Upgrading from Panels-6.x-3.x to Panels-7.x-3.x - Style and layout plugins may no longer be registered by a central hook. Only the plugin directories method may be used. - Layout 'panels function' is now 'regions function'. - Layout 'panels' key is now 'regions'. - panels_get_pane_title() deprecated. - panels_plugin_get_function() deprecated. - panels_required_context removed. These were deprecated long ago and existed only to prevent crashes. - panels_optional_context removed. - $renderer->plugins['layout']['panels'] changed to $renderer->plugin['layout']['regions'] - display_renderer class is now in 'renderer', not 'handler'.