Use 'C-x t' for tab-prefix-map instead of 'C-x 6' still used by 2C-mode-map.

* doc/emacs/commands.texi (Keys): Add 'C-x t'.
* doc/emacs/frames.texi (Tab Bars): Replace 'C-x 6' with 'C-x t'.
* doc/lispref/keymaps.texi (Prefix Keys): Add 'C-x t' (tab-prefix-map).
* doc/lispref/maps.texi (Standard Keymaps): Add tab-prefix-map, tab-bar-map.

* lisp/dired.el: Rebind 'C-x 6 d' to 'C-x t d'.  Use tab-prefix-map.

* lisp/subr.el (ctl-x-6-map, ctl-x-6-prefix, ctl-x-t-prefix): Remove.
(tab-prefix-map): New keymap bound to 'C-x t'.

* lisp/tab-bar.el: Use tab-prefix-map instead of ctl-x-6-map.

* lisp/textmodes/two-column.el: Restore autoload global setting of
"\C-x6" to 2C-command.

* lisp/ldefs-boot.el: Update to add setting "\C-x6" to 2C-command.

* doc/emacs/commands.texi (Keys):
* doc/emacs/text.texi (Two-Column):
* doc/lispref/keymaps.texi (Prefix Keys):
* doc/lispref/maps.texi (Standard Keymaps):
Restore 'C-x 6' bound to '2C-mode-map'.

11 files changed, 82 insertions, 72 deletions

diff --git a/doc/emacs/commands.texi b/doc/emacs/commands.texi
index 17e0d20f358..5eb3b304175 100644
--- a/doc/emacs/commands.texi
+++ b/doc/emacs/commands.texi
@@ -117,13 +117,14 @@ C-k} is two key sequences, not one.
 
   By default, the prefix keys in Emacs are @kbd{C-c}, @kbd{C-h},
 @kbd{C-x}, @kbd{C-x @key{RET}}, @kbd{C-x @@}, @kbd{C-x a}, @kbd{C-x
-n}, @kbd{C-x r}, @kbd{C-x v}, @kbd{C-x 4}, @kbd{C-x 5}, @kbd{C-x 6},
-@key{ESC}, @kbd{M-g}, @kbd{M-o} and @key{F2}.  (@key{F1} is an alias
-for @kbd{C-h}.)  This list is not cast in stone; if you customize
-Emacs, you can make new prefix keys.  You could even eliminate some of
-the standard ones, though this is not recommended for most users; for
-example, if you remove the prefix definition of @kbd{C-x 4}, then
-@kbd{C-x 4 C-f} becomes an invalid key sequence.  @xref{Key Bindings}.
+n}, @kbd{C-x r}, @kbd{C-x t}, @kbd{C-x v}, @kbd{C-x 4}, @kbd{C-x 5},
+@kbd{C-x 6}, @key{ESC}, @kbd{M-g}, and @kbd{M-o}.  (@key{F1} and
+@key{F2} are aliases for @kbd{C-h} and @kbd{C-x 6}.)  This list is not
+cast in stone; if you customize Emacs, you can make new prefix keys.
+You could even eliminate some of the standard ones, though this is not
+recommended for most users; for example, if you remove the prefix
+definition of @kbd{C-x 4}, then @kbd{C-x 4 C-f} becomes an invalid key
+sequence.  @xref{Key Bindings}.
 
   Typing the help character (@kbd{C-h} or @key{F1}) after a prefix key
 displays a list of the commands starting with that prefix.  The sole
diff --git a/doc/emacs/frames.texi b/doc/emacs/frames.texi
index 452c167c726..cac1f7fea6d 100644
--- a/doc/emacs/frames.texi
+++ b/doc/emacs/frames.texi
@@ -1257,32 +1257,32 @@ use persistent named window configurations without using the tab bar
 by typing the related commands: @kbd{M-x tab-new}, @kbd{M-x tab-next},
 @kbd{M-x tab-list}, @kbd{M-x tab-close}, etc.
 
-@kindex C-x 6
-  The prefix key @kbd{C-x 6} is analogous to @kbd{C-x 5}.
+@kindex C-x t
+  The prefix key @kbd{C-x t} is analogous to @kbd{C-x 5}.
 Whereas each @kbd{C-x 5} command pops up a buffer in a different frame
-(@pxref{Creating Frames}), the @kbd{C-x 6} commands use a different
+(@pxref{Creating Frames}), the @kbd{C-x t} commands use a different
 tab with a different window configuration in the selected frame.
 
-  The various @kbd{C-x 6} commands differ in how they find or create the
+  The various @kbd{C-x t} commands differ in how they find or create the
 buffer to select:
 
 @table @kbd
-@item C-x 6 2
-@kindex C-x 6 2
+@item C-x t 2
+@kindex C-x t 2
 @findex tab-new
 Add a new tab (@code{tab-new}).  You can control the choice of the
 buffer displayed in a new tab by customizing the variable
 @code{tab-bar-new-tab-choice}.
-@item C-x 6 b @var{bufname} @key{RET}
+@item C-x t b @var{bufname} @key{RET}
 Select buffer @var{bufname} in another tab.  This runs
 @code{switch-to-buffer-other-tab}.
-@item C-x 6 f @var{filename} @key{RET}
+@item C-x t f @var{filename} @key{RET}
 Visit file @var{filename} and select its buffer in another tab.  This
 runs @code{find-file-other-tab}.  @xref{Visiting}.
-@item C-x 6 d @var{directory} @key{RET}
+@item C-x t d @var{directory} @key{RET}
 Select a Dired buffer for directory @var{directory} in another tab.
 This runs @code{dired-other-tab}.  @xref{Dired}.
-@item C-x 6 r @var{tabname} @key{RET}
+@item C-x t r @var{tabname} @key{RET}
 Renames the current tab to @var{tabname}.  You can control the
 programmatic name given to a tab by default by customizing the
 variable @code{tab-bar-tab-name-function}.
@@ -1297,14 +1297,14 @@ new tab with other buffers, customize the variable
   The following commands are used to delete and operate on tabs:
 
 @table @kbd
-@item C-x 6 0
-@kindex C-x 6 0
+@item C-x t 0
+@kindex C-x t 0
 @findex tab-close
 Close the selected tab (@code{tab-close}).  It has no effect if there
 is only one tab.
 
-@item C-x 6 o
-@kindex C-x 6 o
+@item C-x t o
+@kindex C-x t o
 @kindex C-TAB
 @findex tab-next
 Switch to another tab.  If you repeat this command, it cycles through
@@ -1312,8 +1312,8 @@ all the tabs on the selected frame.  With a positive numeric argument
 N, it switches to the next Nth tab; with a negative argument −N, it
 switches back to the previous Nth tab.
 
-@item C-x 6 1
-@kindex C-x 6 1
+@item C-x t 1
+@kindex C-x t 1
 @findex tab-close-other
 Close all tabs on the selected frame, except the selected one.
 @end table
diff --git a/doc/emacs/text.texi b/doc/emacs/text.texi
index a837b6580dd..974f79d5232 100644
--- a/doc/emacs/text.texi
+++ b/doc/emacs/text.texi
@@ -2870,8 +2870,9 @@ of text.  It uses two side-by-side windows, each showing its own
 buffer.  There are three ways to enter two-column mode:
 
 @table @asis
-@item @kbd{@key{F2} 2}
+@item @kbd{@key{F2} 2} or @kbd{C-x 6 2}
 @kindex F2 2
+@kindex C-x 6 2
 @findex 2C-two-columns
 Enter two-column mode with the current buffer on the left, and on the
 right, a buffer whose name is based on the current buffer's name
@@ -2882,8 +2883,9 @@ changed.
 This command is appropriate when the current buffer is empty or contains
 just one column and you want to add another column.
 
-@item @kbd{@key{F2} s}
+@item @kbd{@key{F2} s} or @kbd{C-x 6 s}
 @kindex F2 s
+@kindex C-x 6 s
 @findex 2C-split
 Split the current buffer, which contains two-column text, into two
 buffers, and display them side by side (@code{2C-split}).  The current
@@ -2896,19 +2898,21 @@ This command is appropriate when you have a buffer that already contains
 two-column text, and you wish to separate the columns temporarily.
 
 @item @kbd{@key{F2} b @var{buffer} @key{RET}}
+@itemx @kbd{C-x 6 b @var{buffer} @key{RET}}
 @kindex F2 b
+@kindex C-x 6 b
 @findex 2C-associate-buffer
 Enter two-column mode using the current buffer as the left-hand buffer,
 and using buffer @var{buffer} as the right-hand buffer
 (@code{2C-associate-buffer}).
 @end table
 
-  @kbd{@key{F2} s} looks for a column separator, which is a string
-that appears on each line between the two columns.  You can specify
-the width of the separator with a numeric argument to @kbd{@key{F2}
-s}; that many characters, before point, constitute the separator
-string.  By default, the width is 1, so the column separator is the
-character before point.
+  @kbd{@key{F2} s} or @kbd{C-x 6 s} looks for a column separator, which
+is a string that appears on each line between the two columns.  You can
+specify the width of the separator with a numeric argument to
+@kbd{@key{F2} s}; that many characters, before point, constitute the
+separator string.  By default, the width is 1, so the column separator
+is the character before point.
 
   When a line has the separator at the proper place, @kbd{@key{F2} s}
 puts the text after the separator into the right-hand buffer, and
@@ -2920,22 +2924,25 @@ mode: write it in the left-hand buffer, and put an empty line in the
 right-hand buffer.)
 
 @kindex F2 RET
+@kindex C-x 6 RET
 @findex 2C-newline
-  The command @kbd{@key{F2} @key{RET}} (@code{2C-newline}) inserts
-a newline in each of the two buffers at corresponding positions.
-This is the easiest way to add a new line to the two-column text while
-editing it in split buffers.
+  The command @kbd{@key{F2} @key{RET}} or @kbd{C-x 6 @key{RET}}
+(@code{2C-newline}) inserts a newline in each of the two buffers at
+corresponding positions.  This is the easiest way to add a new line to
+the two-column text while editing it in split buffers.
 
 @kindex F2 1
+@kindex C-x 6 1
 @findex 2C-merge
   When you have edited both buffers as you wish, merge them with
-@kbd{@key{F2} 1} (@code{2C-merge}).  This copies the
+@kbd{@key{F2} 1} or @kbd{C-x 6 1} (@code{2C-merge}).  This copies the
 text from the right-hand buffer as a second column in the other buffer.
 To go back to two-column editing, use @kbd{@key{F2} s}.
 
 @kindex F2 d
+@kindex C-x 6 d
 @findex 2C-dissociate
-  Use @kbd{@key{F2} d} to dissociate the two buffers, leaving each as
-it stands (@code{2C-dissociate}).  If the other buffer, the one not
-current when you type @kbd{@key{F2} d}, is empty, @kbd{@key{F2} d}
-kills it.
+  Use @kbd{@key{F2} d} or @kbd{C-x 6 d} to dissociate the two buffers,
+leaving each as it stands (@code{2C-dissociate}).  If the other buffer,
+the one not current when you type @kbd{@key{F2} d}, is empty,
+@kbd{@key{F2} d} kills it.
diff --git a/doc/lispref/keymaps.texi b/doc/lispref/keymaps.texi
index 532e537026a..8ff329bdacb 100644
--- a/doc/lispref/keymaps.texi
+++ b/doc/lispref/keymaps.texi
@@ -545,8 +545,14 @@ key.
 
 @item
 @cindex @kbd{C-x 6}
-@vindex ctl-x-6-map
-@code{ctl-x-6-map} is the global keymap used for the @kbd{C-x 6} prefix
+@vindex 2C-mode-map
+@code{2C-mode-map} is the global keymap used for the @kbd{C-x 6} prefix
+key.
+
+@item
+@cindex @kbd{C-x t}
+@vindex tab-prefix-map
+@code{tab-prefix-map} is the global keymap used for the @kbd{C-x t} prefix
 key.
 
 @item
diff --git a/doc/lispref/maps.texi b/doc/lispref/maps.texi
index 1ee4816b0c7..7743f3cb3c4 100644
--- a/doc/lispref/maps.texi
+++ b/doc/lispref/maps.texi
@@ -21,7 +21,7 @@ keymaps, @pxref{Keymaps}.
 @c Don't add xrefs to things covered in {Keymaps}.
 @table @code
 @item 2C-mode-map
-A sparse keymap for subcommands of the prefix @key{F2}.@*
+A sparse keymap for subcommands of the prefix @kbd{C-x 6}.@*
 @xref{Two-Column,, Two-Column Editing, emacs, The GNU Emacs Manual}.
 
 @item abbrev-map
@@ -42,9 +42,6 @@ A sparse keymap for subcommands of the prefix @kbd{C-x 4}.
 @item ctl-x-5-map
 A sparse keymap for subcommands of the prefix @kbd{C-x 5}.
 
-@item ctl-x-6-map
-A sparse keymap for subcommands of the prefix @kbd{C-x 6}.
-
 @item ctl-x-map
 A full keymap for @kbd{C-x} commands.
 
@@ -181,6 +178,14 @@ A sparse keymap that provides global bindings for search-related commands.
 The keymap used by Special mode.@*
 @xref{Basic Major Modes}.
 
+@item tab-prefix-map
+The global keymap used for the @kbd{C-x t} prefix key for tab-bar related commands.@*
+@xref{Tab Bars,,, emacs, The GNU Emacs Manual}.
+
+@item tab-bar-map
+The keymap defining the contents of the tab bar.@*
+@xref{Tab Bars,,, emacs, The GNU Emacs Manual}.
+
 @item tool-bar-map
 The keymap defining the contents of the tool bar.@*
 @xref{Tool Bar}.
diff --git a/etc/NEWS b/etc/NEWS
index 6ed3fd46085..e49dc0c9982 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2131,9 +2131,9 @@ The new command 'tab-bar-mode' enables the tab bar at the top of each
 frame, where you can use tabs to switch between named persistent
 window configurations.
 
-The 'C-x 6' sequence is the new prefix key for tab-related commands:
-'C-x 6 2' creates a new tab; 'C-x 6 0' deletes the current tab;
-'C-x 6 b' switches to buffer in another tab; 'C-x 6 f' and 'C-x 6 C-f'
+The 'C-x t' sequence is the new prefix key for tab-related commands:
+'C-x t 2' creates a new tab; 'C-x t 0' deletes the current tab;
+'C-x t b' switches to buffer in another tab; 'C-x t f' and 'C-x t C-f'
 edit file in another tab; and 'C-TAB' and 'S-C-TAB' switch to the next
 or previous tab.  You can also switch between tabs and create/delete
 tabs with a mouse.
@@ -2196,11 +2196,6 @@ immediately.  Type 'M-x so-long-commentary' for full documentation.
 * Incompatible Lisp Changes in Emacs 27.1
 
 ---
-** Two-column mode provides its 'C-x 6' prefix map only after loading
-two-column.el.  Its prefix key 'F2' is still available globally
-along with 'C-x 6' used by the tab commands globally.
-
----
 ** Incomplete destructive splicing support has been removed.
 Support for Common Lisp style destructive splicing (",.") was
 incomplete and broken for a long time.  It has now been removed.
diff --git a/lisp/dired.el b/lisp/dired.el
index 574de7ac3eb..3146511305d 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -848,7 +848,7 @@ If DIRNAME is already in a Dired buffer, that buffer is used without refresh."
   (interactive (dired-read-dir-and-switches "in other frame "))
   (switch-to-buffer-other-frame (dired-noselect dirname switches)))
 
-;;;###autoload (define-key ctl-x-6-map "d" 'dired-other-tab)
+;;;###autoload (define-key tab-prefix-map "d" 'dired-other-tab)
 ;;;###autoload
 (defun dired-other-tab (dirname &optional switches)
   "\"Edit\" directory DIRNAME.  Like `dired' but makes a new tab."
diff --git a/lisp/ldefs-boot.el b/lisp/ldefs-boot.el
index 5c20c0526d4..ea111f2d3f1 100644
--- a/lisp/ldefs-boot.el
+++ b/lisp/ldefs-boot.el
@@ -34138,6 +34138,7 @@ resumed later.
 ;;;;;;  0 0))
 ;;; Generated autoloads from textmodes/two-column.el
  (autoload '2C-command "two-column" () t 'keymap)
+ (global-set-key "\C-x6" '2C-command)
  (global-set-key [f2] '2C-command)
 
 (autoload '2C-two-columns "two-column" "\
diff --git a/lisp/subr.el b/lisp/subr.el
index f3371dd2d74..ada078aed9b 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1262,12 +1262,9 @@ The normal global definition of the character C-x indirects to this keymap.")
 (defalias 'ctl-x-5-prefix ctl-x-5-map)
 (define-key ctl-x-map "5" 'ctl-x-5-prefix)
 
-(defvar ctl-x-6-map (make-sparse-keymap)
-  "Keymap for tab commands.")
-(defalias 'ctl-x-6-prefix ctl-x-6-map)
-(define-key ctl-x-map "6" 'ctl-x-6-prefix)
-(defalias 'ctl-x-t-prefix ctl-x-6-map)
-(define-key ctl-x-map "t" 'ctl-x-t-prefix)
+(defvar tab-prefix-map (make-sparse-keymap)
+  "Keymap for tab-bar related commands.")
+(define-key ctl-x-map "t" tab-prefix-map)
 
 
 ;;;; Event manipulation functions.
diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index c376f598966..52d06872312 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -962,14 +962,14 @@ Like \\[find-file-other-frame] (which see), but creates a new tab."
           value)
       (switch-to-buffer-other-tab value))))
 
-(define-key ctl-x-6-map "2" 'tab-new)
-(define-key ctl-x-6-map "1" 'tab-close-other)
-(define-key ctl-x-6-map "0" 'tab-close)
-(define-key ctl-x-6-map "o" 'tab-next)
-(define-key ctl-x-6-map "b" 'switch-to-buffer-other-tab)
-(define-key ctl-x-6-map "f" 'find-file-other-tab)
-(define-key ctl-x-6-map "\C-f" 'find-file-other-tab)
-(define-key ctl-x-6-map "r" 'tab-rename)
+(define-key tab-prefix-map "2" 'tab-new)
+(define-key tab-prefix-map "1" 'tab-close-other)
+(define-key tab-prefix-map "0" 'tab-close)
+(define-key tab-prefix-map "o" 'tab-next)
+(define-key tab-prefix-map "b" 'switch-to-buffer-other-tab)
+(define-key tab-prefix-map "f" 'find-file-other-tab)
+(define-key tab-prefix-map "\C-f" 'find-file-other-tab)
+(define-key tab-prefix-map "r" 'tab-rename)
 
 
 (provide 'tab-bar)
diff --git a/lisp/textmodes/two-column.el b/lisp/textmodes/two-column.el
index 5bc70d0bd5f..e1ebf1a02a0 100644
--- a/lisp/textmodes/two-column.el
+++ b/lisp/textmodes/two-column.el
@@ -184,9 +184,7 @@ minus this value."
 ;; This one is for historical reasons and simple keyboards, it is not
 ;; at all mnemonic.  All usual sequences containing 2 were used, and
 ;; f2 could not be set up in a standard way under Emacs 18.
-;; This prefix is bound only after loading this package
-;; to not conflict with the C-x 6 prefix used by tab commands.
-(global-set-key "\C-x6" '2C-command)
+;;;###autoload (global-set-key "\C-x6" '2C-command)
 
 ;;;###autoload (global-set-key [f2] '2C-command)