[PATCH 2/2] emacs: skip forward to visible text in notmuch-show-message-extent

[Dmitry Kurochkin <dmitry.kurochkin@gmail.com>]

The patch rewrites `notmuch-show-message-extent' to be more
robust.  The main goal is to make it work as expected if point is
invisible.  Besides, there are no more point movements and
property search functions are used instead manual loops.  The
comment regarding properties strangeness is removed since there
is no strangeness here: property ranges (as well as overlay, and
many others, I believe) are given as [begin, end), not [begin,
end].
---
 emacs/notmuch-show.el |   19 +++++++++++--------
 1 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index f96743b..cf8b405 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -933,15 +933,18 @@ All currently available key bindings:
 
 ;; Movement related functions.
 
-;; There's some strangeness here where a text property applied to a
-;; region a->b is not found when point is at b. We walk backwards
-;; until finding the property.
 (defun notmuch-show-message-extent ()
-  (let (r)
-    (save-excursion
-      (while (not (setq r (get-text-property (point) :notmuch-message-extent)))
-	(backward-char)))
-    r))
+  (let ((p (point)))
+    ;; if point is invisible, skip forward to visible text
+    (while (invisible-p p)
+      (setq p (next-single-char-property-change p 'invisible)))
+    ;; if no visible text found, use the point
+    (or p (setq p (point)))
+    (or (get-text-property p :notmuch-message-extent)
+	;; if there is no text property, skip to the previous message
+	(and (setq p (previous-single-char-property-change
+		      p :notmuch-message-extent))
+	     (get-text-property p :notmuch-message-extent)))))
 
 (defun notmuch-show-message-top ()
   (car (notmuch-show-message-extent)))
-- 
1.7.5.4