feat(ui): add `'winbar'`

Adds support for a bar at the top of each window, enabled through the
`'winbar'` option.

Co-authored-by: Björn Linse <bjorn.linse@gmail.com>

26 files changed, 538 insertions, 169 deletions

diff --git a/runtime/doc/api.txt b/runtime/doc/api.txt
index 812208ca31..820eaad99a 100644
--- a/runtime/doc/api.txt
+++ b/runtime/doc/api.txt
@@ -844,8 +844,11 @@ nvim_eval_statusline({str}, {*opts})                  *nvim_eval_statusline()*
                               Treated as single-width even if it isn't.
                             • highlights: (boolean) Return highlight
                               information.
+                            • use_winbar: (boolean) Evaluate winbar instead of
+                              statusline.
                             • use_tabline: (boolean) Evaluate tabline instead
                               of statusline. When |TRUE|, {winid} is ignored.
+                              Mutually exclusive with {use_winbar}.
 
                 Return: ~
                     Dictionary containing statusline information, with these
diff --git a/runtime/doc/index.txt b/runtime/doc/index.txt
index 5c36eaf8e5..58d49b5843 100644
--- a/runtime/doc/index.txt
+++ b/runtime/doc/index.txt
@@ -1501,8 +1501,9 @@ tag		command		action ~
 |:recover|	:rec[over]	recover a file from a swap file
 |:redo|		:red[o]		redo one undone change
 |:redir|	:redi[r]	redirect messages to a file or register
-|:redraw|	:redr[aw]	  force a redraw of the display
-|:redrawstatus|	:redraws[tatus]	  force a redraw of the status line(s)
+|:redraw|	:redr[aw]	force a redraw of the display
+|:redrawstatus|	:redraws[tatus]	force a redraw of the status line(s) and
+				window bar(s)
 |:redrawtabline|  :redrawt[abline]  force a redraw of the tabline
 |:registers|	:reg[isters]	display the contents of registers
 |:resize|	:res[ize]	change current window height
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 4d6f589714..4022bc4334 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2452,6 +2452,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	  item		default		Used for ~
 	  stl:c		' ' or '^'	statusline of the current window
 	  stlnc:c	' ' or '='	statusline of the non-current windows
+	  wbr:c		' '		window bar
 	  horiz:c	'─' or '-'	horizontal separators |:split|
 	  horizup:c	'┴' or '-'	upwards facing horizontal separator
 	  horizdown:c	'┬' or '-'	downwards facing horizontal separator
@@ -2492,6 +2493,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	  item		highlight group ~
 	  stl:c		StatusLine		|hl-StatusLine|
 	  stlnc:c	StatusLineNC		|hl-StatusLineNC|
+	  wbr:c		WinBar			|hl-WinBar| or |hl-WinBarNC|
 	  horiz:c	WinSeparator		|hl-WinSeparator|
 	  horizup:c	WinSeparator		|hl-WinSeparator|
 	  horizdown:c	WinSeparator		|hl-WinSeparator|
@@ -7045,6 +7047,19 @@ A jump table for the options with a short description can be found at |Q_op|.
 	key is never used for the menu.
 	This option is not used for <F10>; on Win32.
 
+						*'winbar'* *'wbr'*
+'winbar' 'wbr'		string (default empty)
+			global or local to window |global-local|
+	When non-empty, this option enables the window bar and determines its
+	contents. The window bar is a bar that's shown at the top of every
+	window with it enabled. The value of 'winbar' is evaluated like with
+	'statusline'.
+
+	When changing something that is used in 'winbar' that does not trigger
+	it to be updated, use |:redrawstatus|.
+
+	This option cannot be set in a modeline when 'modelineexpr' is off.
+
 						*'winblend'* *'winbl'*
 'winblend' 'winbl'		number	(default 0)
 			local to window
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 0aceb30ce0..c3ad704bb7 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -5244,6 +5244,10 @@ Whitespace	"nbsp", "space", "tab", "multispace", "lead" and "trail"
 		in 'listchars'.
 							*hl-WildMenu*
 WildMenu	Current match in 'wildmenu' completion.
+							*hl-WinBar*
+WinBar		Window bar of current window.
+							*hl-WinBarNC*
+WinBarNC	Window bar of not-current windows.
 
 					*hl-User1* *hl-User1..9* *hl-User9*
 The 'statusline' syntax allows the use of 9 different highlights in the
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index 75ee0fdfdf..0a25904104 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -30,10 +30,10 @@ CTRL-L			Clears and redraws the screen.  The redraw may happen
 			function (or a mapping if 'lazyredraw' set).
 
 						*:redraws* *:redrawstatus*
-:redraws[tatus][!]	Redraws the status line of the current window, or all
-			status lines if "!" is included.
-			Useful if 'statusline' includes an item that doesn't
-			cause automatic updating.
+:redraws[tatus][!]	Redraws the status line and window bar of the current
+			window, or all status lines and window bars if "!" is
+			included. Useful if 'statusline' or 'winbar' includes
+			an item that doesn't cause automatic updating.
 
 						*:redrawt* *:redrawtabline*
 :redrawt[abline]	Redraw the tabline.  Useful to update the tabline when
diff --git a/src/nvim/api/keysets.lua b/src/nvim/api/keysets.lua
index 78f8ed3cca..27228204e0 100644
--- a/src/nvim/api/keysets.lua
+++ b/src/nvim/api/keysets.lua
@@ -80,6 +80,7 @@ return {
     "maxwidth";
     "fillchar";
     "highlights";
+    "use_winbar";
     "use_tabline";
   };
   option = {
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index dcede27bcb..7bd68f277b 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -1418,14 +1418,14 @@ bool set_mark(buf_T *buf, String name, Integer line, Integer col, Error *err)
 }
 
 /// Get default statusline highlight for window
-const char *get_default_stl_hl(win_T *wp)
+const char *get_default_stl_hl(win_T *wp, bool use_winbar)
 {
   if (wp == NULL) {
     return "TabLineFill";
-  } else if (wp == curwin) {
-    return "StatusLine";
+  } else if (use_winbar) {
+    return (wp == curwin) ? "WinBar" : "WinBarNC";
   } else {
-    return "StatusLineNC";
+    return (wp == curwin) ? "StatusLine" : "StatusLineNC";
   }
 }
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index a257dd6478..3c378e73e1 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2274,8 +2274,9 @@ Array nvim_get_mark(String name, Dictionary opts, Error *err)
 ///           - fillchar: (string) Character to fill blank spaces in the statusline (see
 ///                                'fillchars'). Treated as single-width even if it isn't.
 ///           - highlights: (boolean) Return highlight information.
+///           - use_winbar: (boolean) Evaluate winbar instead of statusline.
 ///           - use_tabline: (boolean) Evaluate tabline instead of statusline. When |TRUE|, {winid}
-///                                    is ignored.
+///                                    is ignored. Mutually exclusive with {use_winbar}.
 ///
 /// @param[out] err Error details, if any.
 /// @return Dictionary containing statusline information, with these keys:
@@ -2294,6 +2295,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
   int maxwidth;
   int fillchar = 0;
   Window window = 0;
+  bool use_winbar = false;
   bool use_tabline = false;
   bool highlights = false;
 
@@ -2313,7 +2315,6 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
     window = (Window)opts->winid.data.integer;
   }
-
   if (HAS_KEY(opts->fillchar)) {
     if (opts->fillchar.type != kObjectTypeString || opts->fillchar.data.string.size == 0
         || ((size_t)utf_ptr2len(opts->fillchar.data.string.data)
@@ -2323,7 +2324,6 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
     }
     fillchar = utf_ptr2char(opts->fillchar.data.string.data);
   }
-
   if (HAS_KEY(opts->highlights)) {
     highlights = api_object_to_bool(opts->highlights, "highlights", false, err);
 
@@ -2331,7 +2331,13 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
       return result;
     }
   }
+  if (HAS_KEY(opts->use_winbar)) {
+    use_winbar = api_object_to_bool(opts->use_winbar, "use_winbar", false, err);
 
+    if (ERROR_SET(err)) {
+      return result;
+    }
+  }
   if (HAS_KEY(opts->use_tabline)) {
     use_tabline = api_object_to_bool(opts->use_tabline, "use_tabline", false, err);
 
@@ -2339,6 +2345,10 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
       return result;
     }
   }
+  if (use_winbar && use_tabline) {
+    api_set_error(err, kErrorTypeValidation, "use_winbar and use_tabline are mutually exclusive");
+    return result;
+  }
 
   win_T *wp, *ewp;
 
@@ -2348,7 +2358,6 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
     fillchar = ' ';
   } else {
     wp = find_window_by_handle(window, err);
-
     if (wp == NULL) {
       api_set_error(err, kErrorTypeException, "unknown winid %d", window);
       return result;
@@ -2356,8 +2365,12 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
     ewp = wp;
 
     if (fillchar == 0) {
-      int attr;
-      fillchar = fillchar_status(&attr, wp);
+      if (use_winbar) {
+        fillchar = wp->w_p_fcs_chars.wbr;
+      } else {
+        int attr;
+        fillchar = fillchar_status(&attr, wp);
+      }
     }
   }
 
@@ -2369,7 +2382,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
     maxwidth = (int)opts->maxwidth.data.integer;
   } else {
-    maxwidth = (use_tabline || global_stl_height() > 0) ? Columns : wp->w_width;
+    maxwidth = (use_tabline || (!use_winbar && global_stl_height() > 0)) ? Columns : wp->w_width;
   }
 
   char buf[MAXPATHL];
@@ -2404,7 +2417,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
     // add the default highlight at the beginning of the highlight list
     if (hltab->start == NULL || ((char *)hltab->start - buf) != 0) {
       Dictionary hl_info = ARRAY_DICT_INIT;
-      grpname = get_default_stl_hl(wp);
+      grpname = get_default_stl_hl(wp, use_winbar);
 
       PUT(hl_info, "start", INTEGER_OBJ(0));
       PUT(hl_info, "group", CSTR_TO_OBJ(grpname));
@@ -2418,22 +2431,18 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
       PUT(hl_info, "start", INTEGER_OBJ((char *)sp->start - buf));
 
       if (sp->userhl == 0) {
-        grpname = get_default_stl_hl(wp);
+        grpname = get_default_stl_hl(wp, use_winbar);
       } else if (sp->userhl < 0) {
         grpname = (char *)syn_id2name(-sp->userhl);
       } else {
         snprintf(user_group, sizeof(user_group), "User%d", sp->userhl);
         grpname = user_group;
       }
-
       PUT(hl_info, "group", CSTR_TO_OBJ(grpname));
-
       ADD(hl_values, DICTIONARY_OBJ(hl_info));
     }
-
     PUT(result, "highlights", ARRAY_OBJ(hl_values));
   }
-
   PUT(result, "str", CSTR_TO_OBJ((char *)buf));
 
   return result;
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 2adeeadbca..9efa540210 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -233,6 +233,8 @@ typedef struct {
 #define w_p_sbr w_onebuf_opt.wo_sbr    // 'showbreak'
   char_u *wo_stl;
 #define w_p_stl w_onebuf_opt.wo_stl     // 'statusline'
+  char *wo_wbr;
+#define w_p_wbr w_onebuf_opt.wo_wbr   // 'winbar'
   int wo_scb;
 #define w_p_scb w_onebuf_opt.wo_scb    // 'scrollbind'
   int wo_diff_saved;           // options were saved for starting diff mode
@@ -1235,6 +1237,7 @@ struct window_S {
   struct {
     int stl;
     int stlnc;
+    int wbr;
     int horiz;
     int horizup;
     int horizdown;
@@ -1282,14 +1285,20 @@ struct window_S {
   //
   int w_winrow;                     // first row of window in screen
   int w_height;                     // number of rows in window, excluding
-                                    // status/command/winbar line(s)
+                                    // status/command line(s)
   int w_status_height;              // number of status lines (0 or 1)
+  int w_winbar_height;              // number of window bars (0 or 1)
   int w_wincol;                     // Leftmost column of window in screen.
   int w_width;                      // Width of window, excluding separation.
   int w_hsep_height;                // Number of horizontal separator rows (0 or 1)
   int w_vsep_width;                 // Number of vertical separator columns (0 or 1).
   pos_save_T w_save_cursor;         // backup of cursor pos and topline
 
+  int w_winrow_off;  ///< offset from winrow to the inner window area
+  int w_wincol_off;  ///< offset from wincol to the inner window area
+                     ///< this includes float border but excludes special columns
+                     ///< implemented in win_line() (i.e. signs, folds, numbers)
+
   // inner size of window, which can be overridden by external UI
   int w_height_inner;
   int w_width_inner;
@@ -1379,6 +1388,7 @@ struct window_S {
   linenr_T w_redraw_top;            // when != 0: first line needing redraw
   linenr_T w_redraw_bot;            // when != 0: last line needing redraw
   bool w_redr_status;               // if true status line must be redrawn
+  bool w_redr_winbar;               // if true window bar must be redrawn
   bool w_redr_border;               // if true border must be redrawn
 
   // remember what is shown in the ruler for this window (if 'ruler' set)
@@ -1408,6 +1418,7 @@ struct window_S {
 
   // A few options have local flags for P_INSECURE.
   uint32_t w_p_stl_flags;           // flags for 'statusline'
+  uint32_t w_p_wbr_flags;           // flags for 'winbar'
   uint32_t w_p_fde_flags;           // flags for 'foldexpr'
   uint32_t w_p_fdt_flags;           // flags for 'foldtext'
   int *w_p_cc_cols;         // array of columns to highlight or NULL
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 9c2069663d..f9c6b6fbb2 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6405,7 +6405,7 @@ dict_T *get_win_info(win_T *wp, int16_t tpnr, int16_t winnr)
   tv_dict_add_nr(dict, S_LEN("winrow"), wp->w_winrow + 1);
   tv_dict_add_nr(dict, S_LEN("topline"), wp->w_topline);
   tv_dict_add_nr(dict, S_LEN("botline"), wp->w_botline - 1);
-  tv_dict_add_nr(dict, S_LEN("winbar"), 0);
+  tv_dict_add_nr(dict, S_LEN("winbar"), wp->w_winbar_height);
   tv_dict_add_nr(dict, S_LEN("width"), wp->w_width);
   tv_dict_add_nr(dict, S_LEN("bufnr"), wp->w_buffer->b_fnum);
   tv_dict_add_nr(dict, S_LEN("wincol"), wp->w_wincol + 1);
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 68c2e37f22..ad133b5b5f 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -3611,8 +3611,8 @@ static void f_getmousepos(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     // necessary for a top border since `row` starts at -1 in that case.
     if (row < height + wp->w_border_adj[2]) {
       winid = wp->handle;
-      winrow = row + 1 + wp->w_border_adj[0];  // Adjust by 1 for top border
-      wincol = col + 1 + wp->w_border_adj[3];  // Adjust by 1 for left border
+      winrow = row + 1 + wp->w_winrow_off;  // Adjust by 1 for top border
+      wincol = col + 1 + wp->w_wincol_off;  // Adjust by 1 for left border
       if (row >= 0 && row < wp->w_height && col >= 0 && col < wp->w_width) {
         (void)mouse_comp_pos(wp, &row, &col, &lnum);
         col = vcol2col(wp, lnum, col);
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index e845073c12..0510faa57d 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -8831,7 +8831,7 @@ static void ex_redraw(exarg_T *eap)
   ui_flush();
 }
 
-/// ":redrawstatus": force redraw of status line(s)
+/// ":redrawstatus": force redraw of status line(s) and window bar(s)
 static void ex_redrawstatus(exarg_T *eap)
 {
   if (State & MODE_CMDPREVIEW) {
@@ -8847,8 +8847,7 @@ static void ex_redrawstatus(exarg_T *eap)
   } else {
     status_redraw_curbuf();
   }
-  update_screen(VIsual_active ? INVERTED :
-                0);
+  update_screen(VIsual_active ? INVERTED : 0);
   RedrawingDisabled = r;
   p_lz = p;
   ui_flush();
diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index 0515842b61..d293865efd 100644
--- a/src/nvim/highlight_defs.h
+++ b/src/nvim/highlight_defs.h
@@ -111,7 +111,9 @@ typedef enum {
   HLF_NFLOAT,     // Floating window
   HLF_MSG,        // Message area
   HLF_BORDER,     // Floating window border
-  HLF_COUNT,  // MUST be the last one
+  HLF_WBR,        // Window bars
+  HLF_WBRNC,      // Window bars of not-current windows
+  HLF_COUNT,      // MUST be the last one
 } hlf_T;
 
 EXTERN const char *hlf_names[] INIT(= {
@@ -172,6 +174,8 @@ EXTERN const char *hlf_names[] INIT(= {
   [HLF_NFLOAT] = "NormalFloat",
   [HLF_MSG] = "MsgArea",
   [HLF_BORDER] = "FloatBorder",
+  [HLF_WBR] = "WinBar",
+  [HLF_WBRNC] = "WinBarNC",
 });
 
 
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 240a96cb4b..0047cb02d6 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -103,9 +103,11 @@ static const char *highlight_init_both[] = {
   "TabLineFill  cterm=reverse gui=reverse",
   "TabLineSel   cterm=bold gui=bold",
   "TermCursor   cterm=reverse gui=reverse",
+  "WinBar       cterm=bold gui=bold",
   "WildMenu     ctermbg=Yellow ctermfg=Black guibg=Yellow guifg=Black",
   "default link VertSplit Normal",
   "default link WinSeparator VertSplit",
+  "default link WinBarNC WinBar",
   "default link EndOfBuffer NonText",
   "default link LineNrAbove LineNr",
   "default link LineNrBelow LineNr",
diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index 8038ba2cad..3a1cc6b557 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -68,12 +68,12 @@ bool is_mouse_key(int c)
 /// mouse was previously on a status line, then the status line may be dragged.
 ///
 /// If flags has MOUSE_MAY_VIS, then VIsual mode will be started before the
-/// cursor is moved unless the cursor was on a status line.
+/// cursor is moved unless the cursor was on a status line or window bar.
 /// This function returns one of IN_UNKNOWN, IN_BUFFER, IN_STATUS_LINE or
 /// IN_SEP_LINE depending on where the cursor was clicked.
 ///
 /// If flags has MOUSE_MAY_STOP_VIS, then Visual mode will be stopped, unless
-/// the mouse is on the status line of the same window.
+/// the mouse is on the status line or window bar of the same window.
 ///
 /// If flags has MOUSE_DID_MOVE, nothing is done if the mouse didn't move since
 /// the last call.
@@ -87,6 +87,7 @@ int jump_to_mouse(int flags, bool *inclusive, int which_button)
 {
   static int on_status_line = 0;        // #lines below bottom of window
   static int on_sep_line = 0;           // on separator right of window
+  static bool on_winbar = false;
   static int prev_row = -1;
   static int prev_col = -1;
   static win_T *dragwin = NULL;         // window being dragged
@@ -126,6 +127,9 @@ retnomove:
     if (on_sep_line) {
       return IN_SEP_LINE;
     }
+    if (on_winbar) {
+      return IN_OTHER_WIN | MOUSE_WINBAR;
+    }
     if (flags & MOUSE_MAY_STOP_VIS) {
       end_visual_mode();
       redraw_curbuf_later(INVERTED);            // delete the inversion
@@ -155,9 +159,11 @@ retnomove:
     fdc = win_fdccol_count(wp);
     dragwin = NULL;
 
-    if (row == -1) {
-      return IN_OTHER_WIN;
+    if (row == -1 + wp->w_winbar_height) {
+      on_winbar = !!wp->w_winbar_height;
+      return IN_OTHER_WIN | (on_winbar ? MOUSE_WINBAR : 0);
     }
+    on_winbar = false;
 
     // winpos and height may change in win_enter()!
     if (grid == DEFAULT_GRID_HANDLE && row >= wp->w_height) {
@@ -253,6 +259,9 @@ retnomove:
       did_drag |= count;
     }
     return IN_SEP_LINE;                         // Cursor didn't move
+  } else if (on_winbar) {
+    // After a click on the window bar don't start Visual mode.
+    return IN_OTHER_WIN | MOUSE_WINBAR;
   } else {
     // keep_window_focus must be true
     // before moving the cursor for a left click, stop Visual mode
@@ -497,6 +506,7 @@ win_T *mouse_find_win(int *gridp, int *rowp, int *colp)
   // exist.
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
     if (wp == fp->fr_win) {
+      *rowp -= wp->w_winrow_off - wp->w_winbar_height;
       return wp;
     }
   }
diff --git a/src/nvim/move.c b/src/nvim/move.c
index 11feb497ea..97ce92f6a9 100644
--- a/src/nvim/move.c
+++ b/src/nvim/move.c
@@ -1016,7 +1016,7 @@ void textpos2screenpos(win_T *wp, pos_T *pos, int *rowp, int *scolp, int *ccolp,
     col -= wp->w_leftcol;
 
     if (col >= 0 && col < wp->w_width) {
-      coloff = col - scol + (local ? 0 : wp->w_wincol + wp->w_border_adj[3]) + 1;
+      coloff = col - scol + (local ? 0 : wp->w_wincol + wp->w_wincol_off) + 1;
     } else {
       scol = ccol = ecol = 0;
       // character is left or right of the window
@@ -1027,7 +1027,7 @@ void textpos2screenpos(win_T *wp, pos_T *pos, int *rowp, int *scolp, int *ccolp,
       }
     }
   }
-  *rowp = (local ? 0 : wp->w_winrow + wp->w_border_adj[0]) + row + rowoff;
+  *rowp = (local ? 0 : wp->w_winrow + wp->w_winrow_off) + row + rowoff;
   *scolp = scol + coloff;
   *ccolp = ccol + coloff;
   *ecolp = ecol + coloff;
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 2826b7dad1..1692970a97 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -1280,7 +1280,8 @@ static void normal_redraw(NormalState *s)
   validate_cursor();
 
   if (VIsual_active) {
-    update_curbuf(INVERTED);  // update inverted part
+    redraw_curbuf_later(INVERTED);  // update inverted part
+    update_screen(INVERTED);
   } else if (must_redraw) {
     update_screen(0);
   } else if (redraw_cmdline || clear_cmdline) {
@@ -1850,6 +1851,11 @@ bool do_mouse(oparg_T *oap, int c, int dir, long count, bool fixindent)
                              oap == NULL ? NULL : &(oap->inclusive),
                              which_button);
 
+  // A click in the window bar has no side effects.
+  if (jump_flags & MOUSE_WINBAR) {
+    return false;
+  }
+
   moved = (jump_flags & CURSOR_MOVED);
   in_status_line = (jump_flags & IN_STATUS_LINE);
   in_sep_line = (jump_flags & IN_SEP_LINE);
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 8267bcf9da..2ee6c175bb 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -2149,6 +2149,8 @@ static uint32_t *insecure_flag(win_T *const wp, int opt_idx, int opt_flags)
     switch ((int)options[opt_idx].indir) {
     case PV_STL:
       return &wp->w_p_stl_flags;
+    case PV_WBR:
+      return &wp->w_p_wbr_flags;
     case PV_FDE:
       return &wp->w_p_fde_flags;
     case PV_FDT:
@@ -2930,8 +2932,8 @@ ambw_end:
       curbuf->b_help = (curbuf->b_p_bt[0] == 'h');
       redraw_titles();
     }
-  } else if (gvarp == &p_stl || varp == &p_tal || varp == &p_ruf) {
-    // 'statusline', 'tabline' or 'rulerformat'
+  } else if (gvarp == &p_stl || gvarp == (char_u **)&p_wbr || varp == &p_tal || varp == &p_ruf) {
+    // 'statusline', 'winbar', 'tabline' or 'rulerformat'
     int wid;
 
     if (varp == &p_ruf) {       // reset ru_wid first
@@ -2950,12 +2952,16 @@ ambw_end:
         errmsg = check_stl_option(p_ruf);
       }
     } else if (varp == &p_ruf || s[0] != '%' || s[1] != '!') {
-      // check 'statusline' or 'tabline' only if it doesn't start with "%!"
+      // check 'statusline', 'winbar' or 'tabline' only if it doesn't start with "%!"
       errmsg = check_stl_option(s);
     }
     if (varp == &p_ruf && errmsg == NULL) {
       comp_col();
     }
+    // add / remove window bars for 'winbar'
+    if (gvarp == (char_u **)&p_wbr) {
+      set_winbar();
+    }
   } else if (gvarp == &p_cpt) {
     // check if it is a valid value for 'complete' -- Acevedo
     for (s = *varp; *s;) {
@@ -3570,6 +3576,7 @@ static char *set_chars_option(win_T *wp, char_u **varp, bool set)
   struct chars_tab fcs_tab[] = {
     { &wp->w_p_fcs_chars.stl,        "stl",        ' '  },
     { &wp->w_p_fcs_chars.stlnc,      "stlnc",      ' '  },
+    { &wp->w_p_fcs_chars.wbr,        "wbr",        ' '  },
     { &wp->w_p_fcs_chars.horiz,      "horiz",      9472 },  // ─
     { &wp->w_p_fcs_chars.horizup,    "horizup",    9524 },  // ┴
     { &wp->w_p_fcs_chars.horizdown,  "horizdown",  9516 },  // ┬
@@ -3612,15 +3619,15 @@ static char *set_chars_option(win_T *wp, char_u **varp, bool set)
     if (*p_ambw == 'd') {
       // XXX: If ambiwidth=double then some characters take 2 columns,
       // which is forbidden (TUI limitation?). Set old defaults.
-      fcs_tab[2].def  = '-';
       fcs_tab[3].def  = '-';
       fcs_tab[4].def  = '-';
-      fcs_tab[5].def  = '|';
+      fcs_tab[5].def  = '-';
       fcs_tab[6].def  = '|';
       fcs_tab[7].def  = '|';
-      fcs_tab[8].def  = '+';
-      fcs_tab[9].def  = '-';
-      fcs_tab[12].def = '|';
+      fcs_tab[8].def  = '|';
+      fcs_tab[9].def  = '+';
+      fcs_tab[10].def  = '-';
+      fcs_tab[13].def = '|';
     }
   }
 
@@ -4766,7 +4773,7 @@ static void check_redraw(uint32_t flags)
   bool doclear = (flags & P_RCLR) == P_RCLR;
   bool all = ((flags & P_RALL) == P_RALL || doclear);
 
-  if ((flags & P_RSTAT) || all) {  // mark all status lines dirty
+  if ((flags & P_RSTAT) || all) {  // mark all status lines and window bars dirty
     status_redraw_all();
   }
 
@@ -5814,6 +5821,9 @@ void unset_global_local_option(char *name, void *from)
   case PV_STL:
     clear_string_option(&((win_T *)from)->w_p_stl);
     break;
+  case PV_WBR:
+    clear_string_option((char_u **)&((win_T *)from)->w_p_wbr);
+    break;
   case PV_UL:
     buf->b_p_ul = NO_LOCAL_UNDOLEVEL;
     break;
@@ -5891,6 +5901,8 @@ static char_u *get_varp_scope(vimoption_T *p, int opt_flags)
       return (char_u *)&(curwin->w_p_sbr);
     case PV_STL:
       return (char_u *)&(curwin->w_p_stl);
+    case PV_WBR:
+      return (char_u *)&(curwin->w_p_wbr);
     case PV_UL:
       return (char_u *)&(curbuf->b_p_ul);
     case PV_LW:
@@ -5984,6 +5996,9 @@ static char_u *get_varp(vimoption_T *p)
   case PV_STL:
     return *curwin->w_p_stl != NUL
            ? (char_u *)&(curwin->w_p_stl) : p->var;
+  case PV_WBR:
+    return *curwin->w_p_wbr != NUL
+           ? (char_u *)&(curwin->w_p_wbr) : p->var;
   case PV_UL:
     return curbuf->b_p_ul != NO_LOCAL_UNDOLEVEL
            ? (char_u *)&(curbuf->b_p_ul) : p->var;
@@ -6252,6 +6267,7 @@ void copy_winopt(winopt_T *from, winopt_T *to)
   to->wo_rlc = vim_strsave(from->wo_rlc);
   to->wo_sbr = vim_strsave(from->wo_sbr);
   to->wo_stl = vim_strsave(from->wo_stl);
+  to->wo_wbr = xstrdup(from->wo_wbr);
   to->wo_wrap = from->wo_wrap;
   to->wo_wrap_save = from->wo_wrap_save;
   to->wo_lbr = from->wo_lbr;
@@ -6327,6 +6343,7 @@ static void check_winopt(winopt_T *wop)
   check_string_option(&wop->wo_fcs);
   check_string_option(&wop->wo_lcs);
   check_string_option(&wop->wo_ve);
+  check_string_option((char_u **)&wop->wo_wbr);
 }
 
 /// Free the allocated memory inside a winopt_T.
@@ -6352,6 +6369,7 @@ void clear_winopt(winopt_T *wop)
   clear_string_option(&wop->wo_fcs);
   clear_string_option(&wop->wo_lcs);
   clear_string_option(&wop->wo_ve);
+  clear_string_option((char_u **)&wop->wo_wbr);
 }
 
 void didset_window_options(win_T *wp)
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index e358a29622..f5c7ae07bb 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -618,6 +618,7 @@ EXTERN int p_stmp;              // 'shelltemp'
 EXTERN int p_ssl;               // 'shellslash'
 #endif
 EXTERN char_u *p_stl;         // 'statusline'
+EXTERN char *p_wbr;         // 'winbar'
 EXTERN int p_sr;                // 'shiftround'
 EXTERN char_u *p_shm;         // 'shortmess'
 EXTERN char_u *p_sbr;         // 'showbreak'
@@ -897,6 +898,7 @@ enum {
   WV_FCS,
   WV_LCS,
   WV_WINBL,
+  WV_WBR,
   WV_COUNT,  // must be the last one
 };
 
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 313cace4b2..eb92d47fc8 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -2832,6 +2832,16 @@ return {
       defaults={if_true="menu"}
     },
     {
+      full_name='winbar', abbreviation='wbr',
+      short_desc=N_("custom format for the window bar"),
+      type='string', scope={'global', 'window'},
+      alloced=true,
+      modelineexpr=true,
+      redraw={'statuslines'},
+      varname='p_wbr',
+      defaults={if_true=""}
+    },
+    {
       full_name='winblend', abbreviation='winbl',
       short_desc=N_("Controls transparency level for floating windows"),
       type='number', scope={'window'},
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 686516f17b..b2490fb9c5 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -276,25 +276,25 @@ void redrawWinline(win_T *wp, linenr_T lnum)
   }
 }
 
-/*
- * update all windows that are editing the current buffer
- */
-void update_curbuf(int type)
-{
-  redraw_curbuf_later(type);
-  update_screen(type);
-}
-
 /// called when the status bars for the buffer 'buf' need to be updated
 void redraw_buf_status_later(buf_T *buf)
 {
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
-    if (wp->w_buffer == buf
-        && (wp->w_status_height || (wp == curwin && global_stl_height()))) {
+    if (wp->w_buffer != buf) {
+      continue;
+    }
+    bool redraw = false;
+
+    if (wp->w_status_height || (wp == curwin && global_stl_height())) {
       wp->w_redr_status = true;
-      if (must_redraw < VALID) {
-        must_redraw = VALID;
-      }
+      redraw = true;
+    }
+    if (wp->w_winbar_height) {
+      wp->w_redr_winbar = true;
+      redraw = true;
+    }
+    if (redraw && must_redraw < VALID) {
+      must_redraw = VALID;
     }
   }
 }
@@ -400,6 +400,9 @@ int update_screen(int type)
           if (wp->w_floating) {
             continue;
           }
+          if (wp->w_winrow + wp->w_winbar_height > valid) {
+            wp->w_redr_winbar = true;
+          }
           if (W_ENDROW(wp) > valid) {
             wp->w_redr_type = MAX(wp->w_redr_type, NOT_VALID);
           }
@@ -431,6 +434,9 @@ int update_screen(int type)
             wp->w_redr_type = REDRAW_TOP;
           } else {
             wp->w_redr_type = NOT_VALID;
+            if (wp->w_winrow + wp->w_winbar_height <= msg_scrolled) {
+              wp->w_redr_winbar = true;
+            }
             if (!is_stl_global && W_ENDROW(wp) + wp->w_status_height <= msg_scrolled) {
               wp->w_redr_status = true;
             }
@@ -585,10 +591,13 @@ int update_screen(int type)
       win_update(wp, &providers);
     }
 
-    // redraw status line after the window to minimize cursor movement
+    // redraw status line and window bar after the window to minimize cursor movement
     if (wp->w_redr_status) {
       win_redr_status(wp);
     }
+    if (wp->w_redr_winbar) {
+      win_redr_winbar(wp);
+    }
   }
 
   end_search_hl();
@@ -743,6 +752,7 @@ static void win_update(win_T *wp, DecorProviders *providers)
 
   if (type >= NOT_VALID) {
     wp->w_redr_status = true;
+    wp->w_redr_winbar = true;
     wp->w_lines_valid = 0;
   }
 
@@ -4528,42 +4538,55 @@ void rl_mirror(char_u *str)
   }
 }
 
-/*
- * mark all status lines for redraw; used after first :cd
- */
+/// Mark all status lines and window bars for redraw; used after first :cd
 void status_redraw_all(void)
 {
-  if (global_stl_height()) {
-    curwin->w_redr_status = true;
-    redraw_later(curwin, VALID);
-  } else {
-    FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
-      if (wp->w_status_height) {
-        wp->w_redr_status = true;
-        redraw_later(wp, VALID);
-      }
+  bool is_stl_global = global_stl_height() != 0;
+
+  FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+    bool redraw = false;
+
+    if ((!is_stl_global && wp->w_status_height) || (is_stl_global && wp == curwin)) {
+      wp->w_redr_status = true;
+      redraw = true;
+    }
+    if (wp->w_winbar_height) {
+      wp->w_redr_winbar = true;
+      redraw = true;
+    }
+    if (redraw) {
+      redraw_later(wp, VALID);
     }
   }
 }
 
-/// Marks all status lines of the current buffer for redraw.
+/// Marks all status lines and window bars of the current buffer for redraw.
 void status_redraw_curbuf(void)
 {
   status_redraw_buf(curbuf);
 }
 
-/// Marks all status lines of the specified buffer for redraw.
+/// Marks all status lines and window bars of the given buffer for redraw.
 void status_redraw_buf(buf_T *buf)
 {
-  if (global_stl_height() != 0 && curwin->w_buffer == buf) {
-    curwin->w_redr_status = true;
-    redraw_later(curwin, VALID);
-  } else {
-    FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
-      if (wp->w_status_height != 0 && wp->w_buffer == buf) {
-        wp->w_redr_status = true;
-        redraw_later(wp, VALID);
-      }
+  bool is_stl_global = global_stl_height() != 0;
+
+  FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+    if (wp->w_buffer != buf) {
+      continue;
+    }
+    bool redraw = false;
+
+    if ((!is_stl_global && wp->w_status_height) || (is_stl_global && wp == curwin)) {
+      wp->w_redr_status = true;
+      redraw = true;
+    }
+    if (wp->w_winbar_height) {
+      wp->w_redr_winbar = true;
+      redraw = true;
+    }
+    if (redraw) {
+      redraw_later(wp, VALID);
     }
   }
 }
@@ -4577,6 +4600,9 @@ void redraw_statuslines(void)
     if (wp->w_redr_status) {
       win_redr_status(wp);
     }
+    if (wp->w_redr_winbar) {
+      win_redr_winbar(wp);
+    }
   }
   if (redraw_tabline) {
     draw_tabline();
@@ -5075,7 +5101,7 @@ static void redraw_custom_statusline(win_T *wp)
   entered = true;
 
   did_emsg = false;
-  win_redr_custom(wp, false);
+  win_redr_custom(wp, false, false);
   if (did_emsg) {
     // When there is an error disable the statusline, otherwise the
     // display is messed up with errors and a redraw triggers the problem
@@ -5088,6 +5114,41 @@ static void redraw_custom_statusline(win_T *wp)
   entered = false;
 }
 
+static void win_redr_winbar(win_T *wp)
+{
+  static bool entered = false;
+
+  // Return when called recursively. This can happen when the winbar contains an expression
+  // that triggers a redraw.
+  if (entered) {
+    return;
+  }
+  entered = true;
+
+  wp->w_redr_winbar = false;
+  if (wp->w_winbar_height == 0) {
+    // No window bar, do nothing.
+  } else if (!redrawing()) {
+    // Don't redraw right now, do it later.
+    wp->w_redr_winbar = true;
+  } else if (*p_wbr != NUL || *wp->w_p_wbr != NUL) {
+    int saved_did_emsg = did_emsg;
+
+    did_emsg = false;
+    win_redr_custom(wp, true, false);
+    if (did_emsg) {
+      // When there is an error disable the winbar, otherwise the
+      // display is messed up with errors and a redraw triggers the problem
+      // again and again.
+      set_string_option_direct("winbar", -1, (char_u *)"",
+                               OPT_FREE | (*wp->w_p_stl != NUL
+                                           ? OPT_LOCAL : OPT_GLOBAL), SID_ERROR);
+    }
+    did_emsg |= saved_did_emsg;
+  }
+  entered = false;
+}
+
 /// Only call if (wp->w_vsep_width != 0).
 ///
 /// @return  true if the status line of window "wp" is connected to the status
@@ -5224,11 +5285,9 @@ bool get_keymap_str(win_T *wp, char_u *fmt, char_u *buf, int len)
   return buf[0] != NUL;
 }
 
-/*
- * Redraw the status line or ruler of window "wp".
- * When "wp" is NULL redraw the tab pages line from 'tabline'.
- */
-static void win_redr_custom(win_T *wp, bool draw_ruler)
+/// Redraw the status line, window bar or ruler of window "wp".
+/// When "wp" is NULL redraw the tab pages line from 'tabline'.
+static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
 {
   static bool entered = false;
   int attr;
@@ -5269,6 +5328,14 @@ static void win_redr_custom(win_T *wp, bool draw_ruler)
     attr = HL_ATTR(HLF_TPF);
     maxwidth = Columns;
     use_sandbox = was_set_insecurely(wp, "tabline", 0);
+  } else if (draw_winbar) {
+    stl = (char_u *)((*wp->w_p_wbr != NUL) ? wp->w_p_wbr : p_wbr);
+    row = wp->w_winrow;
+    col = wp->w_wincol;
+    fillchar = wp->w_p_fcs_chars.wbr;
+    attr = (wp == curwin) ? HL_ATTR(HLF_WBR) : HL_ATTR(HLF_WBRNC);
+    maxwidth = wp->w_width_inner;
+    use_sandbox = was_set_insecurely(wp, "winbar", 0);
   } else {
     row = is_stl_global ? (Rows - p_ch - 1) : W_ENDROW(wp);
     fillchar = fillchar_status(&attr, wp);
@@ -5553,14 +5620,17 @@ void win_grid_alloc(win_T *wp)
   grid->Rows = rows;
   grid->Columns = cols;
 
+  wp->w_winrow_off = wp->w_border_adj[0] + wp->w_winbar_height;
+  wp->w_wincol_off = wp->w_border_adj[3];
+
   if (want_allocation) {
     grid->target = grid_allocated;
-    grid->row_offset = wp->w_border_adj[0];
-    grid->col_offset = wp->w_border_adj[3];
+    grid->row_offset = wp->w_winrow_off;
+    grid->col_offset = wp->w_wincol_off;
   } else {
     grid->target = &default_grid;
-    grid->row_offset = wp->w_winrow;
-    grid->col_offset = wp->w_wincol;
+    grid->row_offset = wp->w_winrow + wp->w_winrow_off;
+    grid->col_offset = wp->w_wincol + wp->w_wincol_off;
   }
 
   // send grid resize event if:
@@ -6220,7 +6290,7 @@ void draw_tabline(void)
     // Check for an error.  If there is one we would loop in redrawing the
     // screen.  Avoid that by making 'tabline' empty.
     did_emsg = false;
-    win_redr_custom(NULL, false);
+    win_redr_custom(NULL, false, false);
     if (did_emsg) {
       set_string_option_direct("tabline", -1,
                                (char_u *)"", OPT_FREE, SID_ERROR);
@@ -6516,7 +6586,7 @@ static void win_redr_ruler(win_T *wp, bool always)
     int save_called_emsg = called_emsg;
 
     called_emsg = false;
-    win_redr_custom(wp, true);
+    win_redr_custom(wp, false, true);
     if (called_emsg) {
       set_string_option_direct("rulerformat", -1, (char_u *)"",
                                OPT_FREE, SID_ERROR);
diff --git a/src/nvim/testdir/test_cursor_func.vim b/src/nvim/testdir/test_cursor_func.vim
index 9ba82e3b70..6c6a6290cb 100644
--- a/src/nvim/testdir/test_cursor_func.vim
+++ b/src/nvim/testdir/test_cursor_func.vim
@@ -102,10 +102,11 @@ func Test_screenpos()
   bwipe!
 
   call assert_equal({'col': 1, 'row': 1, 'endcol': 1, 'curscol': 1}, screenpos(win_getid(), 1, 1))
-  " Needs WinBar
   " nmenu WinBar.TEST :
-  " call assert_equal({'col': 1, 'row': 2, 'endcol': 1, 'curscol': 1}, screenpos(win_getid(), 1, 1))
+  setlocal winbar=TEST
+  call assert_equal({'col': 1, 'row': 2, 'endcol': 1, 'curscol': 1}, screenpos(win_getid(), 1, 1))
   " nunmenu WinBar.TEST
+  setlocal winbar&
 endfunc
 
 func Test_screenpos_number()
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 2c27a5d6a5..51208e7178 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -695,6 +695,7 @@ win_T *win_new_float(win_T *wp, bool last, FloatConfig fconfig, Error *err)
   }
   wp->w_floating = 1;
   wp->w_status_height = 0;
+  wp->w_winbar_height = 0;
   wp->w_hsep_height = 0;
   wp->w_vsep_width = 0;
 
@@ -780,10 +781,8 @@ void win_config_float(win_T *wp, FloatConfig fconfig)
   }
 
   if (!ui_has(kUIMultigrid)) {
-    wp->w_height = MIN(wp->w_height,
-                       Rows - 1 - (wp->w_border_adj[0] + wp->w_border_adj[2]));
-    wp->w_width = MIN(wp->w_width,
-                      Columns - (wp->w_border_adj[1] + wp->w_border_adj[3]));
+    wp->w_height = MIN(wp->w_height, Rows - 1 - win_extra_height(wp));
+    wp->w_width = MIN(wp->w_width, Columns - win_extra_width(wp));
   }
 
   win_set_inner_size(wp);
@@ -1138,15 +1137,12 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
   } else {
     layout = FR_COL;
 
-    /*
-     * Check if we are able to split the current window and compute its
-     * height.
-     */
-    // Current window requires at least 1 space.
-    wmh1 = p_wmh == 0 ? 1 : p_wmh;
+    // Check if we are able to split the current window and compute its height.
+    // Current window requires at least 1 space plus space for the window bar.
+    wmh1 = MAX(p_wmh, 1) + oldwin->w_winbar_height;
     needed = wmh1 + STATUS_HEIGHT;
     if (flags & WSP_ROOM) {
-      needed += p_wh - wmh1;
+      needed += p_wh - wmh1 + oldwin->w_winbar_height;
     }
     if (flags & (WSP_BOT | WSP_TOP)) {
       minheight = frame_minheight(topframe, NOWIN) + need_status;
@@ -1155,8 +1151,7 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
     } else if (p_ea) {
       minheight = frame_minheight(oldwin->w_frame, NOWIN) + need_status;
       prevfrp = oldwin->w_frame;
-      for (frp = oldwin->w_frame->fr_parent; frp != NULL;
-           frp = frp->fr_parent) {
+      for (frp = oldwin->w_frame->fr_parent; frp != NULL; frp = frp->fr_parent) {
         if (frp->fr_layout == FR_COL) {
           FOR_ALL_FRAMES(frp2, frp->fr_child) {
             if (frp2 != prevfrp) {
@@ -1339,6 +1334,7 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
     set_fraction(oldwin);
   }
   wp->w_fraction = oldwin->w_fraction;
+  wp->w_winbar_height = oldwin->w_winbar_height;
 
   if (flags & WSP_VERT) {
     wp->w_p_scr = curwin->w_p_scr;
@@ -1416,9 +1412,9 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
     if (flags & (WSP_TOP | WSP_BOT)) {
       int new_fr_height = curfrp->fr_height - new_size;
 
-      if (!((flags & WSP_BOT) && p_ls == 0) && global_stl_height() == 0) {
+      if (!((flags & WSP_BOT) && p_ls == 0) && !is_stl_global) {
         new_fr_height -= STATUS_HEIGHT;
-      } else if (global_stl_height() > 0) {
+      } else if (is_stl_global) {
         if (flags & WSP_BOT) {
           frame_add_hsep(curfrp);
         } else {
@@ -1452,7 +1448,7 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
         }
       }
     }
-    if ((flags & WSP_BOT) && global_stl_height() == 0) {
+    if ((flags & WSP_BOT) && !is_stl_global) {
       frame_add_statusline(curfrp);
     }
     frame_fix_height(wp);
@@ -1482,10 +1478,7 @@ int win_split_ins(int size, int flags, win_T *new_wp, int dir)
    * equalize the window sizes.
    */
   if (do_equal || dir != 0) {
-    win_equal(wp, true,
-              (flags & WSP_VERT) ? (dir == 'v' ? 'b' : 'h')
-                                               : dir == 'h' ? 'b' :
-              'v');
+    win_equal(wp, true, (flags & WSP_VERT) ? (dir == 'v' ? 'b' : 'h') : (dir == 'h' ? 'b' : 'v'));
   }
 
   // Don't change the window height/width to 'winheight' / 'winwidth' if a
@@ -1675,10 +1668,10 @@ int win_count(void)
 }
 
 /// Make "count" windows on the screen.
-/// Must be called when there is just one window, filling the whole screen
+/// Must be called when there is just one window, filling the whole screen.
 /// (excluding the command line).
 ///
-/// @param vertical  split windows vertically if true
+/// @param vertical  split windows vertically if true.
 ///
 /// @return actual number of windows on the screen.
 int make_windows(int count, bool vertical)
@@ -1687,15 +1680,15 @@ int make_windows(int count, bool vertical)
   int todo;
 
   if (vertical) {
-    // Each window needs at least 'winminwidth' lines and a separator
-    // column.
+    // Each window needs at least 'winminwidth' lines and a separator column.
     maxcount = (curwin->w_width + curwin->w_vsep_width
                 - (p_wiw - p_wmw)) / (p_wmw + 1);
   } else {
-    // Each window needs at least 'winminheight' lines
-    // If statusline isn't global, each window also needs a statusline
+    // Each window needs at least 'winminheight' lines.
+    // If statusline isn't global, each window also needs a statusline.
+    // If 'winbar' is set, each window also needs a winbar.
     maxcount = (curwin->w_height + curwin->w_hsep_height + curwin->w_status_height
-                - (p_wh - p_wmh)) / (p_wmh + STATUS_HEIGHT);
+                - (p_wh - p_wmh)) / (p_wmh + STATUS_HEIGHT + global_winbar_height());
   }
 
   if (maxcount < 2) {
@@ -1705,17 +1698,13 @@ int make_windows(int count, bool vertical)
     count = maxcount;
   }
 
-  /*
-   * add status line now, otherwise first window will be too big
-   */
+  // add status line now, otherwise first window will be too big
   if (count > 1) {
     last_status(true);
   }
 
-  /*
-   * Don't execute autocommands while creating the windows.  Must do that
-   * when putting the buffers in the windows.
-   */
+  // Don't execute autocommands while creating the windows.  Must do that
+  // when putting the buffers in the windows.
   block_autocmds();
 
   // todo is number of windows left to create
@@ -1790,7 +1779,7 @@ static void win_exchange(long Prenum)
    * if wp != wp2
    *    3. remove wp from the list
    *    4. insert wp after wp2
-   * 5. exchange the status line height, hsep height and vsep width.
+   * 5. exchange the status line height, winbar height, hsep height and vsep width.
    */
   wp2 = curwin->w_prev;
   frp2 = curwin->w_frame->fr_prev;
@@ -1897,7 +1886,7 @@ static void win_rotate(bool upwards, int count)
       frame_insert(frp->fr_parent->fr_child, frp);
     }
 
-    // exchange status height, hsep height and vsep width of old and new last window
+    // exchange status height, winbar height, hsep height and vsep width of old and new last window
     n = wp2->w_status_height;
     wp2->w_status_height = wp1->w_status_height;
     wp1->w_status_height = n;
@@ -1988,7 +1977,8 @@ void win_move_after(win_T *win1, win_T *win2)
       return;
     }
 
-    // may need move the status line, horizontal or vertical separator of the last window
+    // may need move the status line, window bar, horizontal or vertical separator of the last
+    // window
     if (win1 == lastwin) {
       height = win1->w_prev->w_status_height;
       win1->w_prev->w_status_height = win1->w_status_height;
@@ -2237,7 +2227,7 @@ static void win_equal_rec(win_T *next_curwin, bool current, frame_T *topfr, int
       } else {
         extra_sep = 0;
       }
-      totwincount = (n + extra_sep) / (p_wmh + STATUS_HEIGHT);
+      totwincount = (n + extra_sep) / (p_wmh + STATUS_HEIGHT + global_winbar_height());
       has_next_curwin = frame_has_win(topfr, next_curwin);
 
       /*
@@ -2272,7 +2262,7 @@ static void win_equal_rec(win_T *next_curwin, bool current, frame_T *topfr, int
           } else {
             // These windows don't use up room.
             totwincount -= (n + (fr->fr_next == NULL
-                                 ? extra_sep : 0)) / (p_wmh + STATUS_HEIGHT);
+                                 ? extra_sep : 0)) / (p_wmh + STATUS_HEIGHT + global_winbar_height());
           }
           room -= new_size - n;
           if (room < 0) {
@@ -2318,7 +2308,7 @@ static void win_equal_rec(win_T *next_curwin, bool current, frame_T *topfr, int
         // Compute the maximum number of windows vert. in "fr".
         n = frame_minheight(fr, NOWIN);
         wincount = (n + (fr->fr_next == NULL ? extra_sep : 0))
-                   / (p_wmh + STATUS_HEIGHT);
+                   / (p_wmh + STATUS_HEIGHT + global_winbar_height());
         m = frame_minheight(fr, next_curwin);
         if (has_next_curwin) {
           hnc = frame_has_win(fr, next_curwin);
@@ -3732,13 +3722,9 @@ static void frame_fix_height(win_T *wp)
   wp->w_frame->fr_height = wp->w_height + wp->w_hsep_height + wp->w_status_height;
 }
 
-/*
- * Compute the minimal height for frame "topfrp".
- * Uses the 'winminheight' option.
- * When "next_curwin" isn't NULL, use p_wh for this window.
- * When "next_curwin" is NOWIN, don't use at least one line for the current
- * window.
- */
+/// Compute the minimal height for frame "topfrp". Uses the 'winminheight' option.
+/// When "next_curwin" isn't NULL, use p_wh for this window.
+/// When "next_curwin" is NOWIN, don't use at least one line for the current window.
 static int frame_minheight(frame_T *topfrp, win_T *next_curwin)
 {
   frame_T *frp;
@@ -3746,12 +3732,14 @@ static int frame_minheight(frame_T *topfrp, win_T *next_curwin)
   int n;
 
   if (topfrp->fr_win != NULL) {
+    // Combined height of window bar and separator column or status line.
+    int extra_height = topfrp->fr_win->w_winbar_height + topfrp->fr_win->w_hsep_height
+                       + topfrp->fr_win->w_status_height;
+
     if (topfrp->fr_win == next_curwin) {
-      m = p_wh + topfrp->fr_win->w_hsep_height + topfrp->fr_win->w_status_height;
+      m = p_wh + extra_height;
     } else {
-      // window: minimal height of the window plus separator column or status line
-      // depending on whether global statusline is enabled
-      m = p_wmh + topfrp->fr_win->w_hsep_height + topfrp->fr_win->w_status_height;
+      m = p_wmh + extra_height;
       if (topfrp->fr_win == curwin && next_curwin == NULL) {
         // Current window is minimal one line high.
         if (p_wmh == 0) {
@@ -3976,7 +3964,7 @@ static void new_frame(win_T *wp)
 void win_init_size(void)
 {
   firstwin->w_height = ROWS_AVAIL;
-  firstwin->w_height_inner = firstwin->w_height;
+  firstwin->w_height_inner = firstwin->w_height - firstwin->w_winbar_height;
   firstwin->w_height_outer = firstwin->w_height;
   topframe->fr_height = ROWS_AVAIL;
   firstwin->w_width = Columns;
@@ -4087,6 +4075,7 @@ int win_new_tabpage(int after, char_u *filename)
 
     newtp->tp_topframe = topframe;
     last_status(false);
+    set_winbar();
 
     redraw_all_later(NOT_VALID);
 
@@ -5460,16 +5449,9 @@ void win_setheight(int height)
  */
 void win_setheight_win(int height, win_T *win)
 {
-  if (win == curwin) {
-    // Always keep current window at least one line high, even when
-    // 'winminheight' is zero.
-    if (height < p_wmh) {
-      height = p_wmh;
-    }
-    if (height == 0) {
-      height = 1;
-    }
-  }
+  // Always keep current window at least one line high, even when 'winminheight' is zero.
+  // Keep window at least two lines high if 'winbar' is enabled.
+  height = MAX(height, (win == curwin ? MAX(p_wmh, 1) : p_wmh) + win->w_winbar_height);
 
   if (win->w_floating) {
     win->w_float_config.height = height;
@@ -6262,7 +6244,7 @@ void win_set_inner_size(win_T *wp)
   int prev_height = wp->w_height_inner;
   int height = wp->w_height_request;
   if (height == 0) {
-    height = wp->w_height;
+    height = wp->w_height - wp->w_winbar_height;
   }
 
   if (height != prev_height) {
@@ -6279,8 +6261,9 @@ void win_set_inner_size(win_T *wp)
         set_fraction(wp);
       }
     }
-    wp->w_height_inner = height;
     wp->w_skipcol = 0;
+    wp->w_height_inner = height;
+    wp->w_winrow_off = wp->w_border_adj[0] + wp->w_winbar_height;
 
     // There is no point in adjusting the scroll position when exiting.  Some
     // values might be invalid.
@@ -6306,10 +6289,18 @@ void win_set_inner_size(win_T *wp)
     terminal_check_size(wp->w_buffer->terminal);
   }
 
-  wp->w_height_outer = (wp->w_height_inner
-                        + wp->w_border_adj[0] + wp->w_border_adj[2]);
-  wp->w_width_outer = (wp->w_width_inner
-                       + wp->w_border_adj[1] + wp->w_border_adj[3]);
+  wp->w_height_outer = (wp->w_height_inner + win_extra_height(wp));
+  wp->w_width_outer = (wp->w_width_inner + win_extra_width(wp));
+}
+
+static int win_extra_height(win_T *wp)
+{
+  return wp->w_border_adj[0] + wp->w_border_adj[2];
+}
+
+static int win_extra_width(win_T *wp)
+{
+  return wp->w_border_adj[1] + wp->w_border_adj[3];
 }
 
 /// Set the width of a window.
@@ -6662,6 +6653,19 @@ static void last_status_rec(frame_T *fr, bool statusline, bool is_stl_global)
   }
 }
 
+// Add or remove window bars from windows depending on the value of 'winbar'.
+void set_winbar(void)
+{
+  FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+    int winbar_height = (*p_wbr != NUL || *wp->w_p_wbr != NUL) ? 1 : 0;
+    if (wp->w_winbar_height != winbar_height) {
+      wp->w_winbar_height = winbar_height;
+      win_set_inner_size(wp);
+      wp->w_redr_winbar = winbar_height;
+    }
+  }
+}
+
 /// Return the number of lines used by the tab page line.
 int tabline_height(void)
 {
@@ -6678,6 +6682,12 @@ int tabline_height(void)
   return 1;
 }
 
+/// Return the number of lines used by default by the window bar.
+int global_winbar_height(void)
+{
+  return *p_wbr != NUL ? 1 : 0;
+}
+
 /// Return the number of lines used by the global statusline
 int global_stl_height(void)
 {
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index ba170ba8c5..c4748cc00d 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -3102,6 +3102,19 @@ describe('API', function()
             'TextWithNoHighlight%#WarningMsg#TextWithWarningHighlight',
             { use_tabline = true, highlights = true }))
       end)
+      it('works with winbar', function()
+        eq({
+            str = 'TextWithNoHighlightTextWithWarningHighlight',
+            width = 43,
+            highlights = {
+              { start = 0, group = 'WinBar' },
+              { start = 19, group = 'WarningMsg' }
+            }
+          },
+          meths.eval_statusline(
+            'TextWithNoHighlight%#WarningMsg#TextWithWarningHighlight',
+            { use_winbar = true, highlights = true }))
+      end)
     end)
   end)
   describe('nvim_parse_cmd', function()
diff --git a/test/functional/ui/cursor_spec.lua b/test/functional/ui/cursor_spec.lua
index 92300a8fa2..d61eebe3ea 100644
--- a/test/functional/ui/cursor_spec.lua
+++ b/test/functional/ui/cursor_spec.lua
@@ -212,10 +212,10 @@ describe('ui/cursor', function()
         if m.blinkwait then m.blinkwait = 700 end
       end
       if m.hl_id then
-          m.hl_id = 62
+          m.hl_id = 64
           m.attr = {background = Screen.colors.DarkGray}
       end
-      if m.id_lm then m.id_lm = 63 end
+      if m.id_lm then m.id_lm = 65 end
     end
 
     -- Assert the new expectation.
diff --git a/test/functional/ui/winbar_spec.lua b/test/functional/ui/winbar_spec.lua
new file mode 100644
index 0000000000..6cf587d47b
--- /dev/null
+++ b/test/functional/ui/winbar_spec.lua
@@ -0,0 +1,180 @@
+local helpers = require('test.functional.helpers')(after_each)
+local Screen = require('test.functional.ui.screen')
+local clear = helpers.clear
+local command = helpers.command
+
+describe('winbar', function()
+  local screen
+
+  before_each(function()
+    clear()
+    screen = Screen.new(60, 13)
+    screen:attach()
+    screen:set_default_attr_ids({
+      [1] = {bold = true},
+      [2] = {reverse = true},
+      [3] = {bold = true, foreground = Screen.colors.Blue},
+      [4] = {bold = true, reverse = true},
+      [5] = {bold = true, foreground = Screen.colors.Red},
+      [6] = {foreground = Screen.colors.Blue},
+    })
+    command('set winbar=Set\\ Up\\ The\\ Bars')
+  end)
+  it('works', function()
+    screen:expect([[
+      {1:Set Up The Bars                                             }|
+      ^                                                            |
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+                                                                  |
+    ]])
+  end)
+  it('works with custom \'fillchars\' value', function()
+    command('set fillchars=wbr:+')
+    screen:expect([[
+      {1:Set Up The Bars+++++++++++++++++++++++++++++++++++++++++++++}|
+      ^                                                            |
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+                                                                  |
+    ]])
+  end)
+  it('works with custom highlight', function()
+    command('hi WinBar guifg=red')
+    screen:expect([[
+      {5:Set Up The Bars                                             }|
+      ^                                                            |
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+                                                                  |
+    ]])
+  end)
+  it('works with splits', function()
+    command('hi WinBar guifg=red')
+    command('hi WinBarNC guifg=blue')
+    command('belowright vsplit | split | split')
+    screen:expect([[
+      {6:Set Up The Bars              }│{5:Set Up The Bars               }|
+                                   │^                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{4:[No Name]                     }|
+      {3:~                            }│{6:Set Up The Bars               }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{2:[No Name]                     }|
+      {3:~                            }│{6:Set Up The Bars               }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {2:[No Name]                     [No Name]                     }|
+                                                                  |
+    ]])
+  end)
+  it('works when switching value of \'winbar\'', function()
+    command('belowright vsplit | split | split | set winbar=')
+    screen:expect([[
+                                   │^                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{4:[No Name]                     }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{2:[No Name]                     }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{3:~                             }|
+      {2:[No Name]                     [No Name]                     }|
+                                                                  |
+    ]])
+    command('set winbar=All\\ Your\\ Bar\\ Are\\ Belong\\ To\\ Us')
+    screen:expect([[
+      {1:All Your Bar Are Belong To Us}│{1:All Your Bar Are Belong To Us }|
+                                   │^                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{4:[No Name]                     }|
+      {3:~                            }│{1:All Your Bar Are Belong To Us }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{2:[No Name]                     }|
+      {3:~                            }│{1:All Your Bar Are Belong To Us }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {2:[No Name]                     [No Name]                     }|
+                                                                  |
+    ]])
+    command('set winbar=Changed\\ winbar')
+    screen:expect([[
+      {1:Changed winbar               }│{1:Changed winbar                }|
+                                   │^                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{4:[No Name]                     }|
+      {3:~                            }│{1:Changed winbar                }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }│{2:[No Name]                     }|
+      {3:~                            }│{1:Changed winbar                }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {2:[No Name]                     [No Name]                     }|
+                                                                  |
+    ]])
+  end)
+  it('works with laststatus=3', function()
+    command('set laststatus=3')
+    screen:expect([[
+      {1:Set Up The Bars                                             }|
+      ^                                                            |
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {3:~                                                           }|
+      {4:[No Name]                                                   }|
+                                                                  |
+    ]])
+    command('belowright vsplit | split | split')
+    screen:expect([[
+      {1:Set Up The Bars              }│{1:Set Up The Bars               }|
+                                   │^                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }├──────────────────────────────|
+      {3:~                            }│{1:Set Up The Bars               }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {3:~                            }├──────────────────────────────|
+      {3:~                            }│{1:Set Up The Bars               }|
+      {3:~                            }│                              |
+      {3:~                            }│{3:~                             }|
+      {4:[No Name]                                                   }|
+                                                                  |
+    ]])
+  end)
+end)