vim-patch:8.1.0706: introduce :redrawtabline #10570

Problem:    Tabline is not always redrawn when something that is used in
            'tabline' changes.
Solution:   Add ":redrawtabline" so that a plugin can at least cause the
            redraw when needed.
e12bab3144

runtime/doc/options.txt

@@ -6027,6 +6027,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 	the text to be displayed.  Use "%1T" for the first label, "%2T" for
 	the second one, etc.  Use "%X" items for closing labels.
 
+	When changing something that is used in 'tabline' that does not
+	trigger it to be updated, use |:redrawtabline|.
 	This option cannot be set in a modeline when 'modelineexpr' is off.
 
 	Keep in mind that only one of the tab pages is the current one, others

runtime/doc/various.txt

@@ -31,6 +31,11 @@ CTRL-L			Clears and redraws the screen.  The redraw may happen
 			Useful if 'statusline' includes an item that doesn't
 			cause automatic updating.
 
+						*:redrawt* *:redrawtabline*
+:redrawt[abline]	Redraw the tabline.  Useful to update the tabline when
+			'tabline' includes an item that doesn't trigger
+			automatic updating.
+
 							*N<Del>*
 <Del>			When entering a number: Remove the last digit.
 			Note: if you like to use <BS> for this, add this

src/nvim/ex_cmds.lua

@@ -2150,6 +2150,12 @@ return {
     addr_type=ADDR_LINES,
     func='ex_redrawstatus',
   },
+  {
+    command='redrawtabline',
+    flags=bit.bor(TRLBAR, CMDWIN),
+    addr_type=ADDR_LINES,
+    func='ex_redrawtabline',
+  },
   {
     command='registers',
     flags=bit.bor(EXTRA, NOTRLCOM, TRLBAR, CMDWIN),

src/nvim/ex_docmd.c

@@ -7874,6 +7874,22 @@ static void ex_redrawstatus(exarg_T *eap)
   ui_flush();
 }
 
+// ":redrawtabline": force redraw of the tabline
+static void ex_redrawtabline(exarg_T *eap FUNC_ATTR_UNUSED)
+{
+  const int r = RedrawingDisabled;
+  const int p = p_lz;
+
+  RedrawingDisabled = 0;
+  p_lz = false;
+
+  draw_tabline();
+
+  RedrawingDisabled = r;
+  p_lz = p;
+  ui_flush();
+}
+
 static void close_redir(void)
 {
   if (redir_fd != NULL) {

src/nvim/screen.c

@@ -6650,7 +6650,7 @@ static void recording_mode(int attr)
 /*
  * Draw the tab pages line at the top of the Vim window.
  */
-static void draw_tabline(void)
+void draw_tabline(void)
 {
   int tabcount = 0;
   int tabwidth = 0;

src/nvim/testdir/test_tabline.vim

@@ -1,19 +1,22 @@
-function! TablineWithCaughtError()
+
+source shared.vim
+
+func TablineWithCaughtError()
   let s:func_in_tabline_called = 1
   try
     call eval('unknown expression')
   catch
   endtry
   return ''
-endfunction
+endfunc
 
-function! TablineWithError()
+func TablineWithError()
   let s:func_in_tabline_called = 1
   call eval('unknown expression')
   return ''
-endfunction
+endfunc
 
-function! Test_caught_error_in_tabline()
+func Test_caught_error_in_tabline()
   let showtabline_save = &showtabline
   set showtabline=2
   let s:func_in_tabline_called = 0
@@ -24,9 +27,9 @@ function! Test_caught_error_in_tabline()
   call assert_equal(tabline, &tabline)
   set tabline=
   let &showtabline = showtabline_save
-endfunction
+endfunc
 
-function! Test_tabline_will_be_disabled_with_error()
+func Test_tabline_will_be_disabled_with_error()
   let showtabline_save = &showtabline
   set showtabline=2
   let s:func_in_tabline_called = 0
@@ -40,4 +43,24 @@ function! Test_tabline_will_be_disabled_with_error()
   call assert_equal('', &tabline)
   set tabline=
   let &showtabline = showtabline_save
-endfunction
+endfunc
+
+func Test_redrawtabline()
+  if has('gui')
+    set guioptions-=e
+  endif
+  let showtabline_save = &showtabline
+  set showtabline=2
+  set tabline=%{bufnr('$')}
+  edit Xtabline1
+  edit Xtabline2
+  redraw
+  call assert_match(bufnr('$') . '', Screenline(1))
+  au BufAdd * redrawtabline
+  badd Xtabline3
+  call assert_match(bufnr('$') . '', Screenline(1))
+
+  set tabline=
+  let &showtabline = showtabline_save
+  au! Bufadd
+endfunc