/src/gui/painting/qregion.cpp

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#include "qregion.h"
#include "qpainterpath.h"
#include "qpolygon.h"
#include "qbuffer.h"
#include "qdatastream.h"
#include "qvariant.h"
#include "qvarlengtharray.h"

#include <qdebug.h>

#if defined(Q_OS_UNIX) || defined(Q_WS_WIN)
#include "qimage.h"
#include "qbitmap.h"
#include <stdlib.h>
#endif

QT_BEGIN_NAMESPACE

/*!
    \class QRegion
    \brief The QRegion class specifies a clip region for a painter.

    \ingroup painting
    \ingroup shared

    QRegion is used with QPainter::setClipRegion() to limit the paint
    area to what needs to be painted. There is also a QWidget::repaint()
    function that takes a QRegion parameter. QRegion is the best tool for
    minimizing the amount of screen area to be updated by a repaint.

    This class is not suitable for constructing shapes for rendering, especially
    as outlines. Use QPainterPath to create paths and shapes for use with
    QPainter.

    QRegion is an \l{implicitly shared} class.

    \section1 Creating and Using Regions

    A region can be created from a rectangle, an ellipse, a polygon or
    a bitmap. Complex regions may be created by combining simple
    regions using united(), intersected(), subtracted(), or xored() (exclusive
    or). You can move a region using translate().

    You can test whether a region isEmpty() or if it
    contains() a QPoint or QRect. The bounding rectangle can be found
    with boundingRect().

    The function rects() gives a decomposition of the region into
    rectangles.

    Example of using complex regions:
    \snippet doc/src/snippets/code/src_gui_painting_qregion.cpp 0

    \section1 Additional License Information

    On Embedded Linux, Windows CE and X11 platforms, parts of this class rely on
    code obtained under the following licenses:

    \legalese
    Copyright (c) 1987  X Consortium

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
    AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    Except as contained in this notice, the name of the X Consortium shall not be
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from the X Consortium.
    \endlegalese

    \br

    \legalese
    Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.

                            All Rights Reserved

    Permission to use, copy, modify, and distribute this software and its
    documentation for any purpose and without fee is hereby granted,
    provided that the above copyright notice appear in all copies and that
    both that copyright notice and this permission notice appear in
    supporting documentation, and that the name of Digital not be
    used in advertising or publicity pertaining to distribution of the
    software without specific, written prior permission.

    DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
    DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
    ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
    WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
    ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
    SOFTWARE.
    \endlegalese

    \sa QPainter::setClipRegion(), QPainter::setClipRect(), QPainterPath
*/


/*!
    \enum QRegion::RegionType

    Specifies the shape of the region to be created.

    \value Rectangle  the region covers the entire rectangle.
    \value Ellipse  the region is an ellipse inside the rectangle.
*/

/*!
    \fn void QRegion::translate(const QPoint &point)

    \overload

    Translates the region \a{point}\e{.x()} along the x axis and
    \a{point}\e{.y()} along the y axis, relative to the current
    position. Positive values move the region to the right and down.

    Translates to the given \a point.
*/

/*!
    \fn Handle QRegion::handle() const

    Returns a platform-specific region handle. The \c Handle type is
    \c HRGN on Windows, \c Region on X11, and \c RgnHandle on Mac OS
    X. On \l{Qt for Embedded Linux} it is \c {void *}.

    \warning This function is not portable.
*/

/*****************************************************************************
  QRegion member functions
 *****************************************************************************/

/*!
    \fn QRegion::QRegion()

    Constructs an empty region.

    \sa isEmpty()
*/

/*!
    \fn QRegion::QRegion(const QRect &r, RegionType t)
    \overload

    Create a region based on the rectange \a r with region type \a t.

    If the rectangle is invalid a null region will be created.

    \sa QRegion::RegionType
*/

/*!
    \fn QRegion::QRegion(const QPolygon &a, Qt::FillRule fillRule)

    Constructs a polygon region from the point array \a a with the fill rule
    specified by \a fillRule.

    If \a fillRule is \l{Qt::WindingFill}, the polygon region is defined
    using the winding algorithm; if it is \l{Qt::OddEvenFill}, the odd-even fill
    algorithm is used.

    \warning This constructor can be used to create complex regions that will
    slow down painting when used.
*/

/*!
    \fn QRegion::QRegion(const QRegion &r)

    Constructs a new region which is equal to region \a r.
*/

/*!
    \fn QRegion::QRegion(const QBitmap &bm)

    Constructs a region from the bitmap \a bm.

    The resulting region consists of the pixels in bitmap \a bm that
    are Qt::color1, as if each pixel was a 1 by 1 rectangle.

    This constructor may create complex regions that will slow down
    painting when used. Note that drawing masked pixmaps can be done
    much faster using QPixmap::setMask().
*/

/*!
    Constructs a rectangular or elliptic region.

    If \a t is \c Rectangle, the region is the filled rectangle (\a x,
    \a y, \a w, \a h). If \a t is \c Ellipse, the region is the filled
    ellipse with center at (\a x + \a w / 2, \a y + \a h / 2) and size
    (\a w ,\a h).
*/
QRegion::QRegion(int x, int y, int w, int h, RegionType t)
{
    QRegion tmp(QRect(x, y, w, h), t);
    tmp.d->ref.ref();
    d = tmp.d;
}

#ifdef QT3_SUPPORT
/*!
    Use the constructor tha takes a Qt::FillRule as the second
    argument instead.
*/
QRegion::QRegion(const QPolygon &pa, bool winding)
{
    new (this) QRegion(pa, winding ? Qt::WindingFill : Qt::OddEvenFill);
}
#endif

/*!
    \fn QRegion::~QRegion()
    \internal

    Destroys the region.
*/

void QRegion::detach()
{
    if (d->ref != 1)
        *this = copy();
#if defined(Q_WS_X11)
    else if (d->xrectangles) {
        free(d->xrectangles);
        d->xrectangles = 0;
    }
#endif
}

// duplicates in qregion_win.cpp and qregion_wce.cpp
#define QRGN_SETRECT          1                // region stream commands
#define QRGN_SETELLIPSE       2                //  (these are internal)
#define QRGN_SETPTARRAY_ALT   3
#define QRGN_SETPTARRAY_WIND  4
#define QRGN_TRANSLATE        5
#define QRGN_OR               6
#define QRGN_AND              7
#define QRGN_SUB              8
#define QRGN_XOR              9
#define QRGN_RECTS            10


#ifndef QT_NO_DATASTREAM

/*
    Executes region commands in the internal buffer and rebuilds the
    original region.

    We do this when we read a region from the data stream.

    If \a ver is non-0, uses the format version \a ver on reading the
    byte array.
*/
void QRegion::exec(const QByteArray &buffer, int ver, QDataStream::ByteOrder byteOrder)
{
    QByteArray copy = buffer;
    QDataStream s(&copy, QIODevice::ReadOnly);
    if (ver)
        s.setVersion(ver);
    s.setByteOrder(byteOrder);
    QRegion rgn;
#ifndef QT_NO_DEBUG
    int test_cnt = 0;
#endif
    while (!s.atEnd()) {
        qint32 id;
        if (s.version() == 1) {
            int id_int;
            s >> id_int;
            id = id_int;
        } else {
            s >> id;
        }
#ifndef QT_NO_DEBUG
        if (test_cnt > 0 && id != QRGN_TRANSLATE)
            qWarning("QRegion::exec: Internal error");
        test_cnt++;
#endif
        if (id == QRGN_SETRECT || id == QRGN_SETELLIPSE) {
            QRect r;
            s >> r;
            rgn = QRegion(r, id == QRGN_SETRECT ? Rectangle : Ellipse);
        } else if (id == QRGN_SETPTARRAY_ALT || id == QRGN_SETPTARRAY_WIND) {
            QPolygon a;
            s >> a;
            rgn = QRegion(a, id == QRGN_SETPTARRAY_WIND ? Qt::WindingFill : Qt::OddEvenFill);
        } else if (id == QRGN_TRANSLATE) {
            QPoint p;
            s >> p;
            rgn.translate(p.x(), p.y());
        } else if (id >= QRGN_OR && id <= QRGN_XOR) {
            QByteArray bop1, bop2;
            QRegion r1, r2;
            s >> bop1;
            r1.exec(bop1);
            s >> bop2;
            r2.exec(bop2);

            switch (id) {
                case QRGN_OR:
                    rgn = r1.united(r2);
                    break;
                case QRGN_AND:
                    rgn = r1.intersected(r2);
                    break;
                case QRGN_SUB:
                    rgn = r1.subtracted(r2);
                    break;
                case QRGN_XOR:
                    rgn = r1.xored(r2);
                    break;
            }
        } else if (id == QRGN_RECTS) {
            // (This is the only form used in Qt 2.0)
            quint32 n;
            s >> n;
            QRect r;
            for (int i=0; i<(int)n; i++) {
                s >> r;
                rgn = rgn.united(QRegion(r));
            }
        }
    }
    *this = rgn;
}


/*****************************************************************************
  QRegion stream functions
 *****************************************************************************/

/*!
    \fn QRegion &QRegion::operator=(const QRegion &r)

    Assigns \a r to this region and returns a reference to the region.
*/

/*!
    \fn void QRegion::swap(QRegion &other)
    \since 4.8

    Swaps region \a other with this region. This operation is very
    fast and never fails.
*/

/*!
    \relates QRegion

    Writes the region \a r to the stream \a s and returns a reference
    to the stream.

    \sa \link datastreamformat.html Format of the QDataStream operators \endlink
*/

QDataStream &operator<<(QDataStream &s, const QRegion &r)
{
    QVector<QRect> a = r.rects();
    if (a.isEmpty()) {
        s << (quint32)0;
    } else {
        if (s.version() == 1) {
            int i;
            for (i = a.size() - 1; i > 0; --i) {
                s << (quint32)(12 + i * 24);
                s << (int)QRGN_OR;
            }
            for (i = 0; i < a.size(); ++i) {
                s << (quint32)(4+8) << (int)QRGN_SETRECT << a[i];
            }
        } else {
            s << (quint32)(4 + 4 + 16 * a.size()); // 16: storage size of QRect
            s << (qint32)QRGN_RECTS;
            s << a;
        }
    }
    return s;
}

/*!
    \relates QRegion

    Reads a region from the stream \a s into \a r and returns a
    reference to the stream.

    \sa \link datastreamformat.html Format of the QDataStream operators \endlink
*/

QDataStream &operator>>(QDataStream &s, QRegion &r)
{
    QByteArray b;
    s >> b;
    r.exec(b, s.version(), s.byteOrder());
    return s;
}
#endif //QT_NO_DATASTREAM

#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug s, const QRegion &r)
{
    QVector<QRect> rects = r.rects();
    s.nospace() << "QRegion(size=" << rects.size() << "), "
                << "bounds = " << r.boundingRect() << '\n';
    for (int i=0; i<rects.size(); ++i)
        s << "- " << i << rects.at(i) << '\n';
    return s;
}
#endif


// These are not inline - they can be implemented better on some platforms
//  (eg. Windows at least provides 3-variable operations).  For now, simple.


/*!
    Applies the united() function to this region and \a r. \c r1|r2 is
    equivalent to \c r1.united(r2).

    \sa united(), operator+()
*/
const QRegion QRegion::operator|(const QRegion &r) const
    { return united(r); }

/*!
    Applies the united() function to this region and \a r. \c r1+r2 is
    equivalent to \c r1.united(r2).

    \sa united(), operator|()
*/
const QRegion QRegion::operator+(const QRegion &r) const
    { return united(r); }

/*!
   \overload
   \since 4.4
 */
const QRegion QRegion::operator+(const QRect &r) const
    { return united(r); }

/*!
    Applies the intersected() function to this region and \a r. \c r1&r2
    is equivalent to \c r1.intersected(r2).

    \sa intersected()
*/
const QRegion QRegion::operator&(const QRegion &r) const
    { return intersected(r); }

/*!
   \overload
   \since 4.4
 */
const QRegion QRegion::operator&(const QRect &r) const
{
    return intersected(r);
}

/*!
    Applies the subtracted() function to this region and \a r. \c r1-r2
    is equivalent to \c r1.subtracted(r2).

    \sa subtracted()
*/
const QRegion QRegion::operator-(const QRegion &r) const
    { return subtracted(r); }

/*!
    Applies the xored() function to this region and \a r. \c r1^r2 is
    equivalent to \c r1.xored(r2).

    \sa xored()
*/
const QRegion QRegion::operator^(const QRegion &r) const
    { return xored(r); }

/*!
    Applies the united() function to this region and \a r and assigns
    the result to this region. \c r1|=r2 is equivalent to \c
    {r1 = r1.united(r2)}.

    \sa united()
*/
QRegion& QRegion::operator|=(const QRegion &r)
    { return *this = *this | r; }

/*!
    \fn QRegion& QRegion::operator+=(const QRect &rect)

    Returns a region that is the union of this region with the specified \a rect.

    \sa united()
*/
/*!
    \fn QRegion& QRegion::operator+=(const QRegion &r)

    Applies the united() function to this region and \a r and assigns
    the result to this region. \c r1+=r2 is equivalent to \c
    {r1 = r1.united(r2)}.

    \sa intersected()
*/
#if !defined (Q_OS_UNIX) && !defined (Q_WS_WIN)
QRegion& QRegion::operator+=(const QRect &r)
{
    return operator+=(QRegion(r));
}
#endif

/*!
  \fn QRegion& QRegion::operator&=(const QRegion &r)

  Applies the intersected() function to this region and \a r and
  assigns the result to this region. \c r1&=r2 is equivalent to \c
  r1 = r1.intersected(r2).

  \sa intersected()
*/
QRegion& QRegion::operator&=(const QRegion &r)
    { return *this = *this & r; }

/*!
   \overload
   \since 4.4
 */
#if defined (Q_OS_UNIX) || defined (Q_WS_WIN)
QRegion& QRegion::operator&=(const QRect &r)
{
    return *this = *this & r;
}
#else
QRegion& QRegion::operator&=(const QRect &r)
{
    return *this &= (QRegion(r));
}
#endif

/*!
  \fn QRegion& QRegion::operator-=(const QRegion &r)

  Applies the subtracted() function to this region and \a r and
  assigns the result to this region. \c r1-=r2 is equivalent to \c
  {r1 = r1.subtracted(r2)}.

  \sa subtracted()
*/
QRegion& QRegion::operator-=(const QRegion &r)
    { return *this = *this - r; }

/*!
    Applies the xored() function to this region and \a r and
    assigns the result to this region. \c r1^=r2 is equivalent to \c
    {r1 = r1.xored(r2)}.

    \sa xored()
*/
QRegion& QRegion::operator^=(const QRegion &r)
    { return *this = *this ^ r; }

/*!
    \fn bool QRegion::operator!=(const QRegion &other) const

    Returns true if this region is different from the \a other region;
    otherwise returns false.
*/

/*!
   Returns the region as a QVariant
*/
QRegion::operator QVariant() const
{
    return QVariant(QVariant::Region, this);
}

/*!
    \fn bool QRegion::operator==(const QRegion &r) const

    Returns true if the region is equal to \a r; otherwise returns
    false.
*/

/*!
    \fn bool QRegion::isNull() const

    Use isEmpty() instead.
*/


/*!
    \fn void QRegion::translate(int dx, int dy)

    Translates (moves) the region \a dx along the X axis and \a dy
    along the Y axis.
*/

/*!
    \fn QRegion QRegion::translated(const QPoint &p) const
    \overload
    \since 4.1

    Returns a copy of the regtion that is translated \a{p}\e{.x()}
    along the x axis and \a{p}\e{.y()} along the y axis, relative to
    the current position.  Positive values move the rectangle to the
    right and down.

    \sa translate()
*/

/*!
    \since 4.1

    Returns a copy of the region that is translated \a dx along the
    x axis and \a dy along the y axis, relative to the current
    position. Positive values move the region to the right and
    down.

    \sa translate()
*/

QRegion
QRegion::translated(int dx, int dy) const
{
    QRegion ret(*this);
    ret.translate(dx, dy);
    return ret;
}


inline bool rect_intersects(const QRect &r1, const QRect &r2)
{
    return (r1.right() >= r2.left() && r1.left() <= r2.right() &&
            r1.bottom() >= r2.top() && r1.top() <= r2.bottom());
}

/*!
    \since 4.2

    Returns true if this region intersects with \a region, otherwise
    returns false.
*/
bool QRegion::intersects(const QRegion &region) const
{
    if (isEmpty() || region.isEmpty())
        return false;

    if (!rect_intersects(boundingRect(), region.boundingRect()))
        return false;
    if (rectCount() == 1 && region.rectCount() == 1)
        return true;

    const QVector<QRect> myRects = rects();
    const QVector<QRect> otherRects = region.rects();

    for (QVector<QRect>::const_iterator i1 = myRects.constBegin(); i1 < myRects.constEnd(); ++i1)
        for (QVector<QRect>::const_iterator i2 = otherRects.constBegin(); i2 < otherRects.constEnd(); ++i2)
            if (rect_intersects(*i1, *i2))
                return true;
    return false;
}

/*!
    \fn bool QRegion::intersects(const QRect &rect) const
    \since 4.2

    Returns true if this region intersects with \a rect, otherwise
    returns false.
*/


#if !defined (Q_OS_UNIX) && !defined (Q_WS_WIN)
/*!
    \overload
    \since 4.4
*/
QRegion QRegion::intersect(const QRect &r) const
{
    return intersect(QRegion(r));
}
#endif

/*!
    \obsolete
    \fn int QRegion::numRects() const
    \since 4.4

    Returns the number of rectangles that will be returned in rects().
*/

/*!
    \fn int QRegion::rectCount() const
    \since 4.6

    Returns the number of rectangles that will be returned in rects().
*/

/*!
    \fn bool QRegion::isEmpty() const

    Returns true if the region is empty; otherwise returns false. An
    empty region is a region that contains no points.

    Example:
    \snippet doc/src/snippets/code/src_gui_painting_qregion_unix.cpp 0
*/

/*!
    \fn bool QRegion::contains(const QPoint &p) const

    Returns true if the region contains the point \a p; otherwise
    returns false.
*/

/*!
    \fn bool QRegion::contains(const QRect &r) const
    \overload

    Returns true if the region overlaps the rectangle \a r; otherwise
    returns false.
*/

/*!
    \fn QRegion QRegion::unite(const QRegion &r) const
    \obsolete

    Use united(\a r) instead.
*/

/*!
    \fn QRegion QRegion::unite(const QRect &rect) const
    \since 4.4
    \obsolete

    Use united(\a rect) instead.
*/

/*!
    \fn QRegion QRegion::united(const QRect &rect) const
    \since 4.4

    Returns a region which is the union of this region and the given \a rect.

    \sa intersected(), subtracted(), xored()
*/

/*!
    \fn QRegion QRegion::united(const QRegion &r) const
    \since 4.2

    Returns a region which is the union of this region and \a r.

    \img runion.png Region Union

    The figure shows the union of two elliptical regions.

    \sa intersected(), subtracted(), xored()
*/

/*!
    \fn QRegion QRegion::intersect(const QRegion &r) const
    \obsolete

    Use intersected(\a r) instead.
*/

/*!
    \fn QRegion QRegion::intersect(const QRect &rect) const
    \since 4.4
    \obsolete

    Use intersected(\a rect) instead.
*/

/*!
    \fn QRegion QRegion::intersected(const QRect &rect) const
    \since 4.4

    Returns a region which is the intersection of this region and the given \a rect.

    \sa subtracted(), united(), xored()
*/

/*!
    \fn QRegion QRegion::intersected(const QRegion &r) const
    \since 4.2

    Returns a region which is the intersection of this region and \a r.

    \img rintersect.png Region Intersection

    The figure shows the intersection of two elliptical regions.

    \sa subtracted(), united(), xored()
*/

/*!
    \fn QRegion QRegion::subtract(const QRegion &r) const
    \obsolete

    Use subtracted(\a r) instead.
*/

/*!
    \fn QRegion QRegion::subtracted(const QRegion &r) const
    \since 4.2

    Returns a region which is \a r subtracted from this region.

    \img rsubtract.png Region Subtraction

    The figure shows the result when the ellipse on the right is
    subtracted from the ellipse on the left (\c {left - right}).

    \sa intersected(), united(), xored()
*/

/*!
    \fn QRegion QRegion::eor(const QRegion &r) const
    \obsolete

    Use xored(\a r) instead.
*/

/*!
    \fn QRegion QRegion::xored(const QRegion &r) const
    \since 4.2

    Returns a region which is the exclusive or (XOR) of this region
    and \a r.

    \img rxor.png Region XORed

    The figure shows the exclusive or of two elliptical regions.

    \sa intersected(), united(), subtracted()
*/

/*!
    \fn QRect QRegion::boundingRect() const

    Returns the bounding rectangle of this region. An empty region
    gives a rectangle that is QRect::isNull().
*/

/*!
    \fn QVector<QRect> QRegion::rects() const

    Returns an array of non-overlapping rectangles that make up the
    region.

    The union of all the rectangles is equal to the original region.
*/

/*!
    \fn void QRegion::setRects(const QRect *rects, int number)

    Sets the region using the array of rectangles specified by \a rects and
    \a number.
    The rectangles \e must be optimally Y-X sorted and follow these restrictions:

    \list
    \o The rectangles must not intersect.
    \o All rectangles with a given top coordinate must have the same height.
    \o No two rectangles may abut horizontally (they should be combined
       into a single wider rectangle in that case).
    \o The rectangles must be sorted in ascending order, with Y as the major
       sort key and X as the minor sort key.
    \endlist
    \omit
    Only some platforms have these restrictions (Qt for Embedded Linux, X11 and Mac OS X).
    \endomit
*/

namespace {

struct Segment
{
    Segment() {}
    Segment(const QPoint &p)
        : added(false)
        , point(p)
    {
    }

    int left() const
    {
        return qMin(point.x(), next->point.x());
    }

    int right() const
    {
        return qMax(point.x(), next->point.x());
    }

    bool overlaps(const Segment &other) const
    {
        return left() < other.right() && other.left() < right();
    }

    void connect(Segment &other)
    {
        next = &other;
        other.prev = this;

        horizontal = (point.y() == other.point.y());
    }

    void merge(Segment &other)
    {
        if (right() <= other.right()) {
            QPoint p = other.point;
            Segment *oprev = other.prev;

            other.point = point;
            other.prev = prev;
            prev->next = &other;

            point = p;
            prev = oprev;
            oprev->next = this;
        } else {
            Segment *onext = other.next;
            other.next = next;
            next->prev = &other;

            next = onext;
            next->prev = this;
        }
    }

    int horizontal : 1;
    int added : 1;

    QPoint point;
    Segment *prev;
    Segment *next;
};

void mergeSegments(Segment *a, int na, Segment *b, int nb)
{
    int i = 0;
    int j = 0;

    while (i != na && j != nb) {
        Segment &sa = a[i];
        Segment &sb = b[j];
        const int ra = sa.right();
        const int rb = sb.right();
        if (sa.overlaps(sb))
            sa.merge(sb);
        i += (rb >= ra);
        j += (ra >= rb);
    }
}

void addSegmentsToPath(Segment *segment, QPainterPath &path)
{
    Segment *current = segment;
    path.moveTo(current->point);

    current->added = true;

    Segment *last = current;
    current = current->next;
    while (current != segment) {
        if (current->horizontal != last->horizontal)
            path.lineTo(current->point);
        current->added = true;
        last = current;
        current = current->next;
    }
}

}

Q_AUTOTEST_EXPORT QPainterPath qt_regionToPath(const QRegion &region)
{
    QPainterPath result;
    if (region.rectCount() == 1) {
        result.addRect(region.boundingRect());
        return result;
    }

    const QVector<QRect> rects = region.rects();

    QVarLengthArray<Segment> segments;
    segments.resize(4 * rects.size());

    const QRect *rect = rects.constData();
    const QRect *end = rect + rects.size();

    int lastRowSegmentCount = 0;
    Segment *lastRowSegments = 0;

    int lastSegment = 0;
    int lastY = 0;
    while (rect != end) {
        const int y = rect[0].y();
        int count = 0;
        while (&rect[count] != end && rect[count].y() == y)
            ++count;

        for (int i = 0; i < count; ++i) {
            int offset = lastSegment + i;
            segments[offset] = Segment(rect[i].topLeft());
            segments[offset += count] = Segment(rect[i].topRight() + QPoint(1, 0));
            segments[offset += count] = Segment(rect[i].bottomRight() + QPoint(1, 1));
            segments[offset += count] = Segment(rect[i].bottomLeft() + QPoint(0, 1));

            offset = lastSegment + i;
            for (int j = 0; j < 4; ++j)
                segments[offset + j * count].connect(segments[offset + ((j + 1) % 4) * count]);
        }

        if (lastRowSegments && lastY == y)
            mergeSegments(lastRowSegments, lastRowSegmentCount, &segments[lastSegment], count);

        lastRowSegments = &segments[lastSegment + 2 * count];
        lastRowSegmentCount = count;
        lastSegment += 4 * count;
        lastY = y + rect[0].height();
        rect += count;
    }

    for (int i = 0; i < lastSegment; ++i) {
        Segment *segment = &segments[i];
        if (!segment->added)
            addSegmentsToPath(segment, result);
    }

    return result;
}

#if defined(Q_OS_UNIX) || defined(Q_WS_WIN)

//#define QT_REGION_DEBUG
/*
 *   clip region
 */

struct QRegionPrivate {
    int numRects;
    QVector<QRect> rects;
    QRect extents;
    QRect innerRect;
    int innerArea;

    inline QRegionPrivate() : numRects(0), innerArea(-1) {}
    inline QRegionPrivate(const QRect &r) {
        numRects = 1;
        extents = r;
        innerRect = r;
        innerArea = r.width() * r.height();
    }

    inline QRegionPrivate(const QRegionPrivate &r) {
        rects = r.rects;
        numRects = r.numRects;
        extents = r.extents;
        innerRect = r.innerRect;
        innerArea = r.innerArea;
    }

    inline QRegionPrivate &operator=(const QRegionPrivate &r) {
        rects = r.rects;
        numRects = r.numRects;
        extents = r.extents;
        innerRect = r.innerRect;
        innerArea = r.innerArea;
        return *this;
    }

    void intersect(const QRect &r);

    /*
     * Returns true if r is guaranteed to be fully contained in this region.
     * A false return value does not guarantee the opposite.
     */
    inline bool contains(const QRegionPrivate &r) const {
        return contains(r.extents);
    }

    inline bool contains(const QRect &r2) const {
        const QRect &r1 = innerRect;
        return r2.left() >= r1.left() && r2.right() <= r1.right()
            && r2.top() >= r1.top() && r2.bottom() <= r1.bottom();
    }

    /*
     * Returns true if this region is guaranteed to be fully contained in r.
     */
    inline bool within(const QRect &r1) const {
        const QRect &r2 = extents;
        return r2.left() >= r1.left() && r2.right() <= r1.right()
            && r2.top() >= r1.top() && r2.bottom() <= r1.bottom();
    }

    inline void updateInnerRect(const QRect &rect) {
        const int area = rect.width() * rect.height();
        if (area > innerArea) {
            innerArea = area;
            innerRect = rect;
        }
    }

    inline void vectorize() {
        if (numRects == 1) {
            if (!rects.size())
                rects.resize(1);
            rects[0] = extents;
        }
    }

    inline void append(const QRect *r);
    void append(const QRegionPrivate *r);
    void prepend(const QRect *r);
    void prepend(const QRegionPrivate *r);
    inline bool canAppend(const QRect *r) const;
    inline bool canAppend(const QRegionPrivate *r) const;
    inline bool canPrepend(const QRect *r) const;
    inline bool canPrepend(const QRegionPrivate *r) const;

    inline bool mergeFromRight(QRect *left, const QRect *right);
    inline bool mergeFromLeft(QRect *left, const QRect *right);
    inline bool mergeFromBelow(QRect *top, const QRect *bottom,
                               const QRect *nextToTop,
                               const QRect *nextToBottom);
    inline bool mergeFromAbove(QRect *bottom, const QRect *top,
                               const QRect *nextToBottom,
                               const QRect *nextToTop);

#ifdef QT_REGION_DEBUG
    void selfTest() const;
#endif
};

static inline bool isEmptyHelper(const QRegionPrivate *preg)
{
    return !preg || preg->numRects == 0;
}

static inline bool canMergeFromRight(const QRect *left, const QRect *right)
{
    return (right->top() == left->top()
            && right->bottom() == left->bottom()
            && right->left() <= (left->right() + 1));
}

static inline bool canMergeFromLeft(const QRect *right, const QRect *left)
{
    return canMergeFromRight(left, right);
}

bool QRegionPrivate::mergeFromRight(QRect *left, const QRect *right)
{
    if (canMergeFromRight(left, right)) {
        left->setRight(right->right());
        updateInnerRect(*left);
        return true;
    }
    return false;
}

bool QRegionPrivate::mergeFromLeft(QRect *right, const QRect *left)
{
    if (canMergeFromLeft(right, left)) {
        right->setLeft(left->left());
        updateInnerRect(*right);
        return true;
    }
    return false;
}

static inline bool canMergeFromBelow(const QRect *top, const QRect *bottom,
                                     const QRect *nextToTop,
                                     const QRect *nextToBottom)
{
    if (nextToTop && nextToTop->y() == top->y())
        return false;
    if (nextToBottom && nextToBottom->y() == bottom->y())
        return false;

    return ((top->bottom() >= (bottom->top() - 1))
            && top->left() == bottom->left()
            && top->right() == bottom->right());
}

bool QRegionPrivate::mergeFromBelow(QRect *top, const QRect *bottom,
                                    const QRect *nextToTop,
                                    const QRect *nextToBottom)
{
    if (canMergeFromBelow(top, bottom, nextToTop, nextToBottom)) {
        top->setBottom(bottom->bottom());
        updateInnerRect(*top);
        return true;
    }
    return false;
}

bool QRegionPrivate::mergeFromAbove(QRect *bottom, const QRect *top,
                                    const QRect *nextToBottom,
                                    const QRect *nextToTop)
{
    if (canMergeFromBelow(top, bottom, nextToTop, nextToBottom)) {
        bottom->setTop(top->top());
        updateInnerRect(*bottom);
        return true;
    }
    return false;
}

static inline QRect qt_rect_intersect_normalized(const QRect &r1,
                                                 const QRect &r2)
{
    QRect r;
    r.setLeft(qMax(r1.left(), r2.left()));
    r.setRight(qMin(r1.right(), r2.right()));
    r.setTop(qMax(r1.top(), r2.top()));
    r.setBottom(qMin(r1.bottom(), r2.bottom()));
    return r;
}

void QRegionPrivate::intersect(const QRect &rect)
{
    Q_ASSERT(extents.intersects(rect));
    Q_ASSERT(numRects > 1);

#ifdef QT_REGION_DEBUG
    selfTest();
#endif

    const QRect r = rect.normalized();
    extents = QRect();
    innerRect = QRect();
    innerArea = -1;

    QRect *dest = rects.data();
    const QRect *src = dest;
    int n = numRects;
    numRects = 0;
    while (n--) {
        *dest = qt_rect_intersect_normalized(*src++, r);
        if (dest->isEmpty())
            continue;

        if (numRects == 0) {
            extents = *dest;
        } else {
            extents.setLeft(qMin(extents.left(), dest->left()));
            // hw: extents.top() will never change after initialization
            //extents.setTop(qMin(extents.top(), dest->top()));
            extents.setRight(qMax(extents.right(), dest->right()));
            extents.setBottom(qMax(extents.bottom(), dest->bottom()));

            const QRect *nextToLast = (numRects > 1 ? dest - 2 : 0);

            // mergeFromBelow inlined and optimized
            if (canMergeFromBelow(dest - 1, dest, nextToLast, 0)) {
                if (!n || src->y() != dest->y() || src->left() > r.right()) {
                    QRect *prev = dest - 1;
                    prev->setBottom(dest->bottom());
                    updateInnerRect(*prev);
                    continue;
                }
            }
        }
        updateInnerRect(*dest);
        ++dest;
        ++numRects;
    }
#ifdef QT_REGION_DEBUG
    selfTest();
#endif
}

void QRegionPrivate::append(const QRect *r)
{
    Q_ASSERT(!r->isEmpty());

    QRect *myLast = (numRects == 1 ? &extents : rects.data() + (numRects - 1));
    if (mergeFromRight(myLast, r)) {
        if (numRects > 1) {
            const QRect *nextToTop = (numRects > 2 ? myLast - 2 : 0);
            if (mergeFromBelow(myLast - 1, myLast, nextToTop, 0))
                --numRects;
        }
    } else if (mergeFromBelow(myLast, r, (numRects > 1 ? myLast - 1 : 0), 0)) {
        // nothing
    } else {
        vectorize();
        ++numRects;
        updateInnerRect(*r);
        if (rects.size() < numRects)
            rects.resize(numRects);
        rects[numRects - 1] = *r;
    }
    extents.setCoords(qMin(extents.left(), r->left()),
                      qMin(extents.top(), r->top()),
                      qMax(extents.right(), r->right()),
                      qMax(extents.bottom(), r->bottom()));

#ifdef QT_REGION_DEBUG
    selfTest();
#endif
}

void QRegionPrivate::append(const QRegionPrivate *r)
{
    Q_ASSERT(!isEmptyHelper(r));

    if (r->numRects == 1) {
        append(&r->extents);
        return;
    }

    vectorize();

    QRect *destRect = rects.data() + numRects;
    const QRect *srcRect = r->rects.constData();
    int numAppend = r->numRects;

    // try merging
    {
        const QRect *rFirst = srcRect;
        QRect *myLast = destRect - 1;
        const QRect *nextToLast = (numRects > 1 ? myLast - 1 : 0);
        if (mergeFromRight(myLast, rFirst)) {
            ++srcRect;
            --numAppend;
            const QRect *rNextToFirst = (numAppend > 1 ? rFirst + 2 : 0);
            if (mergeFromBelow(myLast, rFirst + 1, nextToLast, rNextToFirst)) {
                ++srcRect;
                --numAppend;
            }
            if (numRects  > 1) {
                nextToLast = (numRects > 2 ? myLast - 2 : 0);
                rNextToFirst = (numAppend > 0 ? srcRect : 0);
                if (mergeFromBelow(myLast - 1, myLast, nextToLast, rNextToFirst)) {
                    --destRect;
                    --numRects;
                }
            }
        } else if (mergeFromBelow(myLast, rFirst, nextToLast, rFirst + 1)) {
            ++srcRect;
            --numAppend;
        }
    }

    // append rectangles
    if (numAppend > 0) {
        const int newNumRects = numRects + numAppend;
        if (newNumRects > rects.size()) {
            rects.resize(newNumRects);
            destRect = rects.data() + numRects;
        }
        memcpy(destRect, srcRect, numAppend * sizeof(QRect));

        numRects = newNumRects;
    }

    // update inner rectangle
    if (innerArea < r->innerArea) {
        innerArea = r->innerArea;
        innerRect = r->innerRect;
    }

    // update extents
    destRect = &extents;
    srcRect = &r->extents;
    extents.setCoords(qMin(destRect->left(), srcRect->left()),
                      qMin(destRect->top(), srcRect->top()),
                      qMax(destRect->right(), srcRect->right()),
                      qMax(destRect->bottom(), srcRect->bottom()));

#ifdef QT_REGION_DEBUG
    selfTest();
#endif
}

void QRegionPrivate::prepend(const QRegionPrivate *r)
{
    Q_ASSERT(!isEmptyHelper(r));

    if (r->numRects == 1) {
        prepend(&r->extents);
        return;
    }

    vectorize();

    int numPrepend = r->numRects;
    int numSkip = 0;

    // try merging
    {
        QRect *myFirst = rects.data();
        const QRect *nextToFirst = (numRects > 1 ? myFirst + 1 : 0);
        const QRect *rLast = r->rects.constData() + r->numRects - 1;
        const QRect *rNextToLast = (r->numRects > 1 ? rLast - 1 : 0);
        if (mergeFromLeft(myFirst, rLast)) {
            --numPrepend;
            --rLast;
            rNextToLast = (numPrepend > 1 ? rLast - 1 : 0);
            if (mergeFromAbove(myFirst, rLast, nextToFirst, rNextToLast)) {
                --numPrepend;
                --rLast;
            }
            if (numRects  > 1) {
                nextToFirst = (numRects > 2? myFirst + 2 : 0);
                rNextToLast = (numPrepend > 0 ? rLast : 0);
                if (mergeFromAbove(myFirst + 1, myFirst, nextToFirst, rNextToLast)) {
                    --numRects;
                    ++numSkip;
                }
            }
        } else if (mergeFromAbove(myFirst, rLast, nextToFirst, rNextToLast)) {
            --numPrepend;
        }
    }

    if (numPrepend > 0) {
        const int newNumRects = numRects + numPrepend;
        if (newNumRects > rects.size())
            rects.resize(newNumRects);

        // move existing rectangles
        memmove(rects.data() + numPrepend, rects.constData() + numSkip,
                numRects * sizeof(QRect));

        // prepend new rectangles
        memcpy(rects.data(), r->rects.constData(), numPrepend * sizeof(QRect));

        numRects = newNumRects;
    }

    // update inner rectangle
    if (innerArea < r->innerArea) {
        innerArea = r->innerArea;
        innerRect = r->innerRect;
    }

    // update extents
    extents.setCoords(qMin(extents.left(), r->extents.left()),
                      qMin(extents.top(), r->extents.top()),
                      qMax(extents.right(), r->extents.right()),
                      qMax(extents.bottom(), r->extents.bottom()));

#ifdef QT_REGION_DEBUG
    selfTest();
#endif
}

void QRegionPrivate::prepend(const QRect *r)
{
    Q_ASSERT(!r->isEmpty());

    QRect *myFirst = (numRects == 1 ? &extents : rects.data());
    if (mergeFromLeft(myFirst, r)) {
        if (numRects > 1) {
            const QRect *nextToFirst = (numRects > 2 ? myFirst + 2 : 0);
            if (mergeFromAbove(myFirst + 1, myFirst, nextToFirst, 0)) {
                --numRects;
                memmove(rects.data(), rects.constData() + 1,
                        numRects * sizeof(QRect));
            }
        }
    } else if (mergeFromAbove(myFirst, r, (numRects > 1 ? myFirst + 1 : 0), 0)) {
        // nothing
    } else {
        vectorize();
        ++numRects;
        updateInnerRect(*r);
        rects.prepend(*r);
    }
    extents.setCoords(qMin(extents.left(), r->left()),
                      qMin(extents.top(), r->top()),
                      qMax(extents.right(), r->right()),
                      qMax(extents.bottom(), r->bottom()));

#ifdef QT_REGION_DEBUG
    selfTest();
#endif
}

bool QRegionPrivate::canAppend(const QRect *r) const
{
    Q_ASSERT(!r->isEmpty());

    const QRect *myLast = (numRects == 1) ? &extents : (rects.constData() + (numRects - 1));
    if (r->top() > myLast->bottom())
        return true;
    if (r->top() == myLast->top()
        && r->height() == myLast->height()
        && r->left() > myLast->right())
    {
        return true;
    }

    return false;
}

bool QRegionPrivate::canAppend(const QRegionPrivate *r) const
{
    return canAppend(r->numRects == 1 ? &r->extents : r->rects.constData());
}

bool QRegionPrivate::canPrepend(const QRect *r) const
{
    Q_ASSERT(!r->isEmpty());

    const QRect *myFirst = (numRects == 1) ? &extents : rects.constData();
    if (r->bottom() < myFirst->top()) // not overlapping
        return true;
    if (r->top() == myFirst->top()
        && r->height() == myFirst->height()
        && r->right() < myFirst->left())
    {
        return true;
    }

    return false;
}

bool QRegionPrivate::canPrepend(const QRegionPrivate *r) const
{
    return canPrepend(r->numRects == 1 ? &r->extents : r->rects.constData() + r->numRects - 1);
}

#ifdef QT_REGION_DEBUG
void QRegionPrivate::selfTest() const
{
    if (numRects == 0) {
        Q_ASSERT(extents.isEmpty());
        Q_ASSERT(innerRect.isEmpty());
        return;
    }

    Q_ASSERT(innerArea == (innerRect.width() * innerRect.height()));

    if (numRects == 1) {
        Q_ASSERT(innerRect == extents);
        Q_ASSERT(!innerRect.isEmpty());
        return;
    }

    for (int i = 0; i < numRects; ++i) {
        const QRect r = rects.at(i);
        if ((r.width() * r.height()) > innerArea)
            qDebug() << "selfTest(): innerRect" << innerRect << '<' << r;
    }

    QRect r = rects.first();
    for (int i = 1; i < numRects; ++i) {
        const QRect r2 = rects.at(i);
        Q_ASSERT(!r2.isEmpty());
        if (r2.y() == r.y()) {
            Q_ASSERT(r.bottom() == r2.bottom());
            Q_ASSERT(r.right() < (r2.left() + 1));
        } else {
            Q_ASSERT(r2.y() >= r.bottom());
        }
        r = r2;
    }
}
#endif // QT_REGION_DEBUG

#if defined(Q_WS_X11)
QT_BEGIN_INCLUDE_NAMESPACE
# include "qregion_x11.cpp"
QT_END_INCLUDE_NAMESPACE
#elif defined(Q_WS_MAC)
QT_BEGIN_INCLUDE_NAMESPACE
# include "qregion_mac.cpp"
QT_END_INCLUDE_NAMESPACE
#elif defined(Q_WS_WIN)
QT_BEGIN_INCLUDE_NAMESPACE
# include "qregion_win.cpp"
QT_END_INCLUDE_NAMESPACE
#elif defined(Q_WS_QWS) || defined(Q_WS_QPA)
static QRegionPrivate qrp;
QRegion::QRegionData QRegion::shared_empty = {Q_BASIC_ATOMIC_INITIALIZER(1), &qrp};
#endif

typedef void (*OverlapFunc)(register QRegionPrivate &dest, register const QRect *r1, const QRect *r1End,
                            register const QRect *r2, const QRect *r2End, register int y1, register int y2);
typedef void (*NonOverlapFunc)(register QRegionPrivate &dest, register const QRect *r, const QRect *rEnd,
                               register int y1, register int y2);

static bool EqualRegion(const QRegionPrivate *r1, const QRegionPrivate *r2);
static void UnionRegion(const QRegionPrivate *reg1, const QRegionPrivate *reg2, QRegionPrivate &dest);
static void miRegionOp(register QRegionPrivate &dest, const QRegionPrivate *reg1, const QRegionPrivate *reg2,
                       OverlapFunc overlapFunc, NonOverlapFunc nonOverlap1Func,
                       NonOverlapFunc nonOverlap2Func);

#define RectangleOut 0
#define RectangleIn 1
#define RectanglePart 2
#define EvenOddRule 0
#define WindingRule 1

// START OF region.h extract
/* $XConsortium: region.h,v 11.14 94/04/17 20:22:20 rws Exp $ */
/************************************************************************

Copyright (c) 1987  X Consortium

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of the X Consortium shall not be
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from the X Consortium.


Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of Digital not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

************************************************************************/

#ifndef _XREGION_H
#define _XREGION_H

QT_BEGIN_INCLUDE_NAMESPACE
#include <limits.h>
QT_END_INCLUDE_NAMESPACE

/*  1 if two BOXes overlap.
 *  0 if two BOXes do not overlap.
 *  Remember, x2 and y2 are not in the region
 */
#define EXTENTCHECK(r1, r2) \
        ((r1)->right() >= (r2)->left() && \
         (r1)->left() <= (r2)->right() && \
         (r1)->bottom() >= (r2)->top() && \
         (r1)->top() <= (r2)->bottom())

/*
 *  update region extents
 */
#define EXTENTS(r,idRect){\
            if((r)->left() < (idRect)->extents.left())\
              (idRect)->extents.setLeft((r)->left());\
            if((r)->top() < (idRect)->extents.top())\
              (idRect)->extents.setTop((r)->top());\
            if((r)->right() > (idRect)->extents.right())\
              (idRect)->extents.setRight((r)->right());\
            if((r)->bottom() > (idRect)->extents.bottom())\
              (idRect)->extents.setBottom((r)->bottom());\
        }

/*
 *   Check to see if there is enough memory in the present region.
 */
#define MEMCHECK(dest, rect, firstrect){\
        if ((dest).numRects >= ((dest).rects.size()-1)){\
          firstrect.resize(firstrect.size() * 2); \
          (rect) = (firstrect).data() + (dest).numRects;\
        }\
      }


/*
 * number of points to buffer before sending them off
 * to scanlines(): Must be an even number
 */
#define NUMPTSTOBUFFER 200

/*
 * used to allocate buffers for points and link
 * the buffers together
 */
typedef struct _POINTBLOCK {
    int data[NUMPTSTOBUFFER * sizeof(QPoint)];
    QPoint *pts;
    struct _POINTBLOCK *next;
} POINTBLOCK;

#endif
// END OF region.h extract

// START OF Region.c extract
/* $XConsortium: Region.c /main/30 1996/10/22 14:21:24 kaleb $ */
/************************************************************************

Copyright (c) 1987, 1988