ArrowItem.cpp

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/*
 * Copyright 2011-2016 Universiteit Antwerpen
 *
 * Licensed under the EUPL, Version 1.1 or  as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at: http://ec.europa.eu/idabc/eupl5
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing
 * permissions and limitations under the Licence.
 */
#include "../../cpp_simptshell/mesh_drawer/ArrowItem.h"

#include <cmath>

namespace SimPT_Shell {

using std::sqrt;

ArrowItem::ArrowItem(QGraphicsItem* parent) : QGraphicsLineItem(parent) {}

void ArrowItem::paint(QPainter* p, const QStyleOptionGraphicsItem* , QWidget* )
{
        // construct arrow head
        QPointF const start = line().p1();
        QPointF const end = line().p2();
        QPointF const mid = start + 0.75e0 * (end - start);
        double const vx = end.x() - start.x();
        double const vy = end.y() - start.y();

        double length = sqrt(vx * vx + vy * vy);
        if (length != 0) {
                // perpendicular vector
                double const px = -vy / length;
                double const py = vx / length;

                // Arrow head lines go from end point to points about 3/4 of the total arrow,
                // extending sideways about 1/4 of the arrow length.
                QPointF const arwp1 = mid + QPointF((int) ((length / 4.) * px), (int) ((length / 4.) * py));
                QPointF const arwp2 = mid - QPointF((int) ((length / 4.) * px), (int) ((length / 4.) * py));

                p->setPen(pen());
                // Draw arrow head
                p->drawLine(end, arwp1);
                p->drawLine(end, arwp2);
                // Draw arrow line
                p->drawLine(start, end);
        }
}

} // namespace