Re: [Lib2geom-devel] lib2geom basics: define pathvector, define ellipse, define intersection

[Krzysztof K. <twe...@gm...>]

2012/9/5 mathog <ma...@ca...>:
> On 02-Sep-2012 15:03, Krzysztof Kosiński wrote:
>
>>> 2.  generate a third PathVector "pathC" = INTERSECTION(pathA,pathB).
>>> Just like the Intersection option on the Paths menu.
>>
>> This cannot be done with 2Geom, because the boolean operations code
>> does not work correctly. You need to use the old livarot library,
>> which is undocumented and frankly nobody understands it. Your best
>> bet
>> is copying what the Spray tool does: create an SP object containing
>> an
>> ellipse and a second SP object (SPPath) containing your path, then
>> intersecting them using the relevant function from sp-livarot.h.
>>
>
> splivarot.h functions all (or almost all) have
>
>    SPDesktop *desktop
>
> as a parameter.  That suggests  that they only operate directly on the
> drawing surface.
> This is of course just a guess, based on the parameter name.  However,
> the Spray tool you refer to is interactive,
> and it produces copies of objects on the drawing surface, and that is
> consistent with that guess.
>
> Unfortunately that is not what I need to do.  The shape intersections
> are to go to a file and must
> never be seen on the desktop.
>
> Can livarot be used that way?

Not without modifications.

The relevant function is in splivarot.cpp, lines 115-602. You can try
to take everything after the input validation bits (they end around
line 239) and turn that into a new function that will take
pathvectors, then call this new function from the original.

Regards, Krzysztof