Don't use menuForEvent: in wxDataViewCtrl on macOS

Returning nil from menuForEvent: and then popping up a menu manually
causes some kind of Cocoa internal state confusion if the right-click
was performed by holding down Control and clicking (as is the Mac
alternative to right-click). See https://github.com/vslavik/poedit/issues/849

Implement wxEVT_DATAVIEW_ITEM_CONTEXT_MENU event using a handler for
the regular wxEVT_CONTEXT_MENU event instead.

include/wx/osx/dataview.h

@@ -291,6 +291,8 @@ private:
   virtual wxDataViewItem DoGetCurrentItem() const override;
   virtual void DoSetCurrentItem(const wxDataViewItem& item) override;
 
+  void OnContextMenu(wxContextMenuEvent& event);
+
  //
  // variables
  //

src/osx/cocoa/dataview.mm

@@ -1663,33 +1663,6 @@ outlineView:(NSOutlineView*)outlineView
     }
 }
 
-//
-// contextual menus
-//
--(NSMenu*) menuForEvent:(NSEvent*)theEvent
-{
-    wxUnusedVar(theEvent);
-
-    // this method does not do any special menu event handling but only sends
-    // an event message; therefore, the user has full control if a context
-    // menu should be shown or not
-    wxDataViewCtrl* const dvc = implementation->GetDataViewCtrl();
-
-    // get the item information;
-    // theoretically more than one ID can be returned but the event can only
-    // handle one item, therefore only the first item of the array is
-    // returned:
-    wxDataViewItem item;
-    wxDataViewItemArray selectedItems;
-    if (dvc->GetSelections(selectedItems) > 0)
-        item = selectedItems[0];
-
-    wxDataViewEvent event(wxEVT_DATAVIEW_ITEM_CONTEXT_MENU, dvc, item);
-    dvc->GetEventHandler()->ProcessEvent(event);
-    // nothing is done:
-    return nil;
-}
-
 //
 // delegate methods
 //

src/osx/dataview_osx.cpp

@@ -852,6 +852,21 @@ void wxDataViewCtrl::OnSize(wxSizeEvent& event)
   event.Skip();
 }
 
+void wxDataViewCtrl::OnContextMenu(wxContextMenuEvent& WXUNUSED(e))
+{
+    // get the item information;
+    // theoretically more than one ID can be returned but the event can only
+    // handle one item, therefore only the first item of the array is
+    // returned:
+    wxDataViewItem item;
+    wxDataViewItemArray selectedItems;
+    if (GetSelections(selectedItems) > 0)
+        item = selectedItems[0];
+
+    wxDataViewEvent event(wxEVT_DATAVIEW_ITEM_CONTEXT_MENU, this, item);
+    GetEventHandler()->ProcessEvent(event);
+}
+
 wxSize wxDataViewCtrl::DoGetBestSize() const
 {
     wxSize best = wxControl::DoGetBestSize();
@@ -864,6 +879,7 @@ wxIMPLEMENT_DYNAMIC_CLASS(wxDataViewCtrl,wxDataViewCtrlBase);
 
 wxBEGIN_EVENT_TABLE(wxDataViewCtrl,wxDataViewCtrlBase)
   EVT_SIZE(wxDataViewCtrl::OnSize)
+  EVT_CONTEXT_MENU(wxDataViewCtrl::OnContextMenu)
 wxEND_EVENT_TABLE()
 
 #endif // !wxHAS_GENERIC_DATAVIEWCTRL