get-file in Dialogs

• (get-file message parent directory filename extension style filters) -> path or #f
   message = #f : string or #f
   parent = #f : frame% or dialog% object or #f
   directory = #f : path or #f
   filename = #f : path or #f
   extension = #f : string or #f
   style = null : list of symbols in '(packages enter-packages)
   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 selecting existing files.

  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 use the extension if the user does not supply one; the extension string should not contain a period. The extension is ignored on other platforms.

  If style list matters only under Mac OS X. If the list contains 'packages, a user is allowed to select a package directory, which is a directory with a special suffix (e.g., ``.app'') that the Finder normally displays like a file. If the list contains 'enter-packages, a user is allowed to select a file within a package directory. If the list contains both 'packages and 'enter-packages, the former is ignored.

  Under Windows, filters determines a set of filters from which the user can choose in the dialog. Each element of the filters list contains two strings: a description of the filter as seen by the user, and a filter pattern matched against file names.