feat(ui): add 'statuscolumn' option

Problem:    Unable to customize the column next to a window ('gutter').
Solution:   Add 'statuscolumn' option that follows the 'statusline' syntax,
	    allowing to customize the status column. Also supporting the %@
	    click execute function label. Adds new items @C and @s which
	    will print the fold and sign columns. Line numbers and signs
	    can be clicked, highlighted, aligned, transformed, margined etc.

26 files changed, 681 insertions, 43 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 151036529d..6feb5cbb49 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -2001,10 +2001,10 @@ v:lc_time	The current locale setting for time messages of the runtime
 		command.  See |multi-lang|.
 
 						*v:lnum* *lnum-variable*
-v:lnum		Line number for the 'foldexpr' |fold-expr|, 'formatexpr' and
-		'indentexpr' expressions, tab page number for 'guitablabel'
-		and 'guitabtooltip'.  Only valid while one of these
-		expressions is being evaluated.  Read-only when in the
+v:lnum		Line number for the 'foldexpr' |fold-expr|, 'formatexpr',
+		'indentexpr' and 'statuscolumn' expressions, tab page number
+		for 'guitablabel' and 'guitabtooltip'.  Only valid while one of
+		these expressions is being evaluated.  Read-only when in the
 		|sandbox|.
 
 						*v:lua* *lua-variable*
@@ -2138,6 +2138,10 @@ v:register	The name of the register in effect for the current normal mode
 		'*' or '+'.
 		Also see |getreg()| and |setreg()|
 
+					*v:relnum* *relnum-variable*
+v:relnum	Relative line number for the 'statuscolumn' expression.
+		Read-only.
+
 					*v:scrollstart* *scrollstart-variable*
 v:scrollstart	String describing the script or function that caused the
 		screen to scroll up.  It's only set when it is empty, thus the
@@ -2295,6 +2299,11 @@ v:version	Vim version number: major version times 100 plus minor
 v:vim_did_enter	0 during startup, 1 just before |VimEnter|.
 		Read-only.
 
+						*v:wrap* *wrap-variable*
+v:wrap		Boolean indicating whether 'statuscolumn' is being evaluated
+		for the wrapped part of a line.
+		Read-only.
+
 					*v:warningmsg* *warningmsg-variable*
 v:warningmsg	Last given warning message.
 		Modifiable (can be set).
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 33ac9ddd20..88bad1b7df 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -118,6 +118,11 @@ The following new APIs or features were added.
 
 • |'splitkeep'| option to control the scroll behavior of horizontal splits.
 
+• |'statuscolumn'| option to customize the area to the side of a window,
+  normally containing the fold, sign and number columns. This new option follows
+  the 'statusline' syntax and can be used to transform the line numbers, create
+  mouse click callbacks for |signs|, introduce a custom margin or separator etc.
+
 • |nvim_select_popupmenu_item()| now supports |cmdline-completion| popup menu.
 
 • |'diffopt'| now includes a `linematch` option to enable a second-stage diff
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index ee6c14e73f..aa2f528d1b 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -6001,6 +6001,52 @@ A jump table for the options with a short description can be found at |Q_op|.
 	In case of buffer changing commands the cursor is placed at the column
 	where it was the last time the buffer was edited.
 
+				*'statuscolumn'* *'stc'*
+'statuscolumn' 'stc'	string	(default: empty)
+			local to window
+	EXPERIMENTAL
+	When non-empty, this option determines the content of the area to the
+	side of a window, normally containing the fold, sign and number columns.
+	The format of this option is like that of 'statusline'.
+
+	Some of the items from the 'statusline' format are different for
+	'statuscolumn':
+
+	%l	line number of currently drawn line
+	%r	relative line number of currently drawn line
+	%s	sign column for currently drawn line
+	%C	fold column for currently drawn line
+
+	To draw the sign and fold columns, they must be included in
+	'statuscolumn'.
+
+	The |v:lnum|   variable holds the line number to be drawn.
+	The |v:relnum| variable holds the relative line number to be drawn.
+	The |v:wrap|   variable holds true for the wrapped part of a line.
+
+	Examples: >vim
+		" Relative number with bar separator and click handlers:
+		:set statuscolumn=%@SignCb@%s%=%T%@NumCb@%r│%T
+
+		" Right aligned relative cursor line number:
+		:let &stc='%=%{v:relnum?v:relnum:v:lnum} '
+
+		" Line numbers in hexadecimal for non wrapped part of lines:
+		:let &stc='%=%{v:wrap?"":printf("%x",v:lnum)} '
+
+		" Human readable line numbers with thousands separator:
+		:let &stc='%{substitute(v:lnum,"\\d\\zs\\ze\\'
+			   . '%(\\d\\d\\d\\)\\+$",",","g")}'
+
+		" Both relative and absolute line numbers with different
+		" highlighting for odd and even relative numbers:
+		:let &stc='%#NonText#%{&nu?v:lnum:""}' .
+		 '%=%{&rnu&&(v:lnum%2)?"\ ".v:relnum:""}' .
+		 '%#LineNr#%{&rnu&&!(v:lnum%2)?"\ ".v:relnum:""}'
+
+<	WARNING: this expression is evaluated for each screen line so defining
+	an expensive expression can negatively affect render performance.
+
 			   *'statusline'* *'stl'* *E540* *E542*
 'statusline' 'stl'	string	(default empty)
 			global or local to window |global-local|
diff --git a/runtime/doc/quickref.txt b/runtime/doc/quickref.txt
index d0088f5b9b..d17df3cd61 100644
--- a/runtime/doc/quickref.txt
+++ b/runtime/doc/quickref.txt
@@ -883,6 +883,7 @@ Short explanation of each option:		*option-list*
 'splitkeep'	  'spk'     determines scroll behavior for split windows
 'splitright'	  'spr'     new window is put right of the current one
 'startofline'	  'sol'     commands move cursor to first non-blank in line
+'statuscolumn'	  'stc'	    custom format for the status column
 'statusline'	  'stl'     custom format for the status line
 'suffixes'	  'su'	    suffixes that are ignored with multiple match
 'suffixesadd'	  'sua'     suffixes added when searching for a file
diff --git a/runtime/optwin.vim b/runtime/optwin.vim
index b29b60e145..200254321e 100644
--- a/runtime/optwin.vim
+++ b/runtime/optwin.vim
@@ -452,6 +452,9 @@ call <SID>Header(gettext("multiple windows"))
 call <SID>AddOption("laststatus", gettext("0, 1, 2 or 3; when to use a status line for the last window"))
 call append("$", " \tset ls=" . &ls)
 if has("statusline")
+  call <SID>AddOption("statuscolumn", gettext("custom format for the status column"))
+  call append("$", "\t" .. s:local_to_window)
+  call <SID>OptionG("stc", &stc)
   call <SID>AddOption("statusline", gettext("alternate format to be used for a status line"))
   call <SID>OptionG("stl", &stl)
 endif
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 1e8964d912..65b08ecade 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2238,6 +2238,7 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
                                fillchar,
                                maxwidth,
                                hltab_ptr,
+                               NULL,
                                NULL);
 
   PUT(result, "width", INTEGER_OBJ(width));
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index e6d0dcb8cf..1bba146caf 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -3236,7 +3236,7 @@ void maketitle(void)
     if (*p_titlestring != NUL) {
       if (stl_syntax & STL_IN_TITLE) {
         build_stl_str_hl(curwin, buf, sizeof(buf), p_titlestring,
-                         "titlestring", 0, 0, maxlen, NULL, NULL);
+                         "titlestring", 0, 0, maxlen, NULL, NULL, NULL);
         title_str = buf;
       } else {
         title_str = p_titlestring;
@@ -3342,7 +3342,7 @@ void maketitle(void)
     if (*p_iconstring != NUL) {
       if (stl_syntax & STL_IN_ICON) {
         build_stl_str_hl(curwin, icon_str, sizeof(buf), p_iconstring,
-                         "iconstring", 0, 0, 0, NULL, NULL);
+                         "iconstring", 0, 0, 0, NULL, NULL, NULL);
       } else {
         icon_str = p_iconstring;
       }
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index df4ebdffc0..7442e60024 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -204,6 +204,8 @@ typedef struct {
 #define w_p_cc w_onebuf_opt.wo_cc      // 'colorcolumn'
   char *wo_sbr;
 #define w_p_sbr w_onebuf_opt.wo_sbr    // 'showbreak'
+  char *wo_stc;
+#define w_p_stc w_onebuf_opt.wo_stc     // 'statuscolumn'
   char *wo_stl;
 #define w_p_stl w_onebuf_opt.wo_stl     // 'statusline'
   char *wo_wbr;
@@ -1300,6 +1302,7 @@ struct window_S {
   linenr_T w_redraw_bot;            // when != 0: last line needing redraw
   bool w_redr_status;               // if true statusline/winbar must be redrawn
   bool w_redr_border;               // if true border must be redrawn
+  bool w_redr_statuscol;            // if true 'statuscolumn' must be redrawn
 
   // remember what is shown in the ruler for this window (if 'ruler' set)
   pos_T w_ru_cursor;                // cursor position shown in ruler
@@ -1404,6 +1407,31 @@ struct window_S {
   StlClickDefinition *w_winbar_click_defs;
   // Size of the w_winbar_click_defs array
   size_t w_winbar_click_defs_size;
+
+  // Status column click definitions
+  StlClickDefinition *w_statuscol_click_defs;
+  // Size of the w_statuscol_click_defs array
+  size_t w_statuscol_click_defs_size;
+};
+
+/// Struct to hold info for 'statuscolumn'
+typedef struct statuscol statuscol_T;
+
+struct statuscol {
+  int width;                       // width of the status column
+  int cur_attr;                    // current attributes in text
+  int num_attr;                    // attributes used for line number
+  int fold_attr;                   // attributes used for fold column
+  int sign_attr[SIGN_SHOW_MAX];    // attributes used for signs
+  int truncate;                    // truncated width
+  bool draw;                       // draw statuscolumn or not
+  char fold_text[10];              // text in fold column (%C)
+  char *sign_text[SIGN_SHOW_MAX];  // text in sign column (%s)
+  char text[MAXPATHL];             // text in status column
+  char *textp;                     // current position in text
+  size_t text_len;                 // length of text
+  stl_hlrec_t *hlrec;              // highlight groups
+  stl_hlrec_t *hlrecp;             // current highlight group
 };
 
 /// Macros defined in Vim, but not in Neovim
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index 924251a679..d3e8545b88 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -21,6 +21,7 @@
 #include "nvim/decoration_provider.h"
 #include "nvim/diff.h"
 #include "nvim/drawline.h"
+#include "nvim/eval.h"
 #include "nvim/extmark_defs.h"
 #include "nvim/fold.h"
 #include "nvim/garray.h"
@@ -43,6 +44,7 @@
 #include "nvim/sign.h"
 #include "nvim/spell.h"
 #include "nvim/state.h"
+#include "nvim/statusline.h"
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/terminal.h"
@@ -60,6 +62,7 @@ typedef enum {
   WL_FOLD,       // 'foldcolumn'
   WL_SIGN,       // column for signs
   WL_NR,         // line number
+  WL_STC,        // 'statuscolumn'
   WL_BRI,        // 'breakindent'
   WL_SBR,        // 'showbreak' or 'diff'
   WL_LINE,       // text in the line
@@ -395,6 +398,90 @@ static int get_sign_attrs(buf_T *buf, linenr_T lnum, SignTextAttrs *sattrs, int
   return num_signs;
 }
 
+static void get_statuscol_str(win_T *wp, linenr_T lnum, int row, int startrow, int filler_lines,
+                              int cul_attr, int sign_num_attr, SignTextAttrs *sattrs,
+                              foldinfo_T foldinfo, char_u *extra, statuscol_T *stcp)
+{
+  long relnum;
+  bool wrapped = row != startrow + filler_lines;
+  bool use_cul = use_cursor_line_sign(wp, lnum);
+
+  // Set num, fold and sign text and attrs, empty when wrapped
+  if (row == startrow) {
+    relnum = labs(get_cursor_rel_lnum(wp, lnum));
+    stcp->num_attr = sign_num_attr ? sign_num_attr
+                     : get_line_number_attr(wp, lnum, row, startrow, filler_lines);
+
+    if (compute_foldcolumn(wp, 0)) {
+      size_t n = fill_foldcolumn((char_u *)stcp->fold_text, wp, foldinfo, lnum);
+      stcp->fold_text[n] = NUL;
+      stcp->fold_attr = win_hl_attr(wp, use_cul ? HLF_CLF : HLF_FC);
+    }
+  }
+
+  int i = 0;
+  for (; i < wp->w_scwidth; i++) {
+    SignTextAttrs *sattr = wrapped ? NULL : sign_get_attr(i, sattrs, wp->w_scwidth);
+    stcp->sign_text[i] = sattr && sattr->text ? sattr->text : "  ";
+    stcp->sign_attr[i] = use_cul && cul_attr ? cul_attr : sattr ? sattr->hl_attr_id : 0;
+  }
+  stcp->sign_text[i] = NULL;
+
+  int width = build_statuscol_str(wp, row == startrow, wrapped, lnum, relnum,
+                                  stcp->width, ' ', stcp->text, &stcp->hlrec, stcp);
+  // Force a redraw in case of error or when truncated
+  if (*wp->w_p_stc == NUL || (stcp->truncate > 0 && wp->w_nrwidth < MAX_NUMBERWIDTH)) {
+    if (stcp->truncate) {  // Avoid truncating 'statuscolumn'
+      wp->w_nrwidth = MIN(MAX_NUMBERWIDTH, wp->w_nrwidth + stcp->truncate);
+      wp->w_nrwidth_width = wp->w_nrwidth;
+    } else {  // 'statuscolumn' reset due to error
+      wp->w_nrwidth_line_count = 0;
+      wp->w_nrwidth = (wp->w_p_nu || wp->w_p_rnu) * number_width(wp);
+    }
+    wp->w_redr_statuscol = true;
+    return;
+  }
+
+  // Reset text/highlight pointer and current attr for new line
+  stcp->textp = stcp->text;
+  stcp->hlrecp = stcp->hlrec;
+  stcp->cur_attr = stcp->num_attr;
+  stcp->text_len = strlen(stcp->text);
+
+  int fill = stcp->width - width;
+  if (fill > 0) {
+    // Fill up with ' '
+    memset(&stcp->text[stcp->text_len], ' ', (size_t)fill);
+    stcp->text_len += (size_t)fill;
+    stcp->text[stcp->text_len] = NUL;
+  }
+}
+
+static void get_statuscol_display_info(LineDrawState *draw_state, int *char_attr, int *n_extrap,
+                                       int *c_extrap, int *c_finalp, char_u *extra, char **pp_extra,
+                                       statuscol_T *stcp)
+{
+  *c_extrap = NUL;
+  *c_finalp = NUL;
+  do {
+    *draw_state = WL_STC;
+    *char_attr = stcp->cur_attr;
+    *pp_extra = stcp->textp;
+    *n_extrap = stcp->hlrecp->start ? (int)(stcp->hlrecp->start - stcp->textp)
+                                    : (int)strlen(*pp_extra);
+    // Prepare for next highlight section if not yet at the end
+    if (stcp->textp + *n_extrap < stcp->text + stcp->text_len) {
+      int hl = stcp->hlrecp->userhl;
+      stcp->textp = stcp->hlrecp->start;
+      stcp->cur_attr = hl < 0 ? syn_id2attr(-stcp->hlrecp->userhl)
+                              : hl > 0 ? hl : stcp->num_attr;
+      stcp->hlrecp++;
+      *draw_state = WL_STC - 1;
+    }
+    // Skip over empty highlight sections
+  } while (*n_extrap == 0 && stcp->textp < stcp->text + stcp->text_len);
+}
+
 /// Return true if CursorLineNr highlight is to be used for the number column.
 ///
 /// - 'cursorline' must be set
@@ -1098,6 +1185,13 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
     extra_check = true;
   }
 
+  statuscol_T statuscol = { 0 };
+  if (*wp->w_p_stc != NUL) {
+    // Draw the 'statuscolumn' if option is set.
+    statuscol.draw = true;
+    statuscol.width = win_col_off(wp);
+  }
+
   int sign_idx = 0;
   // Repeat for the whole displayed line.
   for (;;) {
@@ -1125,9 +1219,13 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         }
       }
 
+      // Skip fold, sign and number states if 'statuscolumn' is set.
+      if (draw_state == WL_FOLD - 1 && n_extra == 0 && statuscol.draw) {
+        draw_state = WL_STC - 1;
+      }
+
       if (draw_state == WL_FOLD - 1 && n_extra == 0) {
         int fdc = compute_foldcolumn(wp, 0);
-
         draw_state = WL_FOLD;
         if (fdc > 0) {
           // Draw the 'foldcolumn'.  Allocate a buffer, "extra" may
@@ -1217,7 +1315,23 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         }
       }
 
-      if (draw_state == WL_NR && n_extra == 0) {
+      if (draw_state == WL_STC - 1 && n_extra == 0) {
+        draw_state = WL_STC;
+        // Draw the 'statuscolumn' if option is set.
+        if (statuscol.draw) {
+          if (statuscol.text_len == 0) {
+            get_statuscol_str(wp, lnum, row, startrow, filler_lines, cul_attr,
+                              sign_num_attr, sattrs, foldinfo, extra, &statuscol);
+            if (wp->w_redr_statuscol) {
+              return 0;
+            }
+          }
+          get_statuscol_display_info(&draw_state, &char_attr, &n_extra, &c_extra,
+                                     &c_final, extra, &p_extra, &statuscol);
+        }
+      }
+
+      if (draw_state == WL_STC && n_extra == 0) {
         win_col_offset = off;
       }
 
@@ -1349,7 +1463,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
           && wp == curwin
           && lnum == wp->w_cursor.lnum
           && vcol >= (long)wp->w_virtcol)
-         || (number_only && draw_state > WL_NR))
+         || (number_only && draw_state > WL_STC))
         && filler_todo <= 0) {
       draw_virt_text(wp, buf, win_col_offset, &col, grid->cols, row);
       grid_put_linebuf(grid, row, 0, col, -grid->cols, wp->w_p_rl, wp, bg_attr, false);
@@ -2214,7 +2328,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         && wp->w_p_list
         && (wp->w_p_wrap ? (wp->w_skipcol > 0 && row == 0) : wp->w_leftcol > 0)
         && filler_todo <= 0
-        && draw_state > WL_NR
+        && draw_state > WL_STC
         && c != NUL) {
       c = wp->w_p_lcs_chars.prec;
       lcs_prec_todo = NUL;
@@ -2508,7 +2622,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
         col++;
         // UTF-8: Put a 0 in the second screen char.
         linebuf_char[off][0] = 0;
-        if (draw_state > WL_NR && filler_todo <= 0) {
+        if (draw_state > WL_STC && filler_todo <= 0) {
           vcol++;
         }
         // When "tocol" is halfway through a character, set it to the end of
@@ -2591,7 +2705,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
 
     // Only advance the "vcol" when after the 'number' or 'relativenumber'
     // column.
-    if (draw_state > WL_NR
+    if (draw_state > WL_STC
         && filler_todo <= 0) {
       vcol++;
     }
@@ -2601,7 +2715,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
     }
 
     // restore attributes after "predeces" in 'listchars'
-    if (draw_state > WL_NR && n_attr3 > 0 && --n_attr3 == 0) {
+    if (draw_state > WL_STC && n_attr3 > 0 && --n_attr3 == 0) {
       char_attr = saved_attr3;
     }
 
@@ -2697,6 +2811,16 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
       if (filler_todo <= 0) {
         need_showbreak = true;
       }
+      if (statuscol.draw) {
+        if (row == startrow + 1 || row == startrow + filler_lines) {
+          // Re-evaluate 'statuscolumn' for the first wrapped row and non filler line
+          statuscol.text_len = 0;
+        } else {  // Otherwise just reset the text/hlrec pointers
+          statuscol.textp = statuscol.text;
+          statuscol.hlrecp = statuscol.hlrec;
+        }  // Fall back to default columns if the 'n' flag isn't in 'cpo'
+        statuscol.draw = vim_strchr(p_cpo, CPO_NUMCOL) == NULL;
+      }
       filler_todo--;
       // When the filler lines are actually below the last line of the
       // file, don't draw the line itself, break here.
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index de6bdda71e..568dbe99c0 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -522,7 +522,7 @@ int update_screen(void)
   // TODO(bfredl): special casing curwin here is SÅ JÄVLA BULL.
   // Either this should be done for all windows or not at all.
   if (curwin->w_redr_type < UPD_NOT_VALID
-      && curwin->w_nrwidth != ((curwin->w_p_nu || curwin->w_p_rnu)
+      && curwin->w_nrwidth != ((curwin->w_p_nu || curwin->w_p_rnu || *curwin->w_p_stc)
                                ? number_width(curwin) : 0)) {
     curwin->w_redr_type = UPD_NOT_VALID;
   }
@@ -1032,7 +1032,7 @@ static void win_update(win_T *wp, DecorProviders *providers)
 
   // Force redraw when width of 'number' or 'relativenumber' column
   // changes.
-  int nrwidth = (wp->w_p_nu || wp->w_p_rnu) ? number_width(wp) : 0;
+  int nrwidth = (wp->w_p_nu || wp->w_p_rnu || *wp->w_p_stc) ? number_width(wp) : 0;
   if (wp->w_nrwidth != nrwidth) {
     type = UPD_NOT_VALID;
     wp->w_nrwidth = nrwidth;
@@ -1823,6 +1823,18 @@ static void win_update(win_T *wp, DecorProviders *providers)
       did_update = DID_NONE;
     }
 
+    // 'statuscolumn' width has changed or errored, start from the top.
+    if (wp->w_redr_statuscol) {
+      wp->w_redr_statuscol = false;
+      idx = 0;
+      row = 0;
+      lnum = wp->w_topline;
+      wp->w_lines_valid = 0;
+      wp->w_valid &= ~VALID_WCOL;
+      decor_providers_invoke_win(wp, providers, &line_providers, &provider_err);
+      continue;
+    }
+
     if (lnum > buf->b_ml.ml_line_count) {
       eof = true;
       break;
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index a112a2e447..17eb08cee6 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -267,6 +267,8 @@ static struct vimvar {
   VV(VV__NULL_DICT,       "_null_dict",       VAR_DICT, VV_RO),
   VV(VV__NULL_BLOB,       "_null_blob",       VAR_BLOB, VV_RO),
   VV(VV_LUA,              "lua",              VAR_PARTIAL, VV_RO),
+  VV(VV_RELNUM,           "relnum",           VAR_NUMBER, VV_RO),
+  VV(VV_WRAP,             "wrap",             VAR_BOOL, VV_RO),
 };
 #undef VV
 
diff --git a/src/nvim/eval.h b/src/nvim/eval.h
index 61c1363d54..d67414f12f 100644
--- a/src/nvim/eval.h
+++ b/src/nvim/eval.h
@@ -165,6 +165,8 @@ typedef enum {
   VV__NULL_DICT,  // Dictionary with NULL value. For test purposes only.
   VV__NULL_BLOB,  // Blob with NULL value. For test purposes only.
   VV_LUA,
+  VV_RELNUM,
+  VV_WRAP,
 } VimVarIndex;
 
 /// All recognized msgpack types
diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index b4d6a533f1..88103d1888 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -291,6 +291,7 @@ bool do_mouse(oparg_T *oap, int c, int dir, long count, bool fixindent)
   pos_T start_visual;
   bool moved;                   // Has cursor moved?
   bool in_winbar;               // mouse in window bar
+  bool in_statuscol;            // mouse in status column
   bool in_status_line;          // mouse in status line
   static bool in_tab_line = false;   // mouse clicked in tab line
   bool in_sep_line;             // mouse in vertical separator line
@@ -645,10 +646,11 @@ bool do_mouse(oparg_T *oap, int c, int dir, long count, bool fixindent)
 
   moved = (jump_flags & CURSOR_MOVED);
   in_winbar = (jump_flags & MOUSE_WINBAR);
+  in_statuscol = (jump_flags & MOUSE_STATUSCOL);
   in_status_line = (jump_flags & IN_STATUS_LINE);
   in_sep_line = (jump_flags & IN_SEP_LINE);
 
-  if ((in_winbar || in_status_line) && is_click) {
+  if ((in_winbar || in_status_line || in_statuscol) && is_click) {
     // Handle click event on window bar or status lin
     int click_grid = mouse_grid;
     int click_row = mouse_row;
@@ -659,7 +661,8 @@ bool do_mouse(oparg_T *oap, int c, int dir, long count, bool fixindent)
     }
 
     StlClickDefinition *click_defs = in_status_line ? wp->w_status_click_defs
-                                                    : wp->w_winbar_click_defs;
+                                                    : in_winbar ? wp->w_winbar_click_defs
+                                                                : wp->w_statuscol_click_defs;
 
     if (in_status_line && global_stl_height() > 0) {
       // global statusline is displayed for the current window,
@@ -682,8 +685,8 @@ bool do_mouse(oparg_T *oap, int c, int dir, long count, bool fixindent)
     }
 
     return false;
-  } else if (in_winbar) {
-    // A drag or release event in the window bar has no side effects.
+  } else if (in_winbar || in_statuscol) {
+    // A drag or release event in the window bar and status column has no side effects.
     return false;
   }
 
@@ -1027,6 +1030,7 @@ int jump_to_mouse(int flags, bool *inclusive, int which_button)
   static bool on_status_line = false;
   static bool on_sep_line = false;
   static bool on_winbar = false;
+  static bool on_statuscol = false;
   static int prev_row = -1;
   static int prev_col = -1;
   static int did_drag = false;          // drag was noticed
@@ -1069,6 +1073,9 @@ retnomove:
     if (on_winbar) {
       return IN_OTHER_WIN | MOUSE_WINBAR;
     }
+    if (on_statuscol) {
+      return IN_OTHER_WIN | MOUSE_STATUSCOL;
+    }
     if (flags & MOUSE_MAY_STOP_VIS) {
       end_visual_mode();
       redraw_curbuf_later(UPD_INVERTED);  // delete the inversion
@@ -1103,6 +1110,10 @@ retnomove:
     ? wp->w_winbar_height != 0
     : false;
 
+  on_statuscol = grid == (col < win_col_off(wp))
+    ? *wp->w_p_stc != NUL
+    : false;
+
   on_sep_line = grid == DEFAULT_GRID_HANDLE && col >= wp->w_width
     ? col - wp->w_width + 1 == 1
     : false;
@@ -1130,6 +1141,10 @@ retnomove:
       return IN_OTHER_WIN | MOUSE_WINBAR;
     }
 
+    if (on_statuscol) {
+      return IN_OTHER_WIN | MOUSE_STATUSCOL;
+    }
+
     fdc = win_fdccol_count(wp);
     dragwin = NULL;
 
@@ -1230,6 +1245,9 @@ retnomove:
   } else if (on_winbar && which_button == MOUSE_RIGHT) {
     // After a click on the window bar don't start Visual mode.
     return IN_OTHER_WIN | MOUSE_WINBAR;
+  } else if (on_statuscol && which_button == MOUSE_RIGHT) {
+    // After a click on the status column don't start Visual mode.
+    return IN_OTHER_WIN | MOUSE_STATUSCOL;
   } else {
     // keep_window_focus must be true
     // before moving the cursor for a left click, stop Visual mode
diff --git a/src/nvim/mouse.h b/src/nvim/mouse.h
index d493a479b1..8b2d7e0acd 100644
--- a/src/nvim/mouse.h
+++ b/src/nvim/mouse.h
@@ -9,17 +9,18 @@
 #include "nvim/window.h"
 
 /// jump_to_mouse() returns one of first five these values, possibly with
-/// some of the other four added.
+/// some of the other five added.
 enum {
   IN_UNKNOWN       = 0,
   IN_BUFFER        = 1,
-  IN_STATUS_LINE   = 2,      ///< on status or command line
-  IN_SEP_LINE      = 4,      ///< on vertical separator line
-  IN_OTHER_WIN     = 8,      ///< in other window but can't go there
+  IN_STATUS_LINE   = 2,       ///< on status or command line
+  IN_SEP_LINE      = 4,       ///< on vertical separator line
+  IN_OTHER_WIN     = 8,       ///< in other window but can't go there
   CURSOR_MOVED     = 0x100,
-  MOUSE_FOLD_CLOSE = 0x200,  ///< clicked on '-' in fold column
-  MOUSE_FOLD_OPEN  = 0x400,  ///< clicked on '+' in fold column
-  MOUSE_WINBAR     = 0x800,  ///< in window toolbar
+  MOUSE_FOLD_CLOSE = 0x200,   ///< clicked on '-' in fold column
+  MOUSE_FOLD_OPEN  = 0x400,   ///< clicked on '+' in fold column
+  MOUSE_WINBAR     = 0x800,   ///< in window toolbar
+  MOUSE_STATUSCOL  = 0x1000,  ///< in 'statuscolumn'
 };
 
 /// flags for jump_to_mouse()
diff --git a/src/nvim/move.c b/src/nvim/move.c
index 227e19bca3..0d2a38b041 100644
--- a/src/nvim/move.c
+++ b/src/nvim/move.c
@@ -649,7 +649,8 @@ void validate_cursor_col(void)
 // fold column and sign column (these don't move when scrolling horizontally).
 int win_col_off(win_T *wp)
 {
-  return ((wp->w_p_nu || wp->w_p_rnu) ? number_width(wp) + 1 : 0)
+  return ((wp->w_p_nu || wp->w_p_rnu || (*wp->w_p_stc != NUL)) ?
+          (number_width(wp) + (*wp->w_p_stc == NUL)) : 0)
          + (cmdwin_type == 0 || wp != curwin ? 0 : 1)
          + win_fdccol_count(wp)
          + (win_signcol_count(wp) * win_signcol_width(wp));
diff --git a/src/nvim/option.c b/src/nvim/option.c
index a6ec0a08c2..fe905a5a05 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -2094,6 +2094,9 @@ static char *set_bool_option(const int opt_idx, char_u *const varp, const int va
     if (curwin->w_p_spell) {
       errmsg = did_set_spelllang(curwin);
     }
+  } else if (((int *)varp == &curwin->w_p_nu || (int *)varp == &curwin->w_p_rnu)
+             && *curwin->w_p_stc != NUL) {  // '(relative)number' + 'statuscolumn'
+    curwin->w_nrwidth_line_count = 0;
   }
 
   if ((int *)varp == &curwin->w_p_arab) {
@@ -2316,7 +2319,7 @@ static char *set_num_option(int opt_idx, char_u *varp, long value, char *errbuf,
   } else if (pp == &curwin->w_p_nuw || pp == &curwin->w_allbuf_opt.wo_nuw) {
     if (value < 1) {
       errmsg = e_positive;
-    } else if (value > 20) {
+    } else if (value > MAX_NUMBERWIDTH) {
       errmsg = e_invarg;
     }
   } else if (pp == &curbuf->b_p_iminsert || pp == &p_iminsert) {
@@ -3630,6 +3633,9 @@ void unset_global_local_option(char *name, void *from)
     clear_string_option(&((win_T *)from)->w_p_ve);
     ((win_T *)from)->w_ve_flags = 0;
     break;
+  case PV_STC:
+    clear_string_option(&((win_T *)from)->w_p_stc);
+    break;
   }
 }
 
@@ -4014,6 +4020,8 @@ static char_u *get_varp(vimoption_T *p)
     return (char_u *)&(curwin->w_p_winhl);
   case PV_WINBL:
     return (char_u *)&(curwin->w_p_winbl);
+  case PV_STC:
+    return (char_u *)&(curwin->w_p_stc);
   default:
     iemsg(_("E356: get_varp ERROR"));
   }
@@ -4102,6 +4110,7 @@ void copy_winopt(winopt_T *from, winopt_T *to)
   to->wo_scl = copy_option_val(from->wo_scl);
   to->wo_winhl = copy_option_val(from->wo_winhl);
   to->wo_winbl = from->wo_winbl;
+  to->wo_stc = copy_option_val(from->wo_stc);
 
   // Copy the script context so that we know were the value was last set.
   memmove(to->wo_script_ctx, from->wo_script_ctx, sizeof(to->wo_script_ctx));
@@ -4139,6 +4148,7 @@ static void check_winopt(winopt_T *wop)
   check_string_option(&wop->wo_fcs);
   check_string_option(&wop->wo_ve);
   check_string_option(&wop->wo_wbr);
+  check_string_option(&wop->wo_stc);
 }
 
 /// Free the allocated memory inside a winopt_T.
@@ -4165,6 +4175,7 @@ void clear_winopt(winopt_T *wop)
   clear_string_option(&wop->wo_fcs);
   clear_string_option(&wop->wo_ve);
   clear_string_option(&wop->wo_wbr);
+  clear_string_option(&wop->wo_stc);
 }
 
 void didset_window_options(win_T *wp, bool valid_cursor)
diff --git a/src/nvim/option.h b/src/nvim/option.h
index 6744678044..636257bfe8 100644
--- a/src/nvim/option.h
+++ b/src/nvim/option.h
@@ -19,6 +19,8 @@ typedef enum {
 #define BCO_ALWAYS      2       // always copy the options
 #define BCO_NOHELP      4       // don't touch the help related options
 
+#define MAX_NUMBERWIDTH 20      // used for 'numberwidth' and 'statuscolumn'
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "option.h.generated.h"
 #endif
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index 699a57c2aa..56fdb6de84 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -337,6 +337,8 @@ enum {
   STL_ARGLISTSTAT     = 'a',  ///< Argument list status as (x of y).
   STL_PAGENUM         = 'N',  ///< Page number (when printing).
   STL_SHOWCMD         = 'S',  ///< 'showcmd' buffer
+  STL_FOLDCOL         = 'C',  ///< Fold column for 'statuscolumn'
+  STL_SIGNCOL         = 's',  ///< Sign column for 'statuscolumn'
   STL_VIM_EXPR        = '{',  ///< Start of expression to substitute.
   STL_SEPARATE        = '=',  ///< Separation between alignment sections.
   STL_TRUNCMARK       = '<',  ///< Truncation mark if line is too long.
@@ -354,8 +356,9 @@ enum {
     STL_HELPFLAG, STL_HELPFLAG_ALT, STL_FILETYPE, STL_FILETYPE_ALT, \
     STL_PREVIEWFLAG, STL_PREVIEWFLAG_ALT, STL_MODIFIED, STL_MODIFIED_ALT, \
     STL_QUICKFIX, STL_PERCENTAGE, STL_ALTPERCENT, STL_ARGLISTSTAT, STL_PAGENUM, \
-    STL_SHOWCMD, STL_VIM_EXPR, STL_SEPARATE, STL_TRUNCMARK, STL_USER_HL, \
-    STL_HIGHLIGHT, STL_TABPAGENR, STL_TABCLOSENR, STL_CLICK_FUNC, \
+    STL_SHOWCMD, STL_FOLDCOL, STL_SIGNCOL, STL_VIM_EXPR, STL_SEPARATE, \
+    STL_TRUNCMARK, STL_USER_HL, STL_HIGHLIGHT, STL_TABPAGENR, STL_TABCLOSENR, \
+    STL_CLICK_FUNC, STL_TABPAGENR, STL_TABCLOSENR, STL_CLICK_FUNC, \
     0, \
   })
 
@@ -955,6 +958,7 @@ enum {
   WV_CULOPT,
   WV_CC,
   WV_SBR,
+  WV_STC,
   WV_STL,
   WV_WFH,
   WV_WFW,
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 8c7cf94465..387ccd0888 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -2298,6 +2298,15 @@ return {
       defaults={if_true=false}
     },
     {
+      full_name='statuscolumn', abbreviation='stc',
+      short_desc=N_("custom format for the status column"),
+      type='string', scope={'window'},
+      redraw={'current_window'},
+      secure=true,
+      alloced=true,
+      defaults={if_true=""}
+    },
+    {
       full_name='statusline', abbreviation='stl',
       short_desc=N_("custom format for the status line"),
       type='string', scope={'global', 'window'},
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 0c9d428ce7..a97e9b7c7e 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -1177,12 +1177,14 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
       redraw_titles();
     }
   } else if (gvarp == &p_stl || gvarp == &p_wbr || varp == &p_tal
-             || varp == &p_ruf) {
-    // 'statusline', 'winbar', 'tabline' or 'rulerformat'
+             || varp == &p_ruf || varp == &curwin->w_p_stc) {
+    // 'statusline', 'winbar', 'tabline', 'rulerformat' or 'statuscolumn'
     int wid;
 
     if (varp == &p_ruf) {       // reset ru_wid first
       ru_wid = 0;
+    } else if (varp == &curwin->w_p_stc) {
+      curwin->w_nrwidth_line_count = 0;
     }
     s = *varp;
     if (varp == &p_ruf && *s == '%') {
@@ -1197,7 +1199,8 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
         errmsg = check_stl_option(p_ruf);
       }
     } else if (varp == &p_ruf || s[0] != '%' || s[1] != '!') {
-      // check 'statusline', 'winbar' or 'tabline' only if it doesn't start with "%!"
+      // check 'statusline', 'winbar', 'tabline' or 'statuscolumn'
+      // only if it doesn't start with "%!"
       errmsg = check_stl_option(s);
     }
     if (varp == &p_ruf && errmsg == NULL) {
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 52ab2ad25e..afdb04ebd8 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -780,6 +780,16 @@ int number_width(win_T *wp)
   }
   wp->w_nrwidth_line_count = lnum;
 
+  // make best estimate for 'statuscolumn'
+  if (*wp->w_p_stc != NUL) {
+    char buf[MAXPATHL];
+    wp->w_nrwidth_width = 0;
+    n = build_statuscol_str(wp, true, false, lnum, 0, 0, NUL, buf, NULL, NULL);
+    n = MAX(n, (wp->w_p_nu || wp->w_p_rnu) * (int)wp->w_p_nuw);
+    wp->w_nrwidth_width = MIN(n, MAX_NUMBERWIDTH);
+    return wp->w_nrwidth_width;
+  }
+
   n = 0;
   do {
     lnum /= 10;
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 0f28eae0d8..d548c285fb 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -367,8 +367,9 @@ static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
   // Make a copy, because the statusline may include a function call that
   // might change the option value and free the memory.
   stl = xstrdup(stl);
-  width = build_stl_str_hl(ewp, buf, sizeof(buf), stl, opt_name,
-                           opt_scope, fillchar, maxwidth, &hltab, &tabtab);
+  width = build_stl_str_hl(ewp, buf, sizeof(buf), stl, opt_name, opt_scope,
+                           fillchar, maxwidth, &hltab, &tabtab, NULL);
+
   xfree(stl);
   ewp->w_p_crb = p_crb_save;
 
@@ -867,6 +868,32 @@ void draw_tabline(void)
   redraw_tabline = false;
 }
 
+int build_statuscol_str(win_T *wp, bool setnum, bool wrap, linenr_T lnum, long relnum, int maxwidth,
+                        int fillchar, char *buf, stl_hlrec_t **hlrec, statuscol_T *stcp)
+{
+  if (setnum) {
+    set_vim_var_nr(VV_LNUM, lnum);
+    set_vim_var_nr(VV_RELNUM, relnum);
+  }
+  set_vim_var_bool(VV_WRAP, wrap);
+
+  StlClickRecord *clickrec;
+  char *stc = xstrdup(wp->w_p_stc);
+  int width = build_stl_str_hl(wp, buf, MAXPATHL, stc, "statuscolumn", OPT_LOCAL,
+                               fillchar, maxwidth, hlrec, &clickrec, stcp);
+  xfree(stc);
+
+  // Allocate and fill click def array if width has changed
+  if (wp->w_status_click_defs_size != (size_t)width) {
+    stl_clear_click_defs(wp->w_statuscol_click_defs, wp->w_statuscol_click_defs_size);
+    wp->w_statuscol_click_defs = stl_alloc_click_defs(wp->w_statuscol_click_defs, width,
+                                                      &wp->w_statuscol_click_defs_size);
+    stl_fill_click_defs(wp->w_statuscol_click_defs, clickrec, buf, width, false);
+  }
+
+  return width;
+}
+
 /// Build a string from the status line items in "fmt".
 /// Return length of string in screen cells.
 ///
@@ -890,11 +917,13 @@ void draw_tabline(void)
 /// @param fillchar  Character to use when filling empty space in the statusline
 /// @param maxwidth  The maximum width to make the statusline
 /// @param hltab  HL attributes (can be NULL)
-/// @param tabtab  Tab clicks definition (can be NULL).
+/// @param tabtab  Tab clicks definition (can be NULL)
+/// @param stcp  Status column attributes (can be NULL)
 ///
 /// @return  The final width of the statusline
 int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_name, int opt_scope,
-                     int fillchar, int maxwidth, stl_hlrec_t **hltab, StlClickRecord **tabtab)
+                     int fillchar, int maxwidth, stl_hlrec_t **hltab, StlClickRecord **tabtab,
+                     statuscol_T *stcp)
 {
   static size_t stl_items_len = 20;  // Initial value, grows as needed.
   static stl_item_t *stl_items = NULL;
@@ -1466,8 +1495,9 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
     }
 
     case STL_LINE:
-      num = (wp->w_buffer->b_ml.ml_flags & ML_EMPTY)
-            ? 0L : (long)(wp->w_cursor.lnum);
+      // Overload %l with v:lnum for 'statuscolumn'
+      num = strcmp(opt_name, "statuscolumn") == 0 ? get_vim_var_nr(VV_LNUM)
+            : (wp->w_buffer->b_ml.ml_flags & ML_EMPTY) ? 0L : (long)(wp->w_cursor.lnum);
       break;
 
     case STL_NUMLINES:
@@ -1565,9 +1595,14 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
 
     case STL_ROFLAG:
     case STL_ROFLAG_ALT:
-      itemisflag = true;
-      if (wp->w_buffer->b_p_ro) {
-        str = (opt == STL_ROFLAG_ALT) ? ",RO" : _("[RO]");
+      // Overload %r with v:relnum for 'statuscolumn'
+      if (strcmp(opt_name, "statuscolumn") == 0) {
+        num = get_vim_var_nr(VV_RELNUM);
+      } else {
+        itemisflag = true;
+        if (wp->w_buffer->b_p_ro) {
+          str = (opt == STL_ROFLAG_ALT) ? ",RO" : _("[RO]");
+        }
       }
       break;
 
@@ -1579,6 +1614,33 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
       }
       break;
 
+    case STL_FOLDCOL:    // 'C' for 'statuscolumn'
+    case STL_SIGNCOL: {  // 's' for 'statuscolumn'
+      if (stcp == NULL) {
+        break;
+      }
+
+      bool fold = opt == STL_FOLDCOL;
+      *buf_tmp = NUL;
+      for (int i = 0; i <= 9; i++) {
+        char *p = fold ? stcp->fold_text : stcp->sign_text[i];
+        if ((!p || !*p) && *buf_tmp == NUL) {
+          break;
+        }
+        stl_items[curitem].type = Highlight;
+        stl_items[curitem].start = out_p + strlen(buf_tmp);
+        stl_items[curitem].minwid = !p || (fold && i) ? 0 : fold ? stcp->fold_attr
+                                                                 : stcp->sign_attr[i];
+        curitem++;
+        if (!p || (fold && i)) {
+          str = buf_tmp;
+          break;
+        }
+        STRCAT(buf_tmp, p);
+      }
+      break;
+    }
+
     case STL_FILETYPE:
       // Copy the filetype if it is not null and the formatted string will fit
       // in the temporary buffer
@@ -1850,6 +1912,10 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, char *opt_n
   // What follows is post-processing to handle alignment and highlighting.
 
   int width = vim_strsize(out);
+  // Return truncated width for 'statuscolumn'
+  if (stcp != NULL && width > maxwidth) {
+    stcp->truncate = width - maxwidth;
+  }
   if (maxwidth > 0 && width > maxwidth) {
     // Result is too long, must truncate somewhere.
     int item_idx = 0;
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 4e569ce11f..e836fa50fb 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -5094,6 +5094,9 @@ static void win_free(win_T *wp, tabpage_T *tp)
   stl_clear_click_defs(wp->w_winbar_click_defs, wp->w_winbar_click_defs_size);
   xfree(wp->w_winbar_click_defs);
 
+  stl_clear_click_defs(wp->w_statuscol_click_defs, wp->w_statuscol_click_defs_size);
+  xfree(wp->w_statuscol_click_defs);
+
   // Remove the window from the b_wininfo lists, it may happen that the
   // freed memory is re-used for another window.
   FOR_ALL_BUFFERS(buf) {
diff --git a/test/functional/lua/ffi_spec.lua b/test/functional/lua/ffi_spec.lua
index 3969a7a478..18b13a8959 100644
--- a/test/functional/lua/ffi_spec.lua
+++ b/test/functional/lua/ffi_spec.lua
@@ -29,6 +29,7 @@ describe('ffi.cdef', function()
         typedef struct window_S win_T;
         typedef struct {} stl_hlrec_t;
         typedef struct {} StlClickRecord;
+        typedef struct {} statuscol_T;
         typedef struct {} Error;
 
         win_T *find_window_by_handle(int Window, Error *err);
@@ -43,7 +44,8 @@ describe('ffi.cdef', function()
           int fillchar,
           int maxwidth,
           stl_hlrec_t **hltab,
-          StlClickRecord **tabtab
+          StlClickRecord **tabtab,
+          statuscol_T *scp
         );
       ]]
 
@@ -57,6 +59,7 @@ describe('ffi.cdef', function()
         0,
         0,
         nil,
+        nil,
         nil
       )
     ]=])
diff --git a/test/functional/ui/statuscolumn_spec.lua b/test/functional/ui/statuscolumn_spec.lua
new file mode 100644
index 0000000000..1ee96ed625
--- /dev/null
+++ b/test/functional/ui/statuscolumn_spec.lua
@@ -0,0 +1,273 @@
+local helpers = require('test.functional.helpers')(after_each)
+local Screen = require('test.functional.ui.screen')
+local clear = helpers.clear
+local command = helpers.command
+local eq = helpers.eq
+local eval = helpers.eval
+local meths = helpers.meths
+local pcall_err = helpers.pcall_err
+
+describe('statuscolumn', function()
+  local screen
+  before_each(function()
+    clear('--cmd', 'set number nuw=1 | call setline(1, repeat(["aaaaa"], 16)) | norm GM')
+    screen = Screen.new()
+    screen:attach()
+  end)
+
+  it('fails with invalid \'statuscolumn\'', function()
+    command('set stc=%{v:relnum?v:relnum:(v:lnum==5?invalid:v:lnum)}\\ ')
+    screen:expect([[
+      4  aaaaa                                             |
+      3  aaaaa                                             |
+      2  aaaaa                                             |
+      1  aaaaa                                             |
+      8  ^aaaaa                                             |
+      1  aaaaa                                             |
+      2  aaaaa                                             |
+      3  aaaaa                                             |
+      4  aaaaa                                             |
+      5  aaaaa                                             |
+      6  aaaaa                                             |
+      7  aaaaa                                             |
+      8  aaaaa                                             |
+                                                           |
+    ]])
+    command('norm 5G')
+    eq('Vim(redraw):E121: Undefined variable: invalid', pcall_err(command, 'redraw!'))
+    eq('', eval('&statuscolumn'))
+  end)
+
+  it('widens with irregular \'statuscolumn\' width', function()
+    command('set stc=%{v:relnum?v:relnum:(v:lnum==5?\'bbbbb\':v:lnum)}')
+    command('norm 5G | redraw!')
+    screen:expect([[
+      1    aaaaa                                           |
+      bbbbba^eaaa                                           |
+      1    aaaaa                                           |
+      2    aaaaa                                           |
+      3    aaaaa                                           |
+      4    aaaaa                                           |
+      5    aaaaa                                           |
+      6    aaaaa                                           |
+      7    aaaaa                                           |
+      8    aaaaa                                           |
+      9    aaaaa                                           |
+      10   aaaaa                                           |
+      11   aaaaa                                           |
+                                                           |
+    ]])
+  end)
+
+  it('works with \'statuscolumn\'', function()
+    command([[set stc=%{&nu?v:lnum:''}%=%{&rnu?'\ '.v:relnum:''}│]])
+    screen:expect([[
+      4 │aaaaa                                             |
+      5 │aaaaa                                             |
+      6 │aaaaa                                             |
+      7 │aaaaa                                             |
+      8 │^aaaaa                                             |
+      9 │aaaaa                                             |
+      10│aaaaa                                             |
+      11│aaaaa                                             |
+      12│aaaaa                                             |
+      13│aaaaa                                             |
+      14│aaaaa                                             |
+      15│aaaaa                                             |
+      16│aaaaa                                             |
+                                                           |
+    ]])
+    command('set relativenumber')
+    screen:expect([[
+      4  4│aaaaa                                           |
+      5  3│aaaaa                                           |
+      6  2│aaaaa                                           |
+      7  1│aaaaa                                           |
+      8  0│^aaaaa                                           |
+      9  1│aaaaa                                           |
+      10 2│aaaaa                                           |
+      11 3│aaaaa                                           |
+      12 4│aaaaa                                           |
+      13 5│aaaaa                                           |
+      14 6│aaaaa                                           |
+      15 7│aaaaa                                           |
+      16 8│aaaaa                                           |
+                                                           |
+    ]])
+    command('norm 12GH')
+    screen:expect([[
+      4   0│^aaaaa                                          |
+      5   1│aaaaa                                          |
+      6   2│aaaaa                                          |
+      7   3│aaaaa                                          |
+      8   4│aaaaa                                          |
+      9   5│aaaaa                                          |
+      10  6│aaaaa                                          |
+      11  7│aaaaa                                          |
+      12  8│aaaaa                                          |
+      13  9│aaaaa                                          |
+      14 10│aaaaa                                          |
+      15 11│aaaaa                                          |
+      16 12│aaaaa                                          |
+                                                           |
+    ]])
+  end)
+
+  it('works with highlighted \'statuscolumn\'', function()
+    command([[set stc=%#NonText#%{&nu?v:lnum:''}]] ..
+            [[%=%{&rnu&&(v:lnum%2)?'\ '.v:relnum:''}]] ..
+            [[%#LineNr#%{&rnu&&!(v:lnum%2)?'\ '.v:relnum:''}│]])
+    screen:set_default_attr_ids({
+      [0] = {bold = true, foreground = Screen.colors.Blue},
+      [1] = {foreground = Screen.colors.Brown},
+    })
+    screen:expect([[
+      {0:4 }{1:│}aaaaa                                             |
+      {0:5 }{1:│}aaaaa                                             |
+      {0:6 }{1:│}aaaaa                                             |
+      {0:7 }{1:│}aaaaa                                             |
+      {0:8 }{1:│}^aaaaa                                             |
+      {0:9 }{1:│}aaaaa                                             |
+      {0:10}{1:│}aaaaa                                             |
+      {0:11}{1:│}aaaaa                                             |
+      {0:12}{1:│}aaaaa                                             |
+      {0:13}{1:│}aaaaa                                             |
+      {0:14}{1:│}aaaaa                                             |
+      {0:15}{1:│}aaaaa                                             |
+      {0:16}{1:│}aaaaa                                             |
+                                                           |
+    ]])
+    command('set relativenumber')
+    screen:expect([[
+      {0:4 }{1: 4│}aaaaa                                           |
+      {0:5  3}{1:│}aaaaa                                           |
+      {0:6 }{1: 2│}aaaaa                                           |
+      {0:7  1}{1:│}aaaaa                                           |
+      {0:8 }{1: 0│}^aaaaa                                           |
+      {0:9  1}{1:│}aaaaa                                           |
+      {0:10}{1: 2│}aaaaa                                           |
+      {0:11 3}{1:│}aaaaa                                           |
+      {0:12}{1: 4│}aaaaa                                           |
+      {0:13 5}{1:│}aaaaa                                           |
+      {0:14}{1: 6│}aaaaa                                           |
+      {0:15 7}{1:│}aaaaa                                           |
+      {0:16}{1: 8│}aaaaa                                           |
+                                                           |
+    ]])
+    command('set nonumber')
+    screen:expect([[
+      {1:4│}aaaaa                                              |
+      {0:3}{1:│}aaaaa                                              |
+      {1:2│}aaaaa                                              |
+      {0:1}{1:│}aaaaa                                              |
+      {1:0│}^aaaaa                                              |
+      {0:1}{1:│}aaaaa                                              |
+      {1:2│}aaaaa                                              |
+      {0:3}{1:│}aaaaa                                              |
+      {1:4│}aaaaa                                              |
+      {0:5}{1:│}aaaaa                                              |
+      {1:6│}aaaaa                                              |
+      {0:7}{1:│}aaaaa                                              |
+      {1:8│}aaaaa                                              |
+                                                           |
+    ]])
+  end)
+
+  it('works with wrapped lines, signs and folds', function()
+    command("set stc=%C%s%=%{v:wrap?'':v:lnum}│\\ ")
+    command("call setline(1,repeat([repeat('aaaaa',10)],16))")
+    screen:set_default_attr_ids({
+      [0] = {bold = true, foreground = Screen.colors.Blue},
+      [1] = {foreground = Screen.colors.Brown},
+      [2] = {foreground = Screen.colors.DarkBlue, background = Screen.colors.WebGrey},
+      [3] = {foreground = Screen.colors.DarkBlue, background = Screen.colors.LightGrey},
+    })
+    screen:expect([[
+      {1: 4│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1: 5│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1: 6│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1: 7│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1: 8│ }^aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1: 9│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:  │ }a                                                |
+      {1:10│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa{0:@@@}|
+                                                           |
+    ]])
+    command('set signcolumn=auto:2 foldcolumn=auto')
+    command('sign define piet1 text=>> texthl=LineNr')
+    command('sign define piet2 text=>! texthl=NonText')
+    command('sign place 1 line=4 name=piet1 buffer=1')
+    command('sign place 2 line=5 name=piet2 buffer=1')
+    command('sign place 3 line=6 name=piet1 buffer=1')
+    command('sign place 4 line=6 name=piet2 buffer=1')
+    screen:expect([[
+      {1:>>   4│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {0:>!}{1:   5│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {1:>>}{0:>!}{1: 6│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {1:     7│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {1:     8│ }^aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {1:     9│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {1:      │ }aaaaa                                        |
+      {1:    10│ }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa{0:@@@}|
+                                                           |
+    ]])
+    command('norm zf$')
+    -- Check that alignment works properly with signs after %=
+    command("set stc=%C%=%{v:wrap?'':v:lnum}│%s\\ ")
+    screen:expect([[
+      {2: }{1: 4│>>   }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+      {2: }{1: 5│}{0:>!}{1:   }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+      {2: }{1: 6│>>}{0:>!}{1: }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+      {2: }{1: 7│     }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+      {2:+}{1: 8│     }{3:^+--  1 line: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa}|
+      {2: }{1: 9│     }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+      {2: }{1:10│     }aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa|
+      {2: }{1:  │     }aaaaaa                                      |
+                                                           |
+    ]])
+  end)
+
+  it('works with \'statuscolumn\' clicks', function()
+    command('set mousemodel=extend')
+    command([[
+      function! MyClickFunc(minwid, clicks, button, mods)
+        let g:testvar = printf("%d %d %s %d", a:minwid, a:clicks, a:button, getmousepos().line)
+        if a:mods !=# '    '
+          let g:testvar ..= '(' .. a:mods .. ')'
+        endif
+      endfunction
+      set stc=%0@MyClickFunc@%=%l%T
+    ]])
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    eq('0 1 l 4', eval("g:testvar"))
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    eq('0 2 l 4', eval("g:testvar"))
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    eq('0 3 l 4', eval("g:testvar"))
+    meths.input_mouse('left', 'press', '', 0, 0, 0)
+    eq('0 4 l 4', eval("g:testvar"))
+    meths.input_mouse('right', 'press', '', 0, 3, 0)
+    eq('0 1 r 7', eval("g:testvar"))
+    meths.input_mouse('right', 'press', '', 0, 3, 0)
+    eq('0 2 r 7', eval("g:testvar"))
+    meths.input_mouse('right', 'press', '', 0, 3, 0)
+    eq('0 3 r 7', eval("g:testvar"))
+    meths.input_mouse('right', 'press', '', 0, 3, 0)
+    eq('0 4 r 7', eval("g:testvar"))
+  end)
+end)
diff --git a/test/unit/buffer_spec.lua b/test/unit/buffer_spec.lua
index 4f8a27de09..a54ea8c656 100644
--- a/test/unit/buffer_spec.lua
+++ b/test/unit/buffer_spec.lua
@@ -238,6 +238,7 @@ describe('buffer functions', function()
                                      fillchar,
                                      maximum_cell_count,
                                      NULL,
+                                     NULL,
                                      NULL)
     end