#include <QString>

#include <QFont>
#include <QFontDatabase>

#include <QLabel>
#include <QWidget>

#include <QVBoxLayout>

#include <QMessageBox>

#include <QApplication>


int main(int argc, char *argv[])
{ static constexpr int FONTSIZE = 36; // in points

  // *** ADJUST TO YOUR FONT PATH ***
  static const QString fontpath(QStringLiteral("C:/QtBugReport/FontSelectionIncorrect/Fonts/"));

  static const QString testtext(QStringLiteral("The quick brown fox jumps over the lazy dog. 1234567890"));

  // font engine
  // NO PROBLEM WITH DEFAULT/NATIVE FONT ENGINE (UNDER WINDOWS 10)
  qputenv("QT_QPA_PLATFORM","windows:fontengine=freetype"); // PROBLEM
//  qputenv("QT_QPA_PLATFORM","windows:fontengine=gdi"); // PROBLEM

  QApplication app(argc,argv);

  // add application fonts
  const int fontid1 = QFontDatabase::addApplicationFont(fontpath + "NotoSans-Regular.ttf"),
            fontid2 = QFontDatabase::addApplicationFont(fontpath + "NotoSansCJK-Regular.ttc");
  if(fontid1==-1 || fontid2==-1)
    { QMessageBox::critical(nullptr,QStringLiteral("ERROR"),QStringLiteral("Can't add fonts"));
      return 1;
    }

  // PROBLEM GOES AWAY IF LINE BELOW IS NOT EXECUTED
  QFont::insertSubstitution(QStringLiteral("Noto Sans"),QStringLiteral("Noto Sans CJK JP"));

  // regular without explicit hinting preference
  QFont f1(QStringLiteral("Noto Sans"),FONTSIZE);
  QLabel *l1 = new QLabel(testtext);
  l1->setFont(f1);

  // regular with explicit hinting preference
  QFont f2(QStringLiteral("Noto Sans"),FONTSIZE);
  f2.setHintingPreference(QFont::PreferFullHinting); // PROBLEM IF SET AND FONT ENGINE IS "freetype" or "gdi"
  QLabel *l2 = new QLabel(testtext);
  l2->setFont(f2);

  // main widget
  QWidget widget;
  QVBoxLayout *layout = new QVBoxLayout();
  layout->addWidget(l1);
  layout->addWidget(l2);
  widget.setLayout(layout);

  widget.show();
  return QApplication::exec();
}