qt - 在QChartView上实现选择

我想基于QChart和QChartView实现图表选择。
类的族有很大的优势-easy use of openGL和animations，例如:

QLineSeries *series = new QLineSeries();
series->setUseOpenGL(true); // <==

QChart *chart = new QChart();
chart->addSeries(series);
chart->setAnimationOptions(QChart::AllAnimations); // <==

QChartView *chartView = new QChartView(chart);
chartView->setRenderHint(QPainter::Antialiasing);

QChartView类提供了有用的缩放功能-QChartView::setRubberBand():

chartView->setRubberBand(QChartView::RectangleRubberBand);

主要问题是橡皮筋只能用于缩放，但是我需要将其实现为水平选择而不进行缩放，因为该功能通常在音频编辑器中实现:


现在，当我继承了QChartView时，可以在选择后禁用缩放:

class ChartView : public QChartView
...
bool m_drawRubberBand;
QRubberBand m_rubberBand;
...

ChartView::ChartView(QChart *chart, QWidget *parent)
    : QChartView(chart, parent)
{
    setRubberBand(QChartView::HorizontalRubberBand);
}
...

// Just copy-paste from the Qt 5 sources - file \Src\qtcharts\src\charts\qchartview.cpp:
/*!
If the rubber band rectangle is displayed in the press event specified by
\a event, the event data is used to update the rubber band geometry.
Otherwise, the default QGraphicsView::mouseMoveEvent() implementation is called.
*/
void ChartView::mouseMoveEvent(QMouseEvent *event)
{
    if (m_drawRubberBand && m_rubberBand.isVisible())
    {
        QRect rect = chart()->plotArea().toRect();
        int width = event->pos().x() - m_rubberBandOrigin.x();
        int height = event->pos().y() - m_rubberBandOrigin.y();
        if (!rubberBand().testFlag(VerticalRubberBand))
        {
            m_rubberBandOrigin.setY(rect.top());
            height = rect.height();
        }
        if (!rubberBand().testFlag(HorizontalRubberBand))
        {
            m_rubberBandOrigin.setX(rect.left());
            width = rect.width();
        }
        m_rubberBand.setGeometry(QRect(m_rubberBandOrigin.x(), m_rubberBandOrigin.y(), width, height).normalized());
    }
    else
    {
        QGraphicsView::mouseMoveEvent(event);
    }
}

然后，我不能对鼠标键释放事件执行缩放操作:

void ChartView::mouseReleaseEvent(QMouseEvent *event)
{
    if (m_rubberBand.isVisible())
    {
        if (event->button() == Qt::LeftButton)
        {
            m_drawRubberBand = false;
            do_nothing(); // <==
        }

    }
}

所以，我现在的问题是:

可视橡皮筋的边界如何映射到真实图表的坐标。即，如何将选择映射到图表上的线系列？现在我收到相同的错误坐标:

  void MyView::resizeEvent(QResizeEvent *event)
  {
      QChartView::resizeEvent(event);

      QRect rct(QPoint(10, 10), QPoint(20, 20));
      qDebug() << mapToScene(rct); <==
  }

输出:

QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
QPolygonF(QPointF(10,10)QPointF(21,10)QPointF(21,21)QPointF(10,21))
...

如何与 View 一起按比例调整现有橡胶选择的大小？

编辑:可能是有用的关键字QGraphicsScene::setSelectionArea()。

The Qt 5 chip example which provides nice rubber band selection，但是基于QGraphicsView的示例而不是基于QChartView的示例。

最佳答案

通过回答以下问题，该问题得以解决:Get mouse coordinates in QChartView's axis system

关键时刻:必须调用QChart::mapToValue()来进行正确的坐标转换:

QPointF ChartView::point_to_chart(const QPoint &pnt)
{
    QPointF scene_point = mapToScene(pnt);
    QPointF chart_point = chart()->mapToValue(scene_point);

    return chart_point;
}

和逆变换:

QPoint ChartView::chart_to_view_point(QPointF char_coord)
{
    QPointF scene_point = chart()->mapToPosition(char_coord);
    QPoint view_point = mapFromScene(scene_point);

    return view_point;
}

这就是我在resizeEvent上实现橡皮筋大小调整的方法。
首先，我在鼠标释放事件中保存了当前的橡皮筋:

void ChartView::mouseReleaseEvent(QMouseEvent *event)
{
    if (m_rubberBand.isVisible())
    {
        update_rubber_band(event);
        m_drawRubberBand = false;
        save_current_rubber_band(); <==
    }
}

在哪里:

void ChartView::update_rubber_band(QMouseEvent * event)
{
    QRect rect = chart()->plotArea().toRect();
    int width = event->pos().x() - m_rubberBandOrigin.x();
    int height = event->pos().y() - m_rubberBandOrigin.y();
    if (!rubberBand().testFlag(VerticalRubberBand))
    {
        m_rubberBandOrigin.setY(rect.top());
        height = rect.height();
    }
    if (!rubberBand().testFlag(HorizontalRubberBand))
    {
        m_rubberBandOrigin.setX(rect.left());
        width = rect.width();
    }
    m_rubberBand.setGeometry(QRect(m_rubberBandOrigin.x(), m_rubberBandOrigin.y(), width, height).normalized());
}

和:

void ChartView::save_current_rubber_band()
{
    QRect rect = m_rubberBand.geometry();

    QPointF chart_top_left = point_to_chart(rect.topLeft());
    m_chartRectF.setTopLeft(chart_top_left);

    QPointF chart_bottom_right = point_to_chart(rect.bottomRight());
    m_chartRectF.setBottomRight(chart_bottom_right);
}

以及如何在调整大小事件上重绘(repaint)橡胶:

void ChartView::resizeEvent(QResizeEvent *event)
{
    QChartView::resizeEvent(event);

    if (m_rubberBand.isVisible())
    {
        restore_rubber_band();
    }

    apply_nice_numbers();
}

在哪里:

void ChartView::restore_rubber_band()
{
    QPoint view_top_left = chart_to_view_point(m_chartRectF.topLeft());
    QPoint view_bottom_right = chart_to_view_point(m_chartRectF.bottomRight());

    m_rubberBandOrigin = view_top_left;
    m_rubberBand.setGeometry(QRect(view_top_left, view_bottom_right));
}

并且不要忘记"nice numbers":

void ChartView::apply_nice_numbers()
{
    QList<QAbstractAxis*> axes_list = chart()->axes();
    for each(QAbstractAxis* abstract_axis in axes_list)
    {
        QValueAxis* value_axis = qobject_cast<QValueAxis*>(abstract_axis);
        if (value_axis)
        {
            value_axis->applyNiceNumbers();
        }
    }
}

这种逻辑在起作用。
调整大小之前:


调整大小后: