The code to ban some filters for non-destructive usage was duplicated in
a PDB file and in the XCF load code. Additionally to combining these 2
codes into a single gimp_gegl_op_nde_allowed(), this commit also moves
part of the logic into gimp_gegl_op_blacklisted() which improves the
following:
* It used to be possible to create filters for hidden operations which
were not returned by gimp_drawable_filter_operation_get_available(),
such as "gegl:color" or "gimp:equalize", which would create all sorts
of problems. Now trying to create these filters through the API will
not work and will properly warn with an explicit error message.
I do not consider this an API break since the filters were not
returned in the available lists and therefore were not considered
usable. Anyone who would have used any of these hidden filters was
just going around a weakness in our implementation.
* We make sure that our lists of allowed/forbidden filters are
consistent across usages.
* When getting the list of filters with gimp_gegl_get_op_classes(), we
don't need to do an additional validation step (as we were doing until
now in the PDB call). This is meant to imply that all returned
operations were already validated.
9849f2eff7