Reproducible with the following example. In the beginning the 'o' shows correctly, but if the height of the window is increased the 'o' will disappear, and the process will consume more and more memory, before coming to practically complete stop.

The same code using font.setPixelSize(1) works.

#include <QtGui>

class Widget : public QWidget
{
public:
Widget()
{
}

protected:
void paintEvent(QPaintEvent *e)

{ QPainter painter(this); // logical coordinates from -1 to 1 painter.setWindow(-1, -1, 2, 2); // mapped to the whole widget painter.setViewport(rect()); // cosmetic pen to avoid transformation painter.setPen(QPen(Qt::black, 0)); painter.drawLine(-1, 0, 1, 0); painter.drawLine(0, -1, 0, 1); QFont font; font.setPointSizeF(0.002); //font.setPixelSize(1); painter.setFont(font); painter.drawText(0, 0, "o"); }

};

int main(int argc, char **argv)
{
QApplication a( argc, argv );

Widget widget;
widget.resize(125, 50);
widget.show();

return a.exec();
}