Qt QCustomPlot 鼠标悬浮提示

使用QCustomPlot绘图时，相信大多数童鞋们都会有类似的诉求：希望鼠标移动到节点时，可以显示该节点的数据。这里转载了一篇关于 鼠标悬浮提示 的一篇文章，并对该文章涉及的代码经过了整理，经实践证明是可行的。

鼠标悬浮提示效果图

头文件

 QCPToolTip

class QCPToolTip : public QCPAbstractItem
{
    Q_OBJECT
public:
    explicit QCPToolTip(QCustomPlot *parentPlot);

    void setText(const QString &text);
    void setFont(const QFont &font);
    void setTextColor(const QColor &color);
    void setBorderPen(const QPen &pen);
    void setBrush(const QBrush &brush);
    void setRadius(double xRadius, double yRadius, Qt::SizeMode mode = Qt::AbsoluteSize);
    void setOffset(double xOffset, double yOffset);
    void setPadding(const QMargins &paddings);

    Q_SLOT void handleTriggerEvent(QMouseEvent *event);
    void updatePosition(const QPointF &newPos, bool replot = false);

    void update();
    virtual double selectTest(const QPointF &pos, bool onlySelectable, QVariant *details) const Q_DECL_OVERRIDE;

    QCPItemPosition * const position;

protected:
    bool mPlotReplot;    // 表明是由QCustomPlot刷新的，需要更新位置
    QString mText;
    Qt::Alignment mTextAlignment;
    QFont mFont;
    QColor mTextColor;
    QPen mBorderPen;
    QBrush mBrush;

    QPointF mRadius;
    Qt::SizeMode mSizeMode;

    QPointF mOffset;     // 偏移鼠标的距离
    QMargins mPadding;

    QCPGraph *mHighlightGraph;
    QPointF mGraphDataPos;

    virtual void draw(QCPPainter *painter) Q_DECL_OVERRIDE;
    virtual void drawGraphScatterPlot(QCPPainter *painter, QCPGraph *graph, const QPointF &pos);

    int pickClosest(double target, const QVector<double> &vector);
};

源文件

 QCPToolTip

QCPToolTip::QCPToolTip(QCustomPlot *parentPlot)
    : QCPAbstractItem(parentPlot),
      position(createPosition(QLatin1String("position"))),
      mPlotReplot(true),
      mTextAlignment(Qt::AlignLeft | Qt::AlignVCenter),
      mRadius(6, 6),
      mSizeMode(Qt::AbsoluteSize),
      mHighlightGraph(nullptr)
{
    position->setType(QCPItemPosition::ptAbsolute);
    setSelectable(false);
    setLayer("overlay");

    setBorderPen(Qt::NoPen);
    setBrush(QColor(87, 98, 93, 180));
    setTextColor(Qt::white);
    setOffset(20, 20);
    setPadding(QMargins(6, 6, 6, 6));
    connect(mParentPlot, SIGNAL(mouseMove(QMouseEvent *)), this, SLOT(handleTriggerEvent(QMouseEvent *)));
}
void QCPToolTip::setText(const QString &text)
{
    mText = text;
};
void QCPToolTip::setFont(const QFont &font)
{
    mFont = font;
};
void QCPToolTip::setTextColor(const QColor &color)
{
    mTextColor = color;
};
void QCPToolTip::setBorderPen(const QPen &pen)
{
    mBorderPen = pen;
};
void QCPToolTip::setBrush(const QBrush &brush)
{
    mBrush = brush;
};
void QCPToolTip::setRadius(double xRadius, double yRadius, Qt::SizeMode mode /*= Qt::AbsoluteSize*/)
{
    mRadius = QPointF(xRadius,yRadius);
    mSizeMode = mode;
};
void QCPToolTip::setOffset(double xOffset, double yOffset)
{
    mOffset = QPointF(xOffset,yOffset);
};
void QCPToolTip::setPadding(const QMargins &paddings)
{
    mPadding = paddings;
};

void QCPToolTip::handleTriggerEvent(QMouseEvent *event)
{
    updatePosition(event->pos(), true);   // true 表示需要单独刷新，将调用update函数
}

void QCPToolTip::update()
{
    mPlotReplot = false;    // 表明单独刷新
    layer()->replot();
    mPlotReplot = true;    // 单独刷新完毕
}

// 不需要鼠标点击测试，因为ToolTip是跟随鼠标的，鼠标点击不到
double QCPToolTip::selectTest(const QPointF &pos, bool onlySelectable, QVariant *details) const
{
    Q_UNUSED(pos)
    Q_UNUSED(onlySelectable)
    Q_UNUSED(details)
    return -1;
}
int QCPToolTip::pickClosest(double target, const QVector<double> &vector)
{
    if (vector.size() < 2)
        return 0;

    // 查找第一个大于或等于target的位置
    auto it = std::lower_bound(vector.constBegin(), vector.constEnd(), target);

    if (it == vector.constEnd()) return vector.size() - 1;
    else if (it == vector.constBegin()) return 0;
    else return target - *(it - 1) < *it - target ? (it - vector.constBegin() - 1): (it - vector.constBegin());
}

void QCPToolTip::updatePosition(const QPointF &newPos, bool replot)
{
    mHighlightGraph = nullptr;
    double tolerance = mParentPlot->selectionTolerance();

    for (int i = mParentPlot->graphCount() - 1; i >= 0; --i)
    {
        QCPGraph *graph = mParentPlot->graph(i);
        // graph不可见或者scatter style 为空的时候，不显示ToolTip
        if (!graph->realVisibility() || graph->scatterStyle().isNone())
            continue;

        double limitDistance = tolerance;   // limitDistance 用于选择的范围
        double penWidth = graph->pen().widthF();
        QCPScatterStyle scatterStyle = graph->scatterStyle();

        limitDistance = qMax(scatterStyle.size(), tolerance);
        penWidth = scatterStyle.isPenDefined() ? scatterStyle.pen().widthF() : penWidth;

        // details会返回最接近的一个数据点，selectTest是不精确的，所以后面还要判断
        QVariant details;
        double currentDistance = graph->selectTest(newPos, false, &details);

        QCPDataSelection selection = details.value<QCPDataSelection>();
        if (currentDistance >= 0 && currentDistance < limitDistance + penWidth && !selection.isEmpty())
        {
            // 取出当前key和value值，并且转换为像素位置
            double key = graph->dataMainKey(selection.dataRange().begin());
            double value = graph->dataMainValue(selection.dataRange().begin());
            QPointF pos = graph->coordsToPixels(key, value);

            QRectF rect(pos.x() - limitDistance * 0.5, pos.y() - limitDistance * 0.5, limitDistance, limitDistance);
            rect = rect.adjusted(-penWidth, -penWidth, penWidth, penWidth);

            // 判断鼠标位置是否在数据点上
            if (rect.contains(newPos))
            {
                /*
                 * 解开以下注释，可以使得我们的文字跟轴标签的文字是一样的（但跟轴标签实际的显示效果可能是不一样的，
                 * 这里要注意，例如对于科学计数法，轴可能会使用美化），同时要注意当轴标签不显示的时候tickVectorLabels
                 * 返回的是空的，所以我们要做一下判断
                */
                // 注意这里的方式是不精确的，适用于文字轴这种类型的
                /*int keyIndex = pickClosest(key, graph->keyAxis()->tickVector());
                setText(QString("%1:%2").arg(graph->keyAxis()->tickVectorLabels().at(keyIndex),
                                         QString::number(value)));*/

                setText(QString("%1:%2").arg(QString::number(key), QString::number(value)));
                mHighlightGraph = graph;
                mGraphDataPos = pos;

                mParentPlot->setCursor(Qt::PointingHandCursor);
                position->setPixelPosition(newPos);  // 更新位置
                setVisible(true);

                if (replot) {
                    update();
                }
                break;
            }
        }
    }

    if (!mHighlightGraph && visible())
    {
        mParentPlot->setCursor(Qt::ArrowCursor);
        setVisible(false);
        if (replot) {
            update();
        }
    }
}
void QCPToolTip::draw(QCPPainter *painter)
{
    if (mPlotReplot) {  // 当前是由QCustomPlot的replot函数刷新的，所以要更新位置
        updatePosition(position->pixelPosition(), false);  // false表明不刷新
        if (!visible()) {
            // 由于位置更新之后，ToolTip可能会隐藏掉了，所以此处直接返回
            return;
        }
    }

    drawGraphScatterPlot(painter, mHighlightGraph, mGraphDataPos);

    QPointF pos = position->pixelPosition() + mOffset;
    painter->translate(pos);  // 移动painter的绘制原点位置

    QFontMetrics fontMetrics(mFont);
    QRect textRect = fontMetrics.boundingRect(0, 0, 0, 0, Qt::TextDontClip | mTextAlignment, mText);
    textRect.moveTopLeft(QPoint(mPadding.left(), mPadding.top()));

    QRect textBoxRect = textRect.adjusted(-mPadding.left(), -mPadding.top(), mPadding.right(), mPadding.bottom());
    textBoxRect.moveTopLeft(QPoint());

    // 限制ToolTip不超过QCustomPlot的范围
    if (pos.x() + textBoxRect.width() >= mParentPlot->viewport().right())
        painter->translate(-mOffset.x() * 2 - textBoxRect.width(), 0);
    if (pos.y() + textBoxRect.height() * 2 >= mParentPlot->viewport().bottom())
        painter->translate(0, -mOffset.y() * 2 - textBoxRect.height());

    // 绘制背景和边框
    if ((mBrush != Qt::NoBrush && mBrush.color().alpha() != 0) ||
            (mBorderPen != Qt::NoPen && mBorderPen.color().alpha() != 0))
    {
        double clipPad = mBorderPen.widthF();
        QRect boundingRect = textBoxRect.adjusted(-clipPad, -clipPad, clipPad, clipPad);

        painter->setPen(mBorderPen);
        painter->setBrush(mBrush);
        painter->drawRoundedRect(boundingRect, mRadius.x(), mRadius.y(), mSizeMode);
    }

    // 绘制文字
    painter->setFont(mFont);
    painter->setPen(mTextColor);
    painter->setBrush(Qt::NoBrush);
    painter->drawText(textRect, Qt::TextDontClip | mTextAlignment, mText);
}

void QCPToolTip::drawGraphScatterPlot(QCPPainter *painter, QCPGraph *graph, const QPointF &pos)
{
    if (!graph) return;

    QCPScatterStyle style = graph->scatterStyle();
    if (style.isNone()) return;

    if (graph->selectionDecorator())  // 如果有select decorator，则使用修饰器的风格
        style = graph->selectionDecorator()->getFinalScatterStyle(style);

    style.applyTo(painter, graph->pen());
    style.setSize(style.size() * 1.2); // 放大一点
    style.drawShape(painter, pos);
}

使用方法

if(m_tip == nullptr){
    m_tip = new QCPToolTip(m_plotLine);//m_plotLine is QCustomPlot
}

原文地址

https://blog.csdn.net/qq10097355/article/details/105048146