notmuch.el: Fix notmuch-snow-next-message when on the last message.

Before this just brought the current line to the top of the
window. Now it actually moves to the beginning of the current message.

This is built on a much more solid foundation now with a function to
move to the summary-line of the current message, and then moving from
there.

diff --git a/notmuch.el b/notmuch.el
index 7f087c7240de754e1510af878885129ba3d08a03..667fd6fd35c4193fa095f042c15c40405cac285a 100644 (file)
--- a/notmuch.el
+++ b/notmuch.el
@@ -114,52 +114,47 @@ buffer."
       (if (not (re-search-forward notmuch-show-message-begin-regexp nil t))
          (goto-char (point-max))))))
 
+(defun notmuch-show-move-to-current-message-summary-line ()
+  "Move to the beginning of the one-line summary of the current message.
+
+This gives us a stable place to move to and work from since the
+summary line is always visible. This is important since moving to
+an invisible location is unreliable, (the main command loop moves
+point either forward or backward to the next visible character
+when a command ends with point on an invisible character).
+
+Emits an error if point is not within a valid message, (that is
+not pattern of `notmuch-show-message-begin-regexp' could be found
+by searching backward)."
+  (beginning-of-line)
+  (if (not (looking-at notmuch-show-message-begin-regexp))
+      (if (re-search-backward notmuch-show-message-begin-regexp nil t)
+         (forward-line 2)
+       (error "Not within a valid message."))
+    (forward-line 2)))
+
 (defun notmuch-show-next-message ()
-  "Advance point to the beginning of the next message in the buffer.
+  "Advance to the beginning of the next message in the buffer.
 
-Does nothing if already on the last message."
+Moves to the beginning of the current message if already on the
+last message in the buffer."
   (interactive)
-  ; First, ensure we get off the current message marker
-  (if (not (eobp))
-      (forward-char))
+  (notmuch-show-move-to-current-message-summary-line)
   (re-search-forward notmuch-show-message-begin-regexp nil t)
-  ; This dance might look pointless, but it's important. I originally
-  ; just had (beginning-of-line) here which looked right on the
-  ; display but actually put point all the way back to the first
-  ; character of the first invisible line. That is, it put point into
-  ; the closing markers of the previous message rather than at the
-  ; beginning of the current message. And that in turn meant that
-  ; looking up the current message-ID would actually return the
-  ; previous message ID.
-  ;
-  ; So this dance ensures that we're actually on the current message
-  ; when it looks like we are.
-  (end-of-visible-line)
-  (beginning-of-line)
+  (notmuch-show-move-to-current-message-summary-line)
   (recenter 0))
 
 (defun notmuch-show-previous-message ()
   "Backup to the beginning of the previous message in the buffer.
 
-Does nothing if already on the first message in the buffer."
+Moves to the beginning of the current message if already on the
+first message in the buffer."
   (interactive)
-  ; First, ensure we get off the current message marker
-  (if (not (bobp))
-      (previous-line))
+  (notmuch-show-move-to-current-message-summary-line)
+  ; Go backward twice to skip the current message's marker
   (re-search-backward notmuch-show-message-begin-regexp nil t)
-  ; This dance might look pointless, but it's important. I originally
-  ; just had (beginning-of-line) here which looked right on the
-  ; display but actually put point all the way back to the first
-  ; character of the first invisible line. That is, it put point into
-  ; the closing markers of the previous message rather than at the
-  ; beginning of the current message. And that in turn meant that
-  ; looking up the current message-ID would actually return the
-  ; previous message ID.
-  ;
-  ; So this dance ensures that we're actually on the current message
-  ; when it looks like we are.
-  (end-of-visible-line)
-  (beginning-of-line)
+  (re-search-backward notmuch-show-message-begin-regexp nil t)
+  (notmuch-show-move-to-current-message-summary-line)
   (recenter 0))
 
 (defun notmuch-show-mark-read-then-next-message ()