Pops up a file selector box (the standard one for the platform). The result is a path selected by the user or null if the user cancels the dialog. The returned pathname may or may not exist. The dialog may or may not be modal.
If default-path is not null, it is used as the starting directory for the file selector. If default-filename is not null, it is used as the default filename when appropriate. If default-extension is not null, the return path will use the extension if the user does not supply one (Windows).
The wildcard argument determines what files are displayed in the
file selector (X Windows, Windows). In X Windows, this pattern is used
as a pattern as in the shell. Under Windows, the wildcard can
may be a specification for multiple
types of file with a description for each, such as:
"BMP files (*.bmp) | *.bmp | GIF files (*.gif) | *.gif"
The flags arugument can be any bitwise combination of the following: