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+/****************************************************************************
+**
+** Copyright (C) 2011 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.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#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() :
+ buffer1(0), buffer2(0)
+ {
+ 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
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