Re: [lmi] switch census view to use wxDataViewCtrl

[Greg Chicares]

On 2011-08-11 11:43Z, Greg Chicares wrote:
> On 2011-08-10 11:11Z, Vaclav Slavik wrote:
[...patch to select one cell after deletion...]
> Committed 20110811T0953Z, revision 5239.
> 
> I'll soon commit some refinements to ensure that, after a deletion, the new
> selection is visible;

Committed 20110811T1222Z, revision 5240.

> and to fix this issue:
[...with empty selection, deleting (zero) cells segfaults...]

Committed 20110811T1238Z, revision 5241. But I have two questions:

(1) To ascertain whether the selection is nonempty, I did:

    wxDataViewItemArray selection;
    unsigned int n_sel_items = list_window_->GetSelections(selection);
    e.Enable(0 < n_sel_items);

Is there a better way? It seems wasteful to populate a wxDataViewItemArray
that isn't used.

(2) Concerning this code that predates these latest changes...

void CensusView::UponUpdateSingleItemActions(wxUpdateUIEvent& e)
{
    bool const is_single_sel = list_window_->GetSelection().IsOk();
    e.Enable(is_single_sel);
}

...I observe that enablement occurs iff exactly one cell is selected
(which is good), but I don't understand why. The documentation seems to
say that this code would detect whether one or more cells is selected:

http://docs.wxwidgets.org/trunk/classwx_data_view_ctrl.html#71cd6bc33658d944c65062f789a82f19
| virtual wxDataViewItem wxDataViewCtrl::GetSelection() const [virtual]
| Returns first selected item or an invalid item if none is selected.

If two cells are selected, shouldn't that return the first one, which
should pass the IsOK() test?