Assigning group ID for CListCtrl C++ - c++

Question

I'm currently using a derived class of CListCtrl to build my application upon. I'm trying to add an item to the list, and immediately assign it to a group:
// int row, int grp_id, CString header; - all initialized previously
int ind = m_list.InsertItem(row, header);
VERIFY(m_list.SetRowGroupId(row, grp_id));
Here's an implementation of SetRowGroupID():
BOOL CGridListCtrlGroups::SetRowGroupId(int nRow, int nGroupId)
{
//OBS! Rows not assigned to a group will not show in group-view
LVITEM lvItem = { 0 };
lvItem.mask = LVIF_GROUPID;
lvItem.iItem = nRow;
lvItem.iSubItem = 0;
lvItem.iGroupId = nGroupId;
return SetItem(&lvItem);
}
Nothing too fancy here.
However, the code is asserting false for VERIFY().
While I was searching through MSDN documents to find out why, it seems that the flag I want to use as a mask isn't available for this purpose (refer to Remarks).
Am I not able to change the group ID this way? For the record, I've also tried to use MoveItemToGroup(), which gave me the same result (that is, the item doesn't show up while group view is enabled).

Answer 1

I cannot say why updating a member's group ID does not work directly.
However, setting .iGroupId = I_GROUPIDCALLBACK triggers the message LVN_GETDISPINFO and in its handler you can then assign the group ID.
Outline:
BEGIN_MESSAGE_MAP(CGridListCtrlGroups, CListCtrl)
ON_NOTIFY_REFLECT(LVN_GETDISPINFO, OnGetDispInfo)
END_MESSAGE_MAP()
void CGridListCtrlGroups::CGridListCtrlGroups(NMHDR* pNMHDR, LRESULT* pResult)
{
NMLVDISPINFO* dispInfo = LPNMLVDISPINFOW(pNMHDR);
LVITEM* item = &dispInfo->item;
if (item->mask & LVIF_GROUPID) {
// assign group id
item->iGroupId = ...;
}
*pResult = 0;
}
BOOL CGridListCtrlGroups::RequeryRowGroupId(int nRow)
{
LVITEM lvi = {
.mask = LVIF_GROUPID,
.iItem = nRow,
.iGroupId = I_GROUPIDCALLBACK
};
return SetItem(&lvi);
}