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Labeling thin polygons sometimes fails. #5234
@szekerest reported instances where labeling where thin, simple polygons (think parcels) results in label points outside a polygon. It happens because a edge/distance computation in msPolygonLabelPoint() done after a center of gravity computation drops the label point computation into a second algorithm that uses scan lines to place the label. There is a bug in that second computation that can result in bad label placement.
The fix is easy, simply uncomment a couple of lines in that function, look for:
and the issue is resolved. In cases like this it might be even better to skip the distance check or at least make that more robust, but that's another ticket. I tried allowing a configuration via a layer processing option but since label placement is independent of layer properties it's not trivial to make that value available, especially with MapScript.