[PostGIS] #6065: ValidateTopology fails to report invalid side-labeling

[PostGIS]

#6065: ValidateTopology fails to report invalid side-labeling
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  Reporter:  strk      |      Owner:  strk
      Type:  defect    |     Status:  reopened
  Priority:  medium    |  Milestone:  PostGIS 3.7.0
 Component:  topology  |    Version:  master
Resolution:            |   Keywords:
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Changes (by strk):

 * resolution:  fixed =>
 * status:  closed => reopened

Comment:

 Since the fix for this is platform specific (see #6067) I'm reopening the
 ticket.

 One idea to make the hole/she'll determination more robust: we compute on
 which side of the leftmost edges a farther-left point falls. If the side
 matches the side of the edge in the ring (positive if left, negative if
 right) we can tell it's an hole (clockwise orientation). Note that if the
 leftmost edge appears both as positive and negative we can avoid computing
 side and directly state it's an hole (shells can only have flat components
 on the interior).
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/6065#comment:7>
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