bool QgsPointDistanceRenderer::renderFeature( QgsFeature &feature, QgsRenderContext &context, int layer, bool selected, bool drawVertexMarker )
{
Q_UNUSED( drawVertexMarker );
Q_UNUSED( context );
Q_UNUSED( layer );
/*
* IMPORTANT: This algorithm is ported to Python in the processing "Points Displacement" algorithm.
* Please port any changes/improvements to that algorithm too!
*/
//check if there is already a point at that position
if ( !feature.hasGeometry() )
return false;
QgsMarkerSymbol *symbol = firstSymbolForFeature( feature, context );
//if the feature has no symbol (e.g., no matching rule in a rule-based renderer), skip it
if ( !symbol )
return false;
//point position in screen coords
QgsGeometry geom = feature.geometry();
QgsWkbTypes::Type geomType = geom.wkbType();
if ( QgsWkbTypes::flatType( geomType ) != QgsWkbTypes::Point )
{
//can only render point type
return false;
}
QString label;
if ( mDrawLabels )
{
label = getLabel( feature );
}
QgsCoordinateTransform xform = context.coordinateTransform();
QgsFeature transformedFeature = feature;
if ( xform.isValid() )
{
geom.transform( xform );
transformedFeature.setGeometry( geom );
}
double searchDistance = context.convertToMapUnits( mTolerance, mToleranceUnit, mToleranceMapUnitScale );
QgsPointXY point = transformedFeature.geometry().asPoint();
QList<QgsFeatureId> intersectList = mSpatialIndex->intersects( searchRect( point, searchDistance ) );
if ( intersectList.empty() )
{
mSpatialIndex->insertFeature( transformedFeature );
// create new group
ClusteredGroup newGroup;
newGroup << GroupedFeature( transformedFeature, symbol->clone(), selected, label );
mClusteredGroups.push_back( newGroup );
// add to group index
mGroupIndex.insert( transformedFeature.id(), mClusteredGroups.count() - 1 );
mGroupLocations.insert( transformedFeature.id(), point );
}
else
{
// find group with closest location to this point (may be more than one within search tolerance)
QgsFeatureId minDistFeatureId = intersectList.at( 0 );
double minDist = mGroupLocations.value( minDistFeatureId ).distance( point );
for ( int i = 1; i < intersectList.count(); ++i )
{
QgsFeatureId candidateId = intersectList.at( i );
double newDist = mGroupLocations.value( candidateId ).distance( point );
if ( newDist < minDist )
{
minDist = newDist;
minDistFeatureId = candidateId;
}
}
int groupIdx = mGroupIndex[ minDistFeatureId ];
ClusteredGroup &group = mClusteredGroups[groupIdx];
// calculate new centroid of group
QgsPointXY oldCenter = mGroupLocations.value( minDistFeatureId );
mGroupLocations[ minDistFeatureId ] = QgsPointXY( ( oldCenter.x() * group.size() + point.x() ) / ( group.size() + 1.0 ),
( oldCenter.y() * group.size() + point.y() ) / ( group.size() + 1.0 ) );
// add to a group
group << GroupedFeature( transformedFeature, symbol->clone(), selected, label );
// add to group index
mGroupIndex.insert( transformedFeature.id(), groupIdx );
}
return true;
}
