callout.cpp Example File

callout/callout.cpp
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the Qt Charts module of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:GPL$
 ** Commercial License Usage
 ** Licensees holding valid commercial Qt licenses may use this file in
 ** accordance with the commercial license agreement provided with the
 ** Software or, alternatively, in accordance with the terms contained in
 ** a written agreement between you and The Qt Company. For licensing terms
 ** and conditions see https://www.qt.io/terms-conditions. For further
 ** information use the contact form at https://www.qt.io/contact-us.
 **
 ** GNU General Public License Usage
 ** Alternatively, this file may be used under the terms of the GNU
 ** General Public License version 3 or (at your option) any later version
 ** approved by the KDE Free Qt Foundation. The licenses are as published by
 ** the Free Software Foundation and appearing in the file LICENSE.GPL3
 ** included in the packaging of this file. Please review the following
 ** information to ensure the GNU General Public License requirements will
 ** be met: https://www.gnu.org/licenses/gpl-3.0.html.
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #include "callout.h"
 #include <QtGui/QPainter>
 #include <QtGui/QFontMetrics>
 #include <QtWidgets/QGraphicsSceneMouseEvent>
 #include <QtGui/QMouseEvent>
 #include <QtCharts/QChart>

 Callout::Callout(QChart *chart):
     QGraphicsItem(chart),
     m_chart(chart)
 {
 }

 QRectF Callout::boundingRect() const
 {
     QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
     QRectF rect;
     rect.setLeft(qMin(m_rect.left(), anchor.x()));
     rect.setRight(qMax(m_rect.right(), anchor.x()));
     rect.setTop(qMin(m_rect.top(), anchor.y()));
     rect.setBottom(qMax(m_rect.bottom(), anchor.y()));
     return rect;
 }

 void Callout::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
     Q_UNUSED(option)
     Q_UNUSED(widget)
     QPainterPath path;
     path.addRoundedRect(m_rect, 5, 5);

     QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
     if (!m_rect.contains(anchor)) {
         QPointF point1, point2;

         // establish the position of the anchor point in relation to m_rect
         bool above = anchor.y() <= m_rect.top();
         bool aboveCenter = anchor.y() > m_rect.top() && anchor.y() <= m_rect.center().y();
         bool belowCenter = anchor.y() > m_rect.center().y() && anchor.y() <= m_rect.bottom();
         bool below = anchor.y() > m_rect.bottom();

         bool onLeft = anchor.x() <= m_rect.left();
         bool leftOfCenter = anchor.x() > m_rect.left() && anchor.x() <= m_rect.center().x();
         bool rightOfCenter = anchor.x() > m_rect.center().x() && anchor.x() <= m_rect.right();
         bool onRight = anchor.x() > m_rect.right();

         // get the nearest m_rect corner.
         qreal x = (onRight + rightOfCenter) * m_rect.width();
         qreal y = (below + belowCenter) * m_rect.height();
         bool cornerCase = (above && onLeft) || (above && onRight) || (below && onLeft) || (below && onRight);
         bool vertical = qAbs(anchor.x() - x) > qAbs(anchor.y() - y);

         qreal x1 = x + leftOfCenter * 10 - rightOfCenter * 20 + cornerCase * !vertical * (onLeft * 10 - onRight * 20);
         qreal y1 = y + aboveCenter * 10 - belowCenter * 20 + cornerCase * vertical * (above * 10 - below * 20);;
         point1.setX(x1);
         point1.setY(y1);

         qreal x2 = x + leftOfCenter * 20 - rightOfCenter * 10 + cornerCase * !vertical * (onLeft * 20 - onRight * 10);;
         qreal y2 = y + aboveCenter * 20 - belowCenter * 10 + cornerCase * vertical * (above * 20 - below * 10);;
         point2.setX(x2);
         point2.setY(y2);

         path.moveTo(point1);
         path.lineTo(anchor);
         path.lineTo(point2);
         path = path.simplified();
     }
     painter->setBrush(QColor(255, 255, 255));
     painter->drawPath(path);
     painter->drawText(m_textRect, m_text);
 }

 void Callout::mousePressEvent(QGraphicsSceneMouseEvent *event)
 {
     event->setAccepted(true);
 }

 void Callout::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 {
     if (event->buttons() & Qt::LeftButton){
         setPos(mapToParent(event->pos() - event->buttonDownPos(Qt::LeftButton)));
         event->setAccepted(true);
     } else {
         event->setAccepted(false);
     }
 }

 void Callout::setText(const QString &text)
 {
     m_text = text;
     QFontMetrics metrics(m_font);
     m_textRect = metrics.boundingRect(QRect(0, 0, 150, 150), Qt::AlignLeft, m_text);
     m_textRect.translate(5, 5);
     prepareGeometryChange();
     m_rect = m_textRect.adjusted(-5, -5, 5, 5);
 }

 void Callout::setAnchor(QPointF point)
 {
     m_anchor = point;
 }

 void Callout::updateGeometry()
 {
     prepareGeometryChange();
     setPos(m_chart->mapToPosition(m_anchor) + QPoint(10, -50));
 }