[Inkscape-devel] Document resources?

Hi,

another thing I just stumbled across: A couple of objects like filters, LPEs, gradients, etc. have something like this in their build methods:

/* Register ourselves */ sp_document_add_resource(document, "gradient", object);

... and the corresponding code in the _release() method. What precisely does this do and what is it good for? What kinds of objects should "register themselves" and why?

Thanks, Max