gtk:print-settings-length (settings key unit)

settings -- a gtk:print-settings object
key -- a string with a key
unit -- a gtk:unit value with the unit of the return value
value -- a number with the length

The gtk:print-settings-length function returns the length value of key, converted to unit. The (setf gtk:print-settings-length) function associates a length in units of unit with key.

 (setq settings (make-instance 'gtk:print-settings))
=> #<gtk:print-settings {1004A34623}>
 (setf (gtk:print-settings-length settings "paper-width" :mm) 100.0d0)
 (gtk:print-settings-length settings "paper-width" :mm)
=> 100.0d0