Supported operations for clipPolygon. For a description of the operations, and the roles of subject and clip in each, visit http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Types/ClipType.htm

ClipType

• ClipType.ClipperLib::ctIntersection
  AND operator: Create regions where both subject and clip polygons are filled.
  
• ClipType.ClipperLib::ctUnion
  OR operator: Create regions where either subject or clip polygons (or both) are filled.
  
• ClipType.ClipperLib::ctDifference
  NOT operator: Create regions where subject polygons are filled except where clip polygons are filled.
  
• ClipType.ClipperLib::ctXor
  XOR operator: Create regions where either subject or clip polygons are filled but not where both are filled