diff options
Diffstat (limited to 'lisp/gnus/nnoo.el')
| -rw-r--r-- | lisp/gnus/nnoo.el | 36 |
1 files changed, 34 insertions, 2 deletions
diff --git a/lisp/gnus/nnoo.el b/lisp/gnus/nnoo.el index be38f8d1d75..4f066939d25 100644 --- a/lisp/gnus/nnoo.el +++ b/lisp/gnus/nnoo.el @@ -22,13 +22,42 @@ ;;; Commentary: +;; This file defines Gnus' non-object-oriented polymorphism scheme for +;; server backends. It allows the rest of the code to be relatively +;; agnostic about how particular backends (eg IMAP, maildir, nntp, +;; etc) actually work: it simply calls standard functions on them, and +;; retrieves standard variable values from them. + +;; New backends are created using `nnoo-declare' (functionally +;; equivalent to `defclass'). The macro `defvoo' creates server +;; variables (equivalent to slots in EIEIO). The macro `deffoo' +;; creates server functions (equivalent to generic methods). + +;; The Gnus manual goes into fair detail about this +;; inheritance/polymorphism system, see (info "(gnus) Writing New Back +;; Ends"). + +;; Any time the user switches servers, the function +;; `nnoo-change-servers' copies all the relevant server variables into +;; global variables, to make that server the "current server". + ;;; Code: (require 'nnheader) (eval-when-compile (require 'cl)) -(defvar nnoo-definition-alist nil) -(defvar nnoo-state-alist nil) +(defvar nnoo-definition-alist nil + "A list of all available server backends. +All backends that have been defined with `nnoo-declare' appear +here. Each backend appears as a list of four elements: the +symbol name of the backend, the parent backends it inherits from, +a list of potential server variables, and a list of backend +functions it implements.") + +(defvar nnoo-state-alist nil + "A list of all the current servers. +Includes their server variables and their active groups.") + (defvar nnoo-parent-backend nil) (defmacro defvoo (var init &optional doc &rest map) @@ -57,6 +86,9 @@ (setcar funcs (cons func (car funcs))))) (defmacro nnoo-declare (backend &rest parents) + "Declare BACKEND as a new backend, inheriting from PARENTS. +Any functions or variables not implemented by BACKEND may be used +from PARENTS instead." `(eval-and-compile (if (assq ',backend nnoo-definition-alist) (setcar (cdr (assq ',backend nnoo-definition-alist)) |