Make virtual lists send DESELECTED events consistently on both implementations

In the case when a listctrl is clicked outside of any item, the item is
visually deselected, and it is logical that a DESELECTED is sent.

For non-virtual lists this would happen, but for virtual lists it would
either happen or not happen depending on implementation (MSW/generic)
and mode (single/multi). From now on the DESELECTED event is always sent.

interface/wx/listctrl.h

@@ -1442,7 +1442,7 @@ protected:
         control itself when this event is generated, see @ref
         overview_events_with_mouse_capture "event handling overview".
     @event{EVT_LIST_ITEM_DESELECTED(id, func)}
-        The item has been deselected.
+        The item has been deselected. GetIndex() may be -1 with virtual lists.
     @event{EVT_LIST_ITEM_ACTIVATED(id, func)}
         The item has been activated (ENTER or double click).
     @event{EVT_LIST_ITEM_FOCUSED(id, func)}

src/generic/listctrl.cpp

@@ -2447,7 +2447,8 @@ void wxListMainWindow::OnMouse( wxMouseEvent &event )
     else
         m_dragCount = 0;
 
-    // The only mouse event that can be generated without any valid item is
+    // The only mouse events that can be generated without any valid item are
+    // wxEVT_LIST_ITEM_DESELECTED for virtual lists, and
     // wxEVT_LIST_ITEM_RIGHT_CLICK as it can be useful to have a global
     // popup menu for the list control itself which should be shown even when
     // the user clicks outside of any item.
@@ -2467,6 +2468,10 @@ void wxListMainWindow::OnMouse( wxMouseEvent &event )
         {
             // reset the selection and bail out
             HighlightAll(false);
+            // generate a DESELECTED event for
+            // virtual multi-selection lists
+            if ( IsVirtual() && !IsSingleSel() )
+                SendNotify( m_lineLastClicked, wxEVT_LIST_ITEM_DESELECTED );
         }
 
         return;

src/msw/listctrl.cpp

@@ -2470,20 +2470,23 @@ bool wxListCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
             case LVN_ITEMCHANGED:
                 // we translate this catch all message into more interesting
                 // (and more easy to process) wxWidgets events
-
-                // first of all, we deal with the state change events only and
-                // only for valid items (item == -1 for the virtual list
-                // control)
-                if ( nmLV->uChanged & LVIF_STATE && iItem != -1 )
                 {
                     // temp vars for readability
                     const UINT stOld = nmLV->uOldState;
                     const UINT stNew = nmLV->uNewState;
 
+                    // first of all, we deal with the state change events only and
+                    // only for valid items (item == -1 for the virtual list
+                    // control)
+                    if ( nmLV->uChanged & LVIF_STATE &&
+                         (iItem != -1 || (stNew & LVIS_SELECTED) != (stOld & LVIS_SELECTED)))
+                    {
+
                         event.m_item.SetId(iItem);
                         event.m_item.SetMask(wxLIST_MASK_TEXT |
                                              wxLIST_MASK_IMAGE |
                                              wxLIST_MASK_DATA);
+                        if (iItem != -1)
                             GetItem(event.m_item);
 
                         // has the focus changed?
@@ -2540,6 +2543,7 @@ bool wxListCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
                             event.m_itemIndex = iItem;
                         }
                     }
+                }
 
                 if ( eventType == wxEVT_NULL )
                 {