Allow controlling the look of the line/column indicators

* doc/lispref/modes.texi (Mode Line Variables): Document them.

* lisp/bindings.el (mode-line-position-line-format): New variable
(bug#28648).
(mode-line-position-column-format): Ditto.
(mode-line-position): Use them.

* lisp/simple.el (column-number-mode): Mention them.
(line-number-mode): Ditto.

doc/lispref/modes.texi

@@ -2166,6 +2166,22 @@ Mode line construct for miscellaneous information.  By default, this
 shows the information specified by @code{global-mode-string}.
 @end defvar
 
+@defvar mode-line-position-line-format
+The format used for display line numbers when @code{line-number-mode}
+(@pxref{Optional Mode Line,,, emacs, The GNU Emacs Manual}) is
+switched on.  @samp{%l} in the format will be replaced with the line
+number.
+@end defvar
+
+@defvar mode-line-position-column-format
+The format used for display column numbers when
+@code{column-number-mode} (@pxref{Optional Mode Line,,, emacs, The GNU
+Emacs Manual}) is switched on.  @samp{%c} in the format will be
+replaced with the line number, and this is zero-based if
+@code{column-number-indicator-zero-based} is non-@code{nil}, and
+one-based if @code{column-number-indicator-zero-based} is @code{nil}.
+@end defvar
+
 @defvar minor-mode-alist
 @anchor{Definition of minor-mode-alist}
 This variable holds an association list whose elements specify how the

etc/NEWS

@@ -998,6 +998,14 @@ window after starting).  This variable defaults to nil.
 
 ** Miscellaneous
 
++++
+*** New variables to control the look of line/column numbers in the mode line.
+'mode-line-position-line-format' is the line number format (when
+'line-number-mode') is on, and 'mode-line-position-column-format' is
+the column number format (when 'column-number-mode') is on.  These are
+also used if both modes are on, which leads to the default in that
+case going from "(5,9)" to "(L5,C9)".
+
 +++
 *** New command 'submit-emacs-patch'.
 This works along the lines of 'report-emacs-bug', but is more geared

lisp/bindings.el

@@ -431,6 +431,24 @@ displayed in `mode-line-position', a component of the default
   :group 'mode-line)
 (put 'mode-line-percent-position 'risky-local-variable t)
 
+(defcustom mode-line-position-line-format "L%l"
+  "Format used to display line numbers in the mode line.
+This is used when `line-number-mode' is switched on.  The \"%l\"
+format spec will be replaced by the line number."
+  :type 'string
+  :version "28.1"
+  :group 'mode-line)
+
+(defcustom mode-line-position-column-format "C%c"
+  "Format used to display column numbers in the mode line.
+This is used when `column-number-mode' is switched on.  The
+\"%c\" format spec will be replaced by the column number, which
+is zero-based if `column-number-indicator-zero-based' is non-nil,
+and one-based if `column-number-indicator-zero-based' is nil."
+  :type 'string
+  :version "28.1"
+  :group 'mode-line)
+
 (defvar mode-line-position
   `((:propertize
      mode-line-percent-position
@@ -451,19 +469,24 @@ mouse-1: Display Line and Column Mode Menu")))
      ((column-number-mode
        (column-number-indicator-zero-based
         (10 ,(propertize
-              " (%l,%c)"
+              (format " (%s,%s)"
+                      mode-line-position-line-format
+                      mode-line-position-column-format)
               'local-map mode-line-column-line-number-mode-map
               'mouse-face 'mode-line-highlight
               'help-echo "Line number and Column number\n\
 mouse-1: Display Line and Column Mode Menu"))
         (10 ,(propertize
-              " (%l,%C)"
+              (format " (%s,%s)"
+                      mode-line-position-line-format
+                      (replace-in-string "%c" "%C"
+                                         mode-line-position-column-format))
               'local-map mode-line-column-line-number-mode-map
               'mouse-face 'mode-line-highlight
               'help-echo "Line number and Column number\n\
 mouse-1: Display Line and Column Mode Menu")))
        (6 ,(propertize
-	    " L%l"
+	    (format " %s" mode-line-position-line-format)
 	    'local-map mode-line-column-line-number-mode-map
 	    'mouse-face 'mode-line-highlight
 	    'help-echo "Line Number\n\
@@ -471,13 +494,14 @@ mouse-1: Display Line and Column Mode Menu"))))
      ((column-number-mode
        (column-number-indicator-zero-based
         (5 ,(propertize
-             " C%c"
+             (format " %s" mode-line-position-column-format)
              'local-map mode-line-column-line-number-mode-map
              'mouse-face 'mode-line-highlight
              'help-echo "Column number\n\
 mouse-1: Display Line and Column Mode Menu"))
         (5 ,(propertize
-             " C%C"
+             (format " %s" (replace-in-string "%c" "%C"
+                                              mode-line-position-column-format))
              'local-map mode-line-column-line-number-mode-map
              'mouse-face 'mode-line-highlight
              'help-echo "Column number\n\

lisp/simple.el

@@ -7805,11 +7805,17 @@ a specialization of overwrite mode, entered by setting the
 
 Line numbers do not appear for very large buffers and buffers
 with very long lines; see variables `line-number-display-limit'
-and `line-number-display-limit-width'."
+and `line-number-display-limit-width'.
+
+See `mode-line-position-line-format' for how this number is
+presented."
   :init-value t :global t :group 'mode-line)
 
 (define-minor-mode column-number-mode
-  "Toggle column number display in the mode line (Column Number mode)."
+  "Toggle column number display in the mode line (Column Number mode).
+
+See `mode-line-position-column-format' for how this number is
+presented."
   :global t :group 'mode-line)
 
 (define-minor-mode size-indication-mode