ListModel

Introduction / Purpose

This class prevents the need of deriving a QAbstractListModel class to service a simple list in memory like a std::vector or QList derived instance and through a few signals/callback functions the list can be displayed and controlled.

This class can only service a single QTreeView instance.

Usage

‍Note: Assuming the QTreeView is already available.

When the parent passed at the constructor of sf::ListModel is a QTreeView derived instance, it attaches itself so a call to sf::ListModel::setTreeView can be omitted.

The Data structure & ListModel

The following code declares the needed instances and pointers.

 
    struct Data
    {
        QString name;
        int image{0};
        double amount{0.0};
        QString description;
        bool selected{false};
    };
 
    // Vector for managing the data.
    QList<Data> _data;
    // List model class.
    ListModel* _listModel;

Setup Columns

This code creates and configures the columns.

  int index = 0;
  for (auto str: {"#", "Name", "Amount", "Description"})
  {
    auto col = _listModel->getColumns().add();
    switch (index)
    {
      case 0:
        col->flags = Qt::ItemFlag::ItemIsUserCheckable;
        col->alignment = Qt::AlignRight | Qt::AlignVCenter;
        break;
 
      case 2:
        col->flags = Qt::ItemFlag::ItemIsEditable;
        col->alignment = Qt::AlignRight | Qt::AlignVCenter;
        break;
 
      case 3:
        col->flags = Qt::ItemFlag::ItemIsEditable;
 
      default:
        break;
    }
    col->name = str;
    col->tag.index = index++;
  }

Connecting & Handling of Signals

Connection of only 4 signals.

  connect(_listModel, &ListModel::getRowData, this, &ListViewWindow::getListData);
  connect(_listModel, &ListModel::setRowData, this, &ListViewWindow::setListData);
  connect(_listModel, &ListModel::contextMenuRequested, this, &ListViewWindow::popupMenu);
  connect(_listModel, &ListModel::currentRowChanged, this, &ListViewWindow::rowChanged);

Getting and Setting Data

The signal to get data is implemented like this.

void ListViewWindow::getListData(const QModelIndex& index, int role, QVariant& data)
{
  switch (role)
  {
    // Used for selection of editor type.
    case CommonItemDelegate::TypeRole:
      if (index.column() == 2)
        data = CommonItemDelegate::etDoubleSpinBox;
      break;
 
    case Qt::ItemDataRole::EditRole:
    {
      switch (index.column())
      {
        case 2:
          data = _data.at(index.row()).amount;
          break;
        case 3:
          data = _data.at(index.row()).description;
          break;
        default:;
      }
    }
    break;
 
    case Qt::ItemDataRole::DisplayRole:
    {
      switch (index.column())
      {
        case 0:
          data = index.row() + 1;
          return;
        case 1:
          data = _data.at(index.row()).name;
          break;
        case 2:
          data = _data.at(index.row()).amount;
          break;
        case 3:
          data = _data.at(index.row()).description;
          break;
        default:;
      }
    }
    break;
 
    case Qt::ItemDataRole::DecorationRole:
      if (index.column() > 0)
      {
        if (index.column() == 2)
        {
          data = Resource::getSvgIcon(
            Resource::getSvgIconResource(Resource::Icon::Warning), _data.at(index.row()).amount >= 0.0 ? QColorConstants::Green : QColorConstants::Red
          );
        }
        else
        {
          std::array<Resource::Icon, 3> icons{Resource::Icon::Form, Resource::Icon::Application, Resource::Icon::FloppyDisk};
          data = Resource::getSvgIcon(Resource::getSvgIconResource(icons[index.column() % icons.size()]), QPalette::ColorRole::WindowText);
        }
      }
      break;
 
      // Only when the column us checkable.
    case Qt::ItemDataRole::CheckStateRole:
      if (index.row() < _data.count())
        data = _data.at(index.row()).selected ? Qt::Checked : Qt::Unchecked;
      break;
 
    default:
      break;
  }
}
 

The signal to set data is implemented like this and is used to set the checkbox (selected flag).

void ListViewWindow::setListData(const QModelIndex& index, int role, const QVariant& data)
{
  if (data.isValid())
  {
    switch (role)
    {
      case Qt::ItemDataRole::CheckStateRole:
        _data[index.row()].selected = data.toInt() == Qt::Checked;
        break;
 
      case Qt::ItemDataRole::EditRole:
        if (index.column() == 2)
          _data[index.row()].amount = data.toDouble();
        else if (index.column() == 3)
          _data[index.row()].description = data.toString();
        break;
 
      default:
        break;
    }
  }
}
 

The properties on the QTreeView are set when attached to use a request for a context menu signal.

void ListViewWindow::popupMenu(const QModelIndex& index, const QPoint& pos)
{
  QMenu contextMenu(this);
  // Add the actions wanted for the context menu.
  contextMenu.addAction(ui->actionMoveUp);
  contextMenu.addAction(ui->actionMoveDown);
  contextMenu.addAction(ui->actionInsertRow);
  contextMenu.addAction(ui->actionRemoveRow);
  // Calculate the global position on screen.
  contextMenu.exec(_listModel->getTreeView()->mapToGlobal(pos));
}
 

Inserting & Removing Rows

This shows how a row is inserted and is scrolled in to the visible part of the list.

void ListViewWindow::insertRow()
{
  auto index = _listModel->currentIndex();
  int row = index.isValid() ? index.row() + 1 : 0;
  _listModel->insertRows(row, 1);
  if (_dataSource.count())
  {
    _data.insert(row, std::move(_dataSource.takeAt(row)));
    index = _listModel->index(row);
    _listModel->scrollTo(index);
    _listModel->setCurrentIndex(index);
  }
}
 

This shows how a row is removed.

void ListViewWindow::removeRow()
{
  auto index = _listModel->currentIndex();
  if (index.isValid())
  {
    _data.removeAt(index.row());
    _listModel->removeRow(index);
  }
}
 

Moving Rows

To move a row up and keep it selected.

void ListViewWindow::moveRowUp()
{
  auto index = _listModel->currentIndex();
  if (index.isValid())
  {
    auto row = index.row();
    if (_data.count() > 1 && row > 0)
    {
      _listModel->moveRow(row, row - 1);
      _data.move(row, row - 1);
      _listModel->scrollTo(index);
    }
  }
}
 

To move a row down and keep it selected.

void ListViewWindow::moveRowDown()
{
  auto index = _listModel->currentIndex();
  if (index.isValid())
  {
    auto row = index.row();
    if (_data.count() > 1 && row + 1 < _data.count())
    {
      _listModel->moveRow(row, row + 1);
      _data.move(row, row + 1);
      _listModel->scrollTo(index);
    }
  }
}