QFontMetrics::height always 1 px with specific font

In Linux/Debian drawing text with font "tiaofuheiti.ttf"(already uploaded) , find  QFontMetrics.height always is 1px.

Following code, can get correct font height.

QTextDocument doc(QStringLiteral("1"));
doc.setDocumentMargin(0);
doc.setDefaultFont(font());
doc.adjustSize();
int fontHeight = doc.size().height();

It looks like is a qt's bug why QFontMetrics.height cannot get correct height.

Please check that issue.

Thank u in advance.