Factor out org-scroll and use it in ox.el, org-agenda/attach.el

* lisp/ox.el (org-export--dispatch-ui): Update message in the
header line to promote the use of C-v and M-v while SPC and
DEL are still allowed for backward compatibility reasons.

* lisp/org-macs.el (org-scroll): New function.

* lisp/org-attach.el (org-attach): Use `org-scroll'.

* lisp/org-agenda.el (org-agenda-get-restriction-and-command):
Allow C-v, M-v, C-n and C-p to scroll.

This change adverize C-v, M-v, C-n and C-p as the default keys
for scrolling the window, while SPC and DEL are still available
in the export dispatch window.

In particular, don't use SPC as a way to scroll the window in
the agenda commands dispatch window, as this key might be used
for a custom agenda command.

lisp/org-agenda.el

@@ -3119,7 +3119,7 @@ s   Search for keywords                 M   Like m, but only TODO entries
 	  ;; Hint to navigation if window too small for all information
 	  (setq header-line-format
 		(when (not (pos-visible-in-window-p (point-max)))
-		  "Use SPC, DEL, C-n or C-p to navigate."))
+		  "Use C-v, M-v, C-n or C-p to navigate."))
 
 	  ;; Ask for selection
 	  (cl-loop
@@ -3133,7 +3133,7 @@ s   Search for keywords                 M   Like m, but only TODO entries
 				 " (unrestricted)"))
 			   ""))
 		(setq c (read-char-exclusive)))
-	   until (not (memq c '(14 16 ?\s ?\d)))
+	   until (not (memq c '(14 16 22 134217846)))
 	   do (org-scroll c))
 
 	  (message "")

lisp/org-attach.el

@@ -263,7 +263,7 @@ Shows a list of commands and prompts for another key to execute a command."
 	    (switch-to-buffer-other-window (get-buffer-create "*Org Attach*"))
 	    (erase-buffer)
 	    (setq cursor-type nil
-	      header-line-format "Use SPC, DEL, C-n or C-p to navigate.")
+	      header-line-format "Use C-v, M-v, C-n or C-p to navigate.")
 	    (insert
                (concat "Attachment folder:\n"
 		       (or dir
@@ -290,16 +290,12 @@ Shows a list of commands and prompts for another key to execute a command."
 		                "\n")))))
 	  (org-fit-window-to-buffer (get-buffer-window "*Org Attach*"))
 	  (let ((msg (format "Select command: [%s]"
-			     (concat (mapcar #'caar org-attach-commands)))))
+			     (concat (mapcar #'caar org-attach-commands))))
+		key)
 	    (message msg)
-	    (setq c (read-char-exclusive))
-	    (while (memq c '(14 16 32 127))
-	      (cond ((= c 14) (ignore-errors (call-interactively 'scroll-up-line)))
-		    ((= c 16) (ignore-errors (call-interactively 'scroll-down-line)))
-		    ((= c 32) (ignore-errors (call-interactively 'scroll-up)))
-		    ((= c 127) (ignore-errors (call-interactively 'scroll-down))))
-	      (message msg)
-	      (setq c (read-char-exclusive))))
+	    (while (and (setq key (read-char-exclusive prompt))
+		        (memq key '(14 16 22 134217846)))
+	      (org-scroll key t)))
 	  (and (get-buffer "*Org Attach*") (kill-buffer "*Org Attach*"))))
       (let ((command (cl-some (lambda (entry)
 				(and (memq c (nth 0 entry)) (nth 1 entry)))

lisp/org-macs.el

@@ -1202,31 +1202,36 @@ Return 0. if S is not recognized as a valid value."
        ((string-match org-ts-regexp0 s) (org-2ft s))
        (t 0.)))))
 
-(defun org-scroll (key)
-  "Receive KEY and scroll the current window accordingly."
-  (cl-case key
-    ;; C-n
-    (14 (if (not (pos-visible-in-window-p (point-max)))
-	    (ignore-errors (scroll-up 1))
-	  (message "End of buffer")
-	  (sit-for 1)))
-    ;; C-p
-    (16 (if (not (pos-visible-in-window-p (point-min)))
-	    (ignore-errors (scroll-down 1))
-	  (message "Beginning of buffer")
-	  (sit-for 1)))
-    ;; SPC
-    (?\s (if (not (pos-visible-in-window-p (point-max)))
+(defun org-scroll (key &optional additional-keys)
+  "Receive KEY and scroll the current window accordingly.
+When ADDITIONAL-KEYS is not nil, also include SPC and DEL in the
+allowed keys for scrolling, as expected in the export dispatch
+window."
+  (let ((scrlup (if additional-keys '(?\s 22) 22))
+	(scrldn (if additional-keys `(?\d 134217846) 134217846)))
+    (eval
+     `(case ,key
+	;; C-n
+	(14 (if (not (pos-visible-in-window-p (point-max)))
+		(ignore-errors (scroll-up 1))
+	      (message "End of buffer")
+	      (sit-for 1)))
+	;; C-p
+	(16 (if (not (pos-visible-in-window-p (point-min)))
+		(ignore-errors (scroll-down 1))
+	      (message "Beginning of buffer")
+	      (sit-for 1)))
+	;; SPC or
+	(,scrlup
+	 (if (not (pos-visible-in-window-p (point-max)))
 	     (scroll-up nil)
 	   (message "End of buffer")
 	   (sit-for 1)))
-    ;; DEL
-    (?\d (if (not (pos-visible-in-window-p (point-min)))
-	     (scroll-down nil)
-	   (message "Beginning of buffer")
-	   (sit-for 1)))))
-
-
+	;; DEL
+	(,scrldn (if (not (pos-visible-in-window-p (point-min)))
+		     (scroll-down nil)
+		   (message "Beginning of buffer")
+		   (sit-for 1)))))))
 
 (provide 'org-macs)
 

lisp/ox.el

@@ -6864,7 +6864,7 @@ back to standard interface."
 	(org-switch-to-buffer-other-window
 	 (get-buffer-create "*Org Export Dispatcher*"))
 	(setq cursor-type nil
-	      header-line-format "Use SPC, DEL, C-n or C-p to navigate.")
+	      header-line-format "Use C-v, M-v, C-n or C-p to navigate.")
 	;; Make sure that invisible cursor will not highlight square
 	;; brackets.
 	(set-syntax-table (copy-syntax-table))
@@ -6901,7 +6901,7 @@ options as CDR."
     (while (and (setq key (read-char-exclusive prompt))
 		(not expertp)
 		(memq key '(14 16 ?\s ?\d)))
-      (org-scroll key))
+      (org-scroll key t))
     (cond
      ;; Ignore undefined associations.
      ((not (memq key allowed-keys))