callout.cpp

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** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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** This file is part of the Qt Charts module of the Qt Toolkit.
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#include "callout.h"
#include <QDebug>
#include <QtCharts/QChart>
#include <QtGui/QFontMetrics>
#include <QtGui/QMouseEvent>
#include <QtGui/QPainter>
#include <QtWidgets/QGraphicsSceneMouseEvent>

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

void Callout::setText(const QString& text) {
    text_ = text;
    textRect_ = QFontMetrics{font_}.boundingRect(QRect{0, 0, 150, 150}, Qt::AlignLeft, text_);
    textRect_.translate(5, 5);
    prepareGeometryChange();
    rect_ = textRect_.adjusted(-5, -5, 5, 5);
}

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

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

QRectF Callout::boundingRect() const {
    QPointF anchor = mapFromParent(chart_->mapToPosition(anchor_));
    QRectF rect;
    rect.setLeft(std::min(rect_.left(), anchor.x()));
    rect.setRight(std::max(rect_.right(), anchor.x()));
    rect.setTop(std::min(rect_.top(), anchor.y()));
    rect.setBottom(std::max(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(rect_, 5, 5);

    QPointF anchor = mapFromParent(chart_->mapToPosition(anchor_));
    if(!rect_.contains(anchor)) {
        QPointF point1, point2;

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

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

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

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

        point1.setX(x1);
        point1.setY(y1);

        float x2 = x + leftOfCenter * 20 - rightOfCenter * 10 + cornerCase * !vertical * (onLeft * 20 - onRight * 10);

        float 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(textRect_, 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);
    }
}