QFontInfo::fixedPitch can return true for fonts which are not fixedPitch.

On Windows (with a proportional default font) the following creates a UI with Courier New as expected, on X11 (SuSE Linux 10) this prints the debug statement instead.

include <QtGui>

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

QFont font;
font.setFixedPitch(true);

QFontInfo fontInfo(font);
if (fontInfo.fixedPitch())
qDebug() << "default font exists in fixed pitch";
else

{ font = QFont("Courier New", font.pointSize()); a.setFont(font); }

QTextEdit edit;
edit.show();

return a.exec();
}