Improve customizability and better tab separators.

* lisp/tab-bar.el (tab-bar-tabs-function): New defvar.

* lisp/tab-line.el (tab-line-tab-name-function)
(tab-line-tabs-function): New defvars.

4 files changed, 67 insertions, 51 deletions

diff --git a/etc/images/tabs/close.xpm b/etc/images/tabs/close.xpm
index 48f063fa43b..1c3f4d8fd7d 100644
--- a/etc/images/tabs/close.xpm
+++ b/etc/images/tabs/close.xpm
@@ -2,7 +2,7 @@
 static char * close_xpm[] = {
 "9 9 4 1",
 "       c None",
-".      c #CCCCCC",
+".      c #BFBFBF",
 "+      c #000000",
 "@      c #808080",
 "  .....  ",
diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 7afb39a0dda..3b6415ad13d 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -1,4 +1,4 @@
-;;; tab-bar.el --- frame-local tab bar with named persistent window configurations -*- lexical-binding: t; -*-
+;;; tab-bar.el --- frame-local tabs with named persistent window configurations -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2019 Free Software Foundation, Inc.
 
@@ -23,7 +23,7 @@
 
 ;;; Commentary:
 
-;; Provides `tab-bar-mode' to control display of the tab-bar and
+;; Provides `tab-bar-mode' to control display of the tab bar and
 ;; bindings for the global tab bar.
 
 ;; The normal global binding for [tab-bar] (below) uses the value of
@@ -36,7 +36,7 @@
 
 
 (defgroup tab-bar nil
-  "Frame-local tab bar."
+  "Frame-local tabs."
   :group 'convenience
   :version "27.1")
 
@@ -79,13 +79,6 @@
   :version "27.1"
   :group 'tab-bar-faces)
 
-(defface tab-bar-separator
-  '((t
-     :inverse-video nil))
-  "Tab bar face for separator."
-  :version "27.1"
-  :group 'tab-bar-faces)
-
 
 (define-minor-mode tab-bar-mode
   "Toggle the tab bar in all graphical frames (Tab Bar mode)."
@@ -108,8 +101,8 @@
     (global-set-key [(control tab)]               'tab-bar-switch-to-next-tab)))
 
 (defun tab-bar-handle-mouse (event)
-  "Text-mode emulation of switching tabs on the tab-bar.
-This command is used when you click the mouse in the tab-bar
+  "Text-mode emulation of switching tabs on the tab bar.
+This command is used when you click the mouse in the tab bar
 on a console which has no window system but does have a mouse."
   (interactive "e")
   (let* ((x-position (car (posn-x-y (event-start event))))
@@ -159,8 +152,7 @@ Its main job is to show tabs in the tab bar."
           (puthash key tab-bar-map tab-bar-keymap-cache)))))
 
 
-(defvar tab-bar-separator
-  (propertize " " 'face 'tab-bar-separator))
+(defvar tab-bar-separator nil)
 
 (defvar tab-bar-button-new
   (propertize " + "
@@ -173,7 +165,7 @@ Its main job is to show tabs in the tab bar."
   "Button for creating a new tab.")
 
 (defvar tab-bar-button-close
-  (propertize "x"
+  (propertize " x"
               'display `(image :type xpm
                                :file ,(expand-file-name
                                        "images/tabs/close.xpm"
@@ -188,9 +180,16 @@ Its main job is to show tabs in the tab bar."
   "Generate tab name in the context of the selected frame."
   (mapconcat
    (lambda (w) (buffer-name (window-buffer w)))
-   (window-list)
+   (window-list-1 (frame-first-window) 'nomini)
    ", "))
 
+(defvar tab-bar-tabs-function #'tab-bar-tabs
+  "Function to get a list of tabs to display in the tab bar.
+This function should return a list of alists with parameters
+that include at least the element (name . TAB-NAME).
+For example, '((tab (name . \"Tab 1\")) (current-tab (name . \"Tab 2\")))
+By default, use function `tab-bar-tabs'.")
+
 (defun tab-bar-tabs ()
   "Return a list of tabs belonging to the selected frame.
 Ensure the frame parameter `tabs' is pre-populated.
@@ -203,13 +202,15 @@ Return its existing value or a new value."
 
 (defun tab-bar-make-keymap-1 ()
   "Generate an actual keymap from `tab-bar-map', without caching."
-  (let ((i 0))
+  (let ((separator (or tab-bar-separator (if window-system " " "|")))
+        (i 0))
     (append
      '(keymap (mouse-1 . tab-bar-handle-mouse))
      (mapcan
       (lambda (tab)
         (setq i (1+ i))
         (append
+         `((,(intern (format "sep-%i" i)) menu-item ,separator ignore))
          (cond
           ((eq (car tab) 'current-tab)
            `((current-tab
@@ -233,13 +234,11 @@ Return its existing value or a new value."
             menu-item ""
             ,(lambda ()
                (interactive)
-               (tab-bar-close-tab tab))))
-         (when (and (stringp tab-bar-separator)
-                    (> (length tab-bar-separator) 0))
-           `((,(intern (format "sep-%i" i)) menu-item ,tab-bar-separator ignore)))))
-      (tab-bar-tabs))
+               (tab-bar-close-tab tab))))))
+      (funcall tab-bar-tabs-function))
      (when tab-bar-button-new
-       `((add-tab menu-item ,tab-bar-button-new tab-bar-add-tab
+       `((sep-add-tab menu-item ,separator ignore)
+         (add-tab menu-item ,tab-bar-button-new tab-bar-add-tab
                   :help "New tab"))))))
 
 
diff --git a/lisp/tab-line.el b/lisp/tab-line.el
index 6b1ce03d26e..169f7b82042 100644
--- a/lisp/tab-line.el
+++ b/lisp/tab-line.el
@@ -1,4 +1,4 @@
-;;; tab-line.el --- window-local tab line with window buffers -*- lexical-binding: t; -*-
+;;; tab-line.el --- window-local tabs with window buffers -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2019 Free Software Foundation, Inc.
 
@@ -31,7 +31,7 @@
 
 
 (defgroup tab-line nil
-  "Window-local tab line."
+  "Window-local tabs."
   :group 'convenience
   :version "27.1")
 
@@ -70,7 +70,7 @@
      :background "grey75")
     (t
      :inverse-video t))
-  "Tab line face for non-selected tabs."
+  "Tab line face for non-selected tab."
   :version "27.1"
   :group 'tab-line-faces)
 
@@ -82,7 +82,7 @@
 
 (defface tab-line-close-highlight
   '((t :foreground "red"))
-  "Tab line face for highlighting."
+  "Tab line face for highlighting of the close button."
   :version "27.1"
   :group 'tab-line-faces)
 
@@ -90,11 +90,10 @@
 (defvar tab-line-tab-map
   (let ((map (make-sparse-keymap)))
     (define-key map [tab-line mouse-1] 'tab-line-select-tab)
-    (define-key map [tab-line mouse-2] 'tab-line-select-tab)
+    (define-key map [tab-line mouse-2] 'tab-line-close-tab)
     (define-key map [tab-line mouse-4] 'tab-line-switch-to-prev-tab)
     (define-key map [tab-line mouse-5] 'tab-line-switch-to-next-tab)
     (define-key map "\C-m" 'tab-line-select-tab)
-    (define-key map [follow-link] 'mouse-face)
     map)
   "Local keymap for `tab-line-mode' window tabs.")
 
@@ -103,7 +102,6 @@
     (define-key map [tab-line mouse-1] 'tab-line-add-tab)
     (define-key map [tab-line mouse-2] 'tab-line-add-tab)
     (define-key map "\C-m" 'tab-line-add-tab)
-    (define-key map [follow-link] 'mouse-face)
     map)
   "Local keymap to add `tab-line-mode' window tabs.")
 
@@ -111,12 +109,11 @@
   (let ((map (make-sparse-keymap)))
     (define-key map [tab-line mouse-1] 'tab-line-close-tab)
     (define-key map [tab-line mouse-2] 'tab-line-close-tab)
-    (define-key map [follow-link] 'mouse-face)
     map)
   "Local keymap to close `tab-line-mode' window tabs.")
 
 
-(defvar tab-line-separator " ")
+(defvar tab-line-separator nil)
 
 (defvar tab-line-tab-name-ellipsis
   (if (char-displayable-p ?…) "…" "..."))
@@ -135,7 +132,7 @@
   "Button for creating a new tab.")
 
 (defvar tab-line-button-close
-  (propertize "x"
+  (propertize " x"
               'display `(image :type xpm
                                :file ,(expand-file-name
                                        "images/tabs/close.xpm"
@@ -148,9 +145,16 @@
   "Button for closing the clicked tab.")
 
 
+(defvar tab-line-tab-name-function #'tab-line-tab-name
+  "Function to get a tab name.
+Function gets two arguments: tab to get name for and a list of tabs
+to display.  By default, use function `tab-line-tab-name'.")
+
 (defun tab-line-tab-name (buffer &optional buffers)
   "Generate tab name from BUFFER.
-Reduce tab width proportionally to space taken by other tabs."
+Reduce tab width proportionally to space taken by other tabs.
+This function can be overridden by changing the default value of the
+variable `tab-line-tab-name-function'."
   (let ((tab-name (buffer-name buffer))
         (limit (when buffers
                  (max 1 (- (/ (window-width) (length buffers)) 3)))))
@@ -161,10 +165,22 @@ Reduce tab width proportionally to space taken by other tabs."
                   'help-echo tab-name))))
 
 (defvar tab-line-tabs-limit 15
-  "Maximum number of buffer tabs displayed in the window tab-line.")
-
-(defun tab-line-tabs (&optional window)
-  (let* ((buffer (window-buffer window))
+  "Maximum number of buffer tabs displayed in the tab line.")
+
+(defvar tab-line-tabs-function #'tab-line-tabs
+  "Function to get a list of tabs to display in the tab line.
+This function should return either a list of buffers whose names will
+be displayed, or just a list of strings to display in the tab line.
+By default, use function `tab-line-tabs'.")
+
+(defun tab-line-tabs ()
+  "Return a list of tabs that should be displayed in the tab line.
+By default returns a list of window buffers, i.e. buffers previously
+shown in the same window where the tab line is displayed.
+This list can be overridden by changing the default value of the
+variable `tab-line-tabs-function'."
+  (let* ((window (selected-window))
+         (buffer (window-buffer window))
          (next-buffers (seq-remove (lambda (b) (eq b buffer))
                                    (window-next-buffers window)))
          (next-buffers (seq-filter #'buffer-live-p next-buffers))
@@ -191,25 +207,26 @@ Reduce tab width proportionally to space taken by other tabs."
 (defun tab-line-format ()
   "Template for displaying tab line for selected window."
   (let* ((window (selected-window))
-         (buffer (window-buffer window))
-         (buffer-tabs (tab-line-tabs window)))
+         (selected-buffer (window-buffer window))
+         (tabs (funcall tab-line-tabs-function))
+         (separator (or tab-line-separator (if window-system " " "|"))))
     (append
      (mapcar
-      (lambda (b)
+      (lambda (tab)
         (concat
-         (or tab-line-separator "")
+         separator
          (apply 'propertize (concat (propertize
-                                     (tab-line-tab-name b buffer-tabs)
+                                     (funcall tab-line-tab-name-function tab tabs)
                                      'keymap tab-line-tab-map)
                                     tab-line-button-close)
                 `(
-                  buffer ,b
-                  face ,(if (eq b buffer)
+                  tab ,tab
+                  face ,(if (eq tab selected-buffer)
                             'tab-line-tab
                           'tab-line-tab-inactive)
                   mouse-face tab-line-highlight))))
-      buffer-tabs)
-     (list (concat tab-line-separator tab-line-button-new)))))
+      tabs)
+     (list (concat separator tab-line-button-new)))))
 
 
 (defun tab-line-add-tab (&optional e)
@@ -227,7 +244,7 @@ using the `previous-buffer' command."
   (interactive "e")
   (let* ((posnp (event-start e))
          (window (posn-window posnp))
-         (buffer (get-pos-property 1 'buffer (car (posn-string posnp))))
+         (buffer (get-pos-property 1 'tab (car (posn-string posnp))))
          (window-buffer (window-buffer window))
          (next-buffers (seq-remove (lambda (b) (eq b window-buffer))
                                    (window-next-buffers window)))
@@ -260,7 +277,7 @@ using the `previous-buffer' command."
   (interactive "e")
   (let* ((posnp (event-start e))
          (window (posn-window posnp))
-         (buffer (get-pos-property 1 'buffer (car (posn-string posnp)))))
+         (buffer (get-pos-property 1 'tab (car (posn-string posnp)))))
     (with-selected-window window
       (if (eq buffer (current-buffer))
           (bury-buffer)
diff --git a/src/xdisp.c b/src/xdisp.c
index 197493bfbb8..0fc387b8ffb 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12764,7 +12764,7 @@ build_desired_tab_bar_string (struct frame *f)
   caption = Qnil;
 
   /* Prepare F->desired_tab_bar_string.  Make a new string.  */
-  fset_desired_tab_bar_string (f, build_string (" "));
+  fset_desired_tab_bar_string (f, build_string (""));
 
   /* Put a `display' property on the string for the captions to display,
      put a `menu_item' property on tab-bar items with a value that