#include <QFont>
#include <QFontDatabase>

#include <QString>

#include <QDebug>
#include <QMessageBox>

#include <QPainter>
#include <QPaintEvent>

#include <QWidget>

#include <QGuiApplication>

class MyWidget : public QWidget
{ protected:
    virtual void paintEvent(QPaintEvent *event) override;

  public:
    MyWidget(QWidget *parent=nullptr) : QWidget(parent)
    { QWidget::setMinimumSize(400,400);
    }
};

void MyWidget::paintEvent(QPaintEvent *event)
{ (void)event; // ignore

  QPainter painter(this);
  painter.setRenderHint(QPainter::TextAntialiasing,true);

  // small font
  // problem with "Noto Sans" font, no problem with "Arial" or "Tahoma" font
  QFont fnt(QStringLiteral("Noto Sans"));
  fnt.setPixelSize(20); // small

  // prefer full hinting
  fnt.setHintingPreference(QFont::PreferFullHinting);
  painter.setFont(fnt);

  // horizontal and vertical text
  const int contw = width(), conth = height();
  painter.drawText(0,0,contw,conth,Qt::AlignHCenter|Qt::AlignBottom,QStringLiteral("il12345-+|#$%abcdefghy"));

  painter.setTransform(QTransform(0,-1, +1,0, 0,conth),false);
  painter.drawText(0,0,conth,contw,Qt::AlignHCenter|Qt::AlignVCenter,QStringLiteral("il12345-+|#$%abcdefghy"));
}

int main(int argc, char *argv[])
{
  // uncommenting either of the two lines below gives correct results
  //qputenv("QT_QPA_PLATFORM","windows:fontengine=freetype"); // looks good
  //qputenv("QT_QPA_PLATFORM","windows:fontengine=gdi"); // looks good

  // test was in Window 10 system with OS font scaling at 150%
  // if line below is commented out, the results still look bad, but less so.
  QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::RoundPreferFloor);

  // application
  QApplication app(argc,argv);

  // directory of "Noto Sans" font file
  // for testing, the font files is placed two directories up from the executable
  const QString appdir(QCoreApplication::applicationDirPath()),
                fontdir(QCoreApplication::applicationDirPath()+QStringLiteral("/../../"));
  if(QFontDatabase::addApplicationFont(fontdir+QStringLiteral("NotoSans-Regular.ttf"))==-1)
    { (void)QMessageBox::critical(nullptr,QStringLiteral("Error"),QStringLiteral("Could not open font file"));
      return 1;
    }

  // widget with texts
  MyWidget mywidget;
  mywidget.show();

  return QApplication::exec();
}