Re: emacs-28 d9b0b73 1/2: * doc/emacs/frames.texi (Tab Bars): Describe tab-last.

[Juri Linkov <juri@linkov.net>]

>     >>> *** New optional key binding for 'tab-last'.
>     >>> If you customize the user option 'tab-bar-select-tab-modifiers' to
>     >>> allow selecting tabs using their index numbers, the '<MODIFIER>-9' key
>     >>> is bound to 'tab-last', and switches to the last tab.  Here <MODIFIER>
>     >>> is any of the modifiers in the list that is the value of
>     >>> +'tab-bar-select-tab-modifiers'.  You can also use positive indices,
>     >>> +which count from the last tab: 1 is the last tab, 2 the one before
>     >>> that, etc.
>     >>
>     >> Hi Juri, this contradicts what the docstring for
>     >> `tab-bar-select-tab-modifiers' says about indices.
>
>     Juri> Please try to type 'C-u 2 <MODIFIER>-9'.
>     Juri> It selects the tab before the last tab.
>     Juri> Maybe 'C-u -2 <MODIFIER>-9' should do the same?
>     Juri> E.g. by using '(abs)' on the argument?
>
> Hmm, ok. I got confused by the 'tab-bar-select-tab-modifiers'
> docstring, which says
>
>     List of modifier keys for selecting tab-bar tabs by their numbers.
>     Possible modifier keys are `control', `meta', `shift', `hyper', `super' and
>     `alt'.  Pressing one of the modifiers in the list and a digit selects
>     the tab whose number equals the digit.  Negative numbers count from
>     the end of the tab bar.  The digit 9 selects the last (rightmost) tab.
>     For easier selection of tabs by their numbers, consider customizing
>     `tab-bar-tab-hints', which will show tab numbers alongside the tab name.
>
> Perhaps the option of doing C-u <digit> <MODIFIER>-9 should be
> mentioned there as well?

This is because <MODIFIER>-9 differs from other digits.
For example, '<MODIFIER>-2' selects the second tab,
but 'C-1 <MODIFIER>-2' selects the first tab.  This means that
the prefix argument takes precedence over the modifier digit,
so you can select a tab that has no digit key, e.g.
'C-u 42 <MODIFIER>-2' will select the 42nd tab, and
'C-u -42 <MODIFIER>-2' will select the 42nd tab from the end.

But 'tab-last' is an exception from this rule, and its prefix argument
means to count the relative position from the last tab.

'tab-bar-select-tab' and 'tab-last' should describe their prefix arguments,
so 'tab-bar-select-tab-modifiers' could just link to their docstrings:

diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 5fc5124d47..9173a7b38d 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -91,9 +91,9 @@ tab-bar-tab-ungrouped
 (defcustom tab-bar-select-tab-modifiers '()
   "List of modifier keys for selecting tab-bar tabs by their numbers.
 Possible modifier keys are `control', `meta', `shift', `hyper', `super' and
-`alt'.  Pressing one of the modifiers in the list and a digit selects
-the tab whose number equals the digit.  Negative numbers count from
-the end of the tab bar.  The digit 9 selects the last (rightmost) tab.
+`alt'.  Pressing one of the modifiers in the list and a digit selects the
+tab whose number equals the digit (see more at `tab-bar-select-tab').
+The digit 9 selects the last (rightmost) tab (`tab-last').
 For easier selection of tabs by their numbers, consider customizing
 `tab-bar-tab-hints', which will show tab numbers alongside the tab name."
   :type '(set :tag "Tab selection modifier keys"
@@ -1064,7 +1064,7 @@ tab-bar-select-tab
 using `tab-bar-select-tab-modifiers'), calling it without an argument
 will translate its bound numeric key to the numeric argument.
 TAB-NUMBER counts from 1.  Negative TAB-NUMBER counts tabs from the end of
-the tab bar."
+the tab bar.  The prefix argument takes precedence over the bound digit key."
   (interactive "P")
   (unless (integerp tab-number)
     (let ((key (event-basic-type last-command-event)))
--