bug#68921: File and Buffer register functions.

[Barra Ó Catháin]

Here follows (hopefully) much improved versions of the patches. I have
to admit, a lot of the "decisions" of the last one were just plain
sillyness, but I hope I've correctly formatted the documentation. I
rendered it and it looked correct to my eyes, but that's my own eyes.

Both commands now take a prefix argument to pick a specific file or
buffer, and otherwise default to the currently visited one.

Further comments would be appreciated!

Thanks,
Barra Ó Catháin.

>From d7d6878664ae22c622f60608e9304fbffe29676c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barra=20=C3=93=20Cath=C3=A1in?= <barra@ocathain.ie>
Date: Tue, 6 Feb 2024 22:33:32 +0000
Subject: [PATCH] Added buffer and file to register functions.

* lisp/register.el (register-command-info): Register two new functions.
(file-to-register): New function.
(buffer-to-register): New function.
---
 lisp/register.el | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/lisp/register.el b/lisp/register.el
index 822467a0d72..645bbc4b0ec 100644
--- a/lisp/register.el
+++ b/lisp/register.el
@@ -297,6 +297,18 @@ If NOCONFIRM is non-nil, request confirmation of register 
name by RET."
    :act 'set
    :noconfirm (memq register-use-preview '(nil never))
    :smatch t))
+(cl-defmethod register-command-info ((_command (eql file-to-register)))
+  (make-register-preview-info
+   :types '(all)
+   :msg "File to register `%s'"
+   :act 'set
+   :noconfirm (memq register-use-preview '(nil never))))
+(cl-defmethod register-command-info ((_command (eql buffer-to-register)))
+  (make-register-preview-info
+   :types '(all)
+   :msg "Buffer to register `%s'"
+   :act 'set
+   :noconfirm (memq register-use-preview '(nil never))))
 
 (defun register-preview-forward-line (arg)
   "Move to next or previous line in register preview buffer.
@@ -685,6 +697,35 @@ Interactively, prompt for REGISTER using 
`register-read-with-preview'."
   (let ((val (get-register register)))
     (register-val-jump-to val delete)))
 
+(defun file-to-register (file-name register)
+  "Inserts FILE-NAME in REGISTER.
+To visit the file, use \\[jump-to-register].
+
+Interactively, prompts for REGISTER using `register-read-with-preview'.
+With a prefix-argument, prompts for FILE-NAME using `read-file-name',
+otherwise, uses the currently visited file or directory for FILE-NAME."
+  (interactive (list (if (eq current-prefix-arg nil)
+                         (if (eq major-mode 'dired-mode)
+                             (dired-current-directory)
+                           (buffer-file-name))
+                       (read-file-name "File: "))
+                (register-read-with-preview "File to register: ")))
+  (unless (eq file-name nil)
+    (set-register register (cons 'file file-name))))
+
+(defun buffer-to-register (buffer register)
+  "Inserts BUFFER in REGISTER.
+To visit the buffer, use \\[jump-to-register].
+
+Interactively, prompts for REGISTER using `register-read-with-preview'.
+With a prefix-argument, prompts for BUFFER-NAME using `read-buffer',
+otherwise, uses the current buffer."
+  (interactive (list (if (eq current-prefix-arg nil)
+                         (current-buffer)
+                       (read-buffer "Buffer: "))
+                     (register-read-with-preview "Buffer to register: ")))
+  (set-register register (cons 'buffer buffer)))
+
 (cl-defgeneric register-val-jump-to (_val _arg)
   "Execute the \"jump\" operation of VAL.
 VAL is the contents of a register as returned by `get-register'.
-- 
2.43.0

>From c38e70ad2a93269e46343ea2b1a366ea064cdf84 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barra=20=C3=93=20Cath=C3=A1in?= <barra@ocathain.ie>
Date: Tue, 6 Feb 2024 14:18:47 +0000
Subject: [PATCH 2/3] * lisp/bindings.el (ctl-x-r-map): Added file-to-register
 and buffer-to-register in to keymap, under "F", and "B"

---
 lisp/bindings.el | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lisp/bindings.el b/lisp/bindings.el
index 4690897fed4..64f83efbb0a 100644
--- a/lisp/bindings.el
+++ b/lisp/bindings.el
@@ -1570,7 +1570,9 @@ ctl-x-r-map
   "n"     #'number-to-register
   "+"     #'increment-register
   "w"     #'window-configuration-to-register
-  "f"     #'frameset-to-register)
+  "f"     #'frameset-to-register
+  "F"     #'file-to-register
+  "B"     #'buffer-to-register)
 (define-key ctl-x-map "r" ctl-x-r-map)
 
 (define-key esc-map "q" 'fill-paragraph)
-- 
2.43.0

>From 6c6524f70f93b88378c54be5bf4a7c21f422a8fc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barra=20=C3=93=20Cath=C3=A1in?= <barra@ocathain.ie>
Date: Tue, 6 Feb 2024 22:01:14 +0000
Subject: [PATCH 3/3] Wrote documentation for new to register functions.

* doc/emacs/regs.texi (File and Buffer Registers):
Revised documentation to explain the new commands, rather than the
set-register elisp.
---
 doc/emacs/regs.texi | 55 ++++++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/doc/emacs/regs.texi b/doc/emacs/regs.texi
index cac5b32c566..9dce7557de2 100644
--- a/doc/emacs/regs.texi
+++ b/doc/emacs/regs.texi
@@ -289,41 +289,46 @@ File and Buffer Registers
 @section Keeping File and Buffer Names in Registers
 @cindex saving file name in a register
 @cindex saving buffer name in a register
+@kindex C-x r F
+@kindex C-x r B
 
   If you visit certain file names frequently, you can visit them more
-conveniently if you put their names in registers.  Here's the Lisp code
-used to put a file @var{name} into register @var{r}:
+conveniently if you put their names in registers.  Here's how you can
+put a file into a buffer.
 
-@smallexample
-(set-register @var{r} '(file . @var{name}))
-@end smallexample
-
-@need 3000
-@noindent
-For example,
-
-@smallexample
-(set-register ?z '(file . "/gd/gnu/emacs/19.0/src/ChangeLog"))
-@end smallexample
-
-@noindent
-puts the file name shown in register @samp{z}.
+@table @kbd
+@item C-x r F @var{r}
+@kindex C-x r F
+@findex file-to-register
+Store the currently visited file or directory into register @var{r} 
(@code{file-to-register}).
+@item C-u C-x r F @var{r}
+@kindex C-x r F
+@findex file-to-register
+Prompt for a file, and store into register @var{r} (@code{file-to-register}).
+@end table
 
   To visit the file whose name is in register @var{r}, type @kbd{C-x r j
 @var{r}}.  (This is the same command used to jump to a position or
 restore a frame configuration.)
 
-  Similarly, if there are certain buffers you visit frequently, you
-can put their names in registers.  For instance, if you visit the
-@samp{*Messages*} buffer often, you can use the following snippet to
-put that buffer into the @samp{m} register:
+  Similarly, if there are certain buffers you visit frequently, you can
+put their names in registers. You can use the following command to put a
+buffer into a register.
 
-@smallexample
-(set-register ?m '(buffer . "*Messages*"))
-@end smallexample
+@table @kbd
+@item C-x r B @var{r}
+@kindex C-x r B
+@findex buffer-to-register
+Store the current buffer into register @var{r} (@code{buffer-to-register}).
+@item C-u C-x r B @var{r}
+@kindex C-x r B
+@findex buffer-to-register
+Prompt for a buffer, and store into register @var{r} 
(@code{buffer-to-register}).
+@end table
 
-  To switch to the buffer whose name is in register @var{r}, type
-@kbd{C-x r j @var{r}}.
+  To visit the buffer whose name is in register @var{r}, type @kbd{C-x r
+  j @var{r}}. (This is the same command used to jump to a position or
+  restore a frame configuration.)
 
 @node Keyboard Macro Registers
 @section Keyboard Macro Registers
-- 
2.43.0