(cffi:defcstruct css-location
  (bytes :size)
  (chars :size)
  (lines :size)
  (line-bytes :size)
  (line-chars :size))  

The gtk:css-location structure is used to present a location in a file or other source of data parsed by the CSS engine. The bytes and line-bytes offsets are meant to be used to programmatically match data. The lines and line-chars offsets can be used for printing the location in a file.

Note that the lines parameter starts from 0 and is increased whenever a CSS line break is encountered. CSS defines the C character sequences "\r\n", "\r", "\n" and "\f" as newlines. If your document uses different rules for line breaking, you might want run into problems here. See the gtk:css-section documentation for an example.