OpenType font looks shaggy in Windows.

[shinichy]

I'd like to use Adobe Source Code Pro OpenType font (otf) in QPlainTextEdit, but it looks shaggy when I use it in Qt 5.4.2, Windows 8.1.
TrueType font looks good.
Do I miss something or is this a bug of QPlainTextEdit?

screenshot of otf
screenshot of ttf
https://github.com/adobe-fonts/source-code-pro

#include <QApplication>
#include <QPlainTextEdit>

int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  QPlainTextEdit editWidget;
  editWidget.setFont(QFont("Source Code Pro"));
  editWidget.show();

  return a.exec();
}

Thanks in advance.