put-file in Dialogs

• (put-file message parent directory filename extension style filters) -> string or #f
   message = #f : string or #f
   parent = #f : frame% or dialog% object or #f
   directory = #f : string or #f
   filename = #f : string or #f
   extension = #f : string or #f
   style = null : an empty list of symbols
     filters = '(("Any" "*.*")) : list of 2-string lists

  Obtains a file pathname from the user via the platform-specific standard (modal) dialog, using parent as the parent window if it is specified, and using message as a message at the top of the dialog if it is not #f.

  The result is #f if the user cancels the dialog, the selected pathname otherwise. The returned pathname may or may not exist, although the style of the dialog is directed towards creating a new file.

  If directory is not #f, it is used as the starting directory for the file selector (otherwise the starting directory is chosen automatically in a platform-specific manner, usually based on the current directory and the user's interactions in previous calls to get-file, put-file, etc.). If filename is not #f, it is used as the default filename when appropriate, and it should not contain a directory path prefix.

  Under Windows, if extension is not #f, the returned path will gets a default extension if the user does not supply one. If extension is the empty string, then the extension is derived from the user's filters choice if the corresponding pattern is of the form "*.extension"; if the pattern is "*.*", then no default extension is added. Finally, if extension is any string other than the empty string, extension is used as the default extension when the user's filters choice has the pattern "*.*". Meanwhile, the filters argument has the same format and auxilliary role as for get-file. The extension and filters arguments are ignored on platforms other than Windows.

  The style argument is provided for future extensions. Currently, style must be the empty list.