wxGrid destructor Triggers Breakpoint on - wxwidgets

Question

I'm new to wxWidgets, although I've been able to get an application up and running fairly smoothly up until this point. For the main window, I'm using a wxGrid inside a wxPanel. Everything runs fine until I close the program.
Thanks in advance for any insight.
The grid is a member of a class derived from wxPanel:
class FormDataView
: public wxPanel
{
public:
FormDataView(wxWindow* parent);
virtual ~FormDataView();
private:
wxGrid* grid_;
}
And created in the constructor. The data for the grid comes from another thread, so I create a custom event for actually writing the data.
wxDEFINE_EVENT(FORMDATAVIEW_UPDATE, wxThreadEvent);
FormDataView::FormDataView(wxWindow* parent)
: wxPanel(parent,wxID_ANY )
{
wxBoxSizer* mbox = new wxBoxSizer(wxVERTICAL);
grid_ = new wxGrid(this, wxID_ANY );
grid_->CreateGrid(0, 0);
mbox->Add(grid_,wxSizerFlags(1).Expand());
Bind(FORMDATAVIEW_UPDATE, &FormDataView::onDataUpdate, this);
}
///
/// This function is called by a child thread when data is received.
///
void
FormDataView::onDataReceived(IFORMATTERBASE_PFONDATARECEIVED_ARGS)
{
newHeaders_ = headers;
newData_ = data;
wxThreadEvent* evt = new wxThreadEvent(FORMDATAVIEW_UPDATE);
evt->SetString("Yo.");
wxQueueEvent(this, evt);
}
///
/// Called by the event loop. This function puts the data
/// into the grid.
///
void
FormDataView::onDataUpdate(wxThreadEvent& evt)
{
FormatterStringList& headers = newHeaders_;
FormatterStringList& data = newData_;
if (grid_->GetNumberRows() <= 0)
{
wxGridCellAttr* attr = new wxGridCellAttr();
attr->SetReadOnly(true);
attr->SetAlignment(wxALIGN_CENTRE, wxALIGN_CENTRE);
for (size_t i = 0; i<headers.size(); ++i)
{
if (grid_->GetNumberCols() <= 0)
grid_->InsertCols();
else
grid_->AppendCols();
grid_->SetColLabelValue(i, headers[i].data());
grid_->SetColAttr(i, attr);
}
}
// suspend redrawing while we add data.
grid_->BeginBatch();
// insert a new row at the top of the table
grid_->InsertRows(
0, // position
1, // number of rows to insert
true); // update labels (not current used)
for (size_t i = 0; i<headers.size(); ++i)
{
if (data.size() < i)
{
grid_->SetCellValue(0, i, "");
}
else
{
grid_->SetCellValue(0, i, data[i].data());
}
}
// resume redrawing.
grid_->EndBatch();
}
Everything runs fine, but when I close, I get the following message. I've indicated the line upon which the breakpoint occurs. Is there some short of sequence for clearing data out of the grid I'm supposed to follow?
wxGrid::CellSpan
wxGrid::GetCellSize( int row, int col, int *num_rows, int *num_cols ) const
{
wxGridCellAttr *attr = GetCellAttr(row, col);
attr->GetSize( num_rows, num_cols );
attr->DecRef();
>>>>>>> if ( *num_rows == 1 && *num_cols == 1 )
return CellSpan_None; // just a normal cell
if ( *num_rows < 0 || *num_cols < 0 )
return CellSpan_Inside; // covered by a multi-span cell
// this cell spans multiple cells to its right/bottom
return CellSpan_Main;
}

Answer 1

The problem was with where I was creating the column attribute. I was re-using the same column attribute instance for every column, but each column needs to have its own instance.
BEFORE:
if (grid_->GetNumberRows() <= 0)
{
///
/// NO! The columns will share the same cell attribute
/// instance.
///
wxGridCellAttr* attr = new wxGridCellAttr();
attr->SetReadOnly(true);
attr->SetAlignment(wxALIGN_CENTRE, wxALIGN_CENTRE);
for (size_t i = 0; i<headers.size(); ++i)
{
if (grid_->GetNumberCols() <= 0)
grid_->InsertCols();
else
grid_->AppendCols();
grid_->SetColLabelValue(i, headers[i].data());
grid_->SetColAttr(i, attr);
}
}
CORRECT:
if (grid_->GetNumberRows() <= 0)
{
for (size_t i = 0; i<headers.size(); ++i)
{
if (grid_->GetNumberCols() <= 0)
grid_->InsertCols();
else
grid_->AppendCols();
grid_->SetColLabelValue(i, headers[i].data());
///
/// Each column will have its own cell attribute.
/// Supposedly, the column will take ownership of this
/// instance.
///
wxGridCellAttr* attr = new wxGridCellAttr();
attr->SetReadOnly(true);
attr->SetAlignment(wxALIGN_CENTRE, wxALIGN_CENTRE);
grid_->SetColAttr(i, attr);
}
}