C++ QValueVector::pop_back方法代码示例

/**
 * Does spike-reduction on the given point-array's stack-top.
 *
 * Spikes are path segments of which one goes forward, and the sucessor
 * goes backward on the predecessor's segment:
 *
 * 2      0      1
 * x------x<-----x
 * (0 is stack-top in point-array)
 *
 * This will be reduced to
 * 1      0
 * x------x
 *
 * Preconditions:
 * - No other spikes exist in the whole point-array except at most
 *   one at the end
 * - No two succeeding points are ever equal
 * - For each two succeeding points either p1.x == p2.x or p1.y == p2.y holds
 *   true
 * - No such spike exists where 2 is situated between 0 and 1.
 *
 * Postcondition:
 * - No spikes exist in the whole point-array
 *
 * If no spike is found, the point-array is left unchanged.
 * @return \c true if an actual reduction was done
 */
inline static bool reduceSpike(QValueVector< QPoint > &pointArray)
{
    if(pointArray.size() < 3)
        return false;
    QValueVector< QPoint >::Iterator it = pointArray.end();
    QPoint p0 = *--it;
    QPoint p1 = *--it;
    QPoint p2 = *--it;

    bool elide = false;

    if((p0.x() == p1.x() && p1.x() == p2.x() && ((p1.y() < p0.y() && p0.y() < p2.y()) || (p2.y() < p0.y() && p0.y() < p1.y())
                                                || (p1.y() < p2.y() && p2.y() < p0.y()) || (p0.y() < p2.y() && p2.y() < p1.y())
                                                || (elide = p2.y() == p0.y() && p0.y() < p1.y()) || (elide = p1.y() < p0.y() && p0.y() == p2.y())))
       || (p0.y() == p1.y() && p1.y() == p2.y() && ((p1.x() < p0.x() && p0.x() < p2.x()) || (p2.x() < p0.x() && p0.x() < p1.x())
                                                   || (p1.x() < p2.x() && p2.x() < p0.x()) || (p0.x() < p2.x() && p2.x() < p1.x())
                                                   || (elide = p2.x() == p0.x() && p0.x() < p1.x()) || (elide = p1.x() < p0.x() && p0.x() == p2.x()))))
    {
        //     kdDebug(6040) << "spikered p2" << (elide ? " (elide)" : "") << ": " << p2 << " p1: " << p1 << " p0: " << p0 << endl;
        pointArray.pop_back();
        pointArray.pop_back();
        if(!elide)
            pointArray.push_back(p0);
        return true;
    }
    return false;
}

/**
 * Reduces segment separators.
 *
 * A segment separator separates a segment into two segments, thus causing
 * two adjacent segment with the same orientation.
 *
 * 2       1     0
 * x-------x---->x
 * (0 means stack-top)
 *
 * Here, 1 is a segment separator. As segment separators not only make
 * the line drawing algorithm inefficient, but also make the spike-reduction
 * fail, they must be eliminated:
 *
 * 1             0
 * x------------>x
 *
 * Preconditions:
 * - No other segment separators exist in the whole point-array except
 *   at most one at the end
 * - No two succeeding points are ever equal
 * - For each two succeeding points either p1.x == p2.x or p1.y == p2.y holds
 *   true
 * - No such spike exists where 2 is situated between 0 and 1.
 *
 * Postcondition:
 * - No segment separators exist in the whole point-array
 *
 * If no segment separator is found at the end of the point-array, it is
 * left unchanged.
 * @return \c true if a segment separator was actually reduced.
 */
inline static bool reduceSegmentSeparator(QValueVector< QPoint > &pointArray)
{
    if(pointArray.size() < 3)
        return false;
    QValueVector< QPoint >::Iterator it = pointArray.end();
    QPoint p0 = *--it;
    QPoint p1 = *--it;
    QPoint p2 = *--it;
    //     kdDebug(6040) << "checking p2: " << p2 << " p1: " << p1 << " p0: " << p0 << endl;

    if((p0.x() == p1.x() && p1.x() == p2.x() && ((p2.y() < p1.y() && p1.y() < p0.y()) || (p0.y() < p1.y() && p1.y() < p2.y())))
       || (p0.y() == p1.y() && p1.y() == p2.y() && ((p2.x() < p1.x() && p1.x() < p0.x()) || (p0.x() < p1.x() && p1.x() < p2.x()))))
    {
        //     kdDebug(6040) << "segred p2: " << p2 << " p1: " << p1 << " p0: " << p0 << endl;
        pointArray.pop_back();
        pointArray.pop_back();
        pointArray.push_back(p0);
        return true;
    }
    return false;
}

	void load( const QString& filename )
	{
		QFile file( filename );

		if ( !file.open( IO_ReadOnly ) )
		{
			Console::instance()->send( tr( "Unable to open %1!\n" ).arg( filename ) );
			return;
		}

		filenames.push_back( filename );

		QXmlInputSource input( &file );
		QXmlSimpleReader reader;
		reader.setFeature( "http://trolltech.com/xml/features/report-whitespace-only-CharData", false );

		reader.setContentHandler( this );
		reader.setErrorHandler( this );
		reader.parse( &input, false );

		filenames.pop_back();
	}

	bool endDocument()
	{
		levels.pop_back();
		locators.pop();
		return true;
	}