Ch'gans wrote:

On 9 April 2017 at 12:05, Adam Wulkiewicz <adam.wulkiewicz@gmail.com> wrote:Ch'gans Via Geometry wrote:My custom ring type is defined with an 'open' closure. When i try to compare 2 geometrically equivalent ring and box, bg::equals return false. While investigating using the debugger, i discovered that the call to geometry::collect_vectors() returns 4 points for a box, but only 3 points for a ring, so my 2 geometries can never be equal. In my case, collect_vectors is dispatched to range_collect_vectors, and by the look of it range_collect_vectors doesn't care about the geometry object (and it's closure), since it sees only point (iterator) range.[...]Am i missing something in my custom geometry trait adaptation? is it a bug in BG, or a known limitation?It is a bug. I pushed a fix to develop: https://github.com/boostorg/geometry/commit/657a5c80902edc9640a06571c2762a5dee591067 I'll try to release it with Boost 1.64.Thanks for the fix, this was quick! ;) After adding the QVM dependency, and using Geometry devel branch, I have removed a couple of expected failure from my test suite, great!

I'm glad to hear that.

But unfortunately i still have some left: Comparison for geometry equivalence of a box and a ring. The problem is again in collect_vectors, the specialisation for bbox always collect the points by following the clockwise direction, if your have counterclockwise rings then equals(ring, box) will always return false due to different directions. Not sure what is the best way to fix this, any thoughts?

2 solutions come to mind:

1. Always gather segments/vectors in the same order, like this (pushed to develop):

https://github.com/boostorg/geometry/commit/e3ac044400748e23d7a5a708b47bb8fef9b14758

2. In the constructor of collected_vector use lexicographically smaller point as the origin point, so always store point-order-invariant direction. It'd require to modify these constructors:

https://github.com/boostorg/geometry/blob/develop/include/boost/geometry/algorithms/detail/equals/collect_vectors.hpp#L89

https://github.com/boostorg/geometry/blob/develop/include/boost/geometry/algorithms/detail/equals/collect_vectors.hpp#L179

I've choosen the first solution because it's simpler. I also expect it to be faster but haven't done performance tests.

Adam