QOpenGLWidget, QPainter and QScrollArea do not fit together

#include <QApplication>
#include <QMainWindow>
#include <QOpenGLFunctions_2_1>
#include <QOpenGLWidget>
#include <QPainter>
#include <QScrollArea>

class GLWidget final : public QOpenGLWidget, public QOpenGLFunctions_2_1 {

  auto initializeGL() -> void override {
    initializeOpenGLFunctions();
  }

  auto paintGL() -> void override {
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_TRIANGLES);
    glColor3d(1.0, 0.0, 0.0);
    glVertex3d(0.0, 1.0, 0.0);
    glColor3d(0.0, 1.0, 0.0);
    glVertex3d(-1.0, -1.0, 0.0);
    glColor3d(0.0, 0.0, 1.0);
    glVertex3d(1.0, -1.0, 0.0);
    glEnd();
    auto painter = QPainter{};
    painter.begin(this);
    painter.setPen(QColor{"yellow"});
    painter.drawText(100, 100, "Text");
    painter.end();
  }
};

auto main(int argc, char** argv) -> int {
  auto app = QApplication{argc, argv};
  auto win = QMainWindow{};
  auto widget = new GLWidget{};
  widget->setMinimumSize(QSize{250, 250});
  auto scrollArea = new QScrollArea{};
  scrollArea->setWidget(widget);
  win.setCentralWidget(scrollArea);
  //win.setCentralWidget(widget);
  win.resize(500, 500);
  win.show();
  return QApplication::exec();
}

#include <QApplication>
#include <QMainWindow>
#include <QOpenGLFunctions_2_1>
#include <QOpenGLWidget>
#include <QPainter>
#include <QScrollArea>

class GLWidget final : public QOpenGLWidget, public QOpenGLFunctions_2_1 {

  auto initializeGL() -> void override {
    initializeOpenGLFunctions();
  }

  auto paintGL() -> void override {
    auto painter = QPainter{this};
    painter.fillRect(0, 0, 250, 250, QColor{"black"});
    painter.setPen(QColor{"red"});
    painter.drawLine(QPoint{125, 10}, QPoint{10, 240});
    painter.drawLine(QPoint{10, 240}, QPoint{240, 240});
    painter.drawLine(QPoint{240, 240}, QPoint{125, 10});
    painter.setPen(QColor{"yellow"});
    painter.drawText(100, 100, "Text");
  }
};

auto main(int argc, char** argv) -> int {
  auto app = QApplication{argc, argv};
  auto win = QMainWindow{};
  auto widget = new GLWidget{};
  widget->setMinimumSize(QSize{250, 250});
  auto scrollArea = new QScrollArea{};
  scrollArea->setWidget(widget);
  win.setCentralWidget(scrollArea);
  //win.setCentralWidget(widget);
  win.resize(500, 500);
  win.show();
  return QApplication::exec();
}

#include <QApplication>
#include <QMainWindow>
#include <QOpenGLFunctions_2_1>
#include <QOpenGLWidget>
#include <QPainter>
#include <QScrollArea>
#include <QStackedLayout>

class GLWidget final : public QOpenGLWidget, public QOpenGLFunctions_2_1 {

  auto initializeGL() -> void override {
    initializeOpenGLFunctions();
  }

  auto paintGL() -> void override {
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_TRIANGLES);
    glColor3d(1.0, 0.0, 0.0);
    glVertex3d(0.0, 1.0, 0.0);
    glColor3d(0.0, 1.0, 0.0);
    glVertex3d(-1.0, -1.0, 0.0);
    glColor3d(0.0, 0.0, 1.0);
    glVertex3d(1.0, -1.0, 0.0);
    glEnd();
  }
};

class TextWidget final : public QWidget {
  auto paintEvent(QPaintEvent*) -> void override {
    auto painter = QPainter{};
    painter.begin(this);
    painter.setPen(QColor{"yellow"});
    painter.drawText(100, 100, "Text");
    painter.end();
  }
};

auto main(int argc, char** argv) -> int {
  auto app = QApplication{argc, argv};
  auto win = QMainWindow{};
  auto glWidget = new GLWidget{};
  auto textWidget = new TextWidget{};
  auto stackedLayout = new QStackedLayout{};
  stackedLayout->setStackingMode(QStackedLayout::StackAll);
  stackedLayout->addWidget(glWidget);
  stackedLayout->addWidget(textWidget);
  auto widget = new QWidget{};
  widget->setLayout(stackedLayout);
  widget->setMinimumSize(QSize{250, 250});
  auto scrollArea = new QScrollArea{};
  scrollArea->setWidget(widget);
  win.setCentralWidget(scrollArea);
  //win.setCentralWidget(widget);
  win.resize(500, 500);
  win.show();
  return QApplication::exec();
}