either a Pango.BaselineShift enumeration value or an absolute value (> 1024) in Pango units, relative to the baseline of the previous run. Positive values displace the text upwards.
the newly allocated Pango.Attribute, which should be freed with Pango.Attribute.destroy
Create a new baseline displacement attribute.
The effect of this attribute is to shift the baseline of a run, relative to the run of preceding run.