c_gtk_buildable_custom_tag_start

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
__gshared extern (C)
gboolean function(GtkBuildable* buildable, GtkBuilder* builder, GObject* child, gchar* tagname, GMarkupParser* parser, void** data) c_gtk_buildable_custom_tag_start;

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