Sets the current font matrix to a scale by a factor of size, replacing any font matrix previously set with setFontSize() or setFontMatrix(). This results in a font size of size user space units. (More precisely, this matrix will result in the font's em-square being a size by size square in user space.)

If text is drawn without a call to setFontSize(), (nor setFontMatrix() nor setScaledFont()), the default font size is 10.0.