C++ GeoDataLineString::tessellate方法代码示例

bool GeoDataLineString::operator==( const GeoDataLineString &other ) const
{
    if ( !GeoDataGeometry::equals(other) ||
          size() != other.size() ||
          tessellate() != other.tessellate() ) {
        return false;
    }

    const GeoDataLineStringPrivate* d = p();
    const GeoDataLineStringPrivate* other_d = other.p();

    QVector<GeoDataCoordinates>::const_iterator itCoords = d->m_vector.constBegin();
    QVector<GeoDataCoordinates>::const_iterator otherItCoords = other_d->m_vector.constBegin();
    QVector<GeoDataCoordinates>::const_iterator itEnd = d->m_vector.constEnd();
    QVector<GeoDataCoordinates>::const_iterator otherItEnd = other_d->m_vector.constEnd();

    for ( ; itCoords != itEnd && otherItCoords != otherItEnd; ++itCoords, ++otherItCoords ) {
        if ( *itCoords != *otherItCoords ) {
            return false;
        }
    }

    Q_ASSERT ( itCoords == itEnd && otherItCoords == otherItEnd );
    return true;
}

bool CylindricalProjectionPrivate::lineStringToPolygon( const GeoDataLineString &lineString,
                                              const ViewportParams *viewport,
                                              QVector<QPolygonF *> &polygons ) const
{
    const TessellationFlags f = lineString.tessellationFlags();

    qreal x = 0;
    qreal y = 0;

    qreal previousX = -1.0;
    qreal previousY = -1.0;

    int mirrorCount = 0;
    qreal distance = repeatDistance( viewport );

    polygons.append( new QPolygonF );

    GeoDataLineString::ConstIterator itCoords = lineString.constBegin();
    GeoDataLineString::ConstIterator itPreviousCoords = lineString.constBegin();

    GeoDataLineString::ConstIterator itBegin = lineString.constBegin();
    GeoDataLineString::ConstIterator itEnd = lineString.constEnd();

    bool processingLastNode = false;

    // We use a while loop to be able to cover linestrings as well as linear rings:
    // Linear rings require to tessellate the path from the last node to the first node
    // which isn't really convenient to achieve with a for loop ...

    const bool isLong = lineString.size() > 10;
    const int maximumDetail = levelForResolution(viewport->angularResolution());
    // The first node of optimized linestrings has a non-zero detail value.
    const bool hasDetail = itBegin->detail() != 0;

    while ( itCoords != itEnd )
    {
        // Optimization for line strings with a big amount of nodes
        bool skipNode = (hasDetail ? itCoords->detail() > maximumDetail
                : itCoords != itBegin && isLong && !processingLastNode &&
                !viewport->resolves( *itPreviousCoords, *itCoords ) );

        if ( !skipNode ) {


            Q_Q( const CylindricalProjection );

            q->screenCoordinates( *itCoords, viewport, x, y );

            // Initializing variables that store the values of the previous iteration
            if ( !processingLastNode && itCoords == itBegin ) {
                itPreviousCoords = itCoords;
                previousX = x;
                previousY = y;
            }

            // This if-clause contains the section that tessellates the line
            // segments of a linestring. If you are about to learn how the code of
            // this class works you can safely ignore this section for a start.

            if ( lineString.tessellate() ) {

                mirrorCount = tessellateLineSegment( *itPreviousCoords, previousX, previousY,
                                           *itCoords, x, y,
                                           polygons, viewport,
                                           f, mirrorCount, distance );
            }

            else {
                // special case for polys which cross dateline but have no Tesselation Flag
                // the expected rendering is a screen coordinates straight line between
                // points, but in projections with repeatX things are not smooth
                mirrorCount = crossDateLine( *itPreviousCoords, *itCoords, x, y, polygons, mirrorCount, distance );
            }

            itPreviousCoords = itCoords;
            previousX = x;
            previousY = y;
        }

        // Here we modify the condition to be able to process the
        // first node after the last node in a LinearRing.

        if ( processingLastNode ) {
            break;
        }
        ++itCoords;

        if ( itCoords == itEnd  && lineString.isClosed() ) {
            itCoords = itBegin;
            processingLastNode = true;
        }
    }

    GeoDataLatLonAltBox box = lineString.latLonAltBox();

    // Closing e.g. in the Antarctica case.
    // This code makes the assumption that
    // - the first node is located at 180 E
    // - and the last node is located at 180 W
    // TODO: add a similar pattern in the crossDateLine() code.
//.........这里部分代码省略.........