[PATCH] emacs: jump: make multilevel keys do multilevel jump

[Mark Walters <markwalters1009@gmail.com>]

notmuch jump allows the user to specify a key sequence rather than
just a single key for its bindings. However, it doesn't show what has
already been typed so it can be difficult to see what has
happened. This makes each key press appear, and the jump menu reduce
to the possible follow up keys.

We also bind backspace (emacs symbol DEL) to go back up a level in the
subjumpmaps, and to exit from the top level.
---

This removes the no-op `,() construct from the previous version of
this patch, but is otherwise unchanged.

Best wishes

Mark
            
 emacs/notmuch-jump.el | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/emacs/notmuch-jump.el b/emacs/notmuch-jump.el
index 963253c..3e20b8c 100644
--- a/emacs/notmuch-jump.el
+++ b/emacs/notmuch-jump.el
@@ -104,7 +104,7 @@ not appear in the pop-up buffer.
 	   (copy-sequence minibuffer-prompt-properties)
 	   'face))
 	 ;; Build the keymap with our bindings
-	 (minibuffer-map (notmuch-jump--make-keymap action-map))
+	 (minibuffer-map (notmuch-jump--make-keymap action-map prompt))
 	 ;; The bindings save the the action in notmuch-jump--action
 	 (notmuch-jump--action nil))
     ;; Read the action
@@ -161,18 +161,47 @@ buffer."
     (set-keymap-parent map minibuffer-local-map)
     ;; Make this like a special-mode keymap, with no self-insert-command
     (suppress-keymap map)
+    (define-key map (kbd "DEL") 'exit-minibuffer)
     map)
   "Base keymap for notmuch-jump's minibuffer keymap.")
 
-(defun notmuch-jump--make-keymap (action-map)
+(defun notmuch-jump--make-keymap (action-map prompt)
   "Translate ACTION-MAP into a minibuffer keymap."
   (let ((map (make-sparse-keymap)))
     (set-keymap-parent map notmuch-jump-minibuffer-map)
     (dolist (action action-map)
-      (define-key map (first action)
-	`(lambda () (interactive)
-	   (setq notmuch-jump--action ',(third action))
-	   (exit-minibuffer))))
+      (if (= (length (first action)) 1)
+	  (define-key map (first action)
+	    `(lambda () (interactive)
+	       (setq notmuch-jump--action ',(third action))
+	       (exit-minibuffer)))))
+    ;; By doing this in two passes (and checking if we already have a
+    ;; binding) we avoid problems if the user specifies a binding which
+    ;; is a prefix of another binding.
+    (dolist (action action-map)
+      (if (> (length (first action)) 1)
+	  (let* ((key (elt (first action) 0))
+		 (keystr (string key))
+		 (new-prompt (concat prompt (format-kbd-macro keystr) " "))
+		 (action-submap nil))
+	    (unless (lookup-key map keystr)
+	      (dolist (act action-map)
+		(when (= key (elt (first act) 0))
+		  (push (list (substring (first act) 1)
+			      (second act)
+			      (third act))
+			action-submap)))
+	      ;; We deal with backspace specially
+	      (push (list (kbd "DEL")
+			  "Backup"
+			  (apply-partially #'notmuch-jump action-map prompt))
+		    action-submap)
+	      (setq action-submap (nreverse action-submap))
+	      (define-key map keystr
+		`(lambda () (interactive)
+		   (setq notmuch-jump--action
+			 ',(apply-partially #'notmuch-jump action-submap new-prompt))
+		   (exit-minibuffer)))))))
     map))
 
 ;;
-- 
2.1.4