LWGEOM*
lwgeom_buildarea(const LWGEOM *geom)
{
GEOSGeometry* geos_in;
GEOSGeometry* geos_out;
LWGEOM* geom_out;
int SRID = (int)(geom->srid);
int is3d = FLAGS_GET_Z(geom->flags);
/* Can't build an area from an empty! */
if ( lwgeom_is_empty(geom) )
{
return (LWGEOM*)lwpoly_construct_empty(SRID, is3d, 0);
}
LWDEBUG(3, "buildarea called");
LWDEBUGF(3, "ST_BuildArea got geom @ %p", geom);
initGEOS(lwnotice, lwgeom_geos_error);
geos_in = LWGEOM2GEOS(geom);
if ( 0 == geos_in ) /* exception thrown at construction */
{
lwerror("First argument geometry could not be converted to GEOS: %s", lwgeom_geos_errmsg);
return NULL;
}
geos_out = LWGEOM_GEOS_buildArea(geos_in);
GEOSGeom_destroy(geos_in);
if ( ! geos_out ) /* exception thrown.. */
{
lwerror("LWGEOM_GEOS_buildArea: %s", lwgeom_geos_errmsg);
return NULL;
}
/* If no geometries are in result collection, return NULL */
if ( GEOSGetNumGeometries(geos_out) == 0 )
{
GEOSGeom_destroy(geos_out);
return NULL;
}
geom_out = GEOS2LWGEOM(geos_out, is3d);
GEOSGeom_destroy(geos_out);
#if PARANOIA_LEVEL > 0
if ( geom_out == NULL )
{
lwerror("serialization error");
return NULL;
}
#endif
return geom_out;
}
// Will return NULL on error (expect error handler being called by then)
Q_NOWARN_UNREACHABLE_PUSH
static GEOSGeometry *LWGEOM_GEOS_makeValidPolygon( const GEOSGeometry *gin, QString &errorMessage )
{
GEOSContextHandle_t handle = QgsGeos::getGEOSHandler();
GEOSGeom gout;
GEOSGeom geos_bound;
GEOSGeom geos_cut_edges, geos_area, collapse_points;
GEOSGeometry *vgeoms[3]; // One for area, one for cut-edges
unsigned int nvgeoms = 0;
Q_ASSERT( GEOSGeomTypeId_r( handle, gin ) == GEOS_POLYGON ||
GEOSGeomTypeId_r( handle, gin ) == GEOS_MULTIPOLYGON );
geos_bound = GEOSBoundary_r( handle, gin );
if ( !geos_bound )
return nullptr;
// Use noded boundaries as initial "cut" edges
geos_cut_edges = LWGEOM_GEOS_nodeLines( geos_bound );
if ( !geos_cut_edges )
{
GEOSGeom_destroy_r( handle, geos_bound );
errorMessage = QStringLiteral( "LWGEOM_GEOS_nodeLines() failed" );
return nullptr;
}
// NOTE: the noding process may drop lines collapsing to points.
// We want to retrieve any of those
{
GEOSGeometry *pi = nullptr;
GEOSGeometry *po = nullptr;
try
{
pi = GEOSGeom_extractUniquePoints_r( handle, geos_bound );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_bound );
errorMessage = QStringLiteral( "GEOSGeom_extractUniquePoints(): %1" ).arg( e.what() );
return nullptr;
}
try
{
po = GEOSGeom_extractUniquePoints_r( handle, geos_cut_edges );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_bound );
GEOSGeom_destroy_r( handle, pi );
errorMessage = QStringLiteral( "GEOSGeom_extractUniquePoints(): %1" ).arg( e.what() );
return nullptr;
}
try
{
collapse_points = GEOSDifference_r( handle, pi, po );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_bound );
GEOSGeom_destroy_r( handle, pi );
GEOSGeom_destroy_r( handle, po );
errorMessage = QStringLiteral( "GEOSDifference(): %1" ).arg( e.what() );
return nullptr;
}
GEOSGeom_destroy_r( handle, pi );
GEOSGeom_destroy_r( handle, po );
}
GEOSGeom_destroy_r( handle, geos_bound );
// And use an empty geometry as initial "area"
try
{
geos_area = GEOSGeom_createEmptyPolygon_r( handle );
}
catch ( GEOSException &e )
{
errorMessage = QStringLiteral( "GEOSGeom_createEmptyPolygon(): %1" ).arg( e.what() );
GEOSGeom_destroy_r( handle, geos_cut_edges );
return nullptr;
}
// See if an area can be build with the remaining edges
// and if it can, symdifference with the original area.
// Iterate this until no more polygons can be created
// with left-over edges.
while ( GEOSGetNumGeometries_r( handle, geos_cut_edges ) )
{
GEOSGeometry *new_area = nullptr;
GEOSGeometry *new_area_bound = nullptr;
GEOSGeometry *symdif = nullptr;
GEOSGeometry *new_cut_edges = nullptr;
// ASSUMPTION: cut_edges should already be fully noded
try
{
new_area = LWGEOM_GEOS_buildArea( geos_cut_edges, errorMessage );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_cut_edges );
GEOSGeom_destroy_r( handle, geos_area );
errorMessage = QStringLiteral( "LWGEOM_GEOS_buildArea() threw an error: %1" ).arg( e.what() );
return nullptr;
}
if ( GEOSisEmpty_r( handle, new_area ) )
{
// no more rings can be build with thes edges
GEOSGeom_destroy_r( handle, new_area );
break;
}
// We succeeded in building a ring !
// Save the new ring boundaries first (to compute
// further cut edges later)
try
{
new_area_bound = GEOSBoundary_r( handle, new_area );
}
catch ( GEOSException &e )
{
// We did check for empty area already so
// this must be some other error
errorMessage = QStringLiteral( "GEOSBoundary() threw an error: %1" ).arg( e.what() );
GEOSGeom_destroy_r( handle, new_area );
GEOSGeom_destroy_r( handle, geos_area );
return nullptr;
}
// Now symdiff new and old area
try
{
symdif = GEOSSymDifference_r( handle, geos_area, new_area );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_cut_edges );
GEOSGeom_destroy_r( handle, new_area );
GEOSGeom_destroy_r( handle, new_area_bound );
GEOSGeom_destroy_r( handle, geos_area );
errorMessage = QStringLiteral( "GEOSSymDifference() threw an error: %1" ).arg( e.what() );
return nullptr;
}
GEOSGeom_destroy_r( handle, geos_area );
GEOSGeom_destroy_r( handle, new_area );
geos_area = symdif;
symdif = nullptr;
// Now let's re-set geos_cut_edges with what's left
// from the original boundary.
// ASSUMPTION: only the previous cut-edges can be
// left, so we don't need to reconsider
// the whole original boundaries
//
// NOTE: this is an expensive operation.
try
{
new_cut_edges = GEOSDifference_r( handle, geos_cut_edges, new_area_bound );
}
catch ( GEOSException &e )
{
GEOSGeom_destroy_r( handle, geos_cut_edges );
GEOSGeom_destroy_r( handle, new_area_bound );
GEOSGeom_destroy_r( handle, geos_area );
errorMessage = QStringLiteral( "GEOSDifference() threw an error: %1" ).arg( e.what() );
return nullptr;
}
GEOSGeom_destroy_r( handle, geos_cut_edges );
GEOSGeom_destroy_r( handle, new_area_bound );
geos_cut_edges = new_cut_edges;
}
if ( !GEOSisEmpty_r( handle, geos_area ) )
{
vgeoms[nvgeoms++] = geos_area;
}
else
{
GEOSGeom_destroy_r( handle, geos_area );
}
if ( !GEOSisEmpty_r( handle, geos_cut_edges ) )
{
vgeoms[nvgeoms++] = geos_cut_edges;
}
else
{
GEOSGeom_destroy_r( handle, geos_cut_edges );
}
if ( !GEOSisEmpty_r( handle, collapse_points ) )
{
vgeoms[nvgeoms++] = collapse_points;
}
else
{
GEOSGeom_destroy_r( handle, collapse_points );
}
if ( 1 == nvgeoms )
{
// Return cut edges
gout = vgeoms[0];
}
else
{
// Collect areas and lines (if any line)
try
{
gout = GEOSGeom_createCollection_r( handle, GEOS_GEOMETRYCOLLECTION, vgeoms, nvgeoms );
}
catch ( GEOSException &e )
{
errorMessage = QStringLiteral( "GEOSGeom_createCollection() threw an error: %1" ).arg( e.what() );
// TODO: cleanup!
return nullptr;
}
}
return gout;
}
