Don't use hook pre-redisplay-functions. Set buffer-local tab-line-format.

* lisp/tab-line.el (tab-line-format): Move to C.
(tab-line-update-window-parameter): Remove function.
(global-tab-line-mode): Set the default value of tab-line-format.

* src/buffer.c (syms_of_buffer): Define buffer-local variable
tab-line-format.

* src/buffer.h (struct buffer): Add tab_line_format_.

* src/window.c (window_wants_tab_line):
* src/xdisp.c (pos_visible_p, display_mode_lines):
Check for buffer-local tab_line_format.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/buffer.c b/src/buffer.c
index ad9feee92a4..233a95c2597 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -249,6 +249,11 @@ bset_header_line_format (struct buffer *b, Lisp_Object val)
   b->header_line_format_ = val;
 }
 static void
+bset_tab_line_format (struct buffer *b, Lisp_Object val)
+{
+  b->tab_line_format_ = val;
+}
+static void
 bset_indicate_buffer_boundaries (struct buffer *b, Lisp_Object val)
 {
   b->indicate_buffer_boundaries_ = val;
@@ -5188,6 +5193,7 @@ init_buffer_once (void)
   XSETFASTINT (BVAR (&buffer_local_flags, scroll_up_aggressively), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, scroll_down_aggressively), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, header_line_format), idx); ++idx;
+  XSETFASTINT (BVAR (&buffer_local_flags, tab_line_format), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, cursor_type), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, extra_line_spacing), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, cursor_in_non_selected_windows), idx); ++idx;
@@ -5233,6 +5239,7 @@ init_buffer_once (void)
   /* real setup is done in bindings.el */
   bset_mode_line_format (&buffer_defaults, build_pure_c_string ("%-"));
   bset_header_line_format (&buffer_defaults, Qnil);
+  bset_tab_line_format (&buffer_defaults, Qnil);
   bset_abbrev_mode (&buffer_defaults, Qnil);
   bset_overwrite_mode (&buffer_defaults, Qnil);
   bset_case_fold_search (&buffer_defaults, Qt);
@@ -5504,6 +5511,13 @@ syms_of_buffer (void)
   Fput (Qprotected_field, Qerror_message,
         build_pure_c_string ("Attempt to modify a protected field"));
 
+  DEFVAR_PER_BUFFER ("tab-line-format",
+                     &BVAR (current_buffer, tab_line_format),
+                     Qnil,
+                     doc: /* Analogous to `mode-line-format', but controls the tab line.
+The tab line appears, optionally, at the top of a window;
+the mode line appears at the bottom.  */);
+
   DEFVAR_PER_BUFFER ("header-line-format",
                      &BVAR (current_buffer, header_line_format),
                      Qnil,