[OverlayNG] tests/general/TestOverlayLL.xml fails

[strk]

A simple test is failing with --overlay-ng. Passes with JTS:

        Description: LrL - LinearRing bug
        Geometry A: LINEARRING (0 0, 0 5, 5 5, 5 0, 0 0)
        Geometry B: LINESTRING (2 2, 5 5)
        Expected result: POINT (5 5)
        Obtained result: LINESTRING EMPTY

The test is in the tests/general/TestOverlayLL.xml file

[strk]

Adding debugging to the OverlayNG GEOS class I'm seeing this graph:

OverlayNG::extractResult: graph: OGRPH 
NODEMAP [2]
 2 2 OE( 2 2 .. 5 5 ) A:e/B:eL / Sym: A:e/B:eL
 5 5 OE( 5 5 .. 2 2 ) A:e/B:eL / Sym: A:e/B:eL
EDGES [2]
 OE( 2 2 .. 5 5 ) A:e/B:eL / Sym: A:e/B:eL 
 OE( 5 5 .. 2 2 ) A:e/B:eL / Sym: A:e/B:eL 

The JTS class does not have a toString method, so not sure how to compare (should add one).

[strk]

Changing the LINEARRING type to a POLYGON or LINESTRING fixes the test, so this seems to be a simple bug which was fixed in old OverlayOP but not the new OverlayNG

[strk]

OverlayGraph::addEdge is called only once, in GEOS, while it's called 3 times in JTS. The missing 2 times are for both directions of the linearring edge

[strk]

Found the culprit: EdgeNodingBuilder::add, in GEOS, uses getGeometryTypeID to decide what to do, and decides to do NOTHING for LineaRing. Instead JTS uses an instanceOf operator (like a dynamic cast) which would see LinearRing as being an instance of a LINESTRING

[Sandro Santilli <strk@…>]

In e6ffc18/git:

[OverlayNG] Fix handling of LinearRing

Closes #1043

[pramsey]

Very nice catch.