* lisp/tab-bar.el: Tab groups can be displayed with tab-bar-format-tabs-groups

* lisp/tab-bar.el (tab-bar-format): Turn defvar into defcustom.
Add :options and force-mode-line-update in :set.
(tab-bar--format-tab): New function refactored from tab-bar-format-tabs.
(tab-bar-format-tabs): Move most of code to tab-bar--format-tab and call it.
(tab-bar-tab-group-format-function): New defcustom.
(tab-bar-tab-group-format-default): New function.
(tab-bar--format-tab-group, tab-bar-format-tabs-groups): New functions.
(tab-bar-format-align-right, tab-bar-format-global): Shorten id.
(tab-bar-change-tab-group): Add refs to tab-bar-format in docstring.

1 files changed, 3 insertions, 1 deletions

diff --git a/etc/NEWS b/etc/NEWS
index fa8784db59c..01fd7af65bf 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -519,11 +519,13 @@ It can be used to enable/disable the tab bar individually on each frame
 independently from the value of 'tab-bar-mode' and 'tab-bar-show'.
 
 ---
-*** New variable 'tab-bar-format' defines a list of tab bar items.
+*** New option 'tab-bar-format' defines a list of tab bar items.
 When it contains 'tab-bar-format-global' (possibly appended after
 'tab-bar-format-align-right'), then after enabling 'display-time-mode'
 (or any other mode that uses 'global-mode-string') it displays time
 aligned to the right on the tab bar instead of the mode line.
+When 'tab-bar-format-tabs' is replaced with 'tab-bar-format-tabs-groups',
+then the tab bar displays tab groups.
 
 ---
 *** 'Mod-9' bound to 'tab-last' now switches to the last tab.