for GTK+ 3.6 and later, invalidate cached best size when GTK's style cache is updated, see #16088

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76149 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/toplevel.cpp

@@ -1038,6 +1038,10 @@ bool wxTopLevelWindowGTK::Show( bool show )
         wxSizeEvent event(GetSize(), GetId());
         event.SetEventObject(this);
         HandleWindowEvent(event);
+
+#ifdef __WXGTK3__
+        GTKSizeRevalidate();
+#endif
     }
 
     bool change = base_type::Show(show);
@@ -1291,6 +1295,9 @@ void wxTopLevelWindowGTK::GTKUpdateDecorSize(const DecorSize& decorSize)
         sizeEvent.SetEventObject(this);
         HandleWindowEvent(sizeEvent);
 
+#ifdef __WXGTK3__
+        GTKSizeRevalidate();
+#endif
         gtk_widget_show(m_widget);
 
         wxShowEvent showEvent(GetId(), true);