mu4e: support jumping to next, previous unread message

mu4e-headers-next-unread
mu4e-view-headers-next-unread

Use key-bindings ] and [ to go to next, previous unread message.

mu4e/mu4e-headers.el

@@ -587,8 +587,8 @@ after the end of the search results."
       (define-key map (kbd "<M-up>") 'mu4e-headers-prev)
       (define-key map (kbd "<M-down>") 'mu4e-headers-next)
 
-      (define-key map (kbd "<tab>") 'mu4e-headers-next-unread)
+      (define-key map (kbd "]") 'mu4e-headers-next-unread)
-      (define-key map (kbd "<backtab>")
+      (define-key map (kbd "[")
 	(lambda() (interactive) (mu4e-headers-next-unread t)))
       
       ;; change the number of headers

mu4e/mu4e-view.el

@@ -590,6 +590,10 @@ FUNC should be a function taking two arguments:
       (define-key map (kbd "<M-down>") 'mu4e-view-headers-next)
       (define-key map (kbd "<M-up>") 'mu4e-view-headers-prev)
 
+      (define-key map (kbd "]") 'mu4e-view-headers-next-unread)
+      (define-key map (kbd "[")
+	(lambda() (interactive) (mu4e-view-headers-next-unread t)))
+      
       ;; switching to view mode (if it's visible)
       (define-key map "y" 'mu4e-select-other-view)
 
@@ -807,8 +811,7 @@ Also number them so they can be opened using `mu4e-view-go-to-url'."
 	       "[mouse-1] or [M-RET] to open the link"))
 	  (overlay-put ov 'after-string
 		       (propertize (format "[%d]" num)
-				   'face 'mu4e-url-number-face))
+				   'face 'mu4e-url-number-face)))))))
-	  )))))
 
 
 (defun mu4e~view-hide-cited ()
@@ -819,7 +822,6 @@ Also number them so they can be opened using `mu4e-view-go-to-url'."
       (flush-lines mu4e-cited-regexp)
       (setq mu4e~view-cited-hidden t))))
 
-
 (defmacro mu4e~view-in-headers-context (&rest body)
   "Evaluate BODY in the context of the headers buffer connected to
 this view."
@@ -827,10 +829,12 @@ this view."
      (unless (buffer-live-p mu4e~view-headers-buffer)
        (mu4e-error "no headers-buffer connected"))
      (let* ((msg (mu4e-message-at-point))
-	     (docid (mu4e-message-field msg :docid)))
+	     (docid (mu4e-message-field msg :docid))
+	     (curwin (selected-window)))
        (unless docid
 	 (mu4e-error "message without docid: action is not possible."))
        (with-current-buffer mu4e~view-headers-buffer
+	 (select-window (get-buffer-window))
 	 (if (mu4e~headers-goto-docid docid)
 	   ,@body
 	   (mu4e-error "cannot find message in headers buffer."))))))
@@ -853,6 +857,18 @@ N (prefix argument), to the Nth previous header."
   (mu4e~view-in-headers-context
     (mu4e~headers-move (- (or n 1)))))
 
+(defun mu4e-view-headers-next-unread (&optional backwards)
+  "Move point to the next or previous (when BACKWARDS is non-`nil')
+unread message header in the headers buffer connected with this
+message view. If this succeeds, return the new docid. Otherwise,
+return nil."
+  (interactive "P")
+  (mu4e~view-in-headers-context 
+    (mu4e-headers-next-unread backwards)))
+;; NOTE perhaps nice to have it also _select_ the found message;
+;; but it seems emacs gets a bit confused when we try that.
+
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;; Interactive functions

mu4e/mu4e.texi

@@ -793,7 +793,8 @@ menu bar.
 @verbatim
 key          description
 ===========================================================
-n,p          go to next, previous message
+n,p          view the next, previous message
+],[          move to the next, previous unread message
 y            select the message view (if it's visible)
 RET          open the message at point in the message view
 
@@ -1073,7 +1074,8 @@ or by using the keyboard; the default bindings are:
 @verbatim
 key          description
 ==============================================================
-n,p          go to next, previous message
+n,p          view the next, previous message
+],[          move to the next, previous unread message
 y            select the headers view (if it's visible)
 
 RET          scroll down