QCustomplot 多Y轴实现

老菜鸟的每一天

于 2024-11-14 14:07:21 发布

阅读量906

点赞数 10

CC 4.0 BY-SA版权

分类专栏：《Qt 项目实战经历全记录》文章标签： qt qcustomplot 多坐标轴

本文链接：https://blog.youkuaiyun.com/u011942101/article/details/143769685

项目中需要实现实时曲线的多Y轴实现，对比了qwt和 qcustomplot，觉得后者用起来更简单些，简单记录下：
效果如下
在这里插入图片描述

核心代码如下：

class AxisTag : public QObject
{
   
   
  Q_OBJECT
public:
  explicit AxisTag(QCPAxis *parentAxis);
  virtual ~AxisTag();
  
  // setters:
  void setPen(const QPen &pen);
  void setBrush(const QBrush &brush);
  void setText(const QString &text);
  
  // getters:
  QPen pen() const {
   
    return mLabel->pen(); }
  QBrush brush() const {
   
    return mLabel->brush(); }
  QString text() const {
   
    return mLabel->text(); }
  
  // other methods:
  void updatePosition(double value);
  
protected:
  QCPAxis *mAxis;
  QPointer<QCPItemTracer> mDummyTracer;
  QPointer<QCPItemLine> mArrow;
  QPointer<QCPItemText> mLabel;
};

cpp

#include "axistag.h"

AxisTag::AxisTag(QCPAxis *parentAxis) :
  QObject(parentAxis),
  mAxis(parentAxis)
{
   
   
  // The dummy tracer serves here as an invisible anchor which always sticks to the right side of
  // the axis rect
  mDummyTracer = new QCPItemTracer(mAxis->parentPlot());
  mDummyTracer->setVisible(true);
  mDummyTracer->position->setTypeX(QCPItemPosition::ptAxisRectRatio);
  mDummyTracer->position->setTypeY(QCPItemPosition::ptPlotCoords);
  mDummyTracer->position->setAxisRect(mAxis->axisRect());
  mDummyTracer->position->setAxes(0, mAxis);
  mDummyTracer->position->setCoords(1, 0);

  mDummyTracer->setStyle(QCPItemTracer::tsCircle);
  mDummyTracer->setSize(10);
  
  // the arrow end (head) is set to move along with the dummy tracer by setting it as its parent
  // anchor. Its coordinate system (setCoords) is thus pixels, and this is how the needed horizontal
  // offset for the tag of the second y axis is achieved. This horizontal offset gets dynamically
  // updated in AxisTag::updatePosition. the arrow "start" is simply set to have the "end" as parent
  // anchor. It is given a horizontal offset to the right, which results in a 15 pixel long arrow.
  mArrow = new QCPItemLine(mAxis->parentPlot());
  mArrow->setLayer("overlay");
  mArrow->setClipToAxisRect(false);
  mArrow->setHead(QCPLineEnding::esSpikeArrow);
  mArrow->end->setParentAnchor(mDummyTracer->position);
  mArrow->start->setParentAnchor(mArrow->end);
  mArrow->start->setCoords(15, 0);
  
  // The text label is anchored at the arrow start (tail) and has its "position" aligned at the
  // left, and vertically centered to the text label box.
  mLabel = new QCPItemText(mAxis->parentPlot());
  mLabel->setLayer("overlay");
  mLabel->setClipToAxisRect(false);
  mLabel->setPadding(QMargins(3, 0, 3, 0));
  mLabel->setBrush(QBrush(Qt::white));
  mLabel->setPen(QPen(Qt::blue));
  mLabel->setPositionAlignment(Qt::AlignLeft|Qt::AlignVCenter);
  mLabel->position->setParentAnchor(mArrow->start);
}

AxisTag::~AxisTag()
{
   
   
  if (mDummyTracer)
    mDummyTracer->parentPlot()->removeItem(mDummyTracer);
  if (mArrow)
    mArrow->parentPlot()->removeItem(mArrow);
  if (mLabel)
    mLabel->parentPlot()->removeItem(mLabel);
}

void AxisTag::setPen(const QPen &pen)
{
   
   
  mDummyTracer->setPen(pen);
  mArrow->setPen(pen);
  mLabel->setPen(pen);
}

void AxisTag::setBrush(const QBrush &brush)
{
   
   
   mDummyTracer->setBrush(brush);
  mLabel->setBrush(brush);
}

void AxisTag::setText(const QString &text)
{
   
   
  mLabel->setText(text);
}

void AxisTag::updatePosition(double value)
{
   
   
  // since both the arrow and the text label are chained to the dummy tracer (via anchor