>From c70e38e9ff9678a7105f39a5efff7596d3452e2f Mon Sep 17 00:00:00 2001
From: Arthur Miller <arthur.miller@live.com>
Date: Sat, 25 Sep 2021 22:06:53 +0200
Subject: [PATCH] Run help-mode commands form any buffer

* help-mode.el (help-go-back): Addapted to call form any buufer.
(help-go-forward): Addapted to call form any buufer.
(help-view-source): Addapted to call form any buufer.
(help-goto-info): Addapted to call form any buufer.
(help-command-prefix): New map.
(help-command-prefix-key): New customize option.
Install help-do-command in global-map on C-h M-h key.
---
 lisp/help-mode.el | 80 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 57 insertions(+), 23 deletions(-)

diff --git a/lisp/help-mode.el b/lisp/help-mode.el
index 0b404fe89f..0d5a709d49 100644
--- a/lisp/help-mode.el
+++ b/lisp/help-mode.el
@@ -48,6 +48,23 @@ help-mode-map
     map)
   "Keymap for Help mode.")
 
+(defvar help-command-prefix
+  (let ((map (define-prefix-command 'help-command-prefix)))
+    (define-key map "l" #'help-go-back)
+    (define-key map "r" #'help-go-forward)
+    (define-key map "\C-c\C-b" #'help-go-back)
+    (define-key map "\C-c\C-f" #'help-go-forward)
+    (define-key map [XF86Back] #'help-go-back)
+    (define-key map [XF86Forward] #'help-go-forward)
+    (define-key map "\C-c\C-c" #'help-follow-symbol)
+    (define-key map "s" #'help-view-source)
+    (define-key map "i" #'help-goto-info)
+    (define-key map "c" #'help-customize)
+    (fset 'help-command-prefix help-command-prefix)
+    (setq help-command-prefix help-command-prefix)
+    map)
+  "Keymap for Help command prefix.")
+
 (easy-menu-define help-mode-menu help-mode-map
   "Menu for Help mode."
   '("Help-Mode"
@@ -149,6 +166,12 @@ help-mode-hook
   "Hook run by `help-mode'."
   :type 'hook
   :group 'help)
+
+(defcustom help-command-prefix-key "C-h M-h"
+  "The key HELP-COMMAND-PREFIX is bound to in the global map."
+  :type 'string
+  :group 'help
+  :version "28.1")
 
 ;; Button types used by help
 
@@ -402,7 +425,8 @@ help-mode-finish
   "Finalize Help mode setup in current buffer."
   (when (derived-mode-p 'help-mode)
     (setq buffer-read-only t)
-    (help-make-xrefs (current-buffer))))
+    (help-make-xrefs (current-buffer))
+    (set-window-dedicated-p (get-buffer-window (help-buffer)) t)))
 
 ;; Grokking cross-reference information in doc strings and
 ;; hyperlinking it.
@@ -784,44 +808,54 @@ help-xref-go-forward
 (defun help-go-back ()
   "Go back to previous topic in this help buffer."
   (interactive)
-  (if help-xref-stack
-      (help-xref-go-back (current-buffer))
-    (user-error "No previous help buffer")))
+  (when (get-buffer-window (help-buffer))
+    (with-current-buffer (help-buffer)
+      (if help-xref-stack
+          (help-xref-go-back (current-buffer))
+        (user-error "No previous help buffer")))))
 
 (defun help-go-forward ()
   "Go to the next topic in this help buffer."
   (interactive)
-  (if help-xref-forward-stack
-      (help-xref-go-forward (current-buffer))
-    (user-error "No next help buffer")))
+  (when (get-buffer-window (help-buffer))
+    (with-current-buffer (help-buffer)
+      (if help-xref-forward-stack
+          (help-xref-go-forward (current-buffer))
+        (user-error "No next help buffer")))))
 
 (defun help-view-source ()
   "View the source of the current help item."
   (interactive nil help-mode)
-  (unless (plist-get help-mode--current-data :file)
-    (error "Source file for the current help item is not defined"))
-  (help-function-def--button-function
-   (plist-get help-mode--current-data :symbol)
-   (plist-get help-mode--current-data :file)
-   (plist-get help-mode--current-data :type)))
+  (when (get-buffer-window (help-buffer))
+    (with-current-buffer (help-buffer)
+      (unless (plist-get help-mode--current-data :file)
+        (error "Source file for the current help item is not defined"))
+      (help-function-def--button-function
+       (plist-get help-mode--current-data :symbol)
+       (plist-get help-mode--current-data :file)
+       (plist-get help-mode--current-data :type)))))
 
 (defun help-goto-info ()
   "View the *info* node of the current help item."
   (interactive nil help-mode)
-  (unless help-mode--current-data
-    (error "No symbol to look up in the current buffer"))
-  (info-lookup-symbol (plist-get help-mode--current-data :symbol)
-                      'emacs-lisp-mode))
+  (when (get-buffer-window (help-buffer))
+    (with-current-buffer (help-buffer)
+      (unless help-mode--current-data
+        (error "No symbol to look up in the current buffer"))
+      (info-lookup-symbol (plist-get help-mode--current-data :symbol)
+                          'emacs-lisp-mode))))
 
 (defun help-customize ()
   "Customize variable or face whose doc string is shown in the current buffer."
   (interactive nil help-mode)
-  (let ((sym (plist-get help-mode--current-data :symbol)))
-    (unless (or (boundp sym) (facep sym))
-      (user-error "No variable or face to customize"))
-    (cond
-     ((boundp sym) (customize-variable sym))
-     ((facep sym) (customize-face sym)))))
+  (when (get-buffer-window (help-buffer))
+    (with-current-buffer (help-buffer)
+      (let ((sym (plist-get help-mode--current-data :symbol)))
+        (unless (or (boundp sym) (facep sym))
+          (user-error "No variable or face to customize"))
+        (cond
+         ((boundp sym) (customize-variable sym))
+         ((facep sym) (customize-face sym)))))))
 
 (defun help-do-xref (_pos function args)
   "Call the help cross-reference function FUNCTION with args ARGS.
-- 
2.33.0