Returns the ID of the style to use if the specified @style_id is not present in the current style scheme.
a style ID.
the ID of the style to use if the specified @style_id is not present in the current style scheme or %NULL if the style has no fallback defined. The returned string is owned by the @language and must not be modified.
3.4
See Implementation
Returns the ID of the style to use if the specified @style_id is not present in the current style scheme.