Add a command for redisplay during keyboard macros

* doc/emacs/kmacro.texi (Basic Keyboard Macro): Document it
(bug#39252).

* lisp/kmacro.el (kdb-macro-redisplay): New function.
(kmacro-keymap): Bind it.

doc/emacs/kmacro.texi

@@ -179,6 +179,14 @@ itself counts as the first repetition, since it is executed as you
 define it, so @kbd{C-u 4 C-x )} executes the macro immediately 3
 additional times.
 
+@findex kdb-macro-redisplay
+@kindex C-x C-k Q
+  While executing a long-running keyboard macro, it can sometimes be
+useful to trigger a redisplay (to show how far we've gotten).  The
+@kbd{C-x C-k Q} can be used for this.  As a not very useful example,
+@kbd{C-x ( M-f C-x C-k Q C-x )} will create a macro that will
+redisplay once per iteration when saying @kbd{C-u 42 C-x e}.
+
 @node Keyboard Macro Ring
 @section The Keyboard Macro Ring
 

etc/NEWS

@@ -1577,6 +1577,9 @@ This allows mode-specific alterations to how `thing-at-point' works.
 
 ** Miscellaneous
 
++++
+*** New command `C-x C-k Q' to force redisplay in keyboard macros.
+
 ---
 *** New user option 'remember-diary-regexp'.
 

lisp/kmacro.el

@@ -172,6 +172,7 @@ macro to be executed before appending to it."
     (define-key map "\C-k" 'kmacro-end-or-call-macro-repeat)
     (define-key map "r"    'apply-macro-to-region-lines)
     (define-key map "q"    'kbd-macro-query)  ;; Like C-x q
+    (define-key map "Q"    'kdb-macro-redisplay)
 
     ;; macro ring
     (define-key map "\C-n" 'kmacro-cycle-ring-next)
@@ -1298,6 +1299,16 @@ To customize possible responses, change the \"bindings\" in
       (kmacro-push-ring)
       (setq last-kbd-macro kmacro-step-edit-new-macro))))
 
+(defun kdb-macro-redisplay ()
+  "Force redisplay during kbd macro execution."
+  (interactive)
+  (or executing-kbd-macro
+      defining-kbd-macro
+      (user-error "Not defining or executing kbd macro"))
+  (when executing-kbd-macro
+    (let ((executing-kbd-macro nil))
+      (redisplay))))
+
 (provide 'kmacro)
 
 ;;; kmacro.el ends here