pfontdesc:SetGravity(gravity)
The gravity field specifies how the glyphs should be rotated. If gravity is
#PANGO_GRAVITY_AUTO, this actually unsets the gravity mask on
the font description.
This function is seldom useful to the user. Gravity should normally be set on a Pango context.
See pcontext:SetBaseGravity() for a list of constants that
can be passed in the gravity argument.