DbGridControl's confusion of BrowseBox's column number vs. column ID

[Lionel Elie Mamane]

On Fri, Mar 10, 2017 at 01:52:36PM +0100, Stephan Bergmann wrote:
> svtools' BrowseBox class (include/svtools/brwbox.hxx; effectively a
> collection of BrowseColumn via the BrowseBox::pCols member) apparently
> distinguishes between a column's index/position/number (i.e., the
> BrowseColumn's position within the BrowseBox::pCols vector) and its ID
> (i.e., the BrowseColumn::_nId member, svtools/source/brwbox/datwin.hxx).

> Does anybody (Lionel?) known something about that DbGridControl code? Would
> this be a bug (if so, any idea how to reproduce it at the GUI?) or is it
> maybe an invariant of such a DbGridControl that it's columns' ID always
> match the columns' positions?

No, it is not an invariant. Consider

file fmgridcl.cxx function FmGridControl::InitColumnsByModels

for (i = 0; i < xColumns->getCount(); ++i)
{
    ...
    AppendColumn(aName, (sal_uInt16)nWidth);
    ...
}
// now all columns are inserted with identical id and pos
...
for (i = 0; i < xColumns->getCount(); ++i)
{
    Reference< css::beans::XPropertySet > xCol(
    xColumns->getByIndex(i), css::uno::UNO_QUERY);
    aHidden = xCol->getPropertyValue(FM_PROP_HIDDEN);
    if (::comphelper::getBOOL(aHidden))
       HideColumn(GetColumnIdFromModelPos((sal_uInt16)i));
}

And HideColumn calls

DbGridControl::HideColumn(nId);
which calls
DbGridControl_base::HideColumn(nId);
that is
BrowseBox::RemoveColumn

which does

    BrowserColumns::iterator it = pCols->begin();
    ::std::advance( it, nPos );
    delete *it;
    pCols->erase( it );

As soon as there is a hidden column, the position and id of the
columns after that one don't match anymore.

-- 
Lionel