Subject: [PATCH] `repeat-echo-message-string': support repeat keymap "hints"

From: JD Smith <[email-masked]>
Date: Thu, 25 Apr 2024 18:31:17 -0400

repeat-mode is excellent for informal and very lightweight modal interfaces (great article <https://karthinks.com/software/it-bears-repeating/>).  One limitation it has compared to other such interfaces is it only mentions the keys which can be repeated, without providing hints about what they do.  

A simple patch to `repeat-echo-message-strings' to support displaying a string for keymap definitions of form (STRING . DEFN) is below.  It works nicely to provide "hints" after each repeat key, if the keymap includes them.

Example usage:

(defvar-keymap expreg-repeat-map
    :doc "Repeat map for `expreg' actions."
    :repeat t
    :name "expreg"
    "\\" (cons "expand" 'expreg-expand)
    "|"  (cons "contract"  'expreg-contract))

Example prompt (after one invocation of `expreg-expand'): 

 Repeat with \:expand, |:contract

It might also be useful to provide a custom variable by which a user can disable hint strings, for the experts/minimalists..

Patch:

--- repeat_old.el	2024-04-25 18:22:59
+++ repeat.el	2024-04-25 18:09:11
@@ -553,12 +553,20 @@
 (defun repeat-echo-message-string (keymap)
   "Return a string with the list of repeating keys in KEYMAP."
   (let (keys)
-    (map-keymap (lambda (key cmd) (and cmd (push key keys))) keymap)
+    (map-keymap (lambda (key cmd)
+		  (if (consp cmd)
+		      (push (cons (car cmd) key) keys)
+		    (when cmd (push key keys))))
+		keymap)
     (format-message "Repeat with %s%s"
                     (mapconcat (lambda (key)
-                                 (substitute-command-keys
-                                  (format "\\`%s'"
-                                          (key-description (vector key)))))
+				 (let* ((cmd (when (consp key) (format ":%s" (car key)))))
+				   (if (consp key) (setq key (cdr key)))
+				   (concat
+				    (substitute-command-keys
+				     (format "\\`%s'"
+					     (key-description (vector key))))
+				    cmd)))
                                keys ", ")
                     (if repeat-exit-key
                         (substitute-command-keys