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Review fixes + comment about merging of multi-part geometries

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This commit is contained in:
Martin Dobias 2020-06-19 09:17:30 +02:00
parent 00a102c6b9
commit 21c6573db6
1 changed files with 11 additions and 7 deletions
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18
src/core/geometry/qgsgeos.cpp
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@ -880,8 +880,13 @@ QgsGeometryEngine::EngineOperationResult QgsGeos::splitPolygonGeometry( GEOSGeom
if ( !mGeos )
return InvalidBaseGeometry;
// we will need prepared geometry for intersection tests
const_cast<QgsGeos *>( this )->prepareGeometry();
if ( !mGeosPrepared )
return EngineError;
//first test if linestring intersects geometry. If not, return straight away
if ( !GEOSIntersects_r( geosinit()->ctxt, splitLine, mGeos.get() ) )
if ( !GEOSPreparedIntersects_r( geosinit()->ctxt, mGeosPrepared.get(), splitLine ) )
return NothingHappened;
//first union all the polygon rings together (to get them noded, see JTS developer guide)
@ -896,12 +901,7 @@ QgsGeometryEngine::EngineOperationResult QgsGeos::splitPolygonGeometry( GEOSGeom
return InvalidBaseGeometry;
}
// we will need prepared geometry for intersection tests
const_cast<QgsGeos *>( this )->prepareGeometry();
if ( !mGeosPrepared )
return EngineError;
//test every polygon if contained in original geometry
//test every polygon is contained in original geometry
//include in result if yes
QVector<GEOSGeometry *> testedGeometries;
@ -928,6 +928,10 @@ QgsGeometryEngine::EngineOperationResult QgsGeos::splitPolygonGeometry( GEOSGeom
return NothingHappened;
}
// For multi-part geometries, try to identify parts that have been unchanged and try to merge them back
// to a single multi-part geometry. For example, if there's a multi-polygon with three parts, but only
// one part is being split, this function makes sure that the other two parts will be kept in a multi-part
// geometry rather than being separated into two single-part geometries.
mergeGeometriesMultiTypeSplit( testedGeometries );
int i;