ogr2ogr/shapefile fails to generate valid polygons with hole touching boundary

[llo@…]

Using ogr2ogr to generate a shapefile will produce invalid polygons with hole if the hole touches the outer-boundary in one point. It produces a simple polygon without any hole, and ONLY a self-intersecting boundary.

This ONLY applies to shapefiles, no problems found with postgis or tab-file writer.

Example polygon in WKT that cannot be converted to a valid shapefile: POLYGON ((0 0, 0 3, 3 3, 3 0, 0 0), (0 0, 1 2, 2 1, 0 0))

/Regards Lars

[fredc]

OGR shapefile patched for touching polygons

[fredc]

We (think we) fixed this bug for touching polygons : see attached file shpopen.c, from line 1925 to line 1980.

All polygon pairs were tested for inclusion of its first polygon starting vertex in the other polygon, with a non strict inclusion. So in your case, the outer ring starting vertex was incorrectly considered "inside" the inner ring.

=> the inclusion is now strict in shpopen.c

note : that issue can also appear with outer touching polygons.

[warmerdam]

Mateusz,

Can you look into this for 1.4.2? Once you are happy with the change, I can upstream it to the shapelib repository.