Re: Proposal for an improved `help-for-help'

[Dmitry Gutov <dgutov@yandex.ru>]

On 30.04.2021 20:39, Stefan Kangas wrote:

>> I really like using SPC/S-SPC for scrolling.
>>
>> It also works in other programs (even though Shift-Space rarely shows up
>> in any menus or hints), so it should be helpful to support as well.
> 
> I agree it should be added, and as I pointed out in a different reply
> that is also more consistent with the binding that already exists in
> `special-mode-map'.
> 
> However, the `make-help-screen' macro uses (read-key-sequence nil) to
> get the key, but when I press S-SPC, that function only returns " ".

Try (read-key-sequence nil), S-SPC in some special mode buffer like 
Xref, it will return [33554446].

So I think you just need to define that binding in the local map. The 
below works for me (only in graphical Emacs, though). Not sure what to 
do with the magic number.

diff --git a/lisp/help-macro.el b/lisp/help-macro.el
index 7fe1fb6c3d..8216ddfeb5 100644
--- a/lisp/help-macro.el
+++ b/lisp/help-macro.el
@@ -112,6 +112,7 @@ make-help-screen
               (let ((minor-mode-map-alist nil))
                 (setcdr local-map ,helped-map)
                 (define-key local-map [t] 'undefined)
+               (define-key local-map (kbd "S-SPC") 'undefined)
                 ;; Make the scroll bar keep working normally.
                 (define-key local-map [vertical-scroll-bar]
                   (lookup-key global-map [vertical-scroll-bar]))
@@ -143,6 +144,7 @@ make-help-screen
                   (goto-char (point-min))
                   (while (or (memq char (append help-event-list
                                                 (cons help-char '( ?? 
?\C-v ?\s ?\177 deletechar backspace vertical-scroll-bar ?\M-v
+                                                                  33554464
                                                                    next 
prior up down))))
                              (eq (car-safe char) 'switch-frame)
                              (equal key "\M-v"))
@@ -152,7 +154,7 @@ make-help-screen
                           (handle-switch-frame char))
                          ((memq char '(?\C-v ?\s next))
                           (scroll-up))
-                        ((or (memq char '(?\177 ?\M-v deletechar 
backspace prior))
+                        ((or (memq char '(?\177 ?\M-v deletechar 
backspace prior 33554464))
                               (equal key "\M-v"))
                           (scroll-down))
                          ((memq char '(down))