size, replacing
any font matrix previously set with cairoSetFontSize or
cairoSetFontMatrix. 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.)cairoSetFontSize(cr, size)sizecairoSetFontSize, (nor
cairoSetFontMatrix nor cairoSetScaledFont), the default
font size is 10.0.