QTableView + QAbstractTableModel: Move rows via drag'n'drop - c++

Question

I have a simple QAbstractTableModel-based model and a QTableView for it.
My aim is simple as well: allow to move/reorder rows via drag'n'drop. Notes:
D'n'd changes inside QTableView should be reflected in my model;
D'n'd supposed to be internal - movement should be performed only inside my view, no external MIME exports;
I want to drag and drop whole row. Separate items should not be dragged or dropped;
Dragging horizontal header is not a suitable solution for me because I want headers to be hided and because I want to let user to grab row at any place to drag it;
I'm reeeally close to my aim. But still it doesn't work as I expect. Now I can drag rows, but seems that any cell can accept a drop, although I've specified Qt::ItemIsDropEnabled only for a global table's parent and do not specify this flag for actual table items because I do not want to drop to them, I want somehow to drop "between the rows", just to perform row movement. Because table items for some reason can accept drops I get curious behaviour: if a drop to first cell of any row, I achieve exactly what I want: my row moves correctly. But if I drop to nonfirst cell of any row, it goes totally wrong. But it's better to show a pic of what happens here:
My code (minimal sample that has exactly my problem):
main.cpp
void setupView(QTableView &t)
{
t.verticalHeader()->hide();
t.horizontalHeader()->hide();
t.horizontalHeader()->setStretchLastSection(true);
t.setSelectionBehavior(QAbstractItemView::SelectRows);
t.setSelectionMode(QAbstractItemView::SingleSelection);
t.setDragEnabled(true);
t.setDropIndicatorShown(true);
t.setAcceptDrops(true);
t.viewport()->setAcceptDrops(true);
t.setDefaultDropAction(Qt::MoveAction);
t.setDragDropMode(QTableView::InternalMove);
t.setDragDropOverwriteMode(false);
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow w;
QTableView *table = new QTableView(&w);
setupView(*table);
table->setModel(new TableModel);
w.setCentralWidget(table);
w.show();
return a.exec();
}
tablemodel.cpp
#include "tablemodel.h"
TableModel::TableModel()
{
// m_data is a QList<QStringList>
m_data = {
{"Name", "Kelly"},
{"Age", "19"},
{"Gender", "Female"},
};
}
int TableModel::rowCount(const QModelIndex &parent) const {
return m_data.size();
}
int TableModel::columnCount(const QModelIndex &parent) const {
return 2;
}
QVariant TableModel::data(const QModelIndex &i, int r) const
{
return (r == Qt::DisplayRole) ? m_data[i.row()][i.column()] : QVariant();
}
QVariant TableModel::headerData(int section, Qt::Orientation orientation, int r) const
{
return QVariant();
}
Qt::ItemFlags TableModel::flags(const QModelIndex &index) const
{
Qt::ItemFlags f = Qt::ItemIsEnabled | Qt::ItemIsSelectable
| Qt::ItemIsEditable | Qt::ItemIsDragEnabled;
if(!index.isValid()) {
f |= Qt::ItemIsDropEnabled;
}
return f;
}
Qt::DropActions TableModel::supportedDropActions() const
{
return Qt::MoveAction | Qt::CopyAction;
}
bool TableModel::setData(const QModelIndex &i, const QVariant &v, int r)
{
if(r == Qt::EditRole || r == Qt::DisplayRole) {
m_data[i.row()][i.column()] = v.toString();
return true;
}
return false;
}
bool TableModel::setItemData(const QModelIndex &i, const QMap<int, QVariant> &roles)
{
if(!roles.contains(Qt::EditRole) && !roles.contains(Qt::DisplayRole)) {
return false;
}
m_data[i.row()][i.column()] = roles[Qt::DisplayRole].toString();
return true;
}
bool TableModel::insertRows(int row, int count, const QModelIndex &parent)
{
beginInsertRows(QModelIndex(), row, row + count - 1);
for(int i = 0; i<count; ++i) {
m_data.insert(row, QStringList({"", ""}));
}
endInsertRows();
return true;
}
bool TableModel::removeRows(int row, int count, const QModelIndex &parent)
{
beginRemoveRows(QModelIndex(), row, row + count - 1);
for(int i = 0; i<count; ++i) {
m_data.removeAt(row);
}
endRemoveRows();
return true;
}
bool TableModel::moveRows(const QModelIndex &srcParent, int srcRow, int count,
const QModelIndex &dstParent, int dstChild)
{
beginMoveRows(QModelIndex(), srcRow, srcRow + count - 1, QModelIndex(), dstChild);
for(int i = 0; i<count; ++i) {
m_data.insert(dstChild + i, m_data[srcRow]);
int removeIndex = dstChild > srcRow ? srcRow : srcRow+1;
m_data.removeAt(removeIndex);
}
endMoveRows();
return true;
}
Please, give me some hint, what is wrong with model or view setup now.
UPD
For those who is interested in the solution:
bool TableModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
Q_UNUSED(parent);
Q_UNUSED(column);
if(row == -1) {
row = rowCount();
}
return QAbstractTableModel::dropMimeData(data, action, row, 0, parent);
}

Answer 1

You should add dropMimeData method to your model and implement it properly. If the drop on the first column works fine for you, you could probably simply call QAbstractItemModel::dropMimeData from inside your model's dropMimeData with column parameter equal to 0 regardless of which column the drop was actually made on.

Answer 2

Nitpick: These two lines are not necessary:
t.setAcceptDrops(true);
t.viewport()->setAcceptDrops(true);