vim-patch:9.0.0036: 'fillchars' cannot have window-local values

Problem:    'fillchars' cannot have window-local values.
Solution:   Make 'fillchars' global-local. (closes vim/vim#5206)
https://github.com/vim/vim/commit/96ba25ac01279f73c0ecb5d4aa4ff37aa359e5eb

Cherry-pick g:run_nr from patch 8.2.0454.

N/A patches for version.c:

vim-patch:9.0.0037: build error

Problem:    Build error.
Solution:   Add missing change.
https://github.com/vim/vim/commit/510f03738dfcadfe2099c5b6a58cb75f64dbaa82

10 files changed, 109 insertions, 67 deletions

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 2e0c1f8cc4..164e09ccce 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2454,28 +2454,30 @@ A jump table for the options with a short description can be found at |Q_op|.
 						*'fillchars'* *'fcs'*
 'fillchars' 'fcs'	string	(default "")
 			global or local to window |global-local|
-	Characters to fill the statuslines and vertical separators.
-	It is a comma-separated list of items:
+	Characters to fill the statuslines, vertical separators and special
+	lines in the window.
+	It is a comma-separated list of items.  Each item has a name, a colon
+	and the value of that item:
 
 	  item		default		Used for ~
-	  stl:c		' ' or '^'	statusline of the current window
-	  stlnc:c	' ' or '='	statusline of the non-current windows
-	  wbr:c		' '		window bar
-	  horiz:c	'─' or '-'	horizontal separators |:split|
-	  horizup:c	'┴' or '-'	upwards facing horizontal separator
-	  horizdown:c	'┬' or '-'	downwards facing horizontal separator
-	  vert:c	'│' or '|'	vertical separators |:vsplit|
-	  vertleft:c	'┤' or '|'	left facing vertical separator
-	  vertright:c	'├' or '|'	right facing vertical separator
-	  verthoriz:c	'┼' or '+'	overlapping vertical and horizontal
+	  stl		' ' or '^'	statusline of the current window
+	  stlnc		' ' or '='	statusline of the non-current windows
+	  wbr		' '		window bar
+	  horiz		'─' or '-'	horizontal separators |:split|
+	  horizup	'┴' or '-'	upwards facing horizontal separator
+	  horizdown	'┬' or '-'	downwards facing horizontal separator
+	  vert		'│' or '|'	vertical separators |:vsplit|
+	  vertleft	'┤' or '|'	left facing vertical separator
+	  vertright	'├' or '|'	right facing vertical separator
+	  verthoriz	'┼' or '+'	overlapping vertical and horizontal
 					separator
-	  fold:c	'·' or '-'	filling 'foldtext'
-	  foldopen:c	'-'		mark the beginning of a fold
-	  foldclose:c	'+'		show a closed fold
-	  foldsep:c	'│' or '|'      open fold middle marker
-	  diff:c	'-'		deleted lines of the 'diff' option
-	  msgsep:c	' '		message separator 'display'
-	  eob:c		'~'		empty lines at the end of a buffer
+	  fold		'·' or '-'	filling 'foldtext'
+	  foldopen	'-'		mark the beginning of a fold
+	  foldclose	'+'		show a closed fold
+	  foldsep	'│' or '|'      open fold middle marker
+	  diff		'-'		deleted lines of the 'diff' option
+	  msgsep	' '		message separator 'display'
+	  eob		'~'		empty lines at the end of a buffer
 
 	Any one that is omitted will fall back to the default.  For "stl" and
 	"stlnc" the space will be used when there is highlighting, '^' or '='
@@ -2500,19 +2502,19 @@ A jump table for the options with a short description can be found at |Q_op|.
 
 	The highlighting used for these items:
 	  item		highlight group ~
-	  stl:c		StatusLine		|hl-StatusLine|
-	  stlnc:c	StatusLineNC		|hl-StatusLineNC|
-	  wbr:c		WinBar			|hl-WinBar| or |hl-WinBarNC|
-	  horiz:c	WinSeparator		|hl-WinSeparator|
-	  horizup:c	WinSeparator		|hl-WinSeparator|
-	  horizdown:c	WinSeparator		|hl-WinSeparator|
-	  vert:c	WinSeparator		|hl-WinSeparator|
-	  vertleft:c	WinSeparator		|hl-WinSeparator|
-	  vertright:c	WinSeparator		|hl-WinSeparator|
-	  verthoriz:c	WinSeparator		|hl-WinSeparator|
-	  fold:c	Folded			|hl-Folded|
-	  diff:c	DiffDelete		|hl-DiffDelete|
-	  eob:c		EndOfBuffer		|hl-EndOfBuffer|
+	  stl		StatusLine		|hl-StatusLine|
+	  stlnc		StatusLineNC		|hl-StatusLineNC|
+	  wbr		WinBar			|hl-WinBar| or |hl-WinBarNC|
+	  horiz		WinSeparator		|hl-WinSeparator|
+	  horizup	WinSeparator		|hl-WinSeparator|
+	  horizdown	WinSeparator		|hl-WinSeparator|
+	  vert		WinSeparator		|hl-WinSeparator|
+	  vertleft	WinSeparator		|hl-WinSeparator|
+	  vertright	WinSeparator		|hl-WinSeparator|
+	  verthoriz	WinSeparator		|hl-WinSeparator|
+	  fold		Folded			|hl-Folded|
+	  diff		DiffDelete		|hl-DiffDelete|
+	  eob		EndOfBuffer		|hl-EndOfBuffer|
 
 		*'fixendofline'* *'fixeol'* *'nofixendofline'* *'nofixeol'*
 'fixendofline' 'fixeol'	boolean	(default on)
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index d7d680b0fd..c0d7f8d066 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -257,10 +257,10 @@ typedef struct {
 #define w_p_scl w_onebuf_opt.wo_scl    // 'signcolumn'
   char *wo_winhl;
 #define w_p_winhl w_onebuf_opt.wo_winhl    // 'winhighlight'
-  char *wo_fcs;
-#define w_p_fcs w_onebuf_opt.wo_fcs    // 'fillchars'
   char *wo_lcs;
 #define w_p_lcs w_onebuf_opt.wo_lcs    // 'listchars'
+  char *wo_fcs;
+#define w_p_fcs w_onebuf_opt.wo_fcs    // 'fillchars'
   long wo_winbl;
 #define w_p_winbl w_onebuf_opt.wo_winbl  // 'winblend'
 
diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index f1a808e2bc..22b0f26a1c 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -1247,7 +1247,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
           }
           char_attr = 0;
         } else if (filler_todo > 0) {
-          // draw "deleted" diff line(s)
+          // Draw "deleted" diff line(s)
           if (char2cells(wp->w_p_fcs_chars.diff) > 1) {
             c_extra = '-';
             c_final = NUL;
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 012c4ecb19..cf8178a30f 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -1920,8 +1920,9 @@ win_update_start:
       wp->w_botline = lnum;
     }
 
-    // make sure the rest of the screen is blank
-    // write the 'eob' character to rows that aren't part of the file.
+    // Make sure the rest of the screen is blank.
+    // write the "eob" character from 'fillchars' to rows that aren't part
+    // of the file.
     win_draw_end(wp, wp->w_p_fcs_chars.eob, ' ', false, row, wp->w_grid.rows,
                  HLF_EOB);
   }
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index 83044f209a..ad8718742f 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -1989,8 +1989,7 @@ theend:
 }
 
 /// @return  true if string "s" is a valid utf-8 string.
-/// When "end" is NULL stop at the first NUL.
-/// When "end" is positive stop there.
+/// When "end" is NULL stop at the first NUL.  Otherwise stop at "end".
 bool utf_valid_string(const char_u *s, const char_u *end)
 {
   const char_u *p = s;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index b2525b73a0..6912f93daa 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -4250,6 +4250,14 @@ void win_copy_options(win_T *wp_from, win_T *wp_to)
   didset_window_options(wp_to, true);
 }
 
+static char *copy_option_val(const char *val)
+{
+  if (val == empty_option) {
+    return empty_option;  // no need to allocate memory
+  }
+  return xstrdup(val);
+}
+
 /// Copy the options from one winopt_T to another.
 /// Doesn't free the old option values in "to", use clear_winopt() for that.
 /// The 'scroll' option is not copied, because it depends on the window height.
@@ -4258,21 +4266,23 @@ void copy_winopt(winopt_T *from, winopt_T *to)
 {
   to->wo_arab = from->wo_arab;
   to->wo_list = from->wo_list;
+  to->wo_lcs = copy_option_val(from->wo_lcs);
+  to->wo_fcs = copy_option_val(from->wo_fcs);
   to->wo_nu = from->wo_nu;
   to->wo_rnu = from->wo_rnu;
-  to->wo_ve = xstrdup(from->wo_ve);
+  to->wo_ve = copy_option_val(from->wo_ve);
   to->wo_ve_flags = from->wo_ve_flags;
   to->wo_nuw = from->wo_nuw;
   to->wo_rl  = from->wo_rl;
-  to->wo_rlc = xstrdup(from->wo_rlc);
-  to->wo_sbr = xstrdup(from->wo_sbr);
-  to->wo_stl = xstrdup(from->wo_stl);
-  to->wo_wbr = xstrdup(from->wo_wbr);
+  to->wo_rlc = copy_option_val(from->wo_rlc);
+  to->wo_sbr = copy_option_val(from->wo_sbr);
+  to->wo_stl = copy_option_val(from->wo_stl);
+  to->wo_wbr = copy_option_val(from->wo_wbr);
   to->wo_wrap = from->wo_wrap;
   to->wo_wrap_save = from->wo_wrap_save;
   to->wo_lbr = from->wo_lbr;
   to->wo_bri = from->wo_bri;
-  to->wo_briopt = xstrdup(from->wo_briopt);
+  to->wo_briopt = copy_option_val(from->wo_briopt);
   to->wo_scb = from->wo_scb;
   to->wo_scb_save = from->wo_scb_save;
   to->wo_crb = from->wo_crb;
@@ -4280,30 +4290,28 @@ void copy_winopt(winopt_T *from, winopt_T *to)
   to->wo_spell = from->wo_spell;
   to->wo_cuc = from->wo_cuc;
   to->wo_cul = from->wo_cul;
-  to->wo_culopt = xstrdup(from->wo_culopt);
-  to->wo_cc = xstrdup(from->wo_cc);
+  to->wo_culopt = copy_option_val(from->wo_culopt);
+  to->wo_cc = copy_option_val(from->wo_cc);
   to->wo_diff = from->wo_diff;
   to->wo_diff_saved = from->wo_diff_saved;
-  to->wo_cocu = xstrdup(from->wo_cocu);
+  to->wo_cocu = copy_option_val(from->wo_cocu);
   to->wo_cole = from->wo_cole;
-  to->wo_fdc = xstrdup(from->wo_fdc);
+  to->wo_fdc = copy_option_val(from->wo_fdc);
   to->wo_fdc_save = from->wo_diff_saved ? xstrdup(from->wo_fdc_save) : empty_option;
   to->wo_fen = from->wo_fen;
   to->wo_fen_save = from->wo_fen_save;
-  to->wo_fdi = xstrdup(from->wo_fdi);
+  to->wo_fdi = copy_option_val(from->wo_fdi);
   to->wo_fml = from->wo_fml;
   to->wo_fdl = from->wo_fdl;
   to->wo_fdl_save = from->wo_fdl_save;
-  to->wo_fdm = xstrdup(from->wo_fdm);
+  to->wo_fdm = copy_option_val(from->wo_fdm);
   to->wo_fdm_save = from->wo_diff_saved ? xstrdup(from->wo_fdm_save) : empty_option;
   to->wo_fdn = from->wo_fdn;
-  to->wo_fde = xstrdup(from->wo_fde);
-  to->wo_fdt = xstrdup(from->wo_fdt);
-  to->wo_fmr = xstrdup(from->wo_fmr);
-  to->wo_scl = xstrdup(from->wo_scl);
-  to->wo_winhl = xstrdup(from->wo_winhl);
-  to->wo_fcs = xstrdup(from->wo_fcs);
-  to->wo_lcs = xstrdup(from->wo_lcs);
+  to->wo_fde = copy_option_val(from->wo_fde);
+  to->wo_fdt = copy_option_val(from->wo_fdt);
+  to->wo_fmr = copy_option_val(from->wo_fmr);
+  to->wo_scl = copy_option_val(from->wo_scl);
+  to->wo_winhl = copy_option_val(from->wo_winhl);
   to->wo_winbl = from->wo_winbl;
 
   // Copy the script context so that we know were the value was last set.
@@ -4338,8 +4346,8 @@ static void check_winopt(winopt_T *wop)
   check_string_option(&wop->wo_cocu);
   check_string_option(&wop->wo_briopt);
   check_string_option(&wop->wo_winhl);
-  check_string_option(&wop->wo_fcs);
   check_string_option(&wop->wo_lcs);
+  check_string_option(&wop->wo_fcs);
   check_string_option(&wop->wo_ve);
   check_string_option(&wop->wo_wbr);
 }
@@ -4364,8 +4372,8 @@ void clear_winopt(winopt_T *wop)
   clear_string_option(&wop->wo_cocu);
   clear_string_option(&wop->wo_briopt);
   clear_string_option(&wop->wo_winhl);
-  clear_string_option(&wop->wo_fcs);
   clear_string_option(&wop->wo_lcs);
+  clear_string_option(&wop->wo_fcs);
   clear_string_option(&wop->wo_ve);
   clear_string_option(&wop->wo_wbr);
 }
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index ad8092add2..f9848cb792 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -972,8 +972,8 @@ enum {
   WV_WRAP,
   WV_SCL,
   WV_WINHL,
-  WV_FCS,
   WV_LCS,
+  WV_FCS,
   WV_WINBL,
   WV_WBR,
   WV_COUNT,  // must be the last one
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index e1538e0491..e6847c3ea5 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -960,7 +960,9 @@ char *did_set_string_option(int opt_idx, char_u **varp, char_u *oldval, char *er
       FOR_ALL_TAB_WINDOWS(tp, wp) {
         // If no error was returned above, we don't expect an error
         // here, so ignore the return value.
-        (void)set_chars_option(wp, (char_u **)&wp->w_p_lcs, true);
+        if (*wp->w_p_lcs == NUL) {
+          (void)set_chars_option(wp, (char_u **)&wp->w_p_lcs, true);
+        }
       }
       redraw_all_later(UPD_NOT_VALID);
     }
@@ -977,7 +979,9 @@ char *did_set_string_option(int opt_idx, char_u **varp, char_u *oldval, char *er
       FOR_ALL_TAB_WINDOWS(tp, wp) {
         // If no error was returned above, we don't expect an error
         // here, so ignore the return value.
-        (void)set_chars_option(wp, (char_u **)&wp->w_p_fcs, true);
+        if (*wp->w_p_fcs == NUL) {
+          (void)set_chars_option(wp, (char_u **)&wp->w_p_fcs, true);
+        }
       }
       redraw_all_later(UPD_NOT_VALID);
     }
diff --git a/src/nvim/testdir/runtest.vim b/src/nvim/testdir/runtest.vim
index 206f335751..ce23141c7a 100644
--- a/src/nvim/testdir/runtest.vim
+++ b/src/nvim/testdir/runtest.vim
@@ -425,7 +425,7 @@ for s:test in sort(s:tests)
   set belloff=all
   let prev_error = ''
   let total_errors = []
-  let run_nr = 1
+  let g:run_nr = 1
 
   " A test can set g:test_is_flaky to retry running the test.
   let g:test_is_flaky = 0
@@ -444,10 +444,10 @@ for s:test in sort(s:tests)
       call add(s:messages, 'Found errors in ' . s:test . ':')
       call extend(s:messages, v:errors)
 
-      call add(total_errors, 'Run ' . run_nr . ':')
+      call add(total_errors, 'Run ' . g:run_nr . ':')
       call extend(total_errors, v:errors)
 
-      if run_nr == 5 || prev_error == v:errors[0]
+      if g:run_nr >= 5 || prev_error == v:errors[0]
         call add(total_errors, 'Flaky test failed too often, giving up')
         let v:errors = total_errors
         break
@@ -462,7 +462,7 @@ for s:test in sort(s:tests)
 
       let prev_error = v:errors[0]
       let v:errors = []
-      let run_nr += 1
+      let g:run_nr += 1
 
       call RunTheTest(s:test)
 
diff --git a/src/nvim/testdir/test_display.vim b/src/nvim/testdir/test_display.vim
index a30d57016a..217bb5d781 100644
--- a/src/nvim/testdir/test_display.vim
+++ b/src/nvim/testdir/test_display.vim
@@ -363,6 +363,34 @@ func Test_fold_fillchars()
   set fillchars& fdc& foldmethod& foldenable&
 endfunc
 
+func Test_local_fillchars()
+  CheckScreendump
+
+  let lines =<< trim END
+      call setline(1, ['window 1']->repeat(3))
+      setlocal fillchars=stl:1,stlnc:a,vert:=,eob:x
+      vnew
+      call setline(1, ['window 2']->repeat(3))
+      setlocal fillchars=stl:2,stlnc:b,vert:+,eob:y
+      new
+      wincmd J
+      call setline(1, ['window 3']->repeat(3))
+      setlocal fillchars=stl:3,stlnc:c,vert:<,eob:z
+      vnew
+      call setline(1, ['window 4']->repeat(3))
+      setlocal fillchars=stl:4,stlnc:d,vert:>,eob:o
+  END
+  call writefile(lines, 'Xdisplayfillchars')
+  let buf = RunVimInTerminal('-S Xdisplayfillchars', #{rows: 12})
+  call VerifyScreenDump(buf, 'Test_display_fillchars_1', {})
+
+  call term_sendkeys(buf, ":wincmd k\r")
+  call VerifyScreenDump(buf, 'Test_display_fillchars_2', {})
+
+  call StopVimInTerminal(buf)
+  call delete('Xdisplayfillchars')
+endfunc
+
 func Test_display_linebreak_breakat()
   new
   vert resize 25