = 0; j < lineToken.size(); j++) {
    QString value = lineToken.at(j);
    QStandardItem* item = new QStandardItem(value);
    model->setItem(lineIndex, j, item);
  }
lineIndex++;

}
ui->tableView->setModel(model);
ui->tableView->horizontalHeader()->setSectionsMovable(true);

Note that I have it so that I can drag the column headers around to reorder the columns in the table. This will be important later.

I also have the view set up so that I can select an entire row (or individual cells), hit Ctrl+C, and have the contents of the selection copy to the clipboard. I made a separate model for the selected items/rows:

QApplication::clipboard()->clear();
QItemSelectionModel* selection = ui->tableView->selectionModel();
QModelIndexList indexes = selection->selectedIndexes();

QString clipboardString;
QModelIndexList selectedIndexes = ui->tableView->selectionModel()->selectedIndexes();

I then have some code to handle what happens if the selection spans multiple rows. I set up a QModelIndex for this. The implementation for this is simple. I use a for loop to iterate through the indices of the selected cells. If the next index (column) is on the same row as the current one, I add that data to the variable I will eventually write to the clipboard and append a tab (\t) to it (since I want the copied cells to be delimited by tabs so I can easily copy to the clipboard and paste into Excel if I want). If the next index (column) is on a DIFFERENT row, then I append a line break (\n). Here is the code:

for (int i = 0; i < selectedIndexes.count(); ++i)
{
  QModelIndex current = selectedIndexes[i];
  QString displayText = current.data(Qt::DisplayRole).toString();
  // If there exists another column beyond this one.
  if (i + 1 < selectedIndexes.count()) {
    QModelIndex next = selectedIndexes[i+1];
    // If the column is on different row, the clipboard should take note.
    qDebug() << "next.row()" << next.row();
    qDebug() << "current.row()" << current.row();
    if (next.row() != current.row()){
      displayText.append("\n");
    } else {
      // Otherwise append a column separator.
      displayText.append("\t");
    }
  }
    clipboardString.append(displayText);
}
QApplication::clipboard()->setText(clipboardString);

Here's where I have a problem. If I rearrange the columns in my view, the index check breaks. My untouched view looks like this:

+------+------+
| Col1 | Col2 |
+------+------+
| A    | B    |
| W    | X    |
+------+------+

If I select any of the values in the table, I can Ctrl+C and paste as expected. No problem. A copy and paste after selecting this entire table would result in this output:

A   B
W   X

However, if I drag Col1 over to where Col2 is, effectively switching them to look like this:

+------+------+
| Col2 | Col1 |
+------+------+
| B    | A    |
| X    | W    |
+------+------+

...and select the entire thing and paste it, I get this output:

B
X
A
W

This is obviously not what I want and it seems to be adding a line break (\n) after every selected cell.

My qDebug() outputs for the first, unmodified table are:

next.row() 0
current.row() 0
next.row() 1
current.row() 0
next.row() 1
current.row() 1

My qDebug() outputs for the second, rearranged table are:

next.row() 1
current.row() 0
next.row() 0
current.row() 1
next.row() 1
current.row() 0

What am I doing wrong here? Why would it matter that the columns in the view are rearranged?

Answer 1

For copying the selection in the QTableview with header, you can override the keypressevent and use like this.

void keyPressEvent(QKeyEvent *event) {

this->setSelectionBehavior(QAbstractItemView::SelectRows);
    this->setSelectionMode(QAbstractItemView::MultiSelection);
    QModelIndexList selectedRows = selectionModel()->selectedRows();
    QModelIndexList selectedColumns = selectionModel()->selectedColumns();
if(event->key() == Qt::Key_Insert)
{
    tblview_model->customInsertRows();
}
else if(event->key() == Qt::Key_Delete)
{  if(!selectedRows.isEmpty())
        model()->removeRows(selectedRows.at(0).row(),
                            selectedRows.size());
}
else if(event->matches(QKeySequence::Paste)) {
    if(copyPasteEnabled == true){
        text = QApplication::clipboard()->text();
        if(!text.isEmpty()){
            tblview_model->pasteData(text);
        }
    }
}

if(!selectedIndexes().isEmpty()){
    if(event->matches(QKeySequence::Copy)){
        QString text;
        QStringList hdr_lst;
        const std::vector<std::string>& hdrs = tblview_model->getHeader();

        QItemSelectionRange range = selectionModel()->selection().first();
        if (!selectedColumns.isEmpty())
        {
            for (auto j = 0; j < selectedColumns.size(); ++j)
            {
                std::string hd = hdrs[selectedColumns.at(j).column()];
                if (std::find(hdrs.begin(), hdrs.end(), hd) != hdrs.end())
                    hdr_lst << QString::fromStdString(hd);
            }
            text += hdr_lst.join("\t");
            text += "\n";

            for (auto i = 0; i < tblview_model->rowCount(); ++i)
            {
                QStringList rowContents;
                for (auto j = 0; j < selectedColumns.size(); ++j)
                {
                    if (!isColumnHidden(j)) {
                        
                            rowContents << model()->index(i, selectedColumns.at(j).column()).data().toString();

                    
                }
                text += rowContents.join("\t");
                text += "\n";
            }
        }
        else if (!selectedRows.isEmpty())
        {
            for (auto h : hdrs)
            {
                hdr_lst << QString::fromStdString(h);
            }

            text += hdr_lst.join("\t");
            text += "\n";
            //for (auto i = range.top(); i <= range.bottom(); ++i)
            for (auto i = 0; i < selectedRows.size(); ++i)
            {
                QStringList rowContents;
                for (auto j = 0; j <= tblview_model->columnCount(); ++j)
                {
                    if (!isColumnHidden(j)) {
                        
                            rowContents << model()->index(selectedRows.at(i).row(), j).data().toString();}
                    
                }
                text += rowContents.join("\t");
                text += "\n";
            }
        }
        QApplication::clipboard()->setText(text);

Answer 2

The following appears to work...

std::map<int/* row */, std::map<int/* col */, QString> > stuff;
int minCol = std::numeric_limits<int>::max();
int maxCol = std::numeric_limits<int>::min();
for (int i = 0; i < selectedIndexes.count(); ++i) {
  QModelIndex current = selectedIndexes[i];
  int col = horizontalHeader()->visualIndex(current.column());
  stuff[current.row()][col] = current.data(Qt::DisplayRole).toString();
  minCol = std::min(minCol, current.column());
  maxCol = std::max(maxCol, current.column());
}

QString displayText;
for (const auto &byRow: stuff) {
  for (int col = minCol; col <= maxCol; ++col) {
    auto i = byRow.second.find(col);
    if (i != byRow.second.end())
      displayText += i->second;
    displayText += col == maxCol ? "\n" : "\t";
  }
}

Note how the index columns are mapped using...

int col = horizontalHeader()->visualIndex(current.column());

Anyway, see if that's any closer to what you need.

Answer 3

For your purposes it is better to work with the selection ranges.

// If your selection is continuous, there should be just one range.
QItemSelectionRange range = selection->selection().front();

int row, col;
for (int i = 0; i < range.height(); i++)
{
    QStringList rowStrList;
    for (int j = 0; j < range.width(); j++)
    {
        row = range.top() + i;
        col = range.left() + j;
        rowStrList << model->index(row, col).data(Qt::DisplayRole).toString();
    }

    clipboardString += rowStrList.join("\t");
    clipboardString += "\n";
}

The basic idea is to process selection row by row.

The QItemSelectionModel::selection() retruns QItemSelection which is a list of selection ranges. Selection range is a continuous rectangular set of selected indices.