preferences:set-default in Framework Functions

• (preferences:set-default symbol value test) -> void?
     symbol : symbol?
     value : any/c
     test : (any/c . -> . any)

  This function must be called every time your application starts up, before any call to preferences:get, preferences:set (for any given preference).

  If you use preferences:set-un/marshall, you must call this function before calling it.

  This sets the default value of the preference symbol to value. If the user has chosen a different setting, the user's setting will take precedence over the default value.

  The last argument, test is used as a safeguard. That function is called to determine if a preference read in from a file is a valid preference. If test returns #t, then the preference is treated as valid. If test returns #f then the default is used.