Merges the fields that are set in @desc_to_merge into the fields in
@desc, without copying allocated fields.
This is like [method@Pango.FontDescription.merge], but only a shallow copy
is made of the family name and other allocated fields. @desc can only
be used until @desc_to_merge is modified or freed. This is meant to
be used when the merged font description is only needed temporarily.
Merges the fields that are set in @desc_to_merge into the fields in @desc, without copying allocated fields.
This is like [method@Pango.FontDescription.merge], but only a shallow copy is made of the family name and other allocated fields. @desc can only be used until @desc_to_merge is modified or freed. This is meant to be used when the merged font description is only needed temporarily.