Keep path's custom informations after a boolean operation

Ted, could you take a look at this one?

hye,

here's a patch which solve the problem.
it changes only src/splivarot.cpp

the diff was generated with:
 ~/inkscape-svn$ svn diff -x -u > custom_attr.diff

There's also the problem when you convert a rectangle/ellipse to path, the custom attributes are lost

Mental, I think this is more likely to be code you're familiar with. Can we do with with some "magic namespace" stuff instead of listing the attributes?

I tested this patch but it has a big problem: if you combine stars or ellipses and not paths, it copies over the sodipodi:type attribute and all the rest, and thus the result turns out to be a star as well, exactly the same as original. So boolean operation visibly fails. I agree that listing the attributes is not really a good idea. Mental, what would you suggest?

As Ted Gould suggests it, a way of doing it should be to copy attributes which use a custom namespace

standart namespaces are:
u'sodipodi' :u'http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd',
u'cc' :u'http://web.resource.org/cc/',
u'svg' :u'http://www.w3.org/2000/svg',
u'dc' :u'http://purl.org/dc/elements/1.1/',
u'rdf' :u'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
u'inkscape' :u'http://www.inkscape.org/namespaces/inkscape',
u'xlink' :u'http://www.w3.org/1999/xlink',
u'xml' :u'http://www.w3.org/XML/1998/namespace'

here's a new patch doing the 'magic namespace'.

here's how it works:
add a new attribute to SPXMLNs: bool is_custom
the namespaces from repr-util.cpp are the standart ones, those added by sp_xml_ns_uri_prefix are custom ones.
(new function sp_xml_ns_is_custom to test if a prefix belongs to a custom one.)

when doing a bool operation or converting an object to path, it uses the sp_copy_custom_attributes function which copy the attributes from custom namespaces to the new object.

the sp_copy_custom_attributes function has been added to the repr-util.cpp file.

diff genrated with:
gorse@gorse-desktop:~/bordel/inkscape-0.47-svn/inkscape$ svn diff -x -u > custom_attr_namespace.diff
from svn 21209.

I don't think it's safe to blindly copy over attributes that we don't understand; they won't always make sense in the new context.

So here's what I'm thinking at present; we add something like this to the SVG (probably in <defs>):

<inkscape:extension-attributes>
  <inkscape:extension-attribute ns="http://xmoto.tuxfamily.org/" name="vertex-settings" policy="preserve" />
</inkscape:extension-attributes>

And then any attribute so indicated would be preserved.