c++ - QCustomPlot replot QCPLayer

我试图弄清楚如何使用QCPLayer仅重新绘制图中的某些项目。

qcustomplot documentation指出:



在下面的示例中，我试图这样做:

我正在通过从QCustomPlot继承来创建自定义qcustomplot:

QCustomPlot_custom.h

#pragma once
#include "qcustomplot.h"
#define USING_LAYER false

struct QCPCursor{
   QCPItemLine *hLine;
   QCPItemLine *vLine;
   QCPItemText* cursorText;
};

class QCustomPlot_custom :
   public QCustomPlot
{
   Q_OBJECT
private slots:
   void mouseMove(QMouseEvent*);

public:
   QCustomPlot_custom(QWidget* parent = NULL);
   ~QCustomPlot_custom(){}
private:
   QCPLayer* cursorLayer;
   QCPCursor cursor;
   void manageCursor(double x, double y, QPen pen);
public:
   void init(QVector<double> xdata, QVector<double> ydata);
};

此类使用一些要绘制的数据进行初始化。它还重载了mouseMove事件以控制自定义光标。 USING_LAYER设置为true意味着将自定义光标添加到它自己的图层(cursorLayer)。

通过将USING_LAYER设置为false，可以得到所需的效果，如下所示:



光标通过水平和垂直线以及坐标显示。

如果绘图中有很多图形和/或每个图形中有很多点，则在移动光标时会出现延迟。 (这就是我希望能够通过在图层中设置光标来仅重新绘制光标的原因。)

QCustomPlot_custom.cpp

QCustomPlot_custom::QCustomPlot_custom(QWidget* parent)
{
   connect(this, SIGNAL(mouseMove(QMouseEvent*)), this, SLOT(mouseMove(QMouseEvent*)));
   QCustomPlot::setInteraction(QCP::iRangeDrag, true);
   QCustomPlot::setInteraction(QCP::iRangeZoom, true);
   if (USING_LAYER){
      this->addLayer("cursorLayer", 0, QCustomPlot::limAbove);
      cursorLayer = new QCPLayer(this, "cursorLayer");
      cursorLayer->setMode(QCPLayer::lmBuffered);
   }
}

void QCustomPlot_custom::init(QVector<double> xdata, QVector<double> ydata)
{
   this->addGraph();
   this->graph(0)->setData(xdata, ydata);

   QColor colorPen(10, 25, 180, 255);
   QPen pen;
   pen.setWidth(50);
   pen.setColor(colorPen);
   this->graph()->setLineStyle(QCPGraph::lsLine);
   this->graph()->setPen(QPen(colorPen));
   this->xAxis->setLabel("X-axis");
   this->yAxis->setLabel("Y-axis");
   this->rescaleAxes();
   this->replot();
}

void QCustomPlot_custom::mouseMove(QMouseEvent* event)
{
   //Cursor coordinates:
   double x = this->xAxis->pixelToCoord(event->pos().x());
   double y = this->yAxis->pixelToCoord(event->pos().y());
   manageCursor(x, y, QPen(Qt::DashDotLine));
   if (USING_LAYER)
      cursorLayer->replot();
   else
      this->replot();
}

void QCustomPlot_custom::manageCursor(double x, double y, QPen pen)
{
   if (cursor.hLine)
      this->removeItem(cursor.hLine);
   cursor.hLine = new QCPItemLine(this);
   cursor.hLine->setPen(pen);
   cursor.hLine->start->setCoords(-QCPRange::maxRange, y);
   cursor.hLine->end->setCoords(QCPRange::maxRange, y);

   if (cursor.vLine)
      this->removeItem(cursor.vLine);
   cursor.vLine = new QCPItemLine(this);
   cursor.vLine->setPen(pen);
   cursor.vLine->start->setCoords(x, -QCPRange::maxRange);
   cursor.vLine->end->setCoords(x, QCPRange::maxRange);

   //Coordinates as text:
   if (cursor.cursorText)
      this->removeItem(cursor.cursorText);
   cursor.cursorText = new QCPItemText(this);
   cursor.cursorText->setText(QString("(%1, %2)").arg(x).arg(y));
   cursor.cursorText->position->setCoords(QPointF(x, y));
   QPointF pp = cursor.cursorText->position->pixelPosition() + QPointF(50.0, -15.0);
   cursor.cursorText->position->setPixelPosition(pp);
   cursor.cursorText->setFont(QFont(font().family(), 8));

   //Add to layer:
   if (USING_LAYER){
      cursor.hLine->setLayer(cursorLayer);
      cursor.vLine->setLayer(cursorLayer);
      cursor.cursorText->setLayer(cursorLayer);
   }
}

初始化类成员的函数:

void Qt_PlotTest::testPlot(){
   //Create some data and initalize plot:
   QVector<double> yData, xData;
   int imax = 100000;
   for (int i = 0; i < imax; i++){
      double x = double(i) / imax;
      xData.push_back(x);
      yData.push_back(pow(x, 2)*( 1.0 + 0.5*cos(20*x) + 0.1*sin(500*x - 0.1)));
   }
   ui.custom_QWidgetPlot->init(xData, yData);
}

使用layer方法时，光标不会渲染。我试图理解文档，但是对我来说如何正确使用QCPLayer尚不清楚。

我应该怎么做？

最佳答案

添加图层后

this->addLayer("cursorLayer", 0, QCustomPlot::limAbove);

不要调用QCPLayer构造函数来获取图层指针。将提供的 setter/getter 与层或索引的名称一起使用:

QCPLayer * QCustomPlot::layer ( const QString & name) const

QCPLayer * QCustomPlot::layer ( int index) const

cursorLayer = this->layer("cursorLayer");

同样，每个图和项都添加到currentLayer中，在您的情况下，它不是cursorLayer，而是main。您需要更改当前图层

bool QCustomPlot::setCurrentLayer ( const QString & name)

bool QCustomPlot::setCurrentLayer ( QCPLayer * layer)

即:

this->setCurrentLayer("cursorLayer");
this->addGraph();
...
this->setCurrentLayer("main");

或者，您可以为每个QCPLayerable指定图层

bool QCPLayerable::setLayer ( QCPLayer * layer)

bool QCPLayerable::setLayer ( const QString & layerName)

someGraph->setLayer("cursorLayer);