pango:font-description-set-absolute-size (desc size)

desc -- a pango:font-description instance
size -- a number coerced to a double float for the new size, in Pango units

Sets the size field of a font description, in device units. There are pango:+scale+ Pango units in one device unit. For an output backend where a device unit is a pixel, a size value of (* 10 pango:+scale+) gives a 10 pixel font.

This is mutually exclusive with the pango:font-description-size function which sets the font size in points.