text being parsed was not valid UTF-8
document contained nothing, or only whitespace
error should be set by #GMarkupParser functions; content was invalid
error should be set by #GMarkupParser functions; a required attribute was missing
document was ill-formed
error should be set by #GMarkupParser functions; attribute wasn't known
error should be set by #GMarkupParser functions; element wasn't known
Error codes returned by markup parsing.