vim-patch:8.1.0105: all tab stops are the same

Problem:    All tab stops are the same.
Solution:   Add the variable tabstop feature. (Christian Brabandt,
            closes vim/vim#2711)
https://github.com/vim/vim/commit/04958cbaf25eea27eceedaa987adfb354ad5f7fd

17 files changed, 1403 insertions, 247 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index c42a0e2dad..1daedb90b5 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -282,7 +282,7 @@ int open_buffer(
 
   // Set/reset the Changed flag first, autocmds may change the buffer.
   // Apply the automatic commands, before processing the modelines.
-  // So the modelines have priority over auto commands.
+  // So the modelines have priority over autocommands.
 
   // When reading stdin, the buffer contents always needs writing, so set
   // the changed flag.  Unless in readonly mode: "ls | nvim -R -".
@@ -1946,6 +1946,20 @@ void free_buf_options(buf_T *buf, int free_p_ff)
   clear_string_option(&buf->b_p_fo);
   clear_string_option(&buf->b_p_flp);
   clear_string_option(&buf->b_p_isk);
+  clear_string_option(&buf->b_p_vsts);
+  if (buf->b_p_vsts_nopaste) {
+    xfree(buf->b_p_vsts_nopaste);
+  }
+  buf->b_p_vsts_nopaste = NULL;
+  if (buf->b_p_vsts_array) {
+    xfree(buf->b_p_vsts_array);
+  }
+  buf->b_p_vsts_array = NULL;
+  clear_string_option(&buf->b_p_vts);
+  if (buf->b_p_vts_array) {
+    xfree(buf->b_p_vts_array);
+  }
+  buf->b_p_vts_array = NULL;
   clear_string_option(&buf->b_p_keymap);
   keymap_ga_clear(&buf->b_kmap_ga);
   ga_clear(&buf->b_kmap_ga);
@@ -5375,8 +5389,8 @@ bool bt_terminal(const buf_T *const buf)
   return buf != NULL && buf->b_p_bt[0] == 't';
 }
 
-// Return true if "buf" is a "nofile", "acwrite" or "terminal" buffer.
-// This means the buffer name is not a file name.
+// Return true if "buf" is a "nofile", "acwrite", "terminal" or "prompt"
+// buffer.  This means the buffer name is not a file name.
 bool bt_nofile(const buf_T *const buf)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
@@ -5386,7 +5400,8 @@ bool bt_nofile(const buf_T *const buf)
                          || buf->b_p_bt[0] == 'p');
 }
 
-// Return true if "buf" is a "nowrite", "nofile" or "terminal" buffer.
+// Return true if "buf" is a "nowrite", "nofile", "terminal" or "prompt"
+// buffer.
 bool bt_dontwrite(const buf_T *const buf)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index e8038e7281..a4105e2796 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -743,6 +743,11 @@ struct file_buffer {
   long b_p_wm;                  ///< 'wrapmargin'
   long b_p_wm_nobin;            ///< b_p_wm saved for binary mode
   long b_p_wm_nopaste;          ///< b_p_wm saved for paste mode
+  char_u *b_p_vsts;             ///< 'varsofttabstop'
+  long *b_p_vsts_array;          ///< 'varsofttabstop' in internal format
+  char_u *b_p_vsts_nopaste;     ///< b_p_vsts saved for paste mode
+  char_u *b_p_vts;              ///< 'vartabstop'
+  long *b_p_vts_array;           ///< 'vartabstop' in internal format
   char_u *b_p_keymap;           ///< 'keymap'
 
   // local values for options which are normally global
diff --git a/src/nvim/change.c b/src/nvim/change.c
index 0f5081c94c..38bd591eca 100644
--- a/src/nvim/change.c
+++ b/src/nvim/change.c
@@ -828,6 +828,7 @@ int copy_indent(int size, char_u *src)
   int tab_pad;
   int ind_done;
   int round;
+  int ind_col;
 
   // Round 1: compute the number of characters needed for the indent
   // Round 2: copy the characters.
@@ -835,13 +836,15 @@ int copy_indent(int size, char_u *src)
     todo = size;
     ind_len = 0;
     ind_done = 0;
+    ind_col = 0;
     s = src;
 
     // Count/copy the usable portion of the source line.
     while (todo > 0 && ascii_iswhite(*s)) {
       if (*s == TAB) {
-        tab_pad = (int)curbuf->b_p_ts
-                  - (ind_done % (int)curbuf->b_p_ts);
+        tab_pad = tabstop_padding(ind_done,
+                                  curbuf->b_p_ts,
+                                  curbuf->b_p_vts_array);
 
         // Stop if this tab will overshoot the target.
         if (todo < tab_pad) {
@@ -849,9 +852,11 @@ int copy_indent(int size, char_u *src)
         }
         todo -= tab_pad;
         ind_done += tab_pad;
+        ind_col += tab_pad;
       } else {
         todo--;
         ind_done++;
+        ind_col++;
       }
       ind_len++;
 
@@ -862,11 +867,12 @@ int copy_indent(int size, char_u *src)
     }
 
     // Fill to next tabstop with a tab, if possible.
-    tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
+    tab_pad = tabstop_padding(ind_done, curbuf->b_p_ts, curbuf->b_p_vts_array);
 
     if ((todo >= tab_pad) && !curbuf->b_p_et) {
       todo -= tab_pad;
       ind_len++;
+      ind_col += tab_pad;
 
       if (p != NULL) {
         *p++ = TAB;
@@ -874,12 +880,20 @@ int copy_indent(int size, char_u *src)
     }
 
     // Add tabs required for indent.
-    while (todo >= (int)curbuf->b_p_ts && !curbuf->b_p_et) {
-      todo -= (int)curbuf->b_p_ts;
-      ind_len++;
-
-      if (p != NULL) {
-        *p++ = TAB;
+    if (!curbuf->b_p_et) {
+      for (;;) {
+        tab_pad = tabstop_padding(ind_col,
+                                  curbuf->b_p_ts,
+                                  curbuf->b_p_vts_array);
+        if (todo < tab_pad) {
+          break;
+        }
+        todo -= tab_pad;
+        ind_len++;
+        ind_col += tab_pad;
+        if (p != NULL) {
+          *p++ = TAB;
+        }
       }
     }
 
@@ -1029,7 +1043,9 @@ int open_line(
       || do_si
       ) {
     // count white space on current line
-    newindent = get_indent_str(saved_line, (int)curbuf->b_p_ts, false);
+    newindent = get_indent_str_vtab(saved_line,
+                                    curbuf->b_p_ts,
+                                    curbuf->b_p_vts_array, false);
     if (newindent == 0 && !(flags & OPENLINE_COM_LIST)) {
       newindent = second_line_indent;  // for ^^D command in insert mode
     }
@@ -1453,7 +1469,9 @@ int open_line(
         if (curbuf->b_p_ai
             || do_si
             ) {
-          newindent = get_indent_str(leader, (int)curbuf->b_p_ts, false);
+          newindent = get_indent_str_vtab(leader,
+                                          curbuf->b_p_ts,
+                                          curbuf->b_p_vts_array, false);
         }
 
         // Add the indent offset
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 5ad1fe0dfd..e2d844a351 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -744,8 +744,7 @@ int vim_strnsize(char_u *s, int len)
 /// @return Number of characters.
 #define RET_WIN_BUF_CHARTABSIZE(wp, buf, p, col) \
   if (*(p) == TAB && (!(wp)->w_p_list || wp->w_p_lcs_chars.tab1)) { \
-    const int ts = (int)(buf)->b_p_ts; \
-    return (ts - (int)(col % ts)); \
+    return tabstop_padding(col, (buf)->b_p_ts, (buf)->b_p_vts_array); \
   } else { \
     return ptr2cells(p); \
   }
@@ -1143,8 +1142,9 @@ static int win_nolbr_chartabsize(win_T *wp, char_u *s, colnr_T col, int *headp)
   int n;
 
   if ((*s == TAB) && (!wp->w_p_list || wp->w_p_lcs_chars.tab1)) {
-    n = (int)wp->w_buffer->b_p_ts;
-    return n - (col % n);
+    return tabstop_padding(col,
+                           wp->w_buffer->b_p_ts,
+                           wp->w_buffer->b_p_vts_array);
   }
   n = ptr2cells(s);
 
@@ -1211,6 +1211,7 @@ void getvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor,
   char_u *line;   // start of the line
   int incr;
   int head;
+  long *vts = wp->w_buffer->b_p_vts_array;
   int ts = (int)wp->w_buffer->b_p_ts;
   int c;
 
@@ -1251,7 +1252,7 @@ void getvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor,
 
       // A tab gets expanded, depending on the current column
       if (c == TAB) {
-        incr = ts - (vcol % ts);
+        incr = tabstop_padding(vcol, ts, vts);
       } else {
         // For utf-8, if the byte is >= 0x80, need to look at
         // further bytes to find the cell width.
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index b5d5d67e90..110494bb5c 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -597,7 +597,10 @@ static int insert_check(VimState *state)
     s->mincol = curwin->w_wcol;
     validate_cursor_col();
 
-    if (curwin->w_wcol < s->mincol - curbuf->b_p_ts
+    if (
+        curwin->w_wcol < s->mincol - tabstop_at(get_nolist_virtcol(),
+                                                curbuf->b_p_ts,
+                                                curbuf->b_p_vts_array)
         && curwin->w_wrow == curwin->w_winrow
         + curwin->w_height_inner - 1 - get_scrolloff_value(curwin)
         && (curwin->w_cursor.lnum != curwin->w_topline
@@ -8178,24 +8181,19 @@ static bool ins_bs(int c, int mode, int *inserted_space_p)
     /*
      * Handle deleting one 'shiftwidth' or 'softtabstop'.
      */
-    if (       mode == BACKSPACE_CHAR
-               && ((p_sta && in_indent)
-                   || (get_sts_value() != 0
-                       && curwin->w_cursor.col > 0
-                       && (*(get_cursor_pos_ptr() - 1) == TAB
-                           || (*(get_cursor_pos_ptr() - 1) == ' '
-                               && (!*inserted_space_p
-                                   || arrow_used)))))) {
-      int ts;
+    if (mode == BACKSPACE_CHAR
+        && ((p_sta && in_indent)
+            || ((get_sts_value() != 0
+                 || tabstop_count(curbuf->b_p_vsts_array))
+                && curwin->w_cursor.col > 0
+                && (*(get_cursor_pos_ptr() - 1) == TAB
+                    || (*(get_cursor_pos_ptr() - 1) == ' '
+                        && (!*inserted_space_p || arrow_used)))))) {
       colnr_T vcol;
       colnr_T want_vcol;
       colnr_T start_vcol;
 
-      *inserted_space_p = FALSE;
-      if (p_sta && in_indent)
-        ts = get_sw_value(curbuf);
-      else
-        ts = get_sts_value();
+      *inserted_space_p = false;
       // Compute the virtual column where we want to be.  Since
       // 'showbreak' may get in the way, need to get the last column of
       // the previous character.
@@ -8204,7 +8202,13 @@ static bool ins_bs(int c, int mode, int *inserted_space_p)
       dec_cursor();
       getvcol(curwin, &curwin->w_cursor, NULL, NULL, &want_vcol);
       inc_cursor();
-      want_vcol = (want_vcol / ts) * ts;
+      if (p_sta && in_indent) {
+        want_vcol = (want_vcol / curbuf->b_p_sw) * curbuf->b_p_sw;
+      } else {
+        want_vcol = tabstop_start(want_vcol,
+                                  curbuf->b_p_sts,
+                                  curbuf->b_p_vsts_array);
+      }
 
       // delete characters until we are at or before want_vcol
       while (vcol > want_vcol
@@ -8669,10 +8673,19 @@ static bool ins_tab(void)
     can_cindent = false;
   }
 
-  // When nothing special, insert TAB like a normal character
+  // When nothing special, insert TAB like a normal character.
   if (!curbuf->b_p_et
-      && !(p_sta && ind && curbuf->b_p_ts != get_sw_value(curbuf))
-      && get_sts_value() == 0) {
+      && !(
+          p_sta
+          && ind
+          // These five lines mean 'tabstop' != 'shiftwidth'
+          && ((tabstop_count(curbuf->b_p_vts_array) > 1)
+              || (tabstop_count(curbuf->b_p_vts_array) == 1
+                  && tabstop_first(curbuf->b_p_vts_array)
+                  != get_sw_value(curbuf))
+              || (tabstop_count(curbuf->b_p_vts_array) == 0
+                  && curbuf->b_p_ts != get_sw_value(curbuf))))
+      && tabstop_count(curbuf->b_p_vsts_array) == 0 && get_sts_value() == 0) {
     return true;
   }
 
@@ -8686,16 +8699,22 @@ static bool ins_tab(void)
   can_si_back = false;
   AppendToRedobuff("\t");
 
-  if (p_sta && ind) {  // insert tab in indent, use "shiftwidth"
-    temp = get_sw_value(curbuf);
-  } else if (curbuf->b_p_sts != 0) {  // use "softtabstop" when set
-    temp = get_sts_value();
-  } else {  // otherwise use "tabstop"
-    temp = (int)curbuf->b_p_ts;
+  if (p_sta && ind) {  // insert tab in indent, use 'shiftwidth'
+    temp = (int)curbuf->b_p_sw;
+    temp -= get_nolist_virtcol() % temp;
+  } else if (tabstop_count(curbuf->b_p_vsts_array) > 0
+             || curbuf->b_p_sts > 0) {
+    // use 'softtabstop' when set
+    temp = tabstop_padding(get_nolist_virtcol(),
+                           curbuf->b_p_sts,
+                           curbuf->b_p_vsts_array);
+  } else {
+    // otherwise use 'tabstop'
+    temp = tabstop_padding(get_nolist_virtcol(),
+                           curbuf->b_p_ts,
+                           curbuf->b_p_vts_array);
   }
 
-  temp -= get_nolist_virtcol() % temp;
-
   /*
    * Insert the first space with ins_char().	It will delete one char in
    * replace mode.  Insert the rest with ins_str(); it will not delete any
@@ -8716,7 +8735,9 @@ static bool ins_tab(void)
   /*
    * When 'expandtab' not set: Replace spaces by TABs where possible.
    */
-  if (!curbuf->b_p_et && (get_sts_value() || (p_sta && ind))) {
+  if (!curbuf->b_p_et && (tabstop_count(curbuf->b_p_vsts_array) > 0
+                          || get_sts_value() > 0
+                          || (p_sta && ind))) {
     char_u          *ptr;
     char_u          *saved_line = NULL;         // init for GCC
     pos_T pos;
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 650b4e3882..eeaaf7dbd1 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4312,6 +4312,7 @@ static void f_has(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     "title",
     "user-commands",        // was accidentally included in 5.4
     "user_commands",
+    "vartabs",
     "vertsplit",
     "virtualedit",
     "visual",
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 854faf5377..d679a3c8f8 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -712,14 +712,15 @@ void ex_retab(exarg_T *eap)
   long len;
   long col;
   long vcol;
-  long start_col = 0;                   /* For start of white-space string */
-  long start_vcol = 0;                  /* For start of white-space string */
-  int temp;
+  long start_col = 0;                   // For start of white-space string
+  long start_vcol = 0;                  // For start of white-space string
   long old_len;
   char_u      *ptr;
-  char_u      *new_line = (char_u *)1;      /* init to non-NULL */
-  int did_undo;                         /* called u_save for current line */
-  int new_ts;
+  char_u      *new_line = (char_u *)1;  // init to non-NULL
+  int did_undo;                         // called u_save for current line
+  long *new_ts = 0;
+  char_u *new_ts_str;  // string value of tab argument
+
   int save_list;
   linenr_T first_line = 0;              /* first changed line */
   linenr_T last_line = 0;               /* last changed line */
@@ -727,14 +728,23 @@ void ex_retab(exarg_T *eap)
   save_list = curwin->w_p_list;
   curwin->w_p_list = 0;             /* don't want list mode here */
 
-  new_ts = getdigits_int(&(eap->arg), false, -1);
-  if (new_ts < 0) {
-    EMSG(_(e_positive));
+  new_ts_str = eap->arg;
+  if (!tabstop_set(eap->arg, &new_ts)) {
     return;
   }
-  if (new_ts == 0)
-    new_ts = curbuf->b_p_ts;
-  for (lnum = eap->line1; !got_int && lnum <= eap->line2; ++lnum) {
+  while (ascii_isdigit(*(eap->arg)) || *(eap->arg) == ',') {
+    (eap->arg)++;
+  }
+
+  // This ensures that either new_ts and new_ts_str are freshly allocated,
+  // or new_ts points to an existing array and new_ts_str is null.
+  if (new_ts == 0) {
+    new_ts = curbuf->b_p_vts_array;
+    new_ts_str = NULL;
+  } else {
+    new_ts_str = vim_strnsave(new_ts_str, eap->arg - new_ts_str);
+  }
+  for (lnum = eap->line1; !got_int && lnum <= eap->line2; lnum++) {
     ptr = ml_get(lnum);
     col = 0;
     vcol = 0;
@@ -758,13 +768,14 @@ void ex_retab(exarg_T *eap)
           len = num_spaces = vcol - start_vcol;
           num_tabs = 0;
           if (!curbuf->b_p_et) {
-            temp = new_ts - (start_vcol % new_ts);
-            if (num_spaces >= temp) {
-              num_spaces -= temp;
-              num_tabs++;
-            }
-            num_tabs += num_spaces / new_ts;
-            num_spaces -= (num_spaces / new_ts) * new_ts;
+            int t, s;
+
+            tabstop_fromto(start_vcol, vcol,
+                           tabstop_count(new_ts) ? 0 : curbuf->b_p_ts,
+                           new_ts,
+                           &t, &s);
+            num_tabs = t;
+            num_spaces = s;
           }
           if (curbuf->b_p_et || got_tab
               || (num_spaces + num_tabs < len)) {
@@ -817,15 +828,42 @@ void ex_retab(exarg_T *eap)
   if (got_int)
     EMSG(_(e_interr));
 
-  if (curbuf->b_p_ts != new_ts)
+  // If a single value was given then it can be considered equal to
+  // either the value of 'tabstop' or the value of 'vartabstop'.
+  if (tabstop_count(curbuf->b_p_vts_array) == 0
+      && tabstop_count(new_ts) == 1
+      && curbuf->b_p_ts == tabstop_first(new_ts)) {
+    // not changed
+  } else if (tabstop_count(curbuf->b_p_vts_array) > 0
+             && tabstop_eq(curbuf->b_p_vts_array, new_ts)) {
+    // not changed
+  } else {
     redraw_curbuf_later(NOT_VALID);
+  }
   if (first_line != 0) {
     changed_lines(first_line, 0, last_line + 1, 0L, true);
   }
 
   curwin->w_p_list = save_list;         /* restore 'list' */
 
-  curbuf->b_p_ts = new_ts;
+  if (new_ts_str != NULL) {  // set the new tabstop
+    // If 'vartabstop' is in use or if the value given to retab has more
+    // than one tabstop then update 'vartabstop'.
+    long *old_vts_ary = curbuf->b_p_vts_array;
+
+    if (tabstop_count(old_vts_ary) > 0 || tabstop_count(new_ts) > 1) {
+      set_string_option_direct("vts", -1, new_ts_str,
+                               OPT_FREE | OPT_LOCAL, 0);
+      xfree(new_ts_str);
+      curbuf->b_p_vts_array = new_ts;
+      xfree(old_vts_ary);
+    } else {
+      // 'vartabstop' wasn't in use and a single value was given to
+      // retab then update 'tabstop'.
+      curbuf->b_p_ts = tabstop_first(new_ts);
+      xfree(new_ts);
+    }
+  }
   coladvance(curwin->w_curswant);
 
   u_clearline();
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index 4ec949759c..abba5425e7 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -890,8 +890,11 @@ static colnr_T hardcopy_line(prt_settings_T *psettings, int page_line, prt_pos_T
      * Appropriately expand any tabs to spaces.
      */
     if (line[col] == TAB || tab_spaces != 0) {
-      if (tab_spaces == 0)
-        tab_spaces = (int)(curbuf->b_p_ts - (print_pos % curbuf->b_p_ts));
+      if (tab_spaces == 0) {
+        tab_spaces = tabstop_padding(print_pos,
+                                     curbuf->b_p_ts,
+                                     curbuf->b_p_vts_array);
+      }
 
       while (tab_spaces > 0) {
         need_break = mch_print_text_out((char_u *)" ", 1);
diff --git a/src/nvim/indent.c b/src/nvim/indent.c
index fae971b3b3..92ecbe160b 100644
--- a/src/nvim/indent.c
+++ b/src/nvim/indent.c
@@ -34,14 +34,20 @@
 // Count the size (in window cells) of the indent in the current line.
 int get_indent(void)
 {
-  return get_indent_str(get_cursor_line_ptr(), (int)curbuf->b_p_ts, false);
+  return get_indent_str_vtab(get_cursor_line_ptr(),
+                             curbuf->b_p_ts,
+                             curbuf->b_p_vts_array,
+                             false);
 }
 
 
 // Count the size (in window cells) of the indent in line "lnum".
 int get_indent_lnum(linenr_T lnum)
 {
-  return get_indent_str(ml_get(lnum), (int)curbuf->b_p_ts, false);
+  return get_indent_str_vtab(ml_get(lnum),
+                             curbuf->b_p_ts,
+                             curbuf->b_p_vts_array,
+                             false);
 }
 
 
@@ -49,7 +55,10 @@ int get_indent_lnum(linenr_T lnum)
 // "buf".
 int get_indent_buf(buf_T *buf, linenr_T lnum)
 {
-  return get_indent_str(ml_get_buf(buf, lnum, false), (int)buf->b_p_ts, false);
+  return get_indent_str_vtab(ml_get_buf(buf, lnum, false),
+                             curbuf->b_p_ts,
+                             buf->b_p_vts_array,
+                             false);
 }
 
 
@@ -82,6 +91,30 @@ int get_indent_str(const char_u *ptr, int ts, int list)
   return count;
 }
 
+// Count the size (in window cells) of the indent in line "ptr", using
+// variable tabstops.
+// if "list" is true, count only screen size for tabs.
+int get_indent_str_vtab(const char_u *ptr, long ts, long *vts, bool list)
+{
+  int count = 0;
+
+  for (; *ptr; ptr++) {
+    if (*ptr == TAB) {  // count a tab for what it is worth
+      if (!list || curwin->w_p_lcs_chars.tab1) {
+        count += tabstop_padding(count, ts, vts);
+      } else {
+        // In list mode, when tab is not set, count screen char width
+        // for Tab, displays: ^I
+        count += ptr2cells(ptr);
+      }
+    } else if (*ptr == ' ') {
+      count++;  // count a space for one
+    } else {
+      break;
+    }
+  }
+  return count;
+}
 
 // Set the indent of the current line.
 // Leaves the cursor on the first non-blank in the line.
@@ -104,6 +137,7 @@ int set_indent(int size, int flags)
   int line_len;
   int doit = false;
   int ind_done = 0;  // Measured in spaces.
+  int ind_col = 0;
   int tab_pad;
   int retval = false;
 
@@ -130,7 +164,9 @@ int set_indent(int size, int flags)
       // Count as many characters as we can use.
       while (todo > 0 && ascii_iswhite(*p)) {
         if (*p == TAB) {
-          tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
+          tab_pad = tabstop_padding(ind_done,
+                                    curbuf->b_p_ts,
+                                    curbuf->b_p_vts_array);
 
           // Stop if this tab will overshoot the target.
           if (todo < tab_pad) {
@@ -147,35 +183,41 @@ int set_indent(int size, int flags)
         p++;
       }
 
+      // These diverge from this point.
+      ind_col = ind_done;
       // Set initial number of whitespace chars to copy if we are
       // preserving indent but expandtab is set.
       if (curbuf->b_p_et) {
         orig_char_len = ind_len;
       }
-
       // Fill to next tabstop with a tab, if possible.
-      tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
-
+      tab_pad = tabstop_padding(ind_done,
+                                curbuf->b_p_ts,
+                                curbuf->b_p_vts_array);
       if ((todo >= tab_pad) && (orig_char_len == -1)) {
         doit = true;
         todo -= tab_pad;
         ind_len++;
 
         // ind_done += tab_pad;
+        ind_col += tab_pad;
       }
     }
 
     // Count tabs required for indent.
-    while (todo >= (int)curbuf->b_p_ts) {
+    for (;;) {
+      tab_pad = tabstop_padding(ind_col, curbuf->b_p_ts, curbuf->b_p_vts_array);
+      if (todo < tab_pad) {
+        break;
+      }
       if (*p != TAB) {
         doit = true;
       } else {
         p++;
       }
-      todo -= (int)curbuf->b_p_ts;
+      todo -= tab_pad;
       ind_len++;
-
-      // ind_done += (int)curbuf->b_p_ts;
+      ind_col += tab_pad;
     }
   }
 
@@ -255,7 +297,9 @@ int set_indent(int size, int flags)
 
       while (todo > 0 && ascii_iswhite(*p)) {
         if (*p == TAB) {
-          tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
+          tab_pad = tabstop_padding(ind_done,
+                                    curbuf->b_p_ts,
+                                    curbuf->b_p_vts_array);
 
           // Stop if this tab will overshoot the target.
           if (todo < tab_pad) {
@@ -272,18 +316,28 @@ int set_indent(int size, int flags)
       }
 
       // Fill to next tabstop with a tab, if possible.
-      tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
+      tab_pad = tabstop_padding(ind_done,
+                                curbuf->b_p_ts,
+                                curbuf->b_p_vts_array);
 
       if (todo >= tab_pad) {
         *s++ = TAB;
         todo -= tab_pad;
+        ind_done += tab_pad;
       }
       p = skipwhite(p);
     }
 
-    while (todo >= (int)curbuf->b_p_ts) {
+    for (;;) {
+      tab_pad = tabstop_padding(ind_done,
+                                curbuf->b_p_ts,
+                                curbuf->b_p_vts_array);
+      if (todo < tab_pad) {
+        break;
+      }
       *s++ = TAB;
-      todo -= (int)curbuf->b_p_ts;
+      todo -= tab_pad;
+      ind_done += tab_pad;
     }
   }
 
@@ -387,6 +441,7 @@ int get_breakindent_win(win_T *wp, const char_u *line)
   static long prev_ts = 0;  // Cached tabstop value.
   static const char_u *prev_line = NULL;  // cached pointer to line.
   static varnumber_T prev_tick = 0;  // Changedtick of cached value.
+  static long *prev_vts = NULL;    // Cached vartabs values.
   int bri = 0;
   // window width minus window margin space, i.e. what rests for text
   const int eff_wwidth = wp->w_width_inner
@@ -396,11 +451,16 @@ int get_breakindent_win(win_T *wp, const char_u *line)
 
   // used cached indent, unless pointer or 'tabstop' changed
   if (prev_line != line || prev_ts != wp->w_buffer->b_p_ts
-      || prev_tick != buf_get_changedtick(wp->w_buffer)) {
+      || prev_tick != buf_get_changedtick(wp->w_buffer)
+      || prev_vts != wp->w_buffer->b_p_vts_array) {
     prev_line = line;
     prev_ts = wp->w_buffer->b_p_ts;
     prev_tick = buf_get_changedtick(wp->w_buffer);
-    prev_indent = get_indent_str(line, (int)wp->w_buffer->b_p_ts, wp->w_p_list);
+    prev_vts = wp->w_buffer->b_p_vts_array;
+    prev_indent = get_indent_str_vtab(line,
+                                      wp->w_buffer->b_p_ts,
+                                      wp->w_buffer->b_p_vts_array,
+                                      wp->w_p_list);
   }
   bri = prev_indent + wp->w_briopt_shift;
 
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 71cb345878..cdac4b602a 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -1758,7 +1758,9 @@ void msg_prt_line(char_u *s, int list)
       c = *s++;
       if (c == TAB && (!list || curwin->w_p_lcs_chars.tab1)) {
         // tab amount depends on current column
-        n_extra = curbuf->b_p_ts - col % curbuf->b_p_ts - 1;
+        n_extra = tabstop_padding(col,
+                                  curbuf->b_p_ts,
+                                  curbuf->b_p_vts_array) - 1;
         if (!list) {
           c = ' ';
           c_extra = ' ';
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 0ff427c261..ffa3e3d55f 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -333,7 +333,8 @@ static void shift_block(oparg_T *oap, int amount)
   char_u *newp;
   const int oldcol = curwin->w_cursor.col;
   const int p_sw = get_sw_value(curbuf);
-  const int p_ts = (int)curbuf->b_p_ts;
+  const long p_ts = curbuf->b_p_ts;
+  long *p_vts = curbuf->b_p_vts_array;
   struct block_def bd;
   int incr;
   int i = 0, j = 0;
@@ -383,12 +384,11 @@ static void shift_block(oparg_T *oap, int amount)
     }
     /* OK, now total=all the VWS reqd, and textstart points at the 1st
      * non-ws char in the block. */
-    if (!curbuf->b_p_et)
-      i = ((ws_vcol % p_ts) + total) / p_ts;       /* number of tabs */
-    if (i)
-      j = ((ws_vcol % p_ts) + total) % p_ts;       /* number of spp */
-    else
+    if (!curbuf->b_p_et) {
+      tabstop_fromto(ws_vcol, ws_vcol + total, p_ts, p_vts, &i, &j);
+    } else {
       j = total;
+    }
 
     // if we're splitting a TAB, allow for it
     int col_pre = bd.pre_whitesp_c - (bd.startspaces != 0);
@@ -3061,14 +3061,17 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
     if (gchar_cursor() == TAB) {
       /* Don't need to insert spaces when "p" on the last position of a
        * tab or "P" on the first position. */
+      int viscol = getviscol();
       if (dir == FORWARD
-          ? (int)curwin->w_cursor.coladd < curbuf->b_p_ts - 1
-          : curwin->w_cursor.coladd > 0)
-        coladvance_force(getviscol());
-      else
+          ? tabstop_padding(viscol, curbuf->b_p_ts, curbuf->b_p_vts_array) != 1
+          : curwin->w_cursor.coladd > 0) {
+        coladvance_force(viscol);
+      } else {
         curwin->w_cursor.coladd = 0;
-    } else if (curwin->w_cursor.coladd > 0 || gchar_cursor() == NUL)
+      }
+    } else if (curwin->w_cursor.coladd > 0 || gchar_cursor() == NUL) {
       coladvance_force(getviscol() + (dir == FORWARD));
+    }
   }
 
   lnum = curwin->w_cursor.lnum;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 949558894f..ad4d12ff7b 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -180,6 +180,8 @@ static long p_ts;
 static long p_tw;
 static int p_udf;
 static long p_wm;
+static char_u *p_vsts;
+static char_u *p_vts;
 static char_u   *p_keymap;
 
 // Saved values for when 'bin' is set.
@@ -194,6 +196,7 @@ static int p_et_nopaste;
 static long p_sts_nopaste;
 static long p_tw_nopaste;
 static long p_wm_nopaste;
+static char_u *p_vsts_nopaste;
 
 typedef struct vimoption {
   char        *fullname;        // full option name
@@ -1998,6 +2001,8 @@ static void didset_options2(void)
 
   // Parse default for 'wildmode'.
   check_opt_wim();
+  tabstop_set(curbuf->b_p_vsts, &curbuf->b_p_vsts_array);
+  tabstop_set(curbuf->b_p_vts,  &curbuf->b_p_vts_array);
 }
 
 /// Check for string options that are NULL (normally only termcap options).
@@ -2064,6 +2069,8 @@ void check_buf_options(buf_T *buf)
   check_string_option(&buf->b_p_lw);
   check_string_option(&buf->b_p_bkc);
   check_string_option(&buf->b_p_menc);
+  check_string_option(&buf->b_p_vsts);
+  check_string_option(&buf->b_p_vts);
 }
 
 /// Free the string allocated for an option.
@@ -3110,6 +3117,69 @@ ambw_end:
     if (opt_strings_flags(p_tpf, p_tpf_values, &tpf_flags, true) != OK) {
       errmsg = e_invarg;
     }
+  } else if (varp == &(curbuf->b_p_vsts)) {  // 'varsofttabstop'
+    char_u *cp;
+
+    if (!(*varp)[0] || ((*varp)[0] == '0' && !(*varp)[1])) {
+      if (curbuf->b_p_vsts_array) {
+        xfree(curbuf->b_p_vsts_array);
+        curbuf->b_p_vsts_array = 0;
+      }
+    } else {
+      for (cp = *varp; *cp; cp++) {
+        if (ascii_isdigit(*cp)) {
+          continue;
+        }
+        if