merge

Merges the fields that are set in desc_to_merge into the fields in this.

If replace_existing is false, only fields in this that are not already set are affected. If true, then fields that are already set will be replaced as well.

If desc_to_merge is null, this function performs nothing.

Parameters:

this	a `PangoFontDescription`
desc_to_merge	the `PangoFontDescription` to merge from, or null
replace_existing	if true, replace fields in this with the corresponding values from desc_to_merge, even if they are already exist.