Buffer cases
Recursive Polygons Buffer
rt_w series
rt_w1
rt_w2
This case failed because of a generated x (block) in get_turn_info.hpp
It is fixed by removing them ix etc.
rt_w3
This case failed because it selected the wrong u turn from a cluster (at turn 2 in the picture below, before the fix), having the same target (8).
It is fixed by calculating properties ahead also for these cases, with the same rank.
Therefore it was necessary to add the rank to enrichment_info.
rt_w7
Suffered from a wrong block (at 12). Fixed by removing ix turns in buffer.
rt_w15
Failed until late phase. Actual reason of fix unknown.
rt_w18
This case fails because two colocated turns (87/91) on the border are considered as "within each other". This should be detectable and filtered out (make them both on the border).
rt_w22
Fails because two colocated turns (12/13) on the border are considered as "within each other".
rt_w24
Failed because of a wrong block in get_turn_info. This time it does not make the turn ix,
but ux (instead of uu or cc).
Using the collinear properties ahead functionality fixes this case.
Graph with a "concept fix"
Graph without the fix, and there is a line from 5 to the isolated area,
causing an invalid output.
