refactor(options): use schar_T representation for fillchars and listchars

A bit big, but practically it was a lot simpler to change over all
fillchars and all listchars at once, to not need to maintain two
parallel implementations.

This is mostly an internal refactor, but it also removes an arbitrary
limitation: that 'fillchars' and 'listchars' values can only be
single-codepoint characters. Now any character which fits into a single
screen cell can be used.

1 files changed, 5 insertions, 14 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 6fae90134a..d843c37082 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -6881,15 +6881,8 @@ static void f_screenchar(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   ScreenGrid *grid;
   screenchar_adjust(&grid, &row, &col);
 
-  int c;
-  if (row < 0 || row >= grid->rows || col < 0 || col >= grid->cols) {
-    c = -1;
-  } else {
-    char buf[MAX_SCHAR_SIZE + 1];
-    schar_get(buf, grid_getchar(grid, row, col, NULL));
-    c = utf_ptr2char(buf);
-  }
-  rettv->vval.v_number = c;
+  rettv->vval.v_number = (row < 0 || row >= grid->rows || col < 0 || col >= grid->cols)
+                         ? -1 : schar_get_first_codepoint(grid_getchar(grid, row, col, NULL));
 }
 
 /// "screenchars()" function
@@ -8383,7 +8376,6 @@ static void f_synIDtrans(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 static void f_synconcealed(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   int syntax_flags = 0;
-  int cchar;
   int matchid = 0;
   char str[NUMBUFLEN];
 
@@ -8402,14 +8394,13 @@ static void f_synconcealed(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
 
     // get the conceal character
     if ((syntax_flags & HL_CONCEAL) && curwin->w_p_cole < 3) {
-      cchar = syn_get_sub_char();
+      schar_T cchar = schar_from_char(syn_get_sub_char());
       if (cchar == NUL && curwin->w_p_cole == 1) {
         cchar = (curwin->w_p_lcs_chars.conceal == NUL)
-                ? ' '
-                : curwin->w_p_lcs_chars.conceal;
+                ? schar_from_ascii(' ') : curwin->w_p_lcs_chars.conceal;
       }
       if (cchar != NUL) {
-        utf_char2bytes(cchar, str);
+        schar_get(str, cchar);
       }
     }
   }