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.

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
@@ -2293,6 +2297,11 @@ v:version Vim version number: major version times 100 plus minor
 
  *v:vim_did_enter* *vim_did_enter-variable*
 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*

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

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|

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

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

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));

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;
  }

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