Impossible to delete the last column in a ListView? - c++

Question

I am having a bit of a trouble here. It seems I can't remove all the columns or (reset) a listview. Here is the relevant code:
HWND resultListView = GetDlgItem(hwnd, IDC_RESULTCONTROL);
SendMessage(resultListView, LVM_DELETEALLITEMS, 0, 0); //All items are deleted
//Get numebr of columns
HWND hWndHdr = (HWND)::SendMessage(resultListView, LVM_GETHEADER, 0, 0);
int count = (int)::SendMessage(hWndHdr, HDM_GETITEMCOUNT, 0, 0L);
for (int colIndex = 0; colIndex < count; colIndex++) {
ListView_DeleteColumn(resultListView, colIndex);
}
///... Irrelevant code
HWND listbox = GetDlgItem(hwnd, IDC_SELECTEDLISTBOX);
int numberOfItemsSelected = SendMessage(listbox, LB_GETLISTBOXINFO, 0, 0);
vector<string> selectedItemsStringsVector;
char buf[250];
LVCOLUMN buffer;
//Add Selected Columns
for (int i = 0; i < numberOfItemsSelected; i++) { //In this case always 2 "Date" and "Time" for testing.
SendMessage(listbox, LB_GETTEXT, i, (LPARAM)buf);
selectedItemsStringsVector.push_back(buf);
buffer.mask = LVCF_FMT | LVCF_WIDTH | LVCF_TEXT;
buffer.fmt = LVCFMT_LEFT;
buffer.cx = 100;
buffer.pszText = buf;
buffer.cchTextMax = lstrlen(buf);
buffer.iSubItem = i;
buffer.iImage = 0;
buffer.iOrder = 0;
ListView_InsertColumn(resultListView, i, &buffer); //Works fine. Maybe I add an extra column here??
}
In debug mode, all my variables have the expected values.
FirstButtonClick column count in debug mode (variable count = 2) all good.
SecondButtonClick Column count = 3. But it does not delete them?
English is not my main language and I am kind of stumped right now...

Answer 1

The indices of columns in a header control are always consecutively numbered, starting at 0. User code does not control the index of a column. When deleting a column, the indices of columns towards higher indices are shifted down by 1. This is the reason, why the call to ListView_DeleteColumn eventually fails.
There are two options to solve this:
Delete columns starting at the final index down to 0. Deleting the last column does not change the index of other columns, so they stable throughout the deletion operation.
Always delete the first column (at index 0).
The second option is both easier to implement as well as read. The following loop will delete all columns:
for (int colIndex = 0; colIndex < count; ++colIndex) {
ListView_DeleteColumn(resultListView, 0);
}