Improve appearance of wxTreeListCtrl during live resizing.

When using the generic wxDataViewCtrl version, forcefully refresh it after
changing its size to avoid artefacts during resizing of wxTreeListCtrl.

Closes #13502.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69183 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treelist.cpp

@@ -1608,6 +1608,17 @@ void wxTreeListCtrl::OnSize(wxSizeEvent& event)
         const wxRect rect = GetClientRect();
         m_view->SetSize(rect);
 
+#ifdef wxHAS_GENERIC_DATAVIEWCTRL
+        // The generic implementation doesn't refresh itself immediately which
+        // is annoying during "live resizing", so do it forcefully here to
+        // ensure that the items are re-laid out and the focus rectangle is
+        // redrawn correctly (instead of leaving traces) while our size is
+        // being changed.
+        wxWindow* const view = GetView();
+        view->Refresh();
+        view->Update();
+#endif // wxHAS_GENERIC_DATAVIEWCTRL
+
         // Resize the first column to take the remaining available space.
         const unsigned numColumns = GetColumnCount();
         if ( !numColumns )