src/gui/painting/qregion_qws.cpp
changeset 0 1918ee327afb
child 4 3b1da2848fc7
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/gui/painting/qregion_qws.cpp	Mon Jan 11 14:00:40 2010 +0000
@@ -0,0 +1,3183 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+// XXX - add appropriate friendship relationships
+#define private public
+#include "qregion.h"
+#undef private
+#include "qpainterpath.h"
+#include "qpolygon.h"
+#include "qbuffer.h"
+#include "qimage.h"
+#include <qdebug.h>
+#include "qbitmap.h"
+#include <stdlib.h>
+#include <qatomic.h>
+#include <qsemaphore.h>
+
+QT_BEGIN_NAMESPACE
+
+class QFastMutex
+{
+    QAtomicInt contenders;
+    QSemaphore semaphore;
+public:
+    inline QFastMutex()
+        : contenders(0), semaphore(0)
+    { }
+    inline void lock()
+    {
+        if (contenders.fetchAndAddAcquire(1) != 0) {
+            semaphore.acquire();
+            contenders.deref();
+        }
+    }
+    inline bool tryLock()
+    {
+        return contenders.testAndSetAcquire(0, 1);
+    }
+    inline void unlock()
+    {
+        if (!contenders.testAndSetRelease(1, 0))
+            semaphore.release();
+    }
+};
+
+
+/*
+ *  1 if r1 contains r2
+ *  0 if r1 does not completely contain r2
+ */ 
+#define CONTAINSCHECK(r1, r2) \
+    ((r2).left() >= (r1).left() && (r2).right() <= (r1).right() && \
+     (r2).top() >= (r1).top() && (r2).bottom() <= (r1).bottom())
+
+/*
+ *   clip region
+ */
+struct QRegionPrivate : public QRegion::QRegionData {
+    enum { Single, Vector } mode;
+    int numRects;
+    QVector<QRect> rects;
+    QRect single;
+    QRect extents;
+    QRect innerRect;
+    union {
+        int innerArea;
+        QRegionPrivate *next;
+    };
+
+    inline void vector()
+    {
+        if(mode != Vector && numRects) {
+            if(rects.size() < 1) rects.resize(1);
+            rects[0] = single;
+        }
+        mode = Vector;
+    }
+
+    inline QRegionPrivate() : mode(Single), numRects(0), innerArea(-1) {}
+    inline QRegionPrivate(const QRect &r) : mode(Single) {
+        numRects = 1;
+//        rects[0] = r;
+        single = r;
+        extents = r;
+        innerRect = r;
+        innerArea = r.width() * r.height();
+    }
+
+    inline QRegionPrivate(const QRegionPrivate &r) {
+        mode = r.mode;
+        rects = r.rects;
+        single = r.single;
+        numRects = r.numRects;
+        extents = r.extents;
+        innerRect = r.innerRect;
+        innerArea = r.innerArea;
+    }
+
+    inline QRegionPrivate &operator=(const QRegionPrivate &r) {
+        mode = r.mode;
+        rects = r.rects;
+        single = r.single;
+        numRects = r.numRects;
+        extents = r.extents;
+        innerRect = r.innerRect;
+        innerArea = r.innerArea;
+        return *this;
+    }
+
+    /*
+     * 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 {
+        const QRect &r1 = innerRect;
+        const QRect &r2 = r.extents;
+        return CONTAINSCHECK(r1, r2);
+    }
+
+    inline void updateInnerRect(const QRect &rect) {
+        const int area = rect.width() * rect.height();
+        if (area > innerArea) {
+            innerArea = area;
+            innerRect = rect;
+        }
+    }
+
+    void append(const QRegionPrivate *r);
+    void prepend(const QRegionPrivate *r);
+    inline bool canAppend(const QRegionPrivate *r) const;
+    inline bool canPrepend(const QRegionPrivate *r) const;
+};
+
+static QRegionPrivate *qt_nextRegionPtr = 0;
+static QFastMutex qt_nextRegionLock;
+
+static QRegionPrivate *qt_allocRegionMemory()
+{
+    QRegionPrivate *rv = 0;
+    qt_nextRegionLock.lock();
+
+    if(qt_nextRegionPtr) {
+        rv = qt_nextRegionPtr;
+        qt_nextRegionPtr = rv->next;
+    } else {
+        qt_nextRegionPtr = 
+            (QRegionPrivate *)malloc(256 * sizeof(QRegionPrivate));
+        for(int ii = 0; ii < 256; ++ii) {
+            if(ii == 255) {
+                qt_nextRegionPtr[ii].next = 0;
+            } else {
+                qt_nextRegionPtr[ii].next = &qt_nextRegionPtr[ii + 1];
+            }
+        }
+
+        rv = qt_nextRegionPtr;
+        qt_nextRegionPtr = rv->next;
+    }
+
+    qt_nextRegionLock.unlock();
+    return rv;
+}
+
+static void qt_freeRegionMemory(QRegionPrivate *rp)
+{
+    qt_nextRegionLock.lock();
+    rp->next = qt_nextRegionPtr;
+    qt_nextRegionPtr = rp;
+    qt_nextRegionLock.unlock();
+}
+
+static QRegionPrivate *qt_allocRegion()
+{
+    QRegionPrivate *mem = qt_allocRegionMemory();
+    return new (mem) QRegionPrivate;
+}
+
+static QRegionPrivate *qt_allocRegion(const QRect &r)
+{
+    QRegionPrivate *mem = qt_allocRegionMemory();
+    return new (mem) QRegionPrivate(r);
+}
+
+static QRegionPrivate *qt_allocRegion(const QRegionPrivate &r)
+{
+    QRegionPrivate *mem = qt_allocRegionMemory();
+    return new (mem) QRegionPrivate(r);
+}
+
+void qt_freeRegion(QRegionPrivate *rp)
+{
+    rp->~QRegionPrivate();
+    qt_freeRegionMemory(rp);
+//    delete rp;
+}
+
+static inline bool isEmptyHelper(const QRegionPrivate *preg)
+{
+    return !preg || preg->numRects == 0;
+}
+
+void QRegionPrivate::append(const QRegionPrivate *r)
+{
+    Q_ASSERT(!isEmptyHelper(r));
+
+    vector();
+    QRect *destRect = rects.data() + numRects;
+    const QRect *srcRect = (r->mode==Vector)?r->rects.constData():&r->single;
+    int numAppend = r->numRects;
+
+    // test for merge in x direction
+    {
+        const QRect *rFirst = srcRect;
+        QRect *myLast = rects.data() + (numRects - 1);
+        if (rFirst->top() == myLast->top()
+            && rFirst->height() == myLast->height()
+            && rFirst->left() == (myLast->right() + 1))
+        {
+            myLast->setWidth(myLast->width() + rFirst->width());
+            updateInnerRect(*myLast);
+            ++srcRect;
+            --numAppend;
+        }
+    }
+
+    // append rectangles
+    const int newNumRects = numRects + numAppend;
+    if (newNumRects > rects.size()) {
+        rects.resize(newNumRects);
+        destRect = rects.data() + numRects;
+    }
+    memcpy(destRect, srcRect, numAppend * sizeof(QRect));
+
+    // 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()));
+
+    numRects = newNumRects;
+}
+
+void QRegionPrivate::prepend(const QRegionPrivate *r)
+{
+#if 1
+    Q_UNUSED(r);
+#else
+    // XXX ak: does not respect vectorization of region
+
+    Q_ASSERT(!isEmpty(r));
+
+    // move existing rectangles
+    memmove(rects.data() + r->numRects, rects.constData(),
+            numRects * sizeof(QRect));
+
+    // prepend new rectangles
+    memcpy(rects.data(), r->rects.constData(), r->numRects * sizeof(QRect));
+
+    // 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()));
+
+    numRects = newNumRects;
+#endif
+}
+
+bool QRegionPrivate::canAppend(const QRegionPrivate *r) const
+{
+    Q_ASSERT(!isEmptyHelper(r));
+
+    const QRect *rFirst = (r->mode==Vector)?r->rects.constData():&r->single;
+    const QRect *myLast = (mode==Vector)?(rects.constData() + (numRects - 1)):&single;
+    // XXX: possible improvements:
+    //   - nFirst->top() == myLast->bottom() + 1, must possibly merge bands
+    if (rFirst->top() > (myLast->bottom() + 1)
+        || (rFirst->top() == myLast->top()
+            && rFirst->height() == myLast->height()
+            && rFirst->left() > myLast->right()))
+    {
+        return true;
+    }
+
+    return false;
+}
+
+bool QRegionPrivate::canPrepend(const QRegionPrivate *r) const
+{
+#if 1
+    Q_UNUSED(r);
+    return false;
+#else
+    return r->canAppend(this);
+#endif
+}
+
+#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_QWS)
+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 BOXs overlap.
+ *  0 if two BOXs 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 {
+    QPoint pts[NUMPTSTOBUFFER];
+    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  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, 1988 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.
+
+************************************************************************/
+/*
+ * The functions in this file implement the Region abstraction, similar to one
+ * used in the X11 sample server. A Region is simply an area, as the name
+ * implies, and is implemented as a "y-x-banded" array of rectangles. To
+ * explain: Each Region is made up of a certain number of rectangles sorted
+ * by y coordinate first, and then by x coordinate.
+ *
+ * Furthermore, the rectangles are banded such that every rectangle with a
+ * given upper-left y coordinate (y1) will have the same lower-right y
+ * coordinate (y2) and vice versa. If a rectangle has scanlines in a band, it
+ * will span the entire vertical distance of the band. This means that some
+ * areas that could be merged into a taller rectangle will be represented as
+ * several shorter rectangles to account for shorter rectangles to its left
+ * or right but within its "vertical scope".
+ *
+ * An added constraint on the rectangles is that they must cover as much
+ * horizontal area as possible. E.g. no two rectangles in a band are allowed
+ * to touch.
+ *
+ * Whenever possible, bands will be merged together to cover a greater vertical
+ * distance (and thus reduce the number of rectangles). Two bands can be merged
+ * only if the bottom of one touches the top of the other and they have
+ * rectangles in the same places (of the same width, of course). This maintains
+ * the y-x-banding that's so nice to have...
+ */
+/* $XFree86: xc/lib/X11/Region.c,v 1.1.1.2.2.2 1998/10/04 15:22:50 hohndel Exp $ */
+
+static void UnionRectWithRegion(register const QRect *rect, const QRegionPrivate *source,
+                                QRegionPrivate &dest)
+{
+    if (!rect->width() || !rect->height())
+        return;
+
+    QRegionPrivate region(*rect);
+
+    Q_ASSERT(EqualRegion(source, &dest));
+    Q_ASSERT(!isEmptyHelper(&region));
+
+    if (dest.numRects == 0)
+        dest = region;
+    else if (dest.canAppend(&region))
+        dest.append(&region);
+    else
+        UnionRegion(&region, source, dest);
+}
+
+/*-
+ *-----------------------------------------------------------------------
+ * miSetExtents --
+ *      Reset the extents and innerRect of a region to what they should be.
+ *      Called by miSubtract and miIntersect b/c they can't figure it out
+ *      along the way or do so easily, as miUnion can.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      The region's 'extents' and 'innerRect' structure is overwritten.
+ *
+ *-----------------------------------------------------------------------
+ */
+static void miSetExtents(QRegionPrivate &dest)
+{
+    register const QRect *pBox,
+                         *pBoxEnd;
+    register QRect *pExtents;
+
+    dest.innerRect.setCoords(0, 0, -1, -1);
+    dest.innerArea = -1;
+    if (dest.numRects == 0) {
+        dest.extents.setCoords(0, 0, 0, 0);
+        return;
+    }
+
+    pExtents = &dest.extents;
+    pBox = (dest.mode==QRegionPrivate::Vector)?(dest.rects.constData()):(&dest.single);
+    pBoxEnd = (dest.mode==QRegionPrivate::Vector)?(&pBox[dest.numRects - 1]):(&dest.single);
+
+    /*
+     * Since pBox is the first rectangle in the region, it must have the
+     * smallest y1 and since pBoxEnd is the last rectangle in the region,
+     * it must have the largest y2, because of banding. Initialize x1 and
+     * x2 from  pBox and pBoxEnd, resp., as good things to initialize them
+     * to...
+     */
+    pExtents->setLeft(pBox->left());
+    pExtents->setTop(pBox->top());
+    pExtents->setRight(pBoxEnd->right());
+    pExtents->setBottom(pBoxEnd->bottom());
+
+    Q_ASSERT(pExtents->top() <= pExtents->bottom());
+    while (pBox <= pBoxEnd) {
+        if (pBox->left() < pExtents->left())
+            pExtents->setLeft(pBox->left());
+        if (pBox->right() > pExtents->right())
+            pExtents->setRight(pBox->right());
+        dest.updateInnerRect(*pBox);
+        ++pBox;
+    }
+    Q_ASSERT(pExtents->left() <= pExtents->right());
+}
+
+/* TranslateRegion(pRegion, x, y)
+   translates in place
+   added by raymond
+*/
+
+static void OffsetRegion(register QRegionPrivate &region, register int x, register int y)
+{
+    register int nbox;
+    register QRect *pbox;
+
+    if(region.mode == QRegionPrivate::Single) {
+        region.single.translate(x, y);
+    } else {
+        pbox = region.rects.data();
+        nbox = region.numRects;
+
+        while (nbox--) {
+            pbox->translate(x, y);
+            ++pbox;
+        }
+    } 
+    region.extents.translate(x, y);
+    region.innerRect.translate(x, y);
+}
+
+/*======================================================================
+ *          Region Intersection
+ *====================================================================*/
+/*-
+ *-----------------------------------------------------------------------
+ * miIntersectO --
+ *      Handle an overlapping band for miIntersect.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      Rectangles may be added to the region.
+ *
+ *-----------------------------------------------------------------------
+ */
+static void miIntersectO(register QRegionPrivate &dest, register const QRect *r1, const QRect *r1End,
+                         register const QRect *r2, const QRect *r2End, int y1, int y2)
+{
+    register int x1;
+    register int x2;
+    register QRect *pNextRect;
+
+    pNextRect = dest.rects.data() + dest.numRects;
+
+    while (r1 != r1End && r2 != r2End) {
+        x1 = qMax(r1->left(), r2->left());
+        x2 = qMin(r1->right(), r2->right());
+
+        /*
+         * If there's any overlap between the two rectangles, add that
+         * overlap to the new region.
+         * There's no need to check for subsumption because the only way
+         * such a need could arise is if some region has two rectangles
+         * right next to each other. Since that should never happen...
+         */
+        if (x1 <= x2) {
+            Q_ASSERT(y1 <= y2);
+            MEMCHECK(dest, pNextRect, dest.rects)
+            pNextRect->setCoords(x1, y1, x2, y2);
+            ++dest.numRects;
+            ++pNextRect;
+        }
+
+        /*
+         * Need to advance the pointers. Shift the one that extends
+         * to the right the least, since the other still has a chance to
+         * overlap with that region's next rectangle, if you see what I mean.
+         */
+        if (r1->right() < r2->right()) {
+            ++r1;
+        } else if (r2->right() < r1->right()) {
+            ++r2;
+        } else {
+            ++r1;
+            ++r2;
+        }
+    }
+}
+
+/*======================================================================
+ *          Generic Region Operator
+ *====================================================================*/
+
+/*-
+ *-----------------------------------------------------------------------
+ * miCoalesce --
+ *      Attempt to merge the boxes in the current band with those in the
+ *      previous one. Used only by miRegionOp.
+ *
+ * Results:
+ *      The new index for the previous band.
+ *
+ * Side Effects:
+ *      If coalescing takes place:
+ *          - rectangles in the previous band will have their y2 fields
+ *            altered.
+ *          - dest.numRects will be decreased.
+ *
+ *-----------------------------------------------------------------------
+ */
+static int miCoalesce(register QRegionPrivate &dest, int prevStart, int curStart)
+{
+    register QRect *pPrevBox;   /* Current box in previous band */
+    register QRect *pCurBox;    /* Current box in current band */
+    register QRect *pRegEnd;    /* End of region */
+    int curNumRects;    /* Number of rectangles in current band */
+    int prevNumRects;   /* Number of rectangles in previous band */
+    int bandY1;         /* Y1 coordinate for current band */
+    QRect *rData = dest.rects.data();
+
+    pRegEnd = rData + dest.numRects;
+
+    pPrevBox = rData + prevStart;
+    prevNumRects = curStart - prevStart;
+
+    /*
+     * Figure out how many rectangles are in the current band. Have to do
+     * this because multiple bands could have been added in miRegionOp
+     * at the end when one region has been exhausted.
+     */
+    pCurBox = rData + curStart;
+    bandY1 = pCurBox->top();
+    for (curNumRects = 0; pCurBox != pRegEnd && pCurBox->top() == bandY1; ++curNumRects) {
+        ++pCurBox;
+    }
+
+    if (pCurBox != pRegEnd) {
+        /*
+         * If more than one band was added, we have to find the start
+         * of the last band added so the next coalescing job can start
+         * at the right place... (given when multiple bands are added,
+         * this may be pointless -- see above).
+         */
+        --pRegEnd;
+        while ((pRegEnd - 1)->top() == pRegEnd->top())
+            --pRegEnd;
+        curStart = pRegEnd - rData;
+        pRegEnd = rData + dest.numRects;
+    }
+
+    if (curNumRects == prevNumRects && curNumRects != 0) {
+        pCurBox -= curNumRects;
+        /*
+         * The bands may only be coalesced if the bottom of the previous
+         * matches the top scanline of the current.
+         */
+        if (pPrevBox->bottom() == pCurBox->top() - 1) {
+            /*
+             * Make sure the bands have boxes in the same places. This
+             * assumes that boxes have been added in such a way that they
+             * cover the most area possible. I.e. two boxes in a band must
+             * have some horizontal space between them.
+             */
+            do {
+                if (pPrevBox->left() != pCurBox->left() || pPrevBox->right() != pCurBox->right()) {
+                     // The bands don't line up so they can't be coalesced.
+                    return curStart;
+                }
+                ++pPrevBox;
+                ++pCurBox;
+                --prevNumRects;
+            } while (prevNumRects != 0);
+
+            dest.numRects -= curNumRects;
+            pCurBox -= curNumRects;
+            pPrevBox -= curNumRects;
+
+            /*
+             * The bands may be merged, so set the bottom y of each box
+             * in the previous band to that of the corresponding box in
+             * the current band.
+             */
+            do {
+                pPrevBox->setBottom(pCurBox->bottom());
+                dest.updateInnerRect(*pPrevBox);
+                ++pPrevBox;
+                ++pCurBox;
+                curNumRects -= 1;
+            } while (curNumRects != 0);
+
+            /*
+             * If only one band was added to the region, we have to backup
+             * curStart to the start of the previous band.
+             *
+             * If more than one band was added to the region, copy the
+             * other bands down. The assumption here is that the other bands
+             * came from the same region as the current one and no further
+             * coalescing can be done on them since it's all been done
+             * already... curStart is already in the right place.
+             */
+            if (pCurBox == pRegEnd) {
+                curStart = prevStart;
+            } else {
+                do {
+                    *pPrevBox++ = *pCurBox++;
+                    dest.updateInnerRect(*pPrevBox);
+                } while (pCurBox != pRegEnd);
+            }
+        }
+    }
+    return curStart;
+}
+
+/*-
+ *-----------------------------------------------------------------------
+ * miRegionOp --
+ *      Apply an operation to two regions. Called by miUnion, miInverse,
+ *      miSubtract, miIntersect...
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      The new region is overwritten.
+ *
+ * Notes:
+ *      The idea behind this function is to view the two regions as sets.
+ *      Together they cover a rectangle of area that this function divides
+ *      into horizontal bands where points are covered only by one region
+ *      or by both. For the first case, the nonOverlapFunc is called with
+ *      each the band and the band's upper and lower extents. For the
+ *      second, the overlapFunc is called to process the entire band. It
+ *      is responsible for clipping the rectangles in the band, though
+ *      this function provides the boundaries.
+ *      At the end of each band, the new region is coalesced, if possible,
+ *      to reduce the number of rectangles in the region.
+ *
+ *-----------------------------------------------------------------------
+ */
+static void miRegionOp(register QRegionPrivate &dest, const QRegionPrivate *reg1, const QRegionPrivate *reg2,
+                       OverlapFunc overlapFunc, NonOverlapFunc nonOverlap1Func,
+                       NonOverlapFunc nonOverlap2Func)
+{
+    register const QRect *r1;         // Pointer into first region
+    register const QRect *r2;         // Pointer into 2d region
+    const QRect *r1End;               // End of 1st region
+    const QRect *r2End;               // End of 2d region
+    register int ybot;          // Bottom of intersection
+    register int ytop;          // Top of intersection
+    int prevBand;               // Index of start of previous band in dest
+    int curBand;                // Index of start of current band in dest
+    register const QRect *r1BandEnd;  // End of current band in r1
+    register const QRect *r2BandEnd;  // End of current band in r2
+    int top;                    // Top of non-overlapping band
+    int bot;                    // Bottom of non-overlapping band
+
+    /*
+     * Initialization:
+     *  set r1, r2, r1End and r2End appropriately, preserve the important
+     * parts of the destination region until the end in case it's one of
+     * the two source regions, then mark the "new" region empty, allocating
+     * another array of rectangles for it to use.
+     */
+    r1 = (reg1->mode==QRegionPrivate::Vector)?reg1->rects.data():&reg1->single;
+    r2 = (reg2->mode==QRegionPrivate::Vector)?reg2->rects.data():&reg2->single;
+    r1End = r1 + reg1->numRects;
+    r2End = r2 + reg2->numRects;
+
+    dest.vector();
+    QVector<QRect> oldRects = dest.rects;
+
+    dest.numRects = 0;
+
+    /*
+     * Allocate a reasonable number of rectangles for the new region. The idea
+     * is to allocate enough so the individual functions don't need to
+     * reallocate and copy the array, which is time consuming, yet we don't
+     * have to worry about using too much memory. I hope to be able to
+     * nuke the realloc() at the end of this function eventually.
+     */
+    dest.rects.resize(qMax(reg1->numRects,reg2->numRects) * 2);
+
+    /*
+     * Initialize ybot and ytop.
+     * In the upcoming loop, ybot and ytop serve different functions depending
+     * on whether the band being handled is an overlapping or non-overlapping
+     * band.
+     *  In the case of a non-overlapping band (only one of the regions
+     * has points in the band), ybot is the bottom of the most recent
+     * intersection and thus clips the top of the rectangles in that band.
+     * ytop is the top of the next intersection between the two regions and
+     * serves to clip the bottom of the rectangles in the current band.
+     *  For an overlapping band (where the two regions intersect), ytop clips
+     * the top of the rectangles of both regions and ybot clips the bottoms.
+     */
+    if (reg1->extents.top() < reg2->extents.top())
+        ybot = reg1->extents.top() - 1;
+    else
+        ybot = reg2->extents.top() - 1;
+
+    /*
+     * prevBand serves to mark the start of the previous band so rectangles
+     * can be coalesced into larger rectangles. qv. miCoalesce, above.
+     * In the beginning, there is no previous band, so prevBand == curBand
+     * (curBand is set later on, of course, but the first band will always
+     * start at index 0). prevBand and curBand must be indices because of
+     * the possible expansion, and resultant moving, of the new region's
+     * array of rectangles.
+     */
+    prevBand = 0;
+
+    do {
+        curBand = dest.numRects;
+
+        /*
+         * This algorithm proceeds one source-band (as opposed to a
+         * destination band, which is determined by where the two regions
+         * intersect) at a time. r1BandEnd and r2BandEnd serve to mark the
+         * rectangle after the last one in the current band for their
+         * respective regions.
+         */
+        r1BandEnd = r1;
+        while (r1BandEnd != r1End && r1BandEnd->top() == r1->top())
+            ++r1BandEnd;
+
+        r2BandEnd = r2;
+        while (r2BandEnd != r2End && r2BandEnd->top() == r2->top())
+            ++r2BandEnd;
+
+        /*
+         * First handle the band that doesn't intersect, if any.
+         *
+         * Note that attention is restricted to one band in the
+         * non-intersecting region at once, so if a region has n
+         * bands between the current position and the next place it overlaps
+         * the other, this entire loop will be passed through n times.
+         */
+        if (r1->top() < r2->top()) {
+            top = qMax(r1->top(), ybot + 1);
+            bot = qMin(r1->bottom(), r2->top() - 1);
+
+            if (nonOverlap1Func != 0 && bot >= top)
+                (*nonOverlap1Func)(dest, r1, r1BandEnd, top, bot);
+            ytop = r2->top();
+        } else if (r2->top() < r1->top()) {
+            top = qMax(r2->top(), ybot + 1);
+            bot = qMin(r2->bottom(), r1->top() - 1);
+
+            if (nonOverlap2Func != 0 && bot >= top)
+                (*nonOverlap2Func)(dest, r2, r2BandEnd, top, bot);
+            ytop = r1->top();
+        } else {
+            ytop = r1->top();
+        }
+
+        /*
+         * If any rectangles got added to the region, try and coalesce them
+         * with rectangles from the previous band. Note we could just do
+         * this test in miCoalesce, but some machines incur a not
+         * inconsiderable cost for function calls, so...
+         */
+        if (dest.numRects != curBand)
+            prevBand = miCoalesce(dest, prevBand, curBand);
+
+        /*
+         * Now see if we've hit an intersecting band. The two bands only
+         * intersect if ybot >= ytop
+         */
+        ybot = qMin(r1->bottom(), r2->bottom());
+        curBand = dest.numRects;
+        if (ybot >= ytop)
+            (*overlapFunc)(dest, r1, r1BandEnd, r2, r2BandEnd, ytop, ybot);
+
+        if (dest.numRects != curBand)
+            prevBand = miCoalesce(dest, prevBand, curBand);
+
+        /*
+         * If we've finished with a band (y2 == ybot) we skip forward
+         * in the region to the next band.
+         */
+        if (r1->bottom() == ybot)
+            r1 = r1BandEnd;
+        if (r2->bottom() == ybot)
+            r2 = r2BandEnd;
+    } while (r1 != r1End && r2 != r2End);
+
+    /*
+     * Deal with whichever region still has rectangles left.
+     */
+    curBand = dest.numRects;
+    if (r1 != r1End) {
+        if (nonOverlap1Func != 0) {
+            do {
+                r1BandEnd = r1;
+                while (r1BandEnd < r1End && r1BandEnd->top() == r1->top())
+                    ++r1BandEnd;
+                (*nonOverlap1Func)(dest, r1, r1BandEnd, qMax(r1->top(), ybot + 1), r1->bottom());
+                r1 = r1BandEnd;
+            } while (r1 != r1End);
+        }
+    } else if ((r2 != r2End) && (nonOverlap2Func != 0)) {
+        do {
+            r2BandEnd = r2;
+            while (r2BandEnd < r2End && r2BandEnd->top() == r2->top())
+                 ++r2BandEnd;
+            (*nonOverlap2Func)(dest, r2, r2BandEnd, qMax(r2->top(), ybot + 1), r2->bottom());
+            r2 = r2BandEnd;
+        } while (r2 != r2End);
+    }
+
+    if (dest.numRects != curBand)
+        (void)miCoalesce(dest, prevBand, curBand);
+
+    /*
+     * A bit of cleanup. To keep regions from growing without bound,
+     * we shrink the array of rectangles to match the new number of
+     * rectangles in the region.
+     *
+     * Only do this stuff if the number of rectangles allocated is more than
+     * twice the number of rectangles in the region (a simple optimization).
+     */
+    if (qMax(4, dest.numRects) < (dest.rects.size() >> 1))
+        dest.rects.resize(dest.numRects);
+}
+
+/*======================================================================
+ *          Region Union
+ *====================================================================*/
+
+/*-
+ *-----------------------------------------------------------------------
+ * miUnionNonO --
+ *      Handle a non-overlapping band for the union operation. Just
+ *      Adds the rectangles into the region. Doesn't have to check for
+ *      subsumption or anything.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      dest.numRects is incremented and the final rectangles overwritten
+ *      with the rectangles we're passed.
+ *
+ *-----------------------------------------------------------------------
+ */
+
+static void miUnionNonO(register QRegionPrivate &dest, register const QRect *r, const QRect *rEnd,
+                        register int y1, register int y2)
+{
+    register QRect *pNextRect;
+
+    pNextRect = dest.rects.data() + dest.numRects;
+
+    Q_ASSERT(y1 <= y2);
+
+    while (r != rEnd) {
+        Q_ASSERT(r->left() <= r->right());
+        MEMCHECK(dest, pNextRect, dest.rects)
+        pNextRect->setCoords(r->left(), y1, r->right(), y2);
+        dest.numRects++;
+        ++pNextRect;
+        ++r;
+    }
+}
+
+
+/*-
+ *-----------------------------------------------------------------------
+ * miUnionO --
+ *      Handle an overlapping band for the union operation. Picks the
+ *      left-most rectangle each time and merges it into the region.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      Rectangles are overwritten in dest.rects and dest.numRects will
+ *      be changed.
+ *
+ *-----------------------------------------------------------------------
+ */
+
+static void miUnionO(register QRegionPrivate &dest, register const QRect *r1, const QRect *r1End,
+                     register const QRect *r2, const QRect *r2End, register int y1, register int y2)
+{
+    register QRect *pNextRect;
+
+    pNextRect = dest.rects.data() + dest.numRects;
+
+#define MERGERECT(r)             \
+    if ((dest.numRects != 0) &&  \
+        (pNextRect[-1].top() == y1) &&  \
+        (pNextRect[-1].bottom() == y2) &&  \
+        (pNextRect[-1].right() >= r->left()-1)) { \
+        if (pNextRect[-1].right() < r->right()) { \
+            pNextRect[-1].setRight(r->right());  \
+            dest.updateInnerRect(pNextRect[-1]); \
+            Q_ASSERT(pNextRect[-1].left() <= pNextRect[-1].right()); \
+        }  \
+    } else { \
+        MEMCHECK(dest, pNextRect, dest.rects)  \
+        pNextRect->setCoords(r->left(), y1, r->right(), y2); \
+        dest.updateInnerRect(*pNextRect); \
+        dest.numRects++;  \
+        pNextRect++;  \
+    }  \
+    r++;
+
+    Q_ASSERT(y1 <= y2);
+    while (r1 != r1End && r2 != r2End) {
+        if (r1->left() < r2->left()) {
+            MERGERECT(r1)
+        } else {
+            MERGERECT(r2)
+        }
+    }
+
+    if (r1 != r1End) {
+        do {
+            MERGERECT(r1)
+        } while (r1 != r1End);
+    } else {
+        while (r2 != r2End) {
+            MERGERECT(r2)
+        }
+    }
+}
+
+static void UnionRegion(const QRegionPrivate *reg1, const QRegionPrivate *reg2, QRegionPrivate &dest)
+{
+    Q_ASSERT(!isEmptyHelper(reg1) && !isEmptyHelper(reg2));
+    Q_ASSERT(!reg1->contains(*reg2));
+    Q_ASSERT(!reg2->contains(*reg1));
+    Q_ASSERT(!EqualRegion(reg1, reg2));
+    Q_ASSERT(!reg1->canAppend(reg2));
+    Q_ASSERT(!reg2->canAppend(reg1));
+
+    if (reg1->innerArea > reg2->innerArea) {
+        dest.innerArea = reg1->innerArea;
+        dest.innerRect = reg1->innerRect;
+    } else {
+        dest.innerArea = reg2->innerArea;
+        dest.innerRect = reg2->innerRect;
+    }
+    miRegionOp(dest, reg1, reg2, miUnionO, miUnionNonO, miUnionNonO);
+
+    dest.extents.setCoords(qMin(reg1->extents.left(), reg2->extents.left()),
+                           qMin(reg1->extents.top(), reg2->extents.top()),
+                           qMax(reg1->extents.right(), reg2->extents.right()),
+                           qMax(reg1->extents.bottom(), reg2->extents.bottom()));
+}
+
+/*======================================================================
+ *        Region Subtraction
+ *====================================================================*/
+
+/*-
+ *-----------------------------------------------------------------------
+ * miSubtractNonO --
+ *      Deal with non-overlapping band for subtraction. Any parts from
+ *      region 2 we discard. Anything from region 1 we add to the region.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      dest may be affected.
+ *
+ *-----------------------------------------------------------------------
+ */
+
+static void miSubtractNonO1(register QRegionPrivate &dest, register const QRect *r,
+                            const QRect *rEnd, register int y1, register int y2)
+{
+    register QRect *pNextRect;
+
+    pNextRect = dest.rects.data() + dest.numRects;
+
+    Q_ASSERT(y1<=y2);
+
+    while (r != rEnd) {
+        Q_ASSERT(r->left() <= r->right());
+        MEMCHECK(dest, pNextRect, dest.rects)
+        pNextRect->setCoords(r->left(), y1, r->right(), y2);
+        ++dest.numRects;
+        ++pNextRect;
+        ++r;
+    }
+}
+
+/*-
+ *-----------------------------------------------------------------------
+ * miSubtractO --
+ *      Overlapping band subtraction. x1 is the left-most point not yet
+ *      checked.
+ *
+ * Results:
+ *      None.
+ *
+ * Side Effects:
+ *      dest may have rectangles added to it.
+ *
+ *-----------------------------------------------------------------------
+ */
+
+static void miSubtractO(register QRegionPrivate &dest, register const QRect *r1, const QRect *r1End,
+                        register const QRect *r2, const QRect *r2End, register int y1, register int y2)
+{
+    register QRect *pNextRect;
+    register int x1;
+
+    x1 = r1->left();
+
+    Q_ASSERT(y1 <= y2);
+    pNextRect = dest.rects.data() + dest.numRects;
+
+    while (r1 != r1End && r2 != r2End) {
+        if (r2->right() < x1) {
+            /*
+             * Subtrahend missed the boat: go to next subtrahend.
+             */
+            ++r2;
+        } else if (r2->left() <= x1) {
+            /*
+             * Subtrahend precedes minuend: nuke left edge of minuend.
+             */
+            x1 = r2->right() + 1;
+            if (x1 > r1->right()) {
+                /*
+                 * Minuend completely covered: advance to next minuend and
+                 * reset left fence to edge of new minuend.
+                 */
+                ++r1;
+                if (r1 != r1End)
+                    x1 = r1->left();
+            } else {
+                // Subtrahend now used up since it doesn't extend beyond minuend
+                ++r2;
+            }
+        } else if (r2->left() <= r1->right()) {
+            /*
+             * Left part of subtrahend covers part of minuend: add uncovered
+             * part of minuend to region and skip to next subtrahend.
+             */
+            Q_ASSERT(x1 < r2->left());
+            MEMCHECK(dest, pNextRect, dest.rects)
+            pNextRect->setCoords(x1, y1, r2->left() - 1, y2);
+            ++dest.numRects;
+            ++pNextRect;
+
+            x1 = r2->right() + 1;
+            if (x1 > r1->right()) {
+                /*
+                 * Minuend used up: advance to new...
+                 */
+                ++r1;
+                if (r1 != r1End)
+                    x1 = r1->left();
+            } else {
+                // Subtrahend used up
+                ++r2;
+            }
+        } else {
+            /*
+             * Minuend used up: add any remaining piece before advancing.
+             */
+            if (r1->right() >= x1) {
+                MEMCHECK(dest, pNextRect, dest.rects)
+                pNextRect->setCoords(x1, y1, r1->right(), y2);
+                ++dest.numRects;
+                ++pNextRect;
+            }
+            ++r1;
+            if (r1 != r1End)
+                x1 = r1->left();
+        }
+    }
+
+    /*
+     * Add remaining minuend rectangles to region.
+     */
+    while (r1 != r1End) {
+        Q_ASSERT(x1 <= r1->right());
+        MEMCHECK(dest, pNextRect, dest.rects)
+        pNextRect->setCoords(x1, y1, r1->right(), y2);
+        ++dest.numRects;
+        ++pNextRect;
+
+        ++r1;
+        if (r1 != r1End)
+            x1 = r1->left();
+    }
+}
+
+/*-
+ *-----------------------------------------------------------------------
+ * miSubtract --
+ *      Subtract regS from regM and leave the result in regD.
+ *      S stands for subtrahend, M for minuend and D for difference.
+ *
+ * Side Effects:
+ *      regD is overwritten.
+ *
+ *-----------------------------------------------------------------------
+ */
+
+static void SubtractRegion(QRegionPrivate *regM, QRegionPrivate *regS,
+                           register QRegionPrivate &dest)
+{
+    Q_ASSERT(!isEmptyHelper(regM));
+    Q_ASSERT(!isEmptyHelper(regS));
+    Q_ASSERT(EXTENTCHECK(&regM->extents, &regS->extents));
+    Q_ASSERT(!regS->contains(*regM));
+    Q_ASSERT(!EqualRegion(regM, regS));
+
+    miRegionOp(dest, regM, regS, miSubtractO, miSubtractNonO1, 0);
+
+    /*
+     * Can't alter dest's extents before we call miRegionOp because
+     * it might be one of the source regions and miRegionOp depends
+     * on the extents of those regions being the unaltered. Besides, this
+     * way there's no checking against rectangles that will be nuked
+     * due to coalescing, so we have to examine fewer rectangles.
+     */
+    miSetExtents(dest);
+}
+
+static void XorRegion(QRegionPrivate *sra, QRegionPrivate *srb, QRegionPrivate &dest)
+{
+    Q_ASSERT(!isEmptyHelper(sra) && !isEmptyHelper(srb));
+    Q_ASSERT(EXTENTCHECK(&sra->extents, &srb->extents));
+    Q_ASSERT(!EqualRegion(sra, srb));
+
+    QRegionPrivate tra, trb;
+
+    if (!srb->contains(*sra))
+        SubtractRegion(sra, srb, tra);
+    if (!sra->contains(*srb))
+        SubtractRegion(srb, sra, trb);
+
+    Q_ASSERT(isEmptyHelper(&trb) || !tra.contains(trb));
+    Q_ASSERT(isEmptyHelper(&tra) || !trb.contains(tra));
+
+    if (isEmptyHelper(&tra)) {
+        dest = trb;
+    } else if (isEmptyHelper(&trb)) {
+        dest = tra;
+    } else if (tra.canAppend(&trb)) {
+        dest = tra;
+        dest.append(&trb);
+    } else if (trb.canAppend(&tra)) {
+        dest = trb;
+        dest.append(&tra);
+    } else {
+        UnionRegion(&tra, &trb, dest);
+    }
+}
+
+/*
+ *      Check to see if two regions are equal
+ */
+static bool EqualRegion(const QRegionPrivate *r1, const QRegionPrivate *r2)
+{
+    if (r1->numRects != r2->numRects) {
+        return false;
+    } else if (r1->numRects == 0) {
+        return true;
+    } else if (r1->extents != r2->extents) {
+        return false;
+    } else if (r1->mode == QRegionPrivate::Single && r2->mode == QRegionPrivate::Single) {
+        return r1->single == r2->single;
+    } else {
+        const QRect *rr1 = (r1->mode==QRegionPrivate::Vector)?r1->rects.constData():&r1->single;
+        const QRect *rr2 = (r2->mode==QRegionPrivate::Vector)?r2->rects.constData():&r2->single;
+        for (int i = 0; i < r1->numRects; ++i, ++rr1, ++rr2) {
+            if (*rr1 != *rr2)
+                return false;
+        }
+    }
+
+    return true;
+}
+
+static bool PointInRegion(QRegionPrivate *pRegion, int x, int y)
+{
+    int i;
+
+    if (pRegion->mode == QRegionPrivate::Single)
+        return pRegion->single.contains(x, y);
+    if (isEmptyHelper(pRegion))
+        return false;
+    if (!pRegion->extents.contains(x, y))
+        return false;
+    if (pRegion->innerRect.contains(x, y))
+        return true;
+    for (i = 0; i < pRegion->numRects; ++i) {
+        if (pRegion->rects[i].contains(x, y))
+            return true;
+    }
+    return false;
+}
+
+static bool RectInRegion(register QRegionPrivate *region, int rx, int ry, uint rwidth, uint rheight)
+{
+    register const QRect *pbox;
+    register const QRect *pboxEnd;
+    QRect rect(rx, ry, rwidth, rheight);
+    register QRect *prect = &rect;
+    int partIn, partOut;
+
+    if (!region || region->numRects == 0 || !EXTENTCHECK(&region->extents, prect))
+        return RectangleOut;
+
+    partOut = false;
+    partIn = false;
+
+    /* can stop when both partOut and partIn are true, or we reach prect->y2 */
+    for (pbox = (region->mode==QRegionPrivate::Vector)?region->rects.constData():&region->single, pboxEnd = pbox + region->numRects;
+         pbox < pboxEnd; ++pbox) {
+        if (pbox->bottom() < ry)
+           continue;
+
+        if (pbox->top() > ry) {
+           partOut = true;
+           if (partIn || pbox->top() > prect->bottom())
+              break;
+           ry = pbox->top();
+        }
+
+        if (pbox->right() < rx)
+           continue;            /* not far enough over yet */
+
+        if (pbox->left() > rx) {
+           partOut = true;      /* missed part of rectangle to left */
+           if (partIn)
+              break;
+        }
+
+        if (pbox->left() <= prect->right()) {
+            partIn = true;      /* definitely overlap */
+            if (partOut)
+               break;
+        }
+
+        if (pbox->right() >= prect->right()) {
+           ry = pbox->bottom() + 1;     /* finished with this band */
+           if (ry > prect->bottom())
+              break;
+           rx = prect->left();  /* reset x out to left again */
+        } else {
+            /*
+             * Because boxes in a band are maximal width, if the first box
+             * to overlap the rectangle doesn't completely cover it in that
+             * band, the rectangle must be partially out, since some of it
+             * will be uncovered in that band. partIn will have been set true
+             * by now...
+             */
+            break;
+        }
+    }
+    return partIn ? ((ry <= prect->bottom()) ? RectanglePart : RectangleIn) : RectangleOut;
+}
+// END OF Region.c extract
+// START OF poly.h extract
+/* $XConsortium: poly.h,v 1.4 94/04/17 20:22:19 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.
+
+************************************************************************/
+
+/*
+ *     This file contains a few macros to help track
+ *     the edge of a filled object.  The object is assumed
+ *     to be filled in scanline order, and thus the
+ *     algorithm used is an extension of Bresenham's line
+ *     drawing algorithm which assumes that y is always the
+ *     major axis.
+ *     Since these pieces of code are the same for any filled shape,
+ *     it is more convenient to gather the library in one
+ *     place, but since these pieces of code are also in
+ *     the inner loops of output primitives, procedure call
+ *     overhead is out of the question.
+ *     See the author for a derivation if needed.
+ */
+
+
+/*
+ *  In scan converting polygons, we want to choose those pixels
+ *  which are inside the polygon.  Thus, we add .5 to the starting
+ *  x coordinate for both left and right edges.  Now we choose the
+ *  first pixel which is inside the pgon for the left edge and the
+ *  first pixel which is outside the pgon for the right edge.
+ *  Draw the left pixel, but not the right.
+ *
+ *  How to add .5 to the starting x coordinate:
+ *      If the edge is moving to the right, then subtract dy from the
+ *  error term from the general form of the algorithm.
+ *      If the edge is moving to the left, then add dy to the error term.
+ *
+ *  The reason for the difference between edges moving to the left
+ *  and edges moving to the right is simple:  If an edge is moving
+ *  to the right, then we want the algorithm to flip immediately.
+ *  If it is moving to the left, then we don't want it to flip until
+ *  we traverse an entire pixel.
+ */
+#define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \
+    int dx;      /* local storage */ \
+\
+    /* \
+     *  if the edge is horizontal, then it is ignored \
+     *  and assumed not to be processed.  Otherwise, do this stuff. \
+     */ \
+    if ((dy) != 0) { \
+        xStart = (x1); \
+        dx = (x2) - xStart; \
+        if (dx < 0) { \
+            m = dx / (dy); \
+            m1 = m - 1; \
+            incr1 = -2 * dx + 2 * (dy) * m1; \
+            incr2 = -2 * dx + 2 * (dy) * m; \
+            d = 2 * m * (dy) - 2 * dx - 2 * (dy); \
+        } else { \
+            m = dx / (dy); \
+            m1 = m + 1; \
+            incr1 = 2 * dx - 2 * (dy) * m1; \
+            incr2 = 2 * dx - 2 * (dy) * m; \
+            d = -2 * m * (dy) + 2 * dx; \
+        } \
+    } \
+}
+
+#define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \
+    if (m1 > 0) { \
+        if (d > 0) { \
+            minval += m1; \
+            d += incr1; \
+        } \
+        else { \
+            minval += m; \
+            d += incr2; \
+        } \
+    } else {\
+        if (d >= 0) { \
+            minval += m1; \
+            d += incr1; \
+        } \
+        else { \
+            minval += m; \
+            d += incr2; \
+        } \
+    } \
+}
+
+
+/*
+ *     This structure contains all of the information needed
+ *     to run the bresenham algorithm.
+ *     The variables may be hardcoded into the declarations
+ *     instead of using this structure to make use of
+ *     register declarations.
+ */
+typedef struct {
+    int minor_axis;     /* minor axis        */
+    int d;              /* decision variable */
+    int m, m1;          /* slope and slope+1 */
+    int incr1, incr2;   /* error increments */
+} BRESINFO;
+
+
+#define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \
+        BRESINITPGON(dmaj, min1, min2, bres.minor_axis, bres.d, \
+                     bres.m, bres.m1, bres.incr1, bres.incr2)
+
+#define BRESINCRPGONSTRUCT(bres) \
+        BRESINCRPGON(bres.d, bres.minor_axis, bres.m, bres.m1, bres.incr1, bres.incr2)
+
+
+
+/*
+ *     These are the data structures needed to scan
+ *     convert regions.  Two different scan conversion
+ *     methods are available -- the even-odd method, and
+ *     the winding number method.
+ *     The even-odd rule states that a point is inside
+ *     the polygon if a ray drawn from that point in any
+ *     direction will pass through an odd number of
+ *     path segments.
+ *     By the winding number rule, a point is decided
+ *     to be inside the polygon if a ray drawn from that
+ *     point in any direction passes through a different
+ *     number of clockwise and counter-clockwise path
+ *     segments.
+ *
+ *     These data structures are adapted somewhat from
+ *     the algorithm in (Foley/Van Dam) for scan converting
+ *     polygons.
+ *     The basic algorithm is to start at the top (smallest y)
+ *     of the polygon, stepping down to the bottom of
+ *     the polygon by incrementing the y coordinate.  We
+ *     keep a list of edges which the current scanline crosses,
+ *     sorted by x.  This list is called the Active Edge Table (AET)
+ *     As we change the y-coordinate, we update each entry in
+ *     in the active edge table to reflect the edges new xcoord.
+ *     This list must be sorted at each scanline in case
+ *     two edges intersect.
+ *     We also keep a data structure known as the Edge Table (ET),
+ *     which keeps track of all the edges which the current
+ *     scanline has not yet reached.  The ET is basically a
+ *     list of ScanLineList structures containing a list of
+ *     edges which are entered at a given scanline.  There is one
+ *     ScanLineList per scanline at which an edge is entered.
+ *     When we enter a new edge, we move it from the ET to the AET.
+ *
+ *     From the AET, we can implement the even-odd rule as in
+ *     (Foley/Van Dam).
+ *     The winding number rule is a little trickier.  We also
+ *     keep the EdgeTableEntries in the AET linked by the
+ *     nextWETE (winding EdgeTableEntry) link.  This allows
+ *     the edges to be linked just as before for updating
+ *     purposes, but only uses the edges linked by the nextWETE
+ *     link as edges representing spans of the polygon to
+ *     drawn (as with the even-odd rule).
+ */
+
+/*
+ * for the winding number rule
+ */
+#define CLOCKWISE          1
+#define COUNTERCLOCKWISE  -1
+
+typedef struct _EdgeTableEntry {
+     int ymax;             /* ycoord at which we exit this edge. */
+     BRESINFO bres;        /* Bresenham info to run the edge     */
+     struct _EdgeTableEntry *next;       /* next in the list     */
+     struct _EdgeTableEntry *back;       /* for insertion sort   */
+     struct _EdgeTableEntry *nextWETE;   /* for winding num rule */
+     int ClockWise;        /* flag for winding number rule       */
+} EdgeTableEntry;
+
+
+typedef struct _ScanLineList{
+     int scanline;              /* the scanline represented */
+     EdgeTableEntry *edgelist;  /* header node              */
+     struct _ScanLineList *next;  /* next in the list       */
+} ScanLineList;
+
+
+typedef struct {
+     int ymax;                 /* ymax for the polygon     */
+     int ymin;                 /* ymin for the polygon     */
+     ScanLineList scanlines;   /* header node              */
+} EdgeTable;
+
+
+/*
+ * Here is a struct to help with storage allocation
+ * so we can allocate a big chunk at a time, and then take
+ * pieces from this heap when we need to.
+ */
+#define SLLSPERBLOCK 25
+
+typedef struct _ScanLineListBlock {
+     ScanLineList SLLs[SLLSPERBLOCK];
+     struct _ScanLineListBlock *next;
+} ScanLineListBlock;
+
+
+
+/*
+ *
+ *     a few macros for the inner loops of the fill code where
+ *     performance considerations don't allow a procedure call.
+ *
+ *     Evaluate the given edge at the given scanline.
+ *     If the edge has expired, then we leave it and fix up
+ *     the active edge table; otherwise, we increment the
+ *     x value to be ready for the next scanline.
+ *     The winding number rule is in effect, so we must notify
+ *     the caller when the edge has been removed so he
+ *     can reorder the Winding Active Edge Table.
+ */
+#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \
+   if (pAET->ymax == y) {          /* leaving this edge */ \
+      pPrevAET->next = pAET->next; \
+      pAET = pPrevAET->next; \
+      fixWAET = 1; \
+      if (pAET) \
+         pAET->back = pPrevAET; \
+   } \
+   else { \
+      BRESINCRPGONSTRUCT(pAET->bres) \
+      pPrevAET = pAET; \
+      pAET = pAET->next; \
+   } \
+}
+
+
+/*
+ *     Evaluate the given edge at the given scanline.
+ *     If the edge has expired, then we leave it and fix up
+ *     the active edge table; otherwise, we increment the
+ *     x value to be ready for the next scanline.
+ *     The even-odd rule is in effect.
+ */
+#define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \
+   if (pAET->ymax == y) {          /* leaving this edge */ \
+      pPrevAET->next = pAET->next; \
+      pAET = pPrevAET->next; \
+      if (pAET) \
+         pAET->back = pPrevAET; \
+   } \
+   else { \
+      BRESINCRPGONSTRUCT(pAET->bres) \
+      pPrevAET = pAET; \
+      pAET = pAET->next; \
+   } \
+}
+// END OF poly.h extract
+// START OF PolyReg.c extract
+/* $XConsortium: PolyReg.c,v 11.23 94/11/17 21:59:37 converse 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.
+
+************************************************************************/
+/* $XFree86: xc/lib/X11/PolyReg.c,v 1.1.1.2.8.2 1998/10/04 15:22:49 hohndel Exp $ */
+
+#define LARGE_COORDINATE 1000000
+#define SMALL_COORDINATE -LARGE_COORDINATE
+
+/*
+ *     InsertEdgeInET
+ *
+ *     Insert the given edge into the edge table.
+ *     First we must find the correct bucket in the
+ *     Edge table, then find the right slot in the
+ *     bucket.  Finally, we can insert it.
+ *
+ */
+static void InsertEdgeInET(EdgeTable *ET, EdgeTableEntry *ETE, int scanline,
+                           ScanLineListBlock **SLLBlock, int *iSLLBlock)
+{
+    register EdgeTableEntry *start, *prev;
+    register ScanLineList *pSLL, *pPrevSLL;
+    ScanLineListBlock *tmpSLLBlock;
+
+    /*
+     * find the right bucket to put the edge into
+     */
+    pPrevSLL = &ET->scanlines;
+    pSLL = pPrevSLL->next;
+    while (pSLL && (pSLL->scanline < scanline)) {
+        pPrevSLL = pSLL;
+        pSLL = pSLL->next;
+    }
+
+    /*
+     * reassign pSLL (pointer to ScanLineList) if necessary
+     */
+    if ((!pSLL) || (pSLL->scanline > scanline)) {
+        if (*iSLLBlock > SLLSPERBLOCK-1)
+        {
+            tmpSLLBlock =
+                  (ScanLineListBlock *)malloc(sizeof(ScanLineListBlock));
+            (*SLLBlock)->next = tmpSLLBlock;
+            tmpSLLBlock->next = (ScanLineListBlock *)NULL;
+            *SLLBlock = tmpSLLBlock;
+            *iSLLBlock = 0;
+        }
+        pSLL = &((*SLLBlock)->SLLs[(*iSLLBlock)++]);
+
+        pSLL->next = pPrevSLL->next;
+        pSLL->edgelist = (EdgeTableEntry *)NULL;
+        pPrevSLL->next = pSLL;
+    }
+    pSLL->scanline = scanline;
+
+    /*
+     * now insert the edge in the right bucket
+     */
+    prev = 0;
+    start = pSLL->edgelist;
+    while (start && (start->bres.minor_axis < ETE->bres.minor_axis)) {
+        prev = start;
+        start = start->next;
+    }
+    ETE->next = start;
+
+    if (prev)
+        prev->next = ETE;
+    else
+        pSLL->edgelist = ETE;
+}
+
+/*
+ *     CreateEdgeTable
+ *
+ *     This routine creates the edge table for
+ *     scan converting polygons.
+ *     The Edge Table (ET) looks like:
+ *
+ *    EdgeTable
+ *     --------
+ *    |  ymax  |        ScanLineLists
+ *    |scanline|-->------------>-------------->...
+ *     --------   |scanline|   |scanline|
+ *                |edgelist|   |edgelist|
+ *                ---------    ---------
+ *                    |             |
+ *                    |             |
+ *                    V             V
+ *              list of ETEs   list of ETEs
+ *
+ *     where ETE is an EdgeTableEntry data structure,
+ *     and there is one ScanLineList per scanline at
+ *     which an edge is initially entered.
+ *
+ */
+
+static void CreateETandAET(register int count, register const QPoint *pts,
+                           EdgeTable *ET, EdgeTableEntry *AET, register EdgeTableEntry *pETEs,
+                           ScanLineListBlock *pSLLBlock)
+{
+    register const QPoint *top,
+                          *bottom,
+                          *PrevPt,
+                          *CurrPt;
+    int iSLLBlock = 0;
+    int dy;
+
+    if (count < 2)
+        return;
+
+    /*
+     *  initialize the Active Edge Table
+     */
+    AET->next = 0;
+    AET->back = 0;
+    AET->nextWETE = 0;
+    AET->bres.minor_axis = SMALL_COORDINATE;
+
+    /*
+     *  initialize the Edge Table.
+     */
+    ET->scanlines.next = 0;
+    ET->ymax = SMALL_COORDINATE;
+    ET->ymin = LARGE_COORDINATE;
+    pSLLBlock->next = 0;
+
+    PrevPt = &pts[count - 1];
+
+    /*
+     *  for each vertex in the array of points.
+     *  In this loop we are dealing with two vertices at
+     *  a time -- these make up one edge of the polygon.
+     */
+    while (count--) {
+        CurrPt = pts++;
+
+        /*
+         *  find out which point is above and which is below.
+         */
+        if (PrevPt->y() > CurrPt->y()) {
+            bottom = PrevPt;
+            top = CurrPt;
+            pETEs->ClockWise = 0;
+        } else {
+            bottom = CurrPt;
+            top = PrevPt;
+            pETEs->ClockWise = 1;
+        }
+
+        /*
+         * don't add horizontal edges to the Edge table.
+         */
+        if (bottom->y() != top->y()) {
+            pETEs->ymax = bottom->y() - 1;  /* -1 so we don't get last scanline */
+
+            /*
+             *  initialize integer edge algorithm
+             */
+            dy = bottom->y() - top->y();
+            BRESINITPGONSTRUCT(dy, top->x(), bottom->x(), pETEs->bres)
+
+            InsertEdgeInET(ET, pETEs, top->y(), &pSLLBlock, &iSLLBlock);
+
+            if (PrevPt->y() > ET->ymax)
+                ET->ymax = PrevPt->y();
+            if (PrevPt->y() < ET->ymin)
+                ET->ymin = PrevPt->y();
+            ++pETEs;
+        }
+
+        PrevPt = CurrPt;
+    }
+}
+
+/*
+ *     loadAET
+ *
+ *     This routine moves EdgeTableEntries from the
+ *     EdgeTable into the Active Edge Table,
+ *     leaving them sorted by smaller x coordinate.
+ *
+ */
+
+static void loadAET(register EdgeTableEntry *AET, register EdgeTableEntry *ETEs)
+{
+    register EdgeTableEntry *pPrevAET;
+    register EdgeTableEntry *tmp;
+
+    pPrevAET = AET;
+    AET = AET->next;
+    while (ETEs) {
+        while (AET && AET->bres.minor_axis < ETEs->bres.minor_axis) {
+            pPrevAET = AET;
+            AET = AET->next;
+        }
+        tmp = ETEs->next;
+        ETEs->next = AET;
+        if (AET)
+            AET->back = ETEs;
+        ETEs->back = pPrevAET;
+        pPrevAET->next = ETEs;
+        pPrevAET = ETEs;
+
+        ETEs = tmp;
+    }
+}
+
+/*
+ *     computeWAET
+ *
+ *     This routine links the AET by the
+ *     nextWETE (winding EdgeTableEntry) link for
+ *     use by the winding number rule.  The final
+ *     Active Edge Table (AET) might look something
+ *     like:
+ *
+ *     AET
+ *     ----------  ---------   ---------
+ *     |ymax    |  |ymax    |  |ymax    |
+ *     | ...    |  |...     |  |...     |
+ *     |next    |->|next    |->|next    |->...
+ *     |nextWETE|  |nextWETE|  |nextWETE|
+ *     ---------   ---------   ^--------
+ *         |                   |       |
+ *         V------------------->       V---> ...
+ *
+ */
+static void computeWAET(register EdgeTableEntry *AET)
+{
+    register EdgeTableEntry *pWETE;
+    register int inside = 1;
+    register int isInside = 0;
+
+    AET->nextWETE = 0;
+    pWETE = AET;
+    AET = AET->next;
+    while (AET) {
+        if (AET->ClockWise)
+            ++isInside;
+        else
+            --isInside;
+
+        if (!inside && !isInside || inside && isInside) {
+            pWETE->nextWETE = AET;
+            pWETE = AET;
+            inside = !inside;
+        }
+        AET = AET->next;
+    }
+    pWETE->nextWETE = 0;
+}
+
+/*
+ *     InsertionSort
+ *
+ *     Just a simple insertion sort using
+ *     pointers and back pointers to sort the Active
+ *     Edge Table.
+ *
+ */
+
+static int InsertionSort(register EdgeTableEntry *AET)
+{
+    register EdgeTableEntry *pETEchase;
+    register EdgeTableEntry *pETEinsert;
+    register EdgeTableEntry *pETEchaseBackTMP;
+    register int changed = 0;
+
+    AET = AET->next;
+    while (AET) {
+        pETEinsert = AET;
+        pETEchase = AET;
+        while (pETEchase->back->bres.minor_axis > AET->bres.minor_axis)
+            pETEchase = pETEchase->back;
+
+        AET = AET->next;
+        if (pETEchase != pETEinsert) {
+            pETEchaseBackTMP = pETEchase->back;
+            pETEinsert->back->next = AET;
+            if (AET)
+                AET->back = pETEinsert->back;
+            pETEinsert->next = pETEchase;
+            pETEchase->back->next = pETEinsert;
+            pETEchase->back = pETEinsert;
+            pETEinsert->back = pETEchaseBackTMP;
+            changed = 1;
+        }
+    }
+    return changed;
+}
+
+/*
+ *     Clean up our act.
+ */
+static void FreeStorage(register ScanLineListBlock *pSLLBlock)
+{
+    register ScanLineListBlock *tmpSLLBlock;
+
+    while (pSLLBlock) {
+        tmpSLLBlock = pSLLBlock->next;
+        free(pSLLBlock);
+        pSLLBlock = tmpSLLBlock;
+    }
+}
+
+/*
+ *     Create an array of rectangles from a list of points.
+ *     If indeed these things (POINTS, RECTS) are the same,
+ *     then this proc is still needed, because it allocates
+ *     storage for the array, which was allocated on the
+ *     stack by the calling procedure.
+ *
+ */
+static void PtsToRegion(register int numFullPtBlocks, register int iCurPtBlock,
+                       POINTBLOCK *FirstPtBlock, QRegionPrivate *reg)
+{
+    register QRect *rects;
+    register QPoint *pts;
+    register POINTBLOCK *CurPtBlock;
+    register int i;
+    register QRect *extents;
+    register int numRects;
+
+    extents = &reg->extents;
+    numRects = ((numFullPtBlocks * NUMPTSTOBUFFER) + iCurPtBlock) >> 1;
+
+    reg->rects.resize(numRects);
+
+    CurPtBlock = FirstPtBlock;
+    rects = reg->rects.data() - 1;
+    numRects = 0;
+    extents->setLeft(INT_MAX);
+    extents->setRight(INT_MIN);
+    reg->innerArea = -1;
+
+    for (; numFullPtBlocks >= 0; --numFullPtBlocks) {
+        /* the loop uses 2 points per iteration */
+        i = NUMPTSTOBUFFER >> 1;
+        if (!numFullPtBlocks)
+            i = iCurPtBlock >> 1;
+        if(i) {
+            for (pts = CurPtBlock->pts; i--; pts += 2) {
+                if (pts->x() == pts[1].x())
+                    continue;
+                if (numRects && pts->x() == rects->left() && pts->y() == rects->bottom() + 1
+                    && pts[1].x() == rects->right()+1 && (numRects == 1 || rects[-1].top() != rects->top())
+                                                          && (i && pts[2].y() > pts[1].y())) {
+                        rects->setBottom(pts[1].y());
+                        reg->updateInnerRect(*rects);
+                        continue;
+                }
+                ++numRects;
+                ++rects;
+                rects->setCoords(pts->x(), pts->y(), pts[1].x() - 1, pts[1].y());
+                if (rects->left() < extents->left())
+                    extents->setLeft(rects->left());
+                if (rects->right() > extents->right())
+                    extents->setRight(rects->right());
+                reg->updateInnerRect(*rects);
+            }
+        }
+        CurPtBlock = CurPtBlock->next;
+    }
+
+    if (numRects) {
+        extents->setTop(reg->rects[0].top());
+        extents->setBottom(rects->bottom());
+    } else {
+        extents->setCoords(0, 0, 0, 0);
+    }
+    reg->numRects = numRects;
+}
+
+/*
+ *     polytoregion
+ *
+ *     Scan converts a polygon by returning a run-length
+ *     encoding of the resultant bitmap -- the run-length
+ *     encoding is in the form of an array of rectangles.
+ */
+static QRegionPrivate *PolygonRegion(const QPoint *Pts, int Count, int rule,
+                                     QRegionPrivate *region)
+    //Point     *Pts;                /* the pts                 */
+    //int       Count;                 /* number of pts           */
+    //int       rule;                        /* winding rule */
+{
+    register EdgeTableEntry *pAET;   /* Active Edge Table       */
+    register int y;                  /* current scanline        */
+    register int iPts = 0;           /* number of pts in buffer */
+    register EdgeTableEntry *pWETE;  /* Winding Edge Table Entry*/
+    register ScanLineList *pSLL;     /* current scanLineList    */
+    register QPoint *pts;             /* output buffer           */
+    EdgeTableEntry *pPrevAET;        /* ptr to previous AET     */
+    EdgeTable ET;                    /* header node for ET      */
+    EdgeTableEntry AET;              /* header node for AET     */
+    EdgeTableEntry *pETEs;           /* EdgeTableEntries pool   */
+    ScanLineListBlock SLLBlock;      /* header for scanlinelist */
+    int fixWAET = false;
+    POINTBLOCK FirstPtBlock, *curPtBlock; /* PtBlock buffers    */
+    POINTBLOCK *tmpPtBlock;
+    int numFullPtBlocks = 0;
+
+    region->vector();
+
+    /* special case a rectangle */
+    if (((Count == 4) ||
+         ((Count == 5) && (Pts[4].x() == Pts[0].x()) && (Pts[4].y() == Pts[0].y())))
+         && (((Pts[0].y() == Pts[1].y()) && (Pts[1].x() == Pts[2].x()) && (Pts[2].y() == Pts[3].y())
+               && (Pts[3].x() == Pts[0].x())) || ((Pts[0].x() == Pts[1].x())
+               && (Pts[1].y() == Pts[2].y()) && (Pts[2].x() == Pts[3].x())
+               && (Pts[3].y() == Pts[0].y())))) {
+        int x = qMin(Pts[0].x(), Pts[2].x());
+        region->extents.setLeft(x);
+        int y = qMin(Pts[0].y(), Pts[2].y());
+        region->extents.setTop(y);
+        region->extents.setWidth(qMax(Pts[0].x(), Pts[2].x()) - x);
+        region->extents.setHeight(qMax(Pts[0].y(), Pts[2].y()) - y);
+        if ((region->extents.left() <= region->extents.right()) &&
+            (region->extents.top() <= region->extents.bottom())) {
+            region->numRects = 1;
+            region->rects.resize(1);
+            region->rects[0] = region->extents;
+            region->innerRect = region->extents;
+            region->innerArea = region->innerRect.width() * region->innerRect.height();
+        }
+        return region;
+    }
+
+    if (!(pETEs = static_cast<EdgeTableEntry *>(malloc(sizeof(EdgeTableEntry) * Count))))
+        return 0;
+
+    pts = FirstPtBlock.pts;
+    CreateETandAET(Count, Pts, &ET, &AET, pETEs, &SLLBlock);
+    pSLL = ET.scanlines.next;
+    curPtBlock = &FirstPtBlock;
+
+    if (rule == EvenOddRule) {
+        /*
+         *  for each scanline
+         */
+        for (y = ET.ymin; y < ET.ymax; ++y) {
+            /*
+             *  Add a new edge to the active edge table when we
+             *  get to the next edge.
+             */
+            if (pSLL && y == pSLL->scanline) {
+                loadAET(&AET, pSLL->edgelist);
+                pSLL = pSLL->next;
+            }
+            pPrevAET = &AET;
+            pAET = AET.next;
+
+            /*
+             *  for each active edge
+             */
+            while (pAET) {
+                pts->setX(pAET->bres.minor_axis);
+                pts->setY(y);
+                ++pts;
+                ++iPts;
+
+                /*
+                 *  send out the buffer
+                 */
+                if (iPts == NUMPTSTOBUFFER) {
+                    tmpPtBlock = (POINTBLOCK *)malloc(sizeof(POINTBLOCK));
+                    curPtBlock->next = tmpPtBlock;
+                    curPtBlock = tmpPtBlock;
+                    pts = curPtBlock->pts;
+                    ++numFullPtBlocks;
+                    iPts = 0;
+                }
+                EVALUATEEDGEEVENODD(pAET, pPrevAET, y)
+            }
+            InsertionSort(&AET);
+        }
+    } else {
+        /*
+         *  for each scanline
+         */
+        for (y = ET.ymin; y < ET.ymax; ++y) {
+            /*
+             *  Add a new edge to the active edge table when we
+             *  get to the next edge.
+             */
+            if (pSLL && y == pSLL->scanline) {
+                loadAET(&AET, pSLL->edgelist);
+                computeWAET(&AET);
+                pSLL = pSLL->next;
+            }
+            pPrevAET = &AET;
+            pAET = AET.next;
+            pWETE = pAET;
+
+            /*
+             *  for each active edge
+             */
+            while (pAET) {
+                /*
+                 *  add to the buffer only those edges that
+                 *  are in the Winding active edge table.
+                 */
+                if (pWETE == pAET) {
+                    pts->setX(pAET->bres.minor_axis);
+                    pts->setY(y);
+                    ++pts;
+                    ++iPts;
+
+                    /*
+                     *  send out the buffer
+                     */
+                    if (iPts == NUMPTSTOBUFFER) {
+                        tmpPtBlock = static_cast<POINTBLOCK *>(malloc(sizeof(POINTBLOCK)));
+                        curPtBlock->next = tmpPtBlock;
+                        curPtBlock = tmpPtBlock;
+                        pts = curPtBlock->pts;
+                        ++numFullPtBlocks;
+                        iPts = 0;
+                    }
+                    pWETE = pWETE->nextWETE;
+                }
+                EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET)
+            }
+
+            /*
+             *  recompute the winding active edge table if
+             *  we just resorted or have exited an edge.
+             */
+            if (InsertionSort(&AET) || fixWAET) {
+                computeWAET(&AET);
+                fixWAET = false;
+            }
+        }
+    }
+    FreeStorage(SLLBlock.next);
+    PtsToRegion(numFullPtBlocks, iPts, &FirstPtBlock, region);
+    for (curPtBlock = FirstPtBlock.next; --numFullPtBlocks >= 0;) {
+        tmpPtBlock = curPtBlock->next;
+        free(curPtBlock);
+        curPtBlock = tmpPtBlock;
+    }
+    free(pETEs);
+    return region;
+}
+// END OF PolyReg.c extract
+
+QRegionPrivate *qt_bitmapToRegion(const QBitmap& bitmap, QRegionPrivate *region)
+{
+    region->vector();
+
+    QImage image = bitmap.toImage();
+
+    QRect xr;
+
+#define AddSpan \
+        { \
+            xr.setCoords(prev1, y, x-1, y); \
+            UnionRectWithRegion(&xr, region, *region); \
+        }
+
+    const uchar zero = 0;
+    bool little = image.format() == QImage::Format_MonoLSB;
+
+    int x,
+        y;
+    for (y = 0; y < image.height(); ++y) {
+        uchar *line = image.scanLine(y);
+        int w = image.width();
+        uchar all = zero;
+        int prev1 = -1;
+        for (x = 0; x < w;) {
+            uchar byte = line[x / 8];
+            if (x > w - 8 || byte!=all) {
+                if (little) {
+                    for (int b = 8; b > 0 && x < w; --b) {
+                        if (!(byte & 0x01) == !all) {
+                            // More of the same
+                        } else {
+                            // A change.
+                            if (all!=zero) {
+                                AddSpan
+                                all = zero;
+                            } else {
+                                prev1 = x;
+                                all = ~zero;
+                            }
+                        }
+                        byte >>= 1;
+                        ++x;
+                    }
+                } else {
+                    for (int b = 8; b > 0 && x < w; --b) {
+                        if (!(byte & 0x80) == !all) {
+                            // More of the same
+                        } else {
+                            // A change.
+                            if (all != zero) {
+                                AddSpan
+                                all = zero;
+                            } else {
+                                prev1 = x;
+                                all = ~zero;
+                            }
+                        }
+                        byte <<= 1;
+                        ++x;
+                    }
+                }
+            } else {
+                x += 8;
+            }
+        }
+        if (all != zero) {
+            AddSpan
+        }
+    }
+#undef AddSpan
+
+    return region;
+}
+
+/*
+    Constructs an empty region.
+
+    \sa isEmpty()
+*/
+
+QRegion::QRegion()
+    : d(&shared_empty)
+{
+    d->ref.ref();
+}
+
+/*
+    \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
+*/
+
+QRegion::QRegion(const QRect &r, RegionType t)
+{
+    if (r.isEmpty()) {
+        d = &shared_empty;
+        d->ref.ref();
+    } else {
+//        d = new QRegionData;
+        QRegionPrivate *rp = 0;
+        if (t == Rectangle) {
+//            rp = new QRegionPrivate(r);
+            rp = qt_allocRegion(r);
+        } else if (t == Ellipse) {
+            QPainterPath path;
+            path.addEllipse(r.x(), r.y(), r.width(), r.height());
+            QPolygon a = path.toSubpathPolygons().at(0).toPolygon();
+            rp = qt_allocRegion();
+//            rp = new QRegionPrivate;
+            PolygonRegion(a.constData(), a.size(), EvenOddRule, rp);
+        }
+        d = rp;
+        d->ref = 1;
+#if defined(Q_WS_X11)
+        d->rgn = 0;
+        d->xrectangles = 0;
+#elif defined(Q_WS_MAC)
+        d->rgn = 0;
+#endif
+        d->qt_rgn = rp;
+    }
+}
+
+/*
+    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.
+*/
+
+QRegion::QRegion(const QPolygon &a, Qt::FillRule fillRule)
+{
+    if (a.count() > 2) {
+        //d =  new QRegionData;
+        // QRegionPrivate *rp = new QRegionPrivate;
+        QRegionPrivate *rp = qt_allocRegion();
+        PolygonRegion(a.constData(), a.size(),
+                fillRule == Qt::WindingFill ? WindingRule : EvenOddRule, rp);
+        d = rp;
+        d->ref = 1;
+#if defined(Q_WS_X11)
+        d->rgn = 0;
+        d->xrectangles = 0;
+#elif defined(Q_WS_MAC)
+        d->rgn = 0;
+#endif
+        d->qt_rgn = rp;
+    } else {
+        d = &shared_empty;
+        d->ref.ref();
+    }
+}
+
+
+/*
+    Constructs a new region which is equal to region \a r.
+*/
+
+QRegion::QRegion(const QRegion &r)
+{
+    d = r.d;
+    d->ref.ref();
+}
+
+
+/*
+    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().
+*/
+QRegion::QRegion(const QBitmap &bm)
+{
+    if (bm.isNull()) {
+        d = &shared_empty;
+        d->ref.ref();
+    } else {
+        // d = new QRegionData;
+//        QRegionPrivate *rp = new QRegionPrivate;
+        QRegionPrivate *rp = qt_allocRegion();
+
+        qt_bitmapToRegion(bm, rp);
+        d = rp;
+        d->ref = 1;
+#if defined(Q_WS_X11)
+        d->rgn = 0;
+        d->xrectangles = 0;
+#elif defined(Q_WS_MAC)
+        d->rgn = 0;
+#endif
+        d->qt_rgn = rp;
+    }
+}
+
+void QRegion::cleanUp(QRegion::QRegionData *x)
+{
+    // delete x->qt_rgn;
+#if defined(Q_WS_X11)
+    if (x->rgn)
+        XDestroyRegion(x->rgn);
+    if (x->xrectangles)
+        free(x->xrectangles);
+#elif defined(Q_WS_MAC)
+    if (x->rgn)
+        qt_mac_dispose_rgn(x->rgn);
+#endif
+    if(x->qt_rgn) {
+//        delete x->qt_rgn;
+        qt_freeRegion(x->qt_rgn);
+    } else {
+        delete x;
+    }
+}
+
+/*
+    Destroys the region.
+*/
+
+QRegion::~QRegion()
+{
+    if (!d->ref.deref())
+        cleanUp(d);
+}
+
+
+/*
+    Assigns \a r to this region and returns a reference to the region.
+*/
+
+QRegion &QRegion::operator=(const QRegion &r)
+{
+    r.d->ref.ref();
+    if (!d->ref.deref()) 
+        cleanUp(d);
+    d = r.d;
+    return *this;
+}
+
+
+/*
+    \internal
+*/
+
+QRegion QRegion::copy() const
+{
+    QRegion r;
+    QRegionData *x = 0; // new QRegionData;
+    QRegionPrivate *rp = 0;
+    if (d->qt_rgn)
+//        rp = new QRegionPrivate(*d->qt_rgn);
+        rp = qt_allocRegion(*d->qt_rgn);
+    else
+        rp = qt_allocRegion();
+    x = rp;
+    x->qt_rgn = rp;
+    x->ref = 1;
+#if defined(Q_WS_X11)
+    x->rgn = 0;
+    x->xrectangles = 0;
+#elif defined(Q_WS_MAC)
+    x->rgn = 0;
+#endif
+
+    if (!r.d->ref.deref())
+        cleanUp(r.d);
+    r.d = x;
+    return r;
+}
+
+/*
+    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_qws.cpp 0
+*/
+
+bool QRegion::isEmpty() const
+{
+    return d == &shared_empty || d->qt_rgn->numRects == 0;
+}
+
+
+/*
+    Returns true if the region contains the point \a p; otherwise
+    returns false.
+*/
+
+bool QRegion::contains(const QPoint &p) const
+{
+    return PointInRegion(d->qt_rgn, p.x(), p.y());
+}
+
+/*
+    \overload
+
+    Returns true if the region overlaps the rectangle \a r; otherwise
+    returns false.
+*/
+
+bool QRegion::contains(const QRect &r) const
+{
+    if(!d->qt_rgn)
+        return false;
+    if(d->qt_rgn->mode == QRegionPrivate::Single)
+        return d->qt_rgn->single.contains(r);
+
+    return RectInRegion(d->qt_rgn, r.left(), r.top(), r.width(), r.height()) != RectangleOut;
+}
+
+
+
+/*
+    Translates (moves) the region \a dx along the X axis and \a dy
+    along the Y axis.
+*/
+
+void QRegion::translate(int dx, int dy)
+{
+    if ((dx == 0 && dy == 0) || isEmptyHelper(d->qt_rgn))
+        return;
+
+    detach();
+    OffsetRegion(*d->qt_rgn, dx, dy);
+#if defined(Q_WS_X11)
+    if (d->xrectangles) {
+        free(d->xrectangles);
+        d->xrectangles = 0;
+    }
+#elif defined(Q_WS_MAC)
+    if(d->rgn) {
+        qt_mac_dispose_rgn(d->rgn);
+        d->rgn = 0;
+    }
+#endif
+}
+
+/*
+    \fn QRegion QRegion::unite(const QRegion &r) const
+    \obsolete
+
+    Use united(\a r) instead.
+*/
+
+/*
+    \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()
+*/
+
+QRegion QRegion::unite(const QRegion &r) const
+{
+    if (isEmptyHelper(d->qt_rgn))
+        return r;
+    if (isEmptyHelper(r.d->qt_rgn))
+        return *this;
+
+    if (d->qt_rgn->contains(*r.d->qt_rgn)) {
+        return *this;
+    } else if (r.d->qt_rgn->contains(*d->qt_rgn)) {
+        return r;
+    } else if (d->qt_rgn->canAppend(r.d->qt_rgn)) {
+        QRegion result(*this);
+        result.detach();
+        result.d->qt_rgn->append(r.d->qt_rgn);
+        return result;
+    } else if (r.d->qt_rgn->canAppend(d->qt_rgn)) {
+        QRegion result(r);
+        result.detach();
+        result.d->qt_rgn->append(d->qt_rgn);
+        return result;
+    } else if (EqualRegion(d->qt_rgn, r.d->qt_rgn)) {
+        return *this;
+    } else {
+        QRegion result;
+        result.detach();
+        UnionRegion(d->qt_rgn, r.d->qt_rgn, *result.d->qt_rgn);
+        return result;
+    }
+}
+
+QRegion& QRegion::operator+=(const QRegion &r)
+{
+    if (isEmptyHelper(d->qt_rgn))
+        return *this = r;
+    if (isEmptyHelper(r.d->qt_rgn))
+        return *this;
+
+    if (d->qt_rgn->contains(*r.d->qt_rgn)) {
+        return *this;
+    } else if (r.d->qt_rgn->contains(*d->qt_rgn)) {
+        return *this = r;
+    } else if (d->qt_rgn->canAppend(r.d->qt_rgn)) {
+        detach();
+        d->qt_rgn->append(r.d->qt_rgn);
+        return *this;
+    } else if (d->qt_rgn->canPrepend(r.d->qt_rgn)) {
+        detach();
+        d->qt_rgn->prepend(r.d->qt_rgn);
+        return *this;
+    } else if (EqualRegion(d->qt_rgn, r.d->qt_rgn)) {
+        return *this;
+    }
+
+    return *this = unite(r);
+}
+
+/*
+    \fn QRegion QRegion::intersect(const QRegion &r) const
+    \obsolete
+
+    Use intersected(\a r) instead.
+*/
+
+/*
+    \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.
+*/
+
+QRegion QRegion::intersect(const QRegion &r) const
+{
+    if (isEmptyHelper(d->qt_rgn) || isEmptyHelper(r.d->qt_rgn)
+        || !EXTENTCHECK(&d->qt_rgn->extents, &r.d->qt_rgn->extents))
+        return QRegion();
+
+    /* this is fully contained in r */
+    if (r.d->qt_rgn->contains(*d->qt_rgn))
+        return *this;
+
+    /* r is fully contained in this */
+    if (d->qt_rgn->contains(*r.d->qt_rgn))
+        return r;
+
+    if(r.d->qt_rgn->mode == QRegionPrivate::Single && 
+       d->qt_rgn->mode == QRegionPrivate::Single)
+        return QRegion(r.d->qt_rgn->single.intersected(d->qt_rgn->single));
+#ifdef QT_GREENPHONE_OPT
+    else if(r.d->qt_rgn->mode == QRegionPrivate::Single) 
+        return intersect(r.d->qt_rgn->single);
+    else if(d->qt_rgn->mode == QRegionPrivate::Single)
+        return r.intersect(d->qt_rgn->single);
+#endif
+
+    QRegion result;
+    result.detach();
+    miRegionOp(*result.d->qt_rgn, d->qt_rgn, r.d->qt_rgn, miIntersectO, 0, 0);
+
+    /*
+     * Can't alter dest's extents before we call miRegionOp because
+     * it might be one of the source regions and miRegionOp depends
+     * on the extents of those regions being the same. Besides, this
+     * way there's no checking against rectangles that will be nuked
+     * due to coalescing, so we have to examine fewer rectangles.
+     */
+    miSetExtents(*result.d->qt_rgn);
+    return result;
+}
+
+#ifdef QT_GREENPHONE_OPT
+/*
+  \overload
+  */
+QRegion QRegion::intersect(const QRect &r) const
+{
+    // No intersection
+    if(r.isEmpty() || isEmpty() || !EXTENTCHECK(&r, &d->qt_rgn->extents))
+        return QRegion();
+
+    // This is fully contained in r
+    if(CONTAINSCHECK(r, d->qt_rgn->extents))
+        return *this;
+
+    // r is fully contained in this
+    if(CONTAINSCHECK(d->qt_rgn->innerRect, r))
+        return QRegion(r);
+
+    if(d->qt_rgn->mode == QRegionPrivate::Single) {
+        return QRegion(d->qt_rgn->single & r);
+    } else {
+        QRegion rv(*this);
+        rv.detach();
+
+        rv.d->qt_rgn->extents &= r;
+        rv.d->qt_rgn->innerRect &= r;
+        rv.d->qt_rgn->innerArea = rv.d->qt_rgn->innerRect.height() * 
+                                  rv.d->qt_rgn->innerRect.width();
+
+        int numRects = 0;
+        for(int ii = 0; ii < rv.d->qt_rgn->numRects; ++ii) {
+            QRect result = rv.d->qt_rgn->rects[ii] & r;
+            if(!result.isEmpty())
+                rv.d->qt_rgn->rects[numRects++] = result;
+        }
+        rv.d->qt_rgn->numRects = numRects;
+        return rv;
+    }
+}
+
+/*
+   \overload
+ */
+const QRegion QRegion::operator&(const QRect &r) const
+{
+    return intersect(r);
+}
+
+/*
+   \overload
+ */
+QRegion& QRegion::operator&=(const QRect &r)
+{
+    if(isEmpty() || CONTAINSCHECK(r, d->qt_rgn->extents)) {
+        // Do nothing
+    } else if(r.isEmpty() || !EXTENTCHECK(&r, &d->qt_rgn->extents)) {
+        *this = QRegion();
+    } else if(CONTAINSCHECK(d->qt_rgn->innerRect, r)) {
+        *this = QRegion(r);
+    } else {
+        detach();
+        if(d->qt_rgn->mode == QRegionPrivate::Single) {
+            QRect result = d->qt_rgn->single & r;
+            d->qt_rgn->single = result;
+            d->qt_rgn->extents = result;
+            d->qt_rgn->innerRect = result;
+            d->qt_rgn->innerArea = result.height() * result.width();
+        } else {
+            d->qt_rgn->extents &= r;
+            d->qt_rgn->innerRect &= r;
+            d->qt_rgn->innerArea = d->qt_rgn->innerRect.height() *
+                                   d->qt_rgn->innerRect.width();
+
+            int numRects = 0;
+            for(int ii = 0; ii < d->qt_rgn->numRects; ++ii) {
+                QRect result = d->qt_rgn->rects[ii] & r;
+                if(!result.isEmpty())
+                    d->qt_rgn->rects[numRects++] = result;
+            }
+            d->qt_rgn->numRects = numRects;
+        }
+    }
+    return *this;
+}
+#endif
+
+/*
+    \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()
+*/
+
+QRegion QRegion::subtract(const QRegion &r) const
+{
+    if (isEmptyHelper(d->qt_rgn) || isEmptyHelper(r.d->qt_rgn))
+        return *this;
+    if (r.d->qt_rgn->contains(*d->qt_rgn))
+        return QRegion();
+    if (!EXTENTCHECK(&d->qt_rgn->extents, &r.d->qt_rgn->extents))
+        return *this;
+    if (EqualRegion(d->qt_rgn, r.d->qt_rgn))
+        return QRegion();
+
+    QRegion result;
+    result.detach();
+    SubtractRegion(d->qt_rgn, r.d->qt_rgn, *result.d->qt_rgn);
+    return result;
+}
+
+/*
+    \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()
+*/
+
+QRegion QRegion::eor(const QRegion &r) const
+{
+    if (isEmptyHelper(d->qt_rgn)) {
+        return r;
+    } else if (isEmptyHelper(r.d->qt_rgn)) {
+        return *this;
+    } else if (!EXTENTCHECK(&d->qt_rgn->extents, &r.d->qt_rgn->extents)) {
+        return (*this + r);
+    } else if (EqualRegion(d->qt_rgn, r.d->qt_rgn)) {
+        return QRegion();
+    } else {
+        QRegion result;
+        result.detach();
+        XorRegion(d->qt_rgn, r.d->qt_rgn, *result.d->qt_rgn);
+        return result;
+    }
+}
+
+/*
+    Returns the bounding rectangle of this region. An empty region
+    gives a rectangle that is QRect::isNull().
+*/
+
+QRect QRegion::boundingRect() const
+{
+    if (isEmpty())
+        return QRect();
+    return d->qt_rgn->extents;
+}
+
+/* \internal
+    Returns true if \a rect is guaranteed to be fully contained in \a region.
+    A false return value does not guarantee the opposite.
+*/
+bool qt_region_strictContains(const QRegion &region, const QRect &rect)
+{
+    if (isEmptyHelper(region.d->qt_rgn) || !rect.isValid())
+        return false;
+
+#if 0 // TEST_INNERRECT
+    static bool guard = false;
+    if (guard)
+        return QRect();
+    guard = true;
+    QRegion inner = region.d->qt_rgn->innerRect;
+    Q_ASSERT((inner - region).isEmpty());
+    guard = false;
+
+    int maxArea = 0;
+    for (int i = 0; i < region.d->qt_rgn->numRects; ++i) {
+        const QRect r = region.d->qt_rgn->rects.at(i);
+        if (r.width() * r.height() > maxArea)
+            maxArea = r.width() * r.height();
+    }
+
+    if (maxArea > region.d->qt_rgn->innerArea) {
+        qDebug() << "not largest rectangle" << region << region.d->qt_rgn->innerRect;
+    }
+    Q_ASSERT(maxArea <= region.d->qt_rgn->innerArea);
+#endif
+
+    const QRect r1 = region.d->qt_rgn->innerRect;
+    return (rect.left() >= r1.left() && rect.right() <= r1.right()
+            && rect.top() >= r1.top() && rect.bottom() <= r1.bottom());
+}
+
+/*
+    Returns an array of non-overlapping rectangles that make up the
+    region.
+
+    The union of all the rectangles is equal to the original region.
+*/
+QVector<QRect> QRegion::rects() const
+{
+    if (d->qt_rgn) {
+        d->qt_rgn->vector();
+        d->qt_rgn->rects.resize(d->qt_rgn->numRects);
+        return d->qt_rgn->rects;
+    } else {
+        return QVector<QRect>();
+    }
+}
+
+/*
+  \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
+*/
+void QRegion::setRects(const QRect *rects, int num)
+{
+    *this = QRegion();
+    if (!rects || num == 0 || (num == 1 && rects->isEmpty()))
+        return;
+
+    detach();
+
+    if(num == 1) {
+        d->qt_rgn->single = *rects;
+        d->qt_rgn->mode = QRegionPrivate::Single;
+        d->qt_rgn->numRects = num;
+        d->qt_rgn->extents = *rects;
+        d->qt_rgn->innerRect = *rects;
+    } else {
+        d->qt_rgn->mode = QRegionPrivate::Vector;
+        d->qt_rgn->rects.resize(num);
+        d->qt_rgn->numRects = num;
+        int left = INT_MAX,
+            right = INT_MIN,
+            top = INT_MAX,
+            bottom = INT_MIN;
+        for (int i = 0; i < num; ++i) {
+            const QRect &rect = rects[i];
+            d->qt_rgn->rects[i] = rect;
+            left = qMin(rect.left(), left);
+            right = qMax(rect.right(), right);
+            top = qMin(rect.top(), top);
+            bottom = qMax(rect.bottom(), bottom);
+            d->qt_rgn->updateInnerRect(rect);
+        }
+        d->qt_rgn->extents = QRect(QPoint(left, top), QPoint(right, bottom));
+    }
+}
+
+/*
+    Returns true if the region is equal to \a r; otherwise returns
+    false.
+*/
+
+bool QRegion::operator==(const QRegion &r) const
+{
+    if (!d->qt_rgn || !r.d->qt_rgn)
+        return r.d->qt_rgn == d->qt_rgn;
+
+    if (d == r.d)
+        return true;
+    else
+        return EqualRegion(d->qt_rgn, r.d->qt_rgn);
+}
+
+#ifdef QT_GREENPHONE_OPT
+bool QRegion::isRect() const
+{
+    return d->qt_rgn && d->qt_rgn->mode == QRegionPrivate::Single;
+}
+#endif
+
+QT_END_NAMESPACE