/**
 * @defgroup ExternalRenderer External Shared Object Renderer
 * @ingroup GdsOutputRenderer
 *
 * @section ExternalRendererProps Properties
 * This class inherits all properties from its parent @ref GdsOutputRenderer.
 * In addition to that, it implements the following properties:
 *
 * Property Name    | Description
 * -----------------|----------------------------------------------------------------
 * shared-object-path  | Path to the shared object used for rendering
 * param-string | Command line parameters passed to external renderer's init function
 *
 * All these properties have to be set for rendering.
 *
 * @section ExternalRendererFuncs Necessary Functions
 *
 * The following functions and variables are necessary for an external renderer to implement:
 *
 * Code Define 				| Prototype  																	|  Description
 * ---------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------
 * @ref EXTERNAL_LIBRARY_RENDER_FUNCTION	| int EXTERNAL_LIBRARY_RENDER_FUNCTION(struct gds_cell *toplevel, GList *layer_info_list, const char *output_file_name, double scale)		| Render cell to output file
 * @ref EXTERNAL_LIBRARY_INIT_FUNCTION		| int EXTERNAL_LIBRARY_INIT_FUNCTION(const char *option_string, const char *version_string)							| Init function. Executed before rendering. This is given the command line parameters specified for the external renderer and the version string of the currently running gds-render program.
 * @ref EXTERNAL_LIBRARY_FORK_REQUEST		| int EXTERNAL_LIBRARY_FORK_REQUEST;														| The pure presence of this integer results in the execution inside a subprocess of hte whole shared object's code
 * @ref EXTERNAL_LIBRARY_FINALIZE_FUNCTION | int EXTERNAL_LIBRARY_FINALIZE_FUNCTION(void) | Called after rendering
 *
 */