void QgsExpression::initGeomCalculator( const QgsExpressionContext *context )
{
// Set the geometry calculator from the context if it has not been set by setGeomCalculator()
if ( context && ! d->mCalc )
{
QString ellipsoid = context->variable( QStringLiteral( "project_ellipsoid" ) ).toString();
QgsCoordinateReferenceSystem crs = context->variable( QStringLiteral( "_layer_crs" ) ).value<QgsCoordinateReferenceSystem>();
QgsCoordinateTransformContext tContext = context->variable( QStringLiteral( "_project_transform_context" ) ).value<QgsCoordinateTransformContext>();
if ( crs.isValid() )
{
d->mCalc = std::shared_ptr<QgsDistanceArea>( new QgsDistanceArea() );
d->mCalc->setEllipsoid( ellipsoid.isEmpty() ? GEO_NONE : ellipsoid );
d->mCalc->setSourceCrs( crs, tContext );
}
}
// Set the distance units from the context if it has not been set by setDistanceUnits()
if ( context && distanceUnits() == QgsUnitTypes::DistanceUnknownUnit )
{
QString distanceUnitsStr = context->variable( QStringLiteral( "project_distance_units" ) ).toString();
if ( ! distanceUnitsStr.isEmpty() )
setDistanceUnits( QgsUnitTypes::stringToDistanceUnit( distanceUnitsStr ) );
}
// Set the area units from the context if it has not been set by setAreaUnits()
if ( context && areaUnits() == QgsUnitTypes::AreaUnknownUnit )
{
QString areaUnitsStr = context->variable( QStringLiteral( "project_area_units" ) ).toString();
if ( ! areaUnitsStr.isEmpty() )
setAreaUnits( QgsUnitTypes::stringToAreaUnit( areaUnitsStr ) );
}
}
double QgsDistanceArea::convertAreaMeasurement( double area, QgsUnitTypes::AreaUnit toUnits ) const
{
// get the conversion factor between the specified units
QgsUnitTypes::AreaUnit measureUnits = areaUnits();
double factorUnits = QgsUnitTypes::fromUnitToUnitFactor( measureUnits, toUnits );
double result = area * factorUnits;
QgsDebugMsg( QString( "Converted area of %1 %2 to %3 %4" ).arg( area )
.arg( QgsUnitTypes::toString( measureUnits ) )
.arg( result )
.arg( QgsUnitTypes::toString( toUnits ) ) );
return result;
}
