From 84379e0c711ca6d817f1994ae39c93476c77dc65 Mon Sep 17 00:00:00 2001
From: Lars Magne Ingebrigtsen <larsi@quimbies.gnus.org>
Date: Wed, 20 Oct 2010 18:39:37 +0200
Subject: [PATCH] Allow gnus-blocked-images to be a function.

---
 lisp/ChangeLog    |  5 +++++
 lisp/gnus-art.el  | 19 +++++++++++++++++--
 lisp/gnus-html.el |  6 +++---
 texi/ChangeLog    |  5 +++++
 texi/gnus.texi    | 13 +++++++++----
 5 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 22f989efd..33e55c63d 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2010-10-20  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+	* gnus-art.el (gnus-blocked-images): New function.  Allow the
+	`gnus-blocked-images' to be a function.
+
 2010-10-20  Julien Danjou  <julien@danjou.info>
 
 	* spam.el (spam-list-of-processors): Mark as obsolete.
diff --git a/lisp/gnus-art.el b/lisp/gnus-art.el
index 537ae4da8..f42838d08 100644
--- a/lisp/gnus-art.el
+++ b/lisp/gnus-art.el
@@ -1639,8 +1639,11 @@ This requires GNU Libidn, and by default only enabled if it is found."
   :group 'gnus-article
   :type 'boolean)
 
-(defcustom gnus-blocked-images "."
-  "Images that have URLs matching this regexp will be blocked."
+(defcustom gnus-blocked-images 'gnus-block-private-groups
+  "Images that have URLs matching this regexp will be blocked.
+This can also be a function to be evaluated.  If so, it will be
+called with the group name as the parameter, and should return a
+regexp."
   :version "24.1"
   :group 'gnus-art
   :type 'regexp)
@@ -6896,6 +6899,18 @@ If given a prefix, show the hidden text instead."
 			    (point))
 	  (set-buffer buf))))))
 
+(defun gnus-block-private-groups (group)
+  (if (gnus-news-group-p group)
+      ;; Block nothing in news groups.
+      nil
+    ;; Block everything anywhere else.
+    "."))
+
+(defun gnus-blocked-images ()
+  (if (functionp gnus-blocked-images)
+      (funcall gnus-blocked-images gnus-newsgroup-name)
+    gnus-blocked-images))
+
 ;;;
 ;;; Article editing
 ;;;
diff --git a/lisp/gnus-html.el b/lisp/gnus-html.el
index c1472118c..861ad73d0 100644
--- a/lisp/gnus-html.el
+++ b/lisp/gnus-html.el
@@ -205,8 +205,8 @@ CHARS is a regexp-like character alternative (e.g., \"[)$]\")."
                  url
                  (if (buffer-live-p gnus-summary-buffer)
                      (with-current-buffer gnus-summary-buffer
-                       gnus-blocked-images)
-                   gnus-blocked-images))
+                       (gnus-blocked-images))
+                   (gnus-blocked-images)))
                 (progn
                   (widget-convert-button
                    'link start end
@@ -491,7 +491,7 @@ This only works if the article in question is HTML."
 (defun gnus-html-prefetch-images (summary)
   (when (buffer-live-p summary)
     (let ((blocked-images (with-current-buffer summary
-                            gnus-blocked-images)))
+                            (gnus-blocked-images))))
       (save-match-data
 	(while (re-search-forward "<img[^>]+src=[\"']\\([^\"']+\\)" nil t)
 	  (let ((url (gnus-html-encode-url (match-string 1))))
diff --git a/texi/ChangeLog b/texi/ChangeLog
index f61eeccdd..4641b4819 100644
--- a/texi/ChangeLog
+++ b/texi/ChangeLog
@@ -1,3 +1,8 @@
+2010-10-20  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+	* gnus.texi (HTML): Document the function value of
+	gnus-blocked-images.
+
 2010-10-20  Julien Danjou  <julien@danjou.info>
 
 	* emacs-mime.texi (Flowed text): Add a note about mml-enable-flowed
diff --git a/texi/gnus.texi b/texi/gnus.texi
index acfe0aa67..337e85cf1 100644
--- a/texi/gnus.texi
+++ b/texi/gnus.texi
@@ -12462,15 +12462,20 @@ that's based on @code{w3m}.
 
 @item gnus-blocked-images
 @vindex gnus-blocked-images
-Images that have @acronym{URL}s that match this regexp won't be
-fetched and displayed.  For instance, do block all @acronym{URL}s that
-have the string ``ads'' in them, do the following:
+External images that have @acronym{URL}s that match this regexp won't
+be fetched and displayed.  For instance, do block all @acronym{URL}s
+that have the string ``ads'' in them, do the following:
 
 @lisp
 (setq gnus-blocked-images "ads")
 @end lisp
 
-The default is to block all external images.
+This can also be a function to be evaluated.  If so, it will be
+called with the group name as the parameter.  The default value is
+@code{gnus-block-private-groups}, which will return @samp{"."} for
+anything that isn't a newsgroup.  This means that no external images
+will be fetched as a result of reading mail, so that nobody can use
+web bugs (and the like) to track whether you've read email.
 
 @item gnus-html-cache-directory
 @vindex gnus-html-cache-directory
-- 
2.25.1