diff --git a/src/nvim/cursor.c b/src/nvim/cursor.c
index d8a63c1d7b..6c0a81838f 100644
--- a/src/nvim/cursor.c
+++ b/src/nvim/cursor.c
@@ -141,17 +141,18 @@ static int coladvance2(pos_T *pos, bool addspaces, bool finetune, colnr_T wcol_a
       }
     }
 
-    chartabsize_T cts;
-    init_chartabsize_arg(&cts, curwin, pos->lnum, 0, line, line);
-    while (cts.cts_vcol <= wcol && *cts.cts_ptr != NUL) {
-      // Count a tab for what it's worth (if list mode not on)
-      csize = win_lbr_chartabsize(&cts, &head);
-      MB_PTR_ADV(cts.cts_ptr);
-      cts.cts_vcol += csize;
+    CharsizeArg arg;
+    CSType cstype = init_charsize_arg(&arg, curwin, pos->lnum, line);
+    StrCharInfo ci = utf_ptr2StrCharInfo(line);
+    col = 0;
+    while (col <= wcol && *ci.ptr != NUL) {
+      CharSize cs = win_charsize(cstype, col, ci.ptr, ci.chr.value, &arg);
+      csize = cs.width;
+      head = cs.head;
+      col += cs.width;
+      ci = utfc_next(ci);
     }
-    col = cts.cts_vcol;
-    idx = (int)(cts.cts_ptr - line);
-    clear_chartabsize_arg(&cts);
+    idx = (int)(ci.ptr - line);
 
     // Handle all the special cases.  The virtual_active() check
     // is needed to ensure that a virtual position off the end of
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index cc0fa441ca..616fd24460 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -1336,30 +1336,30 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
 
   if (start_col > 0 && col_rows == 0) {
     char *prev_ptr = ptr;
-    chartabsize_T cts;
-    int charsize = 0;
-    int head = 0;
+    CharSize cs = { 0 };
 
-    init_chartabsize_arg(&cts, wp, lnum, wlv.vcol, line, ptr);
-    cts.cts_max_head_vcol = start_col;
-    while (cts.cts_vcol < start_col && *cts.cts_ptr != NUL) {
-      head = 0;
-      charsize = win_lbr_chartabsize(&cts, &head);
-      cts.cts_vcol += charsize;
-      prev_ptr = cts.cts_ptr;
-      MB_PTR_ADV(cts.cts_ptr);
+    CharsizeArg arg;
+    CSType cstype = init_charsize_arg(&arg, wp, lnum, line);
+    arg.max_head_vcol = start_col;
+    int vcol = wlv.vcol;
+    StrCharInfo ci = utf_ptr2StrCharInfo(ptr);
+    while (vcol < start_col && *ci.ptr != NUL) {
+      cs = win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg);
+      vcol += cs.width;
+      prev_ptr = ci.ptr;
+      ci = utfc_next(ci);
       if (wp->w_p_list) {
-        in_multispace = *prev_ptr == ' ' && (*cts.cts_ptr == ' '
+        in_multispace = *prev_ptr == ' ' && (*ci.ptr == ' '
                                              || (prev_ptr > line && prev_ptr[-1] == ' '));
         if (!in_multispace) {
           multispace_pos = 0;
-        } else if (cts.cts_ptr >= line + leadcol
+        } else if (ci.ptr >= line + leadcol
                    && wp->w_p_lcs_chars.multispace != NULL) {
           multispace_pos++;
           if (wp->w_p_lcs_chars.multispace[multispace_pos] == NUL) {
             multispace_pos = 0;
           }
-        } else if (cts.cts_ptr < line + leadcol
+        } else if (ci.ptr < line + leadcol
                    && wp->w_p_lcs_chars.leadmultispace != NULL) {
           multispace_pos++;
           if (wp->w_p_lcs_chars.leadmultispace[multispace_pos] == NUL) {
@@ -1368,9 +1368,10 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
         }
       }
     }
-    wlv.vcol = cts.cts_vcol;
-    ptr = cts.cts_ptr;
-    clear_chartabsize_arg(&cts);
+    wlv.vcol = vcol;
+    ptr = ci.ptr;
+    int charsize = cs.width;
+    int head = cs.head;
 
     // When:
     // - 'cuc' is set, or
@@ -2081,12 +2082,12 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, int col_rows, s
             && vim_isbreak(mb_c) && !vim_isbreak((uint8_t)(*ptr))) {
           int mb_off = utf_head_off(line, ptr - 1);
           char *p = ptr - (mb_off + 1);
-          chartabsize_T cts;
 
+          CharsizeArg arg;
           // lnum == 0, do not want virtual text to be counted here
-          init_chartabsize_arg(&cts, wp, 0, wlv.vcol, line, p);
-          wlv.n_extra = win_lbr_chartabsize(&cts, NULL) - 1;
-          clear_chartabsize_arg(&cts);
+          CSType cstype = init_charsize_arg(&arg, wp, 0, line);
+          wlv.n_extra = win_charsize(cstype, wlv.vcol, p, utf_ptr2CharInfo(p).value,
+                                     &arg).width - 1;
 
           if (on_last_col && mb_c != TAB) {
             // Do not continue search/match highlighting over the
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 6f05ba5905..0e320056bb 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -1679,33 +1679,37 @@ void change_indent(int type, int amount, int round, int replaced, bool call_chan
   } else {
     // Compute the screen column where the cursor should be.
     vcol = get_indent() - vcol;
-    curwin->w_virtcol = (colnr_T)((vcol < 0) ? 0 : vcol);
+    int const end_vcol = (colnr_T)((vcol < 0) ? 0 : vcol);
+    curwin->w_virtcol = end_vcol;
 
     // Advance the cursor until we reach the right screen column.
-    int last_vcol = 0;
-    char *ptr = get_cursor_line_ptr();
-    chartabsize_T cts;
-    init_chartabsize_arg(&cts, curwin, 0, 0, ptr, ptr);
-    while (cts.cts_vcol <= (int)curwin->w_virtcol) {
-      last_vcol = cts.cts_vcol;
-      if (cts.cts_vcol > 0) {
-        MB_PTR_ADV(cts.cts_ptr);
+    new_cursor_col = 0;
+    char *const line = get_cursor_line_ptr();
+    vcol = 0;
+    if (*line != NUL) {
+      CharsizeArg arg;
+      CSType cstype = init_charsize_arg(&arg, curwin, 0, line);
+      StrCharInfo ci = utf_ptr2StrCharInfo(line);
+      while (true) {
+        int next_vcol = vcol + win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+        if (next_vcol > end_vcol) {
+          break;
+        }
+        vcol = next_vcol;
+        ci = utfc_next(ci);
+        if (*ci.ptr == NUL) {
+          break;
+        }
       }
-      if (*cts.cts_ptr == NUL) {
-        break;
-      }
-      cts.cts_vcol += lbr_chartabsize(&cts);
+      new_cursor_col = (int)(ci.ptr - line);
     }
-    vcol = last_vcol;
-    new_cursor_col = (int)(cts.cts_ptr - cts.cts_line);
-    clear_chartabsize_arg(&cts);
 
     // May need to insert spaces to be able to position the cursor on
     // the right screen column.
     if (vcol != (int)curwin->w_virtcol) {
       curwin->w_cursor.col = (colnr_T)new_cursor_col;
       size_t i = (size_t)(curwin->w_virtcol - vcol);
-      ptr = xmallocz(i);
+      char *ptr = xmallocz(i);
       memset(ptr, ' ', i);
       new_cursor_col += (int)i;
       ins_str(ptr);
@@ -4347,14 +4351,16 @@ static bool ins_tab(void)
     getvcol(curwin, cursor, &want_vcol, NULL, NULL);
 
     char *tab = "\t";
-    chartabsize_T cts;
-    init_chartabsize_arg(&cts, curwin, 0, vcol, tab, tab);
+    int32_t tab_v = (uint8_t)(*tab);
+
+    CharsizeArg arg;
+    CSType cstype = init_charsize_arg(&arg, curwin, 0, tab);
 
     // Use as many TABs as possible.  Beware of 'breakindent', 'showbreak'
     // and 'linebreak' adding extra virtual columns.
     while (ascii_iswhite(*ptr)) {
-      int i = lbr_chartabsize(&cts);
-      if (cts.cts_vcol + i > want_vcol) {
+      int i = win_charsize(cstype, vcol, tab, tab_v, &arg).width;
+      if (vcol + i > want_vcol) {
         break;
       }
       if (*ptr != TAB) {
@@ -4369,23 +4375,18 @@ static bool ins_tab(void)
       }
       fpos.col++;
       ptr++;
-      cts.cts_vcol += i;
+      vcol += i;
     }
-    vcol = cts.cts_vcol;
-    clear_chartabsize_arg(&cts);
 
     if (change_col >= 0) {
       int repl_off = 0;
       // Skip over the spaces we need.
-      init_chartabsize_arg(&cts, curwin, 0, vcol, ptr, ptr);
-      while (cts.cts_vcol < want_vcol && *cts.cts_ptr == ' ') {
-        cts.cts_vcol += lbr_chartabsize(&cts);
-        cts.cts_ptr++;
+      cstype = init_charsize_arg(&arg, curwin, 0, ptr);
+      while (vcol < want_vcol && *ptr == ' ') {
+        vcol += win_charsize(cstype, vcol, ptr, (uint8_t)(' '), &arg).width;
+        ptr++;
         repl_off++;
       }
-      ptr = cts.cts_ptr;
-      vcol = cts.cts_vcol;
-      clear_chartabsize_arg(&cts);
 
       if (vcol > want_vcol) {
         // Must have a char with 'showbreak' just before it.
@@ -4556,8 +4557,6 @@ static int ins_digraph(void)
 // Returns the char to be inserted, or NUL if none found.
 int ins_copychar(linenr_T lnum)
 {
-  char *ptr;
-
   if (lnum < 1 || lnum > curbuf->b_ml.ml_line_count) {
     vim_beep(BO_COPY);
     return NUL;
@@ -4565,24 +4564,22 @@ int ins_copychar(linenr_T lnum)
 
   // try to advance to the cursor column
   validate_virtcol();
+  int const end_vcol = curwin->w_virtcol;
   char *line = ml_get(lnum);
-  char *prev_ptr = line;
 
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, curwin, lnum, 0, line, line);
-  while (cts.cts_vcol < curwin->w_virtcol && *cts.cts_ptr != NUL) {
-    prev_ptr = cts.cts_ptr;
-    cts.cts_vcol += lbr_chartabsize_adv(&cts);
+  CharsizeArg arg;
+  CSType cstype = init_charsize_arg(&arg, curwin, lnum, line);
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  int vcol = 0;
+  while (vcol < end_vcol && *ci.ptr != NUL) {
+    vcol += win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+    if (vcol > end_vcol) {
+      break;
+    }
+    ci = utfc_next(ci);
   }
 
-  if (cts.cts_vcol > curwin->w_virtcol) {
-    ptr = prev_ptr;
-  } else {
-    ptr = cts.cts_ptr;
-  }
-  clear_chartabsize_arg(&cts);
-
-  int c = utf_ptr2char(ptr);
+  int c = ci.chr.value < 0 ? (uint8_t)(*ci.ptr) : ci.chr.value;
   if (c == NUL) {
     vim_beep(BO_COPY);
   }
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index 23937a6bb5..6515cc84da 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -2502,20 +2502,22 @@ static int vgetorpeek(bool advance)
               // we are expecting to truncate the trailing
               // white-space, so find the last non-white
               // character -- webb
-              if (did_ai
-                  && *skipwhite(get_cursor_line_ptr() + curwin->w_cursor.col) == NUL) {
+              if (did_ai && *skipwhite(get_cursor_line_ptr() + curwin->w_cursor.col) == NUL) {
                 curwin->w_wcol = 0;
                 ptr = get_cursor_line_ptr();
-                chartabsize_T cts;
-                init_chartabsize_arg(&cts, curwin, curwin->w_cursor.lnum, 0, ptr, ptr);
-                while (cts.cts_ptr < ptr + curwin->w_cursor.col) {
-                  if (!ascii_iswhite(*cts.cts_ptr)) {
-                    curwin->w_wcol = cts.cts_vcol;
+                char *endptr = ptr + curwin->w_cursor.col;
+
+                CharsizeArg arg;
+                CSType cstype = init_charsize_arg(&arg, curwin, curwin->w_cursor.lnum, ptr);
+                StrCharInfo ci = utf_ptr2StrCharInfo(ptr);
+                int vcol = 0;
+                while (ci.ptr < endptr) {
+                  if (!ascii_iswhite(ci.chr.value)) {
+                    curwin->w_wcol = vcol;
                   }
-                  cts.cts_vcol += lbr_chartabsize(&cts);
-                  cts.cts_ptr += utfc_ptr2len(cts.cts_ptr);
+                  vcol += win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+                  ci = utfc_next(ci);
                 }
-                clear_chartabsize_arg(&cts);
 
                 curwin->w_wrow = curwin->w_cline_row
                                  + curwin->w_wcol / curwin->w_width_inner;
diff --git a/src/nvim/indent.c b/src/nvim/indent.c
index 080f6f986a..4899a025e5 100644
--- a/src/nvim/indent.c
+++ b/src/nvim/indent.c
@@ -1246,18 +1246,19 @@ int get_lisp_indent(void)
       curwin->w_cursor.col = pos->col;
       colnr_T col = pos->col;
 
-      char *that = get_cursor_line_ptr();
+      char *line = get_cursor_line_ptr();
 
-      char *line = that;
-      chartabsize_T cts;
-      init_chartabsize_arg(&cts, curwin, pos->lnum, 0, line, line);
-      while (*cts.cts_ptr != NUL && col > 0) {
-        cts.cts_vcol += lbr_chartabsize_adv(&cts);
+      CharsizeArg arg;
+      CSType cstype = init_charsize_arg(&arg, curwin, pos->lnum, line);
+
+      StrCharInfo sci = utf_ptr2StrCharInfo(line);
+      amount = 0;
+      while (*sci.ptr != NUL && col > 0) {
+        amount += win_charsize(cstype, amount, sci.ptr, sci.chr.value, &arg).width;
+        sci = utfc_next(sci);
         col--;
       }
-      amount = cts.cts_vcol;
-      that = cts.cts_ptr;
-      clear_chartabsize_arg(&cts);
+      char *that = sci.ptr;
 
       // Some keywords require "body" indenting rules (the
       // non-standard-lisp ones are Scheme special forms):
@@ -1272,15 +1273,10 @@ int get_lisp_indent(void)
         }
         colnr_T firsttry = amount;
 
-        init_chartabsize_arg(&cts, curwin, (colnr_T)(that - line),
-                             amount, line, that);
-        while (ascii_iswhite(*cts.cts_ptr)) {
-          cts.cts_vcol += lbr_chartabsize(&cts);
-          cts.cts_ptr++;
+        while (ascii_iswhite(*that)) {
+          amount += win_charsize(cstype, amount, that, (uint8_t)(*that), &arg).width;
+          that++;
         }
-        that = cts.cts_ptr;
-        amount = cts.cts_vcol;
-        clear_chartabsize_arg(&cts);
 
         if (*that && (*that != ';')) {
           // Not a comment line.
@@ -1292,37 +1288,38 @@ int get_lisp_indent(void)
 
           parencount = 0;
 
-          init_chartabsize_arg(&cts, curwin,
-                               (colnr_T)(that - line), amount, line, that);
-          if (((*that != '"') && (*that != '\'') && (*that != '#')
-               && (((uint8_t)(*that) < '0') || ((uint8_t)(*that) > '9')))) {
+          CharInfo ci = utf_ptr2CharInfo(that);
+          if (((ci.value != '"') && (ci.value != '\'') && (ci.value != '#')
+               && ((ci.value < '0') || (ci.value > '9')))) {
             int quotecount = 0;
-            while (*cts.cts_ptr
-                   && (!ascii_iswhite(*cts.cts_ptr) || quotecount || parencount)) {
-              if (*cts.cts_ptr == '"') {
+            while (*that && (!ascii_iswhite(ci.value) || quotecount || parencount)) {
+              if (ci.value == '"') {
                 quotecount = !quotecount;
               }
-              if (((*cts.cts_ptr == '(') || (*cts.cts_ptr == '[')) && !quotecount) {
+              if (((ci.value == '(') || (ci.value == '[')) && !quotecount) {
                 parencount++;
               }
-              if (((*cts.cts_ptr == ')') || (*cts.cts_ptr == ']')) && !quotecount) {
+              if (((ci.value == ')') || (ci.value == ']')) && !quotecount) {
                 parencount--;
               }
-              if ((*cts.cts_ptr == '\\') && (*(cts.cts_ptr + 1) != NUL)) {
-                cts.cts_vcol += lbr_chartabsize_adv(&cts);
+              if ((ci.value == '\\') && (*(that + 1) != NUL)) {
+                amount += win_charsize(cstype, amount, that, ci.value, &arg).width;
+                StrCharInfo next_sci = utfc_next((StrCharInfo){ that, ci });
+                that = next_sci.ptr;
+                ci = next_sci.chr;
               }
 
-              cts.cts_vcol += lbr_chartabsize_adv(&cts);
+              amount += win_charsize(cstype, amount, that, ci.value, &arg).width;
+              StrCharInfo next_sci = utfc_next((StrCharInfo){ that, ci });
+              that = next_sci.ptr;
+              ci = next_sci.chr;
             }
           }
 
-          while (ascii_iswhite(*cts.cts_ptr)) {
-            cts.cts_vcol += lbr_chartabsize(&cts);
-            cts.cts_ptr++;
+          while (ascii_iswhite(*that)) {
+            amount += win_charsize(cstype, amount, that, (uint8_t)(*that), &arg).width;
+            that++;
           }
-          that = cts.cts_ptr;
-          amount = cts.cts_vcol;
-          clear_chartabsize_arg(&cts);
 
           if (!*that || (*that == ';')) {
             amount = firsttry;
diff --git a/src/nvim/mbyte.h b/src/nvim/mbyte.h
index 68acc5075e..be632ee834 100644
--- a/src/nvim/mbyte.h
+++ b/src/nvim/mbyte.h
@@ -110,3 +110,11 @@ static inline StrCharInfo utfc_next(StrCharInfo cur)
     next += next_len;
   }
 }
+
+static inline StrCharInfo utf_ptr2StrCharInfo(char *ptr)
+  REAL_FATTR_NONNULL_ALL REAL_FATTR_ALWAYS_INLINE REAL_FATTR_PURE;
+
+static inline StrCharInfo utf_ptr2StrCharInfo(char *ptr)
+{
+  return (StrCharInfo){ .ptr = ptr, .chr = utf_ptr2CharInfo(ptr) };
+}
diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index a6da7dd3c7..86de182aee 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -1755,22 +1755,23 @@ colnr_T vcol2col(win_T *wp, linenr_T lnum, colnr_T vcol, colnr_T *coladdp)
 {
   // try to advance to the specified column
   char *line = ml_get_buf(wp->w_buffer, lnum);
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, wp, lnum, 0, line, line);
-  while (cts.cts_vcol < vcol && *cts.cts_ptr != NUL) {
-    int size = win_lbr_chartabsize(&cts, NULL);
-    if (cts.cts_vcol + size > vcol) {
+  CharsizeArg arg;
+  CSType cstype = init_charsize_arg(&arg, wp, lnum, line);
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  int cur_vcol = 0;
+  while (cur_vcol < vcol && *ci.ptr != NUL) {
+    int next_vcol = cur_vcol + win_charsize(cstype, cur_vcol, ci.ptr, ci.chr.value, &arg).width;
+    if (next_vcol > vcol) {
       break;
     }
-    cts.cts_vcol += size;
-    MB_PTR_ADV(cts.cts_ptr);
+    cur_vcol = next_vcol;
+    ci = utfc_next(ci);
   }
-  clear_chartabsize_arg(&cts);
 
   if (coladdp != NULL) {
-    *coladdp = vcol - cts.cts_vcol;
+    *coladdp = vcol - cur_vcol;
   }
-  return (colnr_T)(cts.cts_ptr - line);
+  return (colnr_T)(ci.ptr - line);
 }
 
 /// Set UI mouse depending on current mode and 'mouse'.
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 2819d98208..e6527773f9 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -387,17 +387,18 @@ static void shift_block(oparg_T *oap, int amount)
     }
 
     // TODO(vim): is passing bd.textstart for start of the line OK?
-    chartabsize_T cts;
-    init_chartabsize_arg(&cts, curwin, curwin->w_cursor.lnum,
-                         bd.start_vcol, bd.textstart, bd.textstart);
-    while (ascii_iswhite(*cts.cts_ptr)) {
-      incr = lbr_chartabsize_adv(&cts);
+    CharsizeArg arg;
+    CSType cstype = init_charsize_arg(&arg, curwin, curwin->w_cursor.lnum, bd.textstart);
+    StrCharInfo ci = utf_ptr2StrCharInfo(bd.textstart);
+    int vcol = bd.start_vcol;
+    while (ascii_iswhite(ci.chr.value)) {
+      incr = win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+      ci = utfc_next(ci);
       total += incr;
-      cts.cts_vcol += incr;
+      vcol += incr;
     }
-    bd.textstart = cts.cts_ptr;
-    bd.start_vcol = cts.cts_vcol;
-    clear_chartabsize_arg(&cts);
+    bd.textstart = ci.ptr;
+    bd.start_vcol = vcol;
 
     int tabs = 0;
     int spaces = 0;
@@ -448,16 +449,13 @@ static void shift_block(oparg_T *oap, int amount)
     // The character's column is in "bd.start_vcol".
     colnr_T non_white_col = bd.start_vcol;
 
-    chartabsize_T cts;
-    init_chartabsize_arg(&cts, curwin, curwin->w_cursor.lnum,
-                         non_white_col, bd.textstart, non_white);
-    while (ascii_iswhite(*cts.cts_ptr)) {
-      incr = lbr_chartabsize_adv(&cts);
-      cts.cts_vcol += incr;
+    CharsizeArg arg;
+    CSType cstype = init_charsize_arg(&arg, curwin, curwin->w_cursor.lnum, bd.textstart);
+    while (ascii_iswhite(*non_white)) {
+      incr = win_charsize(cstype, non_white_col, non_white, (uint8_t)(*non_white), &arg).width;
+      non_white_col += incr;
+      non_white++;
     }
-    non_white_col = cts.cts_vcol;
-    non_white = cts.cts_ptr;
-    clear_chartabsize_arg(&cts);
 
     const colnr_T block_space_width = non_white_col - oap->start_vcol;
     // We will shift by "total" or "block_space_width", whichever is less.
@@ -478,19 +476,17 @@ static void shift_block(oparg_T *oap, int amount)
     if (bd.startspaces) {
       verbatim_copy_width -= bd.start_char_vcols;
     }
-    init_chartabsize_arg(&cts, curwin, 0, verbatim_copy_width,
-                         bd.textstart, verbatim_copy_end);
-    while (cts.cts_vcol < destination_col) {
-      incr = lbr_chartabsize(&cts);
-      if (cts.cts_vcol + incr > destination_col) {
+    cstype = init_charsize_arg(&arg, curwin, 0, bd.textstart);
+    StrCharInfo ci = utf_ptr2StrCharInfo(verbatim_copy_end);
+    while (verbatim_copy_width < destination_col) {
+      incr = win_charsize(cstype, verbatim_copy_width, ci.ptr, ci.chr.value, &arg).width;
+      if (verbatim_copy_width + incr > destination_col) {
         break;
       }
-      cts.cts_vcol += incr;
-      MB_PTR_ADV(cts.cts_ptr);
+      verbatim_copy_width += incr;
+      ci = utfc_next(ci);
     }
-    verbatim_copy_width = cts.cts_vcol;
-    verbatim_copy_end = cts.cts_ptr;
-    clear_chartabsize_arg(&cts);
+    verbatim_copy_end = ci.ptr;
 
     // If "destination_col" is different from the width of the initial
     // part of the line that will be copied, it means we encountered a tab
@@ -3250,19 +3246,19 @@ void do_put(int regname, yankreg_T *reg, int dir, int count, int flags)
       }
       // get the old line and advance to the position to insert at
       char *oldp = get_cursor_line_ptr();
-      size_t oldlen = strlen(oldp);
-      chartabsize_T cts;
-      init_chartabsize_arg(&cts, curwin, curwin->w_cursor.lnum, 0, oldp, oldp);
 
-      while (cts.cts_vcol < col && *cts.cts_ptr != NUL) {
-        // Count a tab for what it's worth (if list mode not on)
-        incr = lbr_chartabsize_adv(&cts);
-        cts.cts_vcol += incr;
+      CharsizeArg arg;
+      CSType cstype = init_charsize_arg(&arg, curwin, curwin->w_cursor.lnum, oldp);
+      StrCharInfo ci = utf_ptr2StrCharInfo(oldp);
+      vcol = 0;
+      while (vcol < col && *ci.ptr != NUL) {
+        incr = win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+        vcol += incr;
+        ci = utfc_next(ci);
       }
-      vcol = cts.cts_vcol;
-      char *ptr = cts.cts_ptr;
+      size_t oldlen = (size_t)(ci.ptr - oldp) + strlen(ci.ptr);
+      char *ptr = ci.ptr;
       bd.textcol = (colnr_T)(ptr - oldp);
-      clear_chartabsize_arg(&cts);
 
       shortline = (vcol < col) || (vcol == col && !*ptr);
 
@@ -3286,16 +3282,15 @@ void do_put(int regname, yankreg_T *reg, int dir, int count, int flags)
       yanklen = (int)strlen(y_array[i]);
 
       if ((flags & PUT_BLOCK_INNER) == 0) {
-        // calculate number of spaces required to fill right side of
-        // block
+        // calculate number of spaces required to fill right side of block
         spaces = y_width + 1;
-        init_chartabsize_arg(&cts, curwin, 0, 0, y_array[i], y_array[i]);
-        for (int j = 0; j < yanklen; j++) {
-          spaces -= lbr_chartabsize(&cts);
-          cts.cts_ptr++;
-          cts.cts_vcol = 0;
+
+        cstype = init_charsize_arg(&arg, curwin, 0, y_array[i]);
+        ci = utf_ptr2StrCharInfo(y_array[i]);
+        while (*ci.ptr != NUL) {
+          spaces -= win_charsize(cstype, 0, ci.ptr, ci.chr.value, &arg).width;
+          ci = utfc_next(ci);
         }
-        clear_chartabsize_arg(&cts);
         if (spaces < 0) {
           spaces = 0;
         }
@@ -4228,25 +4223,25 @@ static void block_prep(oparg_T *oap, struct block_def *bdp, linenr_T lnum, bool
   char *line = ml_get(lnum);
   char *prev_pstart = line;
 
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, curwin, lnum, bdp->start_vcol, line, line);
-  while (cts.cts_vcol < oap->start_vcol && *cts.cts_ptr != NUL) {
-    // Count a tab for what it's worth (if list mode not on)
-    incr = lbr_chartabsize(&cts);
-    cts.cts_vcol += incr;
-    if (ascii_iswhite(*cts.cts_ptr)) {
+  CharsizeArg arg;
+  CSType cstype = init_charsize_arg(&arg, curwin, lnum, line);
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  int vcol = bdp->start_vcol;
+  while (vcol < oap->start_vcol && *ci.ptr != NUL) {
+    incr = win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+    vcol += incr;
+    if (ascii_iswhite(ci.chr.value)) {
       bdp->pre_whitesp += incr;
       bdp->pre_whitesp_c++;
     } else {
       bdp->pre_whitesp = 0;
       bdp->pre_whitesp_c = 0;
     }
-    prev_pstart = cts.cts_ptr;
-    MB_PTR_ADV(cts.cts_ptr);
+    prev_pstart = ci.ptr;
+    ci = utfc_next(ci);
   }
-  bdp->start_vcol = cts.cts_vcol;
-  char *pstart = cts.cts_ptr;
-  clear_chartabsize_arg(&cts);
+  bdp->start_vcol = vcol;
+  char *pstart = ci.ptr;
 
   bdp->start_char_vcols = incr;
   if (bdp->start_vcol < oap->start_vcol) {      // line too short
@@ -4283,17 +4278,18 @@ static void block_prep(oparg_T *oap, struct block_def *bdp, linenr_T lnum, bool
         }
       }
     } else {
-      init_chartabsize_arg(&cts, curwin, lnum, bdp->end_vcol, line, pend);
+      cstype = init_charsize_arg(&arg, curwin, lnum, line);
+      ci = utf_ptr2StrCharInfo(pend);
+      vcol = bdp->end_vcol;
       char *prev_pend = pend;
-      while (cts.cts_vcol <= oap->end_vcol && *cts.cts_ptr != NUL) {
-        // Count a tab for what it's worth (if list mode not on)
-        prev_pend = cts.cts_ptr;
-        incr = lbr_chartabsize_adv(&cts);
-        cts.cts_vcol += incr;
+      while (vcol <= oap->end_vcol && *ci.ptr != NUL) {
+        prev_pend = ci.ptr;
+        incr = win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &arg).width;
+        vcol += incr;
+        ci = utfc_next(ci);
       }
-      bdp->end_vcol = cts.cts_vcol;
-      pend = cts.cts_ptr;
-      clear_chartabsize_arg(&cts);
+      bdp->end_vcol = vcol;
+      pend = ci.ptr;
 
       if (bdp->end_vcol <= oap->end_vcol
           && (!is_del
diff --git a/src/nvim/plines.c b/src/nvim/plines.c
index 1fa2812dab..d63c032080 100644
--- a/src/nvim/plines.c
+++ b/src/nvim/plines.c
@@ -51,48 +51,21 @@ int win_chartabsize(win_T *wp, char *p, colnr_T col)
   return ptr2cells(p);
 }
 
-/// Return the number of characters the string 's' will take on the screen,
-/// taking into account the size of a tab.
-///
-/// @param s
-///
-/// @return Number of characters the string will take on the screen.
-int linetabsize_str(char *s)
-{
-  return linetabsize_col(0, s);
-}
-
-/// Like linetabsize_str(), but "s" starts at column "startcol".
+/// Like linetabsize_str(), but "s" starts at virtual column "startvcol".
 ///
 /// @param startcol
 /// @param s
 ///
 /// @return Number of characters the string will take on the screen.
-int linetabsize_col(int startcol, char *s)
+int linetabsize_col(int startvcol, char *s)
 {
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, curwin, 0, startcol, s, s);
-  while (*cts.cts_ptr != NUL) {
-    cts.cts_vcol += lbr_chartabsize_adv(&cts);
+  CharsizeArg arg;
+  CSType const cstype = init_charsize_arg(&arg, curwin, 0, s);
+  if (cstype == kCharsizeFast) {
+    return linesize_fast(&arg, startvcol, MAXCOL);
+  } else {
+    return linesize_regular(&arg, startvcol, MAXCOL);
   }
-  clear_chartabsize_arg(&cts);
-  return cts.cts_vcol;
-}
-
-/// Like linetabsize_str(), but for a given window instead of the current one.
-///
-/// @param wp
-/// @param line
-/// @param len
-///
-/// @return Number of characters the string will take on the screen.
-int win_linetabsize(win_T *wp, linenr_T lnum, char *line, colnr_T len)
-{
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, wp, lnum, 0, line, line);
-  win_linetabsize_cts(&cts, len);
-  clear_chartabsize_arg(&cts);
-  return cts.cts_vcol;
 }
 
 /// Return the number of cells line "lnum" of window "wp" will take on the
@@ -102,128 +75,79 @@ int linetabsize(win_T *wp, linenr_T lnum)
   return win_linetabsize(wp, lnum, ml_get_buf(wp->w_buffer, lnum), (colnr_T)MAXCOL);
 }
 
-void win_linetabsize_cts(chartabsize_T *cts, colnr_T len)
-{
-  for (; *cts->cts_ptr != NUL && (len == MAXCOL || cts->cts_ptr < cts->cts_line + len);
-       MB_PTR_ADV(cts->cts_ptr)) {
-    cts->cts_vcol += win_lbr_chartabsize(cts, NULL);
-  }
-  // check for inline virtual text after the end of the line
-  if (len == MAXCOL && cts->virt_row >= 0 && *cts->cts_ptr == NUL) {
-    (void)win_lbr_chartabsize(cts, NULL);
-    cts->cts_vcol += cts->cts_cur_text_width_left + cts->cts_cur_text_width_right;
-  }
-}
-
-/// Prepare the structure passed to chartabsize functions.
+/// Prepare the structure passed to charsize functions.
 ///
-/// "line" is the start of the line, "ptr" is the first relevant character.
+/// "line" is the start of the line.
 /// When "lnum" is zero do not use inline virtual text.
-void init_chartabsize_arg(chartabsize_T *cts, win_T *wp, linenr_T lnum, colnr_T col, char *line,
-                          char *ptr)
+CSType init_charsize_arg(CharsizeArg *cts, win_T *wp, linenr_T lnum, char *line)
 {
-  cts->cts_win = wp;
-  cts->cts_vcol = col;
-  cts->cts_line = line;
-  cts->cts_ptr = ptr;
-  cts->cts_max_head_vcol = 0;
-  cts->cts_cur_text_width_left = 0;
-  cts->cts_cur_text_width_right = 0;
+  cts->win = wp;
+  cts->line = line;
+  cts->max_head_vcol = 0;
+  cts->cur_text_width_left = 0;
+  cts->cur_text_width_right = 0;
   cts->virt_row = -1;
   cts->indent_width = INT_MIN;
+  cts->use_tabstop = !wp->w_p_list || wp->w_p_lcs_chars.tab1;
 
   if (lnum > 0 && wp->w_buffer->b_virt_text_inline > 0) {
-    marktree_itr_get(wp->w_buffer->b_marktree, lnum - 1, 0, cts->cts_iter);
-    MTKey mark = marktree_itr_current(cts->cts_iter);
+    marktree_itr_get(wp->w_buffer->b_marktree, lnum - 1, 0, cts->iter);
+    MTKey mark = marktree_itr_current(cts->iter);
     if (mark.pos.row == lnum - 1) {
       cts->virt_row = lnum - 1;
     }
   }
-}
 
-/// Free any allocated item in "cts".
-void clear_chartabsize_arg(chartabsize_T *cts)
-{
-}
-
-/// like win_chartabsize(), but also check for line breaks on the screen
-///
-/// @param cts
-///
-/// @return The number of characters taken up on the screen.
-int lbr_chartabsize(chartabsize_T *cts)
-{
-  if (!curwin->w_p_lbr && *get_showbreak_value(curwin) == NUL
-      && !curwin->w_p_bri && cts->virt_row < 0) {
-    if (curwin->w_p_wrap) {
-      return win_nolbr_chartabsize(cts, NULL);
-    }
-    return win_chartabsize(curwin, cts->cts_ptr, cts->cts_vcol);
+  if (cts->virt_row >= 0
+      || (wp->w_p_wrap && (wp->w_p_lbr || wp->w_p_bri || *get_showbreak_value(wp) != NUL))) {
+    return kCharsizeRegular;
+  } else {
+    return kCharsizeFast;
   }
-  return win_lbr_chartabsize(cts, NULL);
 }
 
-/// Call lbr_chartabsize() and advance the pointer.
-///
-/// @param cts
-///
-/// @return The number of characters take up on the screen.
-int lbr_chartabsize_adv(chartabsize_T *cts)
-{
-  int retval = lbr_chartabsize(cts);
-  MB_PTR_ADV(cts->cts_ptr);
-  return retval;
-}
-
-/// Get the number of characters taken up on the screen indicated by "cts".
-/// "cts->cts_cur_text_width_left" and "cts->cts_cur_text_width_right" are set
+/// Get the number of characters taken up on the screen for the given cts and position.
+/// "cts->cur_text_width_left" and "cts->cur_text_width_right" are set
 /// to the extra size for inline virtual text.
 /// This function is used very often, keep it fast!!!!
 ///
-/// If "headp" not NULL, set "*headp" to the size of 'showbreak'/'breakindent'
-/// included in the return value.
-/// When "cts->cts_max_head_vcol" is positive, only count in "*headp" the size
-/// of 'showbreak'/'breakindent' before "cts->cts_max_head_vcol".
-/// When "cts->cts_max_head_vcol" is negative, only count in "*headp" the size
+/// When "cts->max_head_vcol" is positive, only count in "head" the size
+/// of 'showbreak'/'breakindent' before "cts->max_head_vcol".
+/// When "cts->max_head_vcol" is negative, only count in "head" the size
 /// of 'showbreak'/'breakindent' before where cursor should be placed.
-///
-/// Warning: "*headp" may not be set if it's 0, init to 0 before calling.
-int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
+CharSize charsize_regular(CharsizeArg *cts, char *const cur, colnr_T const vcol,
+                          int32_t const cur_char)
 {
-  win_T *wp = cts->cts_win;
-  char *line = cts->cts_line;  // start of the line
-  char *s = cts->cts_ptr;
-  colnr_T vcol = cts->cts_vcol;
+  cts->cur_text_width_left = 0;
+  cts->cur_text_width_right = 0;
+
+  win_T *wp = cts->win;
+  buf_T *buf = wp->w_buffer;
+  char *line = cts->line;
+  bool const use_tabstop = cur_char == TAB && cts->use_tabstop;
   int mb_added = 0;
 
-  cts->cts_cur_text_width_left = 0;
-  cts->cts_cur_text_width_right = 0;
-
-  char *const sbr = get_showbreak_value(wp);
-
-  // No 'linebreak', 'showbreak' and 'breakindent': return quickly.
-  if (!wp->w_p_lbr && !wp->w_p_bri && *sbr == NUL
-      && cts->virt_row < 0) {
-    if (wp->w_p_wrap) {
-      return win_nolbr_chartabsize(cts, headp);
-    }
-    return win_chartabsize(wp, s, vcol);
-  }
-
   bool has_lcs_eol = wp->w_p_list && wp->w_p_lcs_chars.eol != NUL;
 
   // First get normal size, without 'linebreak' or inline virtual text
-  int size = win_chartabsize(wp, s, vcol);
-  if (*s == NUL && !has_lcs_eol) {
-    size = 0;  // NUL is not displayed
+  int size;
+  int is_doublewidth = false;
+  if (use_tabstop) {
+    size = tabstop_padding(vcol, buf->b_p_ts, buf->b_p_vts_array);
+  } else if (*cur == NUL && !has_lcs_eol) {
+    size = 0;
+  } else if (cur_char < 0) {
+    size = kInvalidByteCells;
+  } else {
+    size = char2cells(cur_char);
+    is_doublewidth = size == 2 && cur_char > 0x80;
   }
-  bool is_doublewidth = size == 2 && MB_BYTE2LEN((uint8_t)(*s)) > 1;
 
   if (cts->virt_row >= 0) {
     int tab_size = size;
-    int col = (int)(s - line);
+    int col = (int)(cur - line);
     while (true) {
-      MTKey mark = marktree_itr_current(cts->cts_iter);
+      MTKey mark = marktree_itr_current(cts->iter);
       if (mark.pos.row != cts->virt_row || mark.pos.col > col) {
         break;
       } else if (mark.pos.col == col) {
@@ -233,15 +157,15 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
           while (vt) {
             if (!(vt->flags & kVTIsLines) && vt->pos == kVPosInline) {
               if (mt_right(mark)) {
-                cts->cts_cur_text_width_right += vt->width;
+                cts->cur_text_width_right += vt->width;
               } else {
-                cts->cts_cur_text_width_left += vt->width;
+                cts->cur_text_width_left += vt->width;
               }
               size += vt->width;
-              if (*s == TAB) {
+              if (use_tabstop) {
                 // tab size changes because of the inserted text
                 size -= tab_size;
-                tab_size = win_chartabsize(wp, s, vcol + size);
+                tab_size = tabstop_padding(vcol + size, buf->b_p_ts, buf->b_p_vts_array);
                 size += tab_size;
               }
             }
@@ -249,7 +173,7 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
           }
         }
       }
-      marktree_itr_next(wp->w_buffer->b_marktree, cts->cts_iter);
+      marktree_itr_next(wp->w_buffer->b_marktree, cts->iter);
     }
   }
 
@@ -259,6 +183,8 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
     mb_added = 1;
   }
 
+  char *const sbr = get_showbreak_value(wp);
+
   // May have to add something for 'breakindent' and/or 'showbreak'
   // string at the start of a screen line.
   int head = mb_added;
@@ -267,7 +193,7 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
     int col_off_prev = win_col_off(wp);
     int width2 = wp->w_width_inner - col_off_prev + win_col_off2(wp);
     colnr_T wcol = vcol + col_off_prev;
-    colnr_T max_head_vcol = cts->cts_max_head_vcol;
+    colnr_T max_head_vcol = cts->max_head_vcol;
     int added = 0;
 
     // cells taken by 'showbreak'/'breakindent' before current char
@@ -333,7 +259,7 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
           head += (max_head_vcol - (vcol + head_prev + prev_rem)
                    + width2 - 1) / width2 * head_mid;
         } else if (max_head_vcol < 0) {
-          int off = virt_text_cursor_off(cts, *s == NUL);
+          int off = virt_text_cursor_off(cts, *cur == NUL);
           if (off >= prev_rem) {
             if (size > off) {
               head += (1 + (off - prev_rem) / width) * head_mid;
@@ -348,19 +274,16 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
     size += added;
   }
 
-  if (headp != NULL) {
-    *headp = head;
-  }
-
+  char *s = cur;
   colnr_T vcol_start = 0;  // start from where to consider linebreak
   // If 'linebreak' set check at a blank before a non-blank if the line
   // needs a break here
   if (wp->w_p_lbr && wp->w_p_wrap && wp->w_width_inner != 0) {
-    char *t = cts->cts_line;
+    char *t = cts->line;
     while (vim_isbreak((uint8_t)t[0])) {
       t++;
     }
-    vcol_start = (colnr_T)(t - cts->cts_line);
+    vcol_start = (colnr_T)(t - cts->line);
   }
   if (wp->w_p_lbr && vcol_start <= vcol
       && vim_isbreak((uint8_t)s[0])
@@ -398,39 +321,50 @@ int win_lbr_chartabsize(chartabsize_T *cts, int *headp)
     }
   }
 
-  return size;
+  return (CharSize){ .width = size, .head = head };
 }
 
-/// Like win_lbr_chartabsize(), except that we know 'linebreak' is off and
-/// 'wrap' is on.  This means we need to check for a double-byte character that
-/// doesn't fit at the end of the screen line.
+/// Like charsize_regular(), except it doesn't handle virtual text,
+/// linebreak, breakindent and showbreak. Handles normal characters, tabs and wrapping.
+/// This function is always inlined.
 ///
-/// @param cts
-/// @param headp
-///
-/// @return The number of characters take up on the screen.
-static int win_nolbr_chartabsize(chartabsize_T *cts, int *headp)
+/// @see charsize_regular
+/// @see charsize_fast
+static inline CharSize charsize_fast_impl(win_T *const wp, bool use_tabstop, colnr_T const vcol,
+                                          int32_t const cur_char)
+  FUNC_ATTR_PURE FUNC_ATTR_ALWAYS_INLINE
 {
-  win_T *wp = cts->cts_win;
-  char *s = cts->cts_ptr;
-  colnr_T col = cts->cts_vcol;
-
-  if ((*s == TAB) && (!wp->w_p_list || wp->w_p_lcs_chars.tab1)) {
-    return tabstop_padding(col,
-                           wp->w_buffer->b_p_ts,
-                           wp->w_buffer->b_p_vts_array);
-  }
-  int n = ptr2cells(s);
-
-  // Add one cell for a double-width character in the last column of the
-  // window, displayed with a ">".
-  if ((n == 2) && (MB_BYTE2LEN((uint8_t)(*s)) > 1) && in_win_border(wp, col)) {
-    if (headp != NULL) {
-      *headp = 1;
+  // A tab gets expanded, depending on the current column
+  if (cur_char == TAB && use_tabstop) {
+    return (CharSize){
+      .width = tabstop_padding(vcol, wp->w_buffer->b_p_ts,
+                               wp->w_buffer->b_p_vts_array)
+    };
+  } else {
+    int width;
+    if (cur_char < 0) {
+      width = kInvalidByteCells;
+    } else {
+      width = char2cells(cur_char);
+    }
+
+    // If a double-width char doesn't fit at the end of a line, it wraps to the next line,
+    // and the last column displays a '>'.
+    if (width == 2 && cur_char >= 0x80 && wp->w_p_wrap && in_win_border(wp, vcol)) {
+      return (CharSize){ .width = 3, .head = 1 };
+    } else {
+      return (CharSize){ .width = width };
     }
-    return 3;
   }
-  return n;
+}
+
+/// Like charsize_regular(), except it doesn't handle virtual text,
+/// linebreak, breakindent and showbreak. Handles normal characters, tabs and wrapping.
+/// Can be used if CSType is kCharsizeFast.
+CharSize charsize_fast(CharsizeArg *cts, colnr_T const vcol, int32_t const cur_char)
+  FUNC_ATTR_PURE
+{
+  return charsize_fast_impl(cts->win, cts->use_tabstop, vcol, cur_char);
 }
 
 /// Check that virtual column "vcol" is in the rightmost column of window "wp".
@@ -461,19 +395,63 @@ static bool in_win_border(win_T *wp, colnr_T vcol)
   return (vcol - width1) % width2 == width2 - 1;
 }
 
+/// Calculate virtual column until the given 'len'.
+///
+/// @param arg  Argument to charsize functions.
+/// @param vcol Starting virtual column.
+/// @param len  First byte of the end character, or MAXCOL.
+///
+/// @return virtual column before the character at 'len',
+/// or full size of the line if 'len' is MAXCOL.
+int linesize_regular(CharsizeArg *const arg, int vcol, colnr_T const len)
+{
+  char *const line = arg->line;
+
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  while (ci.ptr - line < len && *ci.ptr != NUL) {
+    vcol += charsize_regular(arg, ci.ptr, vcol, ci.chr.value).width;
+    ci = utfc_next(ci);
+  }
+
+  // Check for inline virtual text after the end of the line.
+  if (len == MAXCOL && arg->virt_row >= 0) {
+    (void)charsize_regular(arg, ci.ptr, vcol, ci.chr.value);
+    vcol += arg->cur_text_width_left + arg->cur_text_width_right;
+  }
+
+  return vcol;
+}
+
+/// Like win_linesize_regular, but can be used when CStype is kCharsizeFast.
+///
+/// @see win_linesize_regular
+int linesize_fast(CharsizeArg const *const arg, int vcol, colnr_T const len)
+{
+  win_T *const wp = arg->win;
+  bool const use_tabstop = arg->use_tabstop;
+
+  char *const line = arg->line;
+
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  while (ci.ptr - line < len && *ci.ptr != NUL) {
+    vcol += charsize_fast_impl(wp, use_tabstop, vcol, ci.chr.value).width;
+    ci = utfc_next(ci);
+  }
+
+  return vcol;
+}
+
 /// Get how many virtual columns inline virtual text should offset the cursor.
 ///
-/// @param cts     should contain information stored by win_lbr_chartabsize()
-///                about widths of left and right gravity virtual text
 /// @param on_NUL  whether this is the end of the line
-static int virt_text_cursor_off(chartabsize_T *cts, bool on_NUL)
+static int virt_text_cursor_off(CharsizeArg *cts, bool on_NUL)
 {
   int off = 0;
   if (!on_NUL || !(State & MODE_NORMAL)) {
-    off += cts->cts_cur_text_width_left;
+    off += cts->cur_text_width_left;
   }
   if (!on_NUL && (State & MODE_NORMAL)) {
-    off += cts->cts_cur_text_width_right;
+    off += cts->cur_text_width_right;
   }
   return off;
 }
@@ -492,95 +470,53 @@ static int virt_text_cursor_off(chartabsize_T *cts, bool on_NUL)
 /// @param end
 void getvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor, colnr_T *end)
 {
-  char *ptr;     // points to current char
-  int incr;
-  int head;
-  colnr_T *vts = wp->w_buffer->b_p_vts_array;
-  int ts = (int)wp->w_buffer->b_p_ts;
+  char *const line = ml_get_buf(wp->w_buffer, pos->lnum);  // start of the line
+  int const end_col = pos->col;
+
+  CharsizeArg arg;
+  bool on_NUL = false;
+  CSType const cstype = init_charsize_arg(&arg, wp, pos->lnum, line);
+  arg.max_head_vcol = -1;
 
   colnr_T vcol = 0;
-  char *line = ptr = ml_get_buf(wp->w_buffer, pos->lnum);  // start of the line
-
-  uintptr_t last_pos = (uintptr_t)(ptr + pos->col);
-  if (last_pos < (uintptr_t)ptr) {
-    last_pos = UINTPTR_MAX;  // unsigned overflow
-  }
-  chartabsize_T cts;
-  bool on_NUL = false;
-  init_chartabsize_arg(&cts, wp, pos->lnum, 0, line, line);
-  cts.cts_max_head_vcol = -1;
-
-  // This function is used very often, do some speed optimizations.
-  // When 'linebreak', 'showbreak' and 'breakindent' are not set
-  // and there are no virtual text use a simple loop.
-  if (!wp->w_p_lbr && !wp->w_p_bri && cts.virt_row < 0 && *get_showbreak_value(wp) == NUL) {
-    bool const special_tab = !wp->w_p_list || wp->w_p_lcs_chars.tab1 != NUL;
-    CharInfo cur_char = utf_ptr2CharInfo(ptr);
+  CharSize char_size;
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  if (cstype == kCharsizeFast) {
+    bool const use_tabstop = arg.use_tabstop;
     while (true) {
-      head = 0;
-      // make sure we don't go past the end of the line
-      if (cur_char.value == 0 && cur_char.len == 1) {
-        // NUL at end of line only takes one column
-        incr = 1;
+      if (*ci.ptr == NUL) {
+        // if cursor is at NUL, it is treated like 1 cell char
+        char_size = (CharSize){ .width = 1 };
         break;
       }
-
-      // A tab gets expanded, depending on the current column
-      if (cur_char.value == TAB && special_tab) {
-        incr = tabstop_padding(vcol, ts, vts);
-      } else {
-        if (cur_char.value < 0) {
-          incr = kInvalidByteCells;
-        } else {
-          incr = char2cells(cur_char.value);
-        }
-
-        // If a double-cell char doesn't fit at the end of a line
-        // it wraps to the next line, it's like this char is three
-        // cells wide.
-        if (incr == 2 && cur_char.value >= 0x80
-            && wp->w_p_wrap && in_win_border(wp, vcol)) {
-          incr++;
-          head = 1;
-        }
-      }
-
-      StrCharInfo const next_char = utfc_next((StrCharInfo){ ptr, cur_char });
-      if ((uintptr_t)next_char.ptr > last_pos) {
+      char_size = charsize_fast_impl(wp, use_tabstop, vcol, ci.chr.value);
+      StrCharInfo const next = utfc_next(ci);
+      if (next.ptr - line > end_col) {
         break;
       }
-
-      cur_char = next_char.chr;
-      ptr = next_char.ptr;
-      vcol += incr;
+      ci = next;
+      vcol += char_size.width;
     }
   } else {
     while (true) {
-      // A tab gets expanded, depending on the current column
-      // Other things also take up space.
-      head = 0;
-      incr = win_lbr_chartabsize(&cts, &head);
-
-      // make sure we don't go past the end of the line
-      if (*cts.cts_ptr == NUL) {
-        // NUL at end of line only takes one column, unless there is virtual text
-        incr = MAX(1, cts.cts_cur_text_width_left + cts.cts_cur_text_width_right);
+      char_size = charsize_regular(&arg, ci.ptr, vcol, ci.chr.value);
+      if (*ci.ptr == NUL) {
+        // if cursor is at NUL, it is treated like 1 cell char unless there is virtual text
+        char_size.width = MAX(1, arg.cur_text_width_left + arg.cur_text_width_right);
         on_NUL = true;
         break;
       }
-
-      char *const next = cts.cts_ptr + utfc_ptr2len(cts.cts_ptr);
-      if ((uintptr_t)next > last_pos) {
+      StrCharInfo const next = utfc_next(ci);
+      if (next.ptr - line > end_col) {
         break;
       }
-
-      cts.cts_ptr = next;
-      cts.cts_vcol += incr;
+      ci = next;
+      vcol += char_size.width;
     }
-    vcol = cts.cts_vcol;
-    ptr = cts.cts_ptr;
   }
-  clear_chartabsize_arg(&cts);
+
+  int head = char_size.head;
+  int incr = char_size.width;
 
   if (start != NULL) {
     *start = vcol + head;
@@ -591,7 +527,7 @@ void getvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor, colnr_T *en
   }
 
   if (cursor != NULL) {
-    if ((*ptr == TAB)
+    if (ci.chr.value == TAB
         && (State & MODE_NORMAL)
         && !wp->w_p_list
         && !virtual_active()
@@ -599,7 +535,7 @@ void getvcol(win_T *wp, pos_T *pos, colnr_T *start, colnr_T *cursor, colnr_T *en
       // cursor at end
       *cursor = vcol + incr - 1;
     } else {
-      vcol += virt_text_cursor_off(&cts, on_NUL);
+      vcol += virt_text_cursor_off(&arg, on_NUL);
       // cursor at start
       *cursor = vcol + head;
     }
@@ -788,14 +724,18 @@ int plines_win_nofill(win_T *wp, linenr_T lnum, bool limit_winheight)
 int plines_win_nofold(win_T *wp, linenr_T lnum)
 {
   char *s = ml_get_buf(wp->w_buffer, lnum);
-  chartabsize_T cts;
-  init_chartabsize_arg(&cts, wp, lnum, 0, s, s);
-  if (*s == NUL && cts.virt_row < 0) {
+  CharsizeArg arg;
+  CSType const cstype = init_charsize_arg(&arg, wp, lnum, s);
+  if (*s == NUL && arg.virt_row < 0) {
     return 1;  // be quick for an empty line
   }
-  win_linetabsize_cts(&cts, (colnr_T)MAXCOL);
-  clear_chartabsize_arg(&cts);
-  int64_t col = cts.cts_vcol;
+
+  int64_t col;
+  if (cstype == kCharsizeFast) {
+    col = linesize_fast(&arg, 0, MAXCOL);
+  } else {
+    col = linesize_regular(&arg, 0, MAXCOL);
+  }
 
   // If list mode is on, then the '$' at the end of the line may take up one
   // extra column.
@@ -834,26 +774,33 @@ int plines_win_col(win_T *wp, linenr_T lnum, long column)
 
   char *line = ml_get_buf(wp->w_buffer, lnum);
 
-  colnr_T col = 0;
-  chartabsize_T cts;
+  CharsizeArg cts;
+  CSType const cstype = init_charsize_arg(&cts, wp, lnum, line);
 
-  init_chartabsize_arg(&cts, wp, lnum, 0, line, line);
-  while (*cts.cts_ptr != NUL && --column >= 0) {
-    cts.cts_vcol += win_lbr_chartabsize(&cts, NULL);
-    MB_PTR_ADV(cts.cts_ptr);
+  colnr_T vcol = 0;
+  StrCharInfo ci = utf_ptr2StrCharInfo(line);
+  if (cstype == kCharsizeFast) {
+    bool const use_tabstop = cts.use_tabstop;
+    while (*ci.ptr != NUL && --column >= 0) {
+      vcol += charsize_fast_impl(wp, use_tabstop, vcol, ci.chr.value).width;
+      ci = utfc_next(ci);
+    }
+  } else {
+    while (*ci.ptr != NUL && --column >= 0) {
+      vcol += charsize_regular(&cts, ci.ptr, vcol, ci.chr.value).width;
+      ci = utfc_next(ci);
+    }
   }
 
-  // If *cts.cts_ptr is a TAB, and the TAB is not displayed as ^I, and we're not
+  // If current char is a TAB, and the TAB is not displayed as ^I, and we're not
   // in MODE_INSERT state, then col must be adjusted so that it represents the
   // last screen position of the TAB.  This only fixes an error when the TAB
   // wraps from one screen line to the next (when 'columns' is not a multiple
   // of 'ts') -- webb.
-  col = cts.cts_vcol;
-  if (*cts.cts_ptr == TAB && (State & MODE_NORMAL)
-      && (!wp->w_p_list || wp->w_p_lcs_chars.tab1)) {
-    col += win_lbr_chartabsize(&cts, NULL) - 1;
+  colnr_T col = vcol;
+  if (ci.chr.value == TAB && (State & MODE_NORMAL) && cts.use_tabstop) {
+    col += win_charsize(cstype, col, ci.ptr, ci.chr.value, &cts).width - 1;
   }
-  clear_chartabsize_arg(&cts);
 
   // Add column offset for 'number', 'relativenumber', 'foldcolumn', etc.
   int width = wp->w_width_inner - win_col_off(wp);
diff --git a/src/nvim/plines.h b/src/nvim/plines.h
index 86ee7ef53c..4611101041 100644
--- a/src/nvim/plines.h
+++ b/src/nvim/plines.h
@@ -4,26 +4,96 @@
 #include <stdint.h>  // IWYU pragma: keep
 
 #include "nvim/marktree_defs.h"
+#include "nvim/mbyte_defs.h"
 #include "nvim/pos_defs.h"  // IWYU pragma: keep
 #include "nvim/types_defs.h"
 
-/// Argument for lbr_chartabsize().
+typedef bool CSType;
+
+enum {
+  kCharsizeRegular,
+  kCharsizeFast,
+};
+
+/// Argument for char size functions.
 typedef struct {
-  win_T *cts_win;
-  char *cts_line;                ///< start of the line
-  char *cts_ptr;                 ///< current position in line
-  int cts_vcol;                  ///< virtual column at current position
-  int indent_width;              ///< width of showbreak and breakindent on wrapped lines
-                                 ///  INT_MIN if not yet calculated
+  win_T *win;
+  char *line;                ///< start of the line
 
-  int virt_row;                  ///< line number, -1 if no virtual text
-  int cts_cur_text_width_left;   ///< width of virtual text left of cursor
-  int cts_cur_text_width_right;  ///< width of virtual text right of cursor
+  bool use_tabstop;          ///< use tabstop for tab insted of counting it as ^I
+  int indent_width;          ///< width of showbreak and breakindent on wrapped lines
+                             ///  INT_MIN if not yet calculated
 
-  int cts_max_head_vcol;         ///< see win_lbr_chartabsize()
-  MarkTreeIter cts_iter[1];
-} chartabsize_T;
+  int virt_row;              ///< line number, -1 if no virtual text
+  int cur_text_width_left;   ///< width of virtual text left of cursor
+  int cur_text_width_right;  ///< width of virtual text right of cursor
+
+  int max_head_vcol;         ///< see charsize_regular()
+  MarkTreeIter iter[1];
+} CharsizeArg;
+
+typedef struct {
+  int width;
+  int head;  // size of breakindent etc. before the character (included in width)
+} CharSize;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "plines.h.generated.h"
 #endif
+
+static inline CharSize win_charsize(CSType cstype, int vcol, char *ptr, int32_t chr,
+                                    CharsizeArg *arg)
+  REAL_FATTR_NONNULL_ALL REAL_FATTR_WARN_UNUSED_RESULT REAL_FATTR_ALWAYS_INLINE;
+
+/// Get the number of cells taken up on the screen by the given character at vcol.
+/// "arg->cur_text_width_left" and "arg->cur_text_width_right" are set
+/// to the extra size for inline virtual text.
+///
+/// When "arg->max_head_vcol" is positive, only count in "head" the size
+/// of 'showbreak'/'breakindent' before "arg->max_head_vcol".
+/// When "arg->max_head_vcol" is negative, only count in "head" the size
+/// of 'showbreak'/'breakindent' before where cursor should be placed.
+static inline CharSize win_charsize(CSType cstype, int vcol, char *ptr, int32_t chr,
+                                    CharsizeArg *arg)
+{
+  if (cstype == kCharsizeFast) {
+    return charsize_fast(arg, vcol, chr);
+  } else {
+    return charsize_regular(arg, ptr, vcol, chr);
+  }
+}
+
+static inline int linetabsize_str(char *s)
+  REAL_FATTR_NONNULL_ALL REAL_FATTR_WARN_UNUSED_RESULT REAL_FATTR_ALWAYS_INLINE;
+
+/// Return the number of characters the string 's' will take on the screen,
+/// taking into account the size of a tab.
+///
+/// @param s
+///
+/// @return Number of characters the string will take on the screen.
+static inline int linetabsize_str(char *s)
+{
+  return linetabsize_col(0, s);
+}
+
+static inline int win_linetabsize(win_T *wp, linenr_T lnum, char *line, colnr_T len)
+  REAL_FATTR_NONNULL_ALL REAL_FATTR_WARN_UNUSED_RESULT REAL_FATTR_ALWAYS_INLINE;
+
+/// Like linetabsize_str(), but for a given window instead of the current one.
+///
+/// @param wp
+/// @param line
+/// @param len
+///
+/// @return Number of characters the string will take on the screen.
+static inline int win_linetabsize(win_T *wp, linenr_T lnum, char *line, colnr_T len)
+{
+  CharsizeArg arg;
+  CSType const cstype = init_charsize_arg(&arg, wp, lnum, line);
+  if (cstype == kCharsizeFast) {
+    return linesize_fast(&arg, 0, len);
+  } else {
+    return linesize_regular(&arg, 0, len);
+  }
+}