[geos-devel] Envelope of empty Polygon

[Mateusz Łoskot]

Hi,

I'm bringing next subject to discuss.

The main question is what should be returned by getEnvelope()
called on empty polygon?

Here is simple use case:

GeometryFactory factory(...);
//...

// create empty polygon
Polygon* poly = factory.createPolygon();

// request for its envelope
Geometry* geo = 0;
geo = poly->getEnvelope();
geo->isEmpty(); // <--- THE PROBLEM


As I revealed, when exterior ring is empty geometry,
getEnvelope() returns or creates instance of envelope object.
This object is initialized by Envelope::setToNull().
So, returned envelope for empty polygon has following coordinates:
minx = -1.0
maxx = 0.0
miny = -1.0
maxx = 0.0

Is this correct behaviour?
Is empty polygon assumed to return non-empty envelope as above?

Cheers
-- 
Mateusz Łoskot
http://mateusz.loskot.net