RDP.h

#ifndef RDP_HPP__
#define RDP_HPP__
 
#include <QBitArray>
#include <QPair>
#include <QPolygonF>
#include <QStack>
 
class RDP {
    // This gets called approximately 10 times per second, and until
    // the associated view resizes, it's going to need exactly the
    // same amount of stack and tracking array as it did last time.
    // Throwing that away and requesting it again every 100ms isn't
    // ideal, which is why this is a functor instead of a function.
 
    QStack<QPair<qsizetype, qsizetype>> stack;
    QBitArray array;
 
  public:
    // Process the provided polygon through the Ramer–Douglas–Peucker
    // algorithm at the requested epsilon level, modifying it in-place
    // and returning an iterator suitable for erase-remove idiom usage,
    // e.g.,
    //
    //   QPolygonF polygon;
    //   RDP       rdp;
    //
    //   polygon.erase(rdp(polygon), polygon.end());
    //
    // Essentially, this acts the same as a std::remove_if() predicate
    // does; points to retain are moved to the range [begin, iterator),
    // while points to be elided are in the tail range [iterator, end].
    // As the polygon remains the same size, the length of the tail is
    // the number of elided points, and as with std::remove_if(), these
    // points exist in memory but in an unspecified state.
 
    QPolygonF::iterator operator()(QPolygonF &polygon, qreal epsilon = 2.0);
};
 
#endif