I have build an Yocto image according to @graugans instructions and Qt support. All ok and working. Only the Fonts in the Qt application are doing strange things. When starting the Qt application it tells me a Helvetica font is loaded and used. But for as far as I know Helvetica is a Sans-Serif type while all letters are in the Serif type. When I overload the default font setting by Code: QApplication::setFont(QFont("DejaVu Sans")); It looks better although a lot of things where set to the font Arial in the application which also result in showing them as Serif while it should have shown a Sans-Serif type of font. Can some one helping me understanding why this is happening?