defaults: 'fillchars'

Most fonts should have these by now. Both are a significant visual
improvement.

- Vertical connecting bar `│` is used by tmux, pstree, Windows 7 cmd.exe
  and nvim-qt.exe.
- Middle dot `·` works on Windows 7 cmd.exe, nvim-qt.exe.

For reference: tmux uses these chars to draw lines: │ ├ ─

src/nvim/globals.h

@@ -951,8 +951,8 @@ EXTERN int lcs_conceal INIT(= ' ');
 /* Characters from 'fillchars' option */
 EXTERN int fill_stl INIT(= ' ');
 EXTERN int fill_stlnc INIT(= ' ');
-EXTERN int fill_vert INIT(= ' ');
-EXTERN int fill_fold INIT(= '-');
+EXTERN int fill_vert INIT(= 9474);  // │
+EXTERN int fill_fold INIT(= 183);   // ·
 EXTERN int fill_diff INIT(= '-');
 
 /* Whether 'keymodel' contains "stopsel" and "startsel". */

src/nvim/options.lua

@@ -812,7 +812,7 @@ return {
       vi_def=true,
       redraw={'all_windows'},
       varname='p_fcs',
-      defaults={if_true={vi="vert:|,fold:-"}}
+      defaults={if_true={vi="vert:│,fold:·"}}
     },
     {
       full_name='fixendofline', abbreviation='fixeol',

src/nvim/screen.c

@@ -7089,7 +7089,7 @@ static int fillchar_vsep(win_T *wp, int *attr)
 {
   *attr = win_hl_attr(wp, HLF_C);
   if (*attr == 0 && fill_vert == ' ') {
-    return '|';
+    return 9474;  // default: "│"
   } else {
     return fill_vert;
   }