Long live Qt 4.5!

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diff --git a/src/gui/painting/qpolygonclipper_p.h b/src/gui/painting/qpolygonclipper_p.h
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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (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 either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QPOLYGONCLIPPER_P_H
+#define QPOLYGONCLIPPER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of other Qt classes.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "private/qdatabuffer_p.h"
+
+QT_BEGIN_NAMESPACE
+
+/* based on sutherland-hodgman line-by-line clipping, as described in
+   Computer Graphics and Principles */
+template <typename InType, typename OutType, typename CastType> class QPolygonClipper
+{
+public:
+    QPolygonClipper()
+    {
+        x1 = y1 = x2 = y2 = 0;
+    }
+
+    ~QPolygonClipper()
+    {
+    }
+
+    void setBoundingRect(const QRect bounds)
+    {
+        x1 = bounds.x();
+        x2 = bounds.x() + bounds.width();
+        y1 = bounds.y();
+        y2 = bounds.y() + bounds.height();
+    }
+
+    QRect boundingRect()
+    {
+        return QRect(QPoint(x1, y1), QPoint(x2, y2));
+    }
+
+    inline OutType intersectLeft(const OutType &p1, const OutType &p2)
+    {
+        OutType t;
+        qreal dy = (p1.y - p2.y) / qreal(p1.x - p2.x);
+        t.x = x1;
+        t.y = static_cast<CastType>(p2.y + (x1 - p2.x) * dy);
+        return t;
+    }
+
+
+    inline OutType intersectRight(const OutType &p1, const OutType &p2)
+    {
+        OutType t;
+        qreal dy = (p1.y - p2.y) / qreal(p1.x - p2.x);
+        t.x = x2;
+        t.y = static_cast<CastType>(p2.y + (x2 - p2.x) * dy);
+        return t;
+    }
+
+
+    inline OutType intersectTop(const OutType &p1, const OutType &p2)
+    {
+        OutType t;
+        qreal dx = (p1.x - p2.x) / qreal(p1.y - p2.y);
+        t.x = static_cast<CastType>(p2.x + (y1 - p2.y) * dx);
+        t.y = y1;
+        return t;
+    }
+
+
+    inline OutType intersectBottom(const OutType &p1, const OutType &p2)
+    {
+        OutType t;
+        qreal dx = (p1.x - p2.x) / qreal(p1.y - p2.y);
+        t.x = static_cast<CastType>(p2.x + (y2 - p2.y) * dx);
+        t.y = y2;
+        return t;
+    }
+
+
+    void clipPolygon(const InType *inPoints, int inCount, OutType **outPoints, int *outCount,
+                     bool closePolygon = true)
+    {
+        Q_ASSERT(outPoints);
+        Q_ASSERT(outCount);
+
+        if (inCount < 2) {
+            *outCount = 0;
+            return;
+        }
+
+        buffer1.reset();
+        buffer2.reset();
+
+        QDataBuffer<OutType> *source = &buffer1;
+        QDataBuffer<OutType> *clipped = &buffer2;
+
+        // Gather some info since we are iterating through the points anyway..
+        bool doLeft = false, doRight = false, doTop = false, doBottom = false;
+        OutType ot;
+        for (int i=0; i<inCount; ++i) {
+            ot = inPoints[i];
+            clipped->add(ot);
+
+            if (ot.x < x1)
+                doLeft = true;
+            else if (ot.x > x2)
+                doRight = true;
+            if (ot.y < y1)
+                doTop = true;
+            else if (ot.y > y2)
+                doBottom = true;
+        }
+
+        if (doLeft && clipped->size() > 1) {
+            QDataBuffer<OutType> *tmp = source;
+            source = clipped;
+            clipped = tmp;
+            clipped->reset();
+            int lastPos, start;
+            if (closePolygon) {
+                lastPos = source->size() - 1;
+                start = 0;
+            } else {
+                lastPos = 0;
+                start = 1;
+                if (source->at(0).x >= x1)
+                    clipped->add(source->at(0));
+            }
+            for (int i=start; i<inCount; ++i) {
+                const OutType &cpt = source->at(i);
+                const OutType &ppt = source->at(lastPos);
+
+                if (cpt.x >= x1) {
+                    if (ppt.x >= x1) {
+                        clipped->add(cpt);
+                    } else {
+                        clipped->add(intersectLeft(cpt, ppt));
+                        clipped->add(cpt);
+                    }
+                } else if (ppt.x >= x1) {
+                    clipped->add(intersectLeft(cpt, ppt));
+                }
+                lastPos = i;
+            }
+        }
+
+        if (doRight && clipped->size() > 1) {
+            QDataBuffer<OutType> *tmp = source;
+            source = clipped;
+            clipped = tmp;
+            clipped->reset();
+            int lastPos, start;
+            if (closePolygon) {
+                lastPos = source->size() - 1;
+                start = 0;
+            } else {
+                lastPos = 0;
+                start = 1;
+                if (source->at(0).x <= x2)
+                    clipped->add(source->at(0));
+            }
+            for (int i=start; i<source->size(); ++i) {
+                const OutType &cpt = source->at(i);
+                const OutType &ppt = source->at(lastPos);
+
+                if (cpt.x <= x2) {
+                    if (ppt.x <= x2) {
+                        clipped->add(cpt);
+                    } else {
+                        clipped->add(intersectRight(cpt, ppt));
+                        clipped->add(cpt);
+                    }
+                } else if (ppt.x <= x2) {
+                    clipped->add(intersectRight(cpt, ppt));
+                }
+
+                lastPos = i;
+            }
+
+        }
+
+        if (doTop && clipped->size() > 1) {
+            QDataBuffer<OutType> *tmp = source;
+            source = clipped;
+            clipped = tmp;
+            clipped->reset();
+            int lastPos, start;
+            if (closePolygon) {
+                lastPos = source->size() - 1;
+                start = 0;
+            } else {
+                lastPos = 0;
+                start = 1;
+                if (source->at(0).y >= y1)
+                    clipped->add(source->at(0));
+            }
+            for (int i=start; i<source->size(); ++i) {
+                const OutType &cpt = source->at(i);
+                const OutType &ppt = source->at(lastPos);
+
+                if (cpt.y >= y1) {
+                    if (ppt.y >= y1) {
+                        clipped->add(cpt);
+                    } else {
+                        clipped->add(intersectTop(cpt, ppt));
+                        clipped->add(cpt);
+                    }
+                } else if (ppt.y >= y1) {
+                    clipped->add(intersectTop(cpt, ppt));
+                }
+
+                lastPos = i;
+            }
+        }
+
+        if (doBottom && clipped->size() > 1) {
+            QDataBuffer<OutType> *tmp = source;
+            source = clipped;
+            clipped = tmp;
+            clipped->reset();
+            int lastPos, start;
+            if (closePolygon) {
+                lastPos = source->size() - 1;
+                start = 0;
+            } else {
+                lastPos = 0;
+                start = 1;
+                if (source->at(0).y <= y2)
+                    clipped->add(source->at(0));
+            }
+            for (int i=start; i<source->size(); ++i) {
+                const OutType &cpt = source->at(i);
+                const OutType &ppt = source->at(lastPos);
+
+                if (cpt.y <= y2) {
+                    if (ppt.y <= y2) {
+                        clipped->add(cpt);
+                    } else {
+                        clipped->add(intersectBottom(cpt, ppt));
+                        clipped->add(cpt);
+                    }
+                } else if (ppt.y <= y2) {
+                    clipped->add(intersectBottom(cpt, ppt));
+                }
+                lastPos = i;
+            }
+        }
+
+        if (closePolygon && clipped->size() > 0) {
+            // close clipped polygon
+            if (clipped->at(0).x != clipped->at(clipped->size()-1).x ||
+                clipped->at(0).y != clipped->at(clipped->size()-1).y) {
+                OutType ot = clipped->at(0);
+                clipped->add(ot);
+            }
+        }
+        *outCount = clipped->size();
+        *outPoints = clipped->data();
+    }
+
+private:
+    int x1, x2, y1, y2;
+    QDataBuffer<OutType> buffer1;
+    QDataBuffer<OutType> buffer2;
+};
+
+QT_END_NAMESPACE
+
+#endif // QPOLYGONCLIPPER_P_H