Summary: Buffer issues

[dr-jts]

Summary and categorization of issues with buffer algorithm.

Artifacts

• Buffer with Flat endcap produces artifacts #1028
• Buffer of closed LineString has "inverted hole" artifact #876
• Buffer has unexpected boundary artifacts #866
• Poor quality buffer curve for Flat endcap #739
• Buffer error - extra polygon fragments #650
• Single-sided Buffer poor quality linework #178
• Negative buffer of a polygon can lie outside the input libgeos/geos#1208
• Negative buffer with join-style mitre  libgeos/geos#1047
• Buffer of a Linestring returns a Polygon with hole artifact libgeos/geos#1217
• GEOSBuffer on a valid Polygon creates MultiPolygon with sliver geometry libgeos/geos#1105 (GEOS only)
• Buffer intersects line it should buffer? libgeos/geos#660
• Buffer of a LinearRing gives unexpected result libgeos/geos#1223

FIXED Artifacts

Fixed by #525 (but see libgeos/geos#1223)

• Buffer of closed LineString fails to have hole for some distance values #523
• Unexpected behavior of buffer with LinearRing object shapely/shapely#790

Missing Result elements

• Buffer by zero loses some elements of MultiPolygon #1131

Error

• Negative Buffer with mitre join fails with TopologyException libgeos/geos#1211
• Buffer op throws exception for multipolygon libgeos/geos#1182

Fixed-Precision bugs

• Geometry.buffer with fixed precision removes hole #979
• Small buffer of a polygon returns an empty geometry #908

Buffer curve Quality

• Negative buffer operation leaves some collinear points (regression from 1.19.0) #1007
• Buffer with mitre join is incorrect due to short input segment #180