Any of the fields in #GMarkupParser can be %NULL, in which case they
will be ignored. Except for the error function, any of these callbacks
can set an error; in particular the %G_MARKUP_ERROR_UNKNOWN_ELEMENT,
%G_MARKUP_ERROR_UNKNOWN_ATTRIBUTE, and %G_MARKUP_ERROR_INVALID_CONTENT
errors are intended to be set from these callbacks. If you set an error
from a callback, g_markup_parse_context_parse() will report that error
back to its caller.
Any of the fields in #GMarkupParser can be %NULL, in which case they will be ignored. Except for the
error
function, any of these callbacks can set an error; in particular the %G_MARKUP_ERROR_UNKNOWN_ELEMENT, %G_MARKUP_ERROR_UNKNOWN_ATTRIBUTE, and %G_MARKUP_ERROR_INVALID_CONTENT errors are intended to be set from these callbacks. If you set an error from a callback, g_markup_parse_context_parse() will report that error back to its caller.