[gedit-list] How determine file path of currently open document

[Peter Bittner <peter bittner gmx net>]

Hi there,

I'm working on a Gedit plugin that needs to determine the file path of
the currently open document (if the content of the document is already
saved as a file). In addition (for unsaved documents) I need to figure
out Gedit's "working directory" (the one displayed with the `Save
As...` dialog).

Is there any API documentation that helps me with that? It seems
surprisingly hard to find anything about this using a Web search. --
Alternatively, where can I find Gedit's source code?

Thanks in advance for any hints,
Peter