QCustomPlot开启opengl

1. 下载freeglut源码

freeglut官网下载地址

或者直接下载编译好的：https://www.transmissionzero.co.uk/software/freeglut-devel/

2. 编译freeglut源码

一种方法是安装Cmake编译，一种方法是直接用vs2017及以上编译（README.cmake）

（1）创建build文件夹，来存放cmake编译之后产生的项目文件

 （2）cmake编译

（3）打开工程，全编译

（4） 路径：dll、lib

 

（1）vs2017打开文件夹

（2）更改cmake设置

（3）修改

 （4）CMake全部生成

3. QCustomPlot添加OpenGL

（1）添加opengl32.lib、freeglut.lib 添加include

（2）main.cpp添加

#include <GL/freeglut.h>

glutInit(&argc, argv);

 （3）customplot初始化

ui.widget->setOpenGl(true);

bool b = ui.widget->openGl();//是否开启成功

 4. QCustomPlot问题

（1）问题一： 当界面上有多张qcustomplot图表时，多张图表的刷新会出现混乱。

#  qcustomplot.cpp

void QCPPaintBufferGlFbo::draw(QCPPainter *painter) const
{
  if (!painter || !painter->isActive())
  {
    qDebug() << Q_FUNC_INFO << "invalid or inactive painter passed";
    return;
  }
  if (!mGlFrameBuffer)
  {
    qDebug() << Q_FUNC_INFO << "OpenGL frame buffer object doesn't exist, reallocateBuffer was not called?";
    return;
  }

// 添加这行代码即可
  if(QOpenGLContext::currentContext() != mGlContext.toStrongRef()){
      mGlContext.toStrongRef()->makeCurrent(mGlContext.toStrongRef()->surface());
  }

  painter->drawImage(0, 0, mGlFrameBuffer->toImage());
}

 （2）问题二： Qt开启高分辨率自适应策略时，QCustomPlot开启opengl之后，图表内的像素比例会出现问题，导致图表显示异常。

#  qcustomplot.cpp

QCustomPlot::QCustomPlot(QWidget *parent) :
  QWidget(parent),
  xAxis(0),
  yAxis(0),
  xAxis2(0),
  yAxis2(0),
  legend(0),
  mBufferDevicePixelRatio(1.0), // will be adapted to primary screen below
  mPlotLayout(0),
  mAutoAddPlottableToLegend(true),
  mAntialiasedElements(QCP::aeNone),
  mNotAntialiasedElements(QCP::aeNone),
  mInteractions(0),
  mSelectionTolerance(8),
  mNoAntialiasingOnDrag(false),
  mBackgroundBrush(Qt::white, Qt::SolidPattern),
  mBackgroundScaled(true),
  mBackgroundScaledMode(Qt::KeepAspectRatioByExpanding),
  mCurrentLayer(0),
  mPlottingHints(QCP::phCacheLabels|QCP::phImmediateRefresh),
  mMultiSelectModifier(Qt::ControlModifier),
  mSelectionRectMode(QCP::srmNone),
  mSelectionRect(0),
  mOpenGl(false),
  mMouseHasMoved(false),
  mMouseEventLayerable(0),
  mMouseSignalLayerable(0),
  mReplotting(false),
  mReplotQueued(false),
  mOpenGlMultisamples(16),
  mOpenGlAntialiasedElementsBackup(QCP::aeNone),
  mOpenGlCacheLabelsBackup(true)
{
  setAttribute(Qt::WA_NoMousePropagation);
  setAttribute(Qt::WA_OpaquePaintEvent);
  setFocusPolicy(Qt::ClickFocus);
  setMouseTracking(true);
  QLocale currentLocale = locale();
  currentLocale.setNumberOptions(QLocale::OmitGroupSeparator);
  setLocale(currentLocale);
#ifdef QCP_DEVICEPIXELRATIO_SUPPORTED
#  ifdef QCP_DEVICEPIXELRATIO_FLOAT
  setBufferDevicePixelRatio(QApplication::desktop()->devicePixelRatioF());	//将代码中获取设备像素比例改成从桌面获取
//  setBufferDevicePixelRatio(QWidget::devicePixelRatioF());
#  else
  setBufferDevicePixelRatio(QWidget::devicePixelRatio());
#  endif
#endif
  
  mOpenGlAntialiasedElementsBackup = mAntialiasedElements;
  mOpenGlCacheLabelsBackup = mPlottingHints.testFlag(QCP::phCacheLabels);
  // create initial layers:
  mLayers.append(new QCPLayer(this, QLatin1String("background")));
  mLayers.append(new QCPLayer(this, QLatin1String("grid")));
  mLayers.append(new QCPLayer(this, QLatin1String("main")));
  mLayers.append(new QCPLayer(this, QLatin1String("axes")));
  mLayers.append(new QCPLayer(this, QLatin1String("legend")));
  mLayers.append(new QCPLayer(this, QLatin1String("overlay")));
  updateLayerIndices();
  setCurrentLayer(QLatin1String("main"));
  layer(QLatin1String("overlay"))->setMode(QCPLayer::lmBuffered);
  
  // create initial layout, axis rect and legend:
  mPlotLayout = new QCPLayoutGrid;
  mPlotLayout->initializeParentPlot(this);
  mPlotLayout->setParent(this); // important because if parent is QWidget, QCPLayout::sizeConstraintsChanged will call QWidget::updateGeometry
  mPlotLayout->setLayer(QLatin1String("main"));
  QCPAxisRect *defaultAxisRect = new QCPAxisRect(this, true);
  mPlotLayout->addElement(0, 0, defaultAxisRect);
  xAxis = defaultAxisRect->axis(QCPAxis::atBottom);
  yAxis = defaultAxisRect->axis(QCPAxis::atLeft);
  xAxis2 = defaultAxisRect->axis(QCPAxis::atTop);
  yAxis2 = defaultAxisRect->axis(QCPAxis::atRight);
  legend = new QCPLegend;
  legend->setVisible(false);
  defaultAxisRect->insetLayout()->addElement(legend, Qt::AlignRight|Qt::AlignTop);
  defaultAxisRect->insetLayout()->setMargins(QMargins(12, 12, 12, 12));
  
  defaultAxisRect->setLayer(QLatin1String("background"));
  xAxis->setLayer(QLatin1String("axes"));
  yAxis->setLayer(QLatin1String("axes"));
  xAxis2->setLayer(QLatin1String("axes"));
  yAxis2->setLayer(QLatin1String("axes"));
  xAxis->grid()->setLayer(QLatin1String("grid"));
  yAxis->grid()->setLayer(QLatin1String("grid"));
  xAxis2->grid()->setLayer(QLatin1String("grid"));
  yAxis2->grid()->setLayer(QLatin1String("grid"));
  legend->setLayer(QLatin1String("legend"));
  
  // create selection rect instance:
  mSelectionRect = new QCPSelectionRect(this);
  mSelectionRect->setLayer(QLatin1String("overlay"));
  
  setViewport(rect()); // needs to be called after mPlotLayout has been created
  
  replot(rpQueuedReplot);
  }