vim-patch:8.2.3424: a sequence of spaces is hard to see in list mode

Problem:    A sequence of spaces is hard to see in list mode.
Solution:   Add the "multispace" option to 'listchars'. (closes vim/vim#8834)
f14b8ba137

runtime/doc/options.txt

@@ -3751,16 +3751,25 @@ A jump table for the options with a short description can be found at |Q_op|.
 							*lcs-space*
 	  space:c	Character to show for a space.  When omitted, spaces
 			are left blank.
+							*lcs-multispace*
+	  multispace:c...
+	 		One or more characters to use cyclically to show for
+	 		multiple consecutive spaces.  Overrides the "space"
+			setting, except for single spaces.  When omitted, the
+			"space" setting is used.  For example,
+			`:set listchars=multispace:---+` shows ten consecutive
+			spaces as:
+				---+---+--
 							*lcs-lead*
 	  lead:c	Character to show for leading spaces.  When omitted,
-			leading spaces are blank.  Overrides the "space"
+			leading spaces are blank.  Overrides the "space" and
-			setting for leading spaces.  You can combine it with
+			"multispace" settings for leading spaces.  You can
-			"tab:", for example: >
+			combine it with "tab:", for example: >
 				:set listchars+=tab:>-,lead:.
 <							*lcs-trail*
 	  trail:c	Character to show for trailing spaces.  When omitted,
-			trailing spaces are blank.  Overrides the "space"
+			trailing spaces are blank.  Overrides the "space" and
-			setting for trailing spaces.
+			"multispace" settings for trailing spaces.
 							*lcs-extends*
 	  extends:c	Character to show in the last column, when 'wrap' is
 			off and the line continues beyond the right of the
@@ -3785,7 +3794,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 	    :set lcs=tab:>-,eol:<,nbsp:%
 	    :set lcs=extends:>,precedes:<
 <	|hl-NonText| highlighting will be used for "eol", "extends" and
-	"precedes". |hl-Whitespace| for "nbsp", "space", "tab" and "trail".
+	"precedes". |hl-Whitespace| for "nbsp", "space", "tab", "multispace",
+	"lead" and "trail".
 
 			*'lpl'* *'nolpl'* *'loadplugins'* *'noloadplugins'*
 'loadplugins' 'lpl'	boolean	(default on)

src/nvim/buffer_defs.h

@@ -1214,6 +1214,7 @@ struct window_S {
     int tab3;                       ///< third tab character
     int lead;
     int trail;
+    int *multispace;
     int conceal;
   } w_p_lcs_chars;
 

src/nvim/message.c

@@ -1707,6 +1707,8 @@ void msg_prt_line(char_u *s, int list)
   int n;
   int attr = 0;
   char_u *lead = NULL;
+  bool in_multispace = false;
+  int multispace_pos = 0;
   char_u *trail = NULL;
   int l;
 
@@ -1771,6 +1773,10 @@ void msg_prt_line(char_u *s, int list)
     } else {
       attr = 0;
       c = *s++;
+      in_multispace = c == ' ' && ((col > 0 && s[-2] == ' ') || *s == ' ');
+      if (!in_multispace) {
+        multispace_pos = 0;
+      }
       if (c == TAB && (!list || curwin->w_p_lcs_chars.tab1)) {
         // tab amount depends on current column
         n_extra = tabstop_padding(col,
@@ -1786,11 +1792,11 @@ void msg_prt_line(char_u *s, int list)
               : curwin->w_p_lcs_chars.tab1;
           c_extra = curwin->w_p_lcs_chars.tab2;
           c_final = curwin->w_p_lcs_chars.tab3;
-          attr = HL_ATTR(HLF_8);
+          attr = HL_ATTR(HLF_0);
         }
       } else if (c == 160 && list && curwin->w_p_lcs_chars.nbsp != NUL) {
         c = curwin->w_p_lcs_chars.nbsp;
-        attr = HL_ATTR(HLF_8);
+        attr = HL_ATTR(HLF_0);
       } else if (c == NUL && list && curwin->w_p_lcs_chars.eol != NUL) {
         p_extra = (char_u *)"";
         c_extra = NUL;
@@ -1807,16 +1813,24 @@ void msg_prt_line(char_u *s, int list)
         c = *p_extra++;
         /* Use special coloring to be able to distinguish <hex> from
          * the same in plain text. */
-        attr = HL_ATTR(HLF_8);
+        attr = HL_ATTR(HLF_0);
-      } else if (c == ' ' && lead != NULL && s <= lead) {
+      } else if (c == ' ') {
-        c = curwin->w_p_lcs_chars.lead;
+        if (lead != NULL && s <= lead) {
-        attr = HL_ATTR(HLF_8);
+          c = curwin->w_p_lcs_chars.lead;
-      } else if (c == ' ' && trail != NULL && s > trail) {
+          attr = HL_ATTR(HLF_0);
-        c = curwin->w_p_lcs_chars.trail;
+        } else if (trail != NULL && s > trail) {
-        attr = HL_ATTR(HLF_8);
+          c = curwin->w_p_lcs_chars.trail;
-      } else if (c == ' ' && list && curwin->w_p_lcs_chars.space != NUL) {
+          attr = HL_ATTR(HLF_0);
-        c = curwin->w_p_lcs_chars.space;
+        } else if (list && in_multispace && curwin->w_p_lcs_chars.multispace != NULL) {
-        attr = HL_ATTR(HLF_8);
+          c = curwin->w_p_lcs_chars.multispace[multispace_pos++];
+          if (curwin->w_p_lcs_chars.multispace[multispace_pos] == NUL) {
+            multispace_pos = 0;
+          }
+          attr = HL_ATTR(HLF_0);
+        } else if (list && curwin->w_p_lcs_chars.space != NUL) {
+          c = curwin->w_p_lcs_chars.space;
+          attr = HL_ATTR(HLF_0);
+        }
       }
     }
 

src/nvim/option.c

@@ -3442,6 +3442,8 @@ static char_u *set_chars_option(win_T *wp, char_u **varp, bool set)
   int c1;
   int c2 = 0;
   int c3 = 0;
+  char_u *last_multispace;  // Last occurrence of "multispace:"
+  int multispace_len = 0;   // Length of lcs-multispace string
 
   struct chars_tab {
     int     *cp;    ///< char value
@@ -3511,6 +3513,15 @@ static char_u *set_chars_option(win_T *wp, char_u **varp, bool set)
       if (varp == &p_lcs || varp == &wp->w_p_lcs) {
         wp->w_p_lcs_chars.tab1 = NUL;
         wp->w_p_lcs_chars.tab3 = NUL;
+        if (wp->w_p_lcs_chars.multispace != NULL) {
+          xfree(wp->w_p_lcs_chars.multispace);
+        }
+        if (multispace_len > 0) {
+          wp->w_p_lcs_chars.multispace = xmalloc((size_t)(multispace_len + 1) * sizeof(int));
+          wp->w_p_lcs_chars.multispace[multispace_len] = NUL;
+        } else {
+          wp->w_p_lcs_chars.multispace = NULL;
+        }
       }
     }
     p = *varp;
@@ -3527,22 +3538,22 @@ static char_u *set_chars_option(win_T *wp, char_u **varp, bool set)
           int c1len = utf_ptr2len(s);
           c1 = mb_cptr2char_adv((const char_u **)&s);
           if (mb_char2cells(c1) > 1 || (c1len == 1 && c1 > 127)) {
-            continue;
+            return e_invarg;
           }
           if (tab[i].cp == &wp->w_p_lcs_chars.tab2) {
             if (*s == NUL) {
-              continue;
+              return e_invarg;
             }
             int c2len = utf_ptr2len(s);
             c2 = mb_cptr2char_adv((const char_u **)&s);
             if (mb_char2cells(c2) > 1 || (c2len == 1 && c2 > 127)) {
-              continue;
+              return e_invarg;
             }
             if (!(*s == ',' || *s == NUL)) {
               int c3len = utf_ptr2len(s);
               c3 = mb_cptr2char_adv((const char_u **)&s);
               if (mb_char2cells(c3) > 1 || (c3len == 1 && c3 > 127)) {
-                continue;
+                return e_invarg;
               }
             }
           }
@@ -3563,7 +3574,42 @@ static char_u *set_chars_option(win_T *wp, char_u **varp, bool set)
       }
 
       if (i == entries) {
-        return e_invarg;
+        len = STRLEN("multispace");
+        if ((varp == &p_lcs || varp == &wp->w_p_lcs)
+            && STRNCMP(p, "multispace", len) == 0
+            && p[len] == ':'
+            && p[len + 1] != NUL) {
+          s = p + len + 1;
+          if (round == 0) {
+            // Get length of lcs-multispace string in the first round
+            last_multispace = p;
+            multispace_len = 0;
+            while (*s != NUL && *s != ',') {
+              int c1len = utf_ptr2len(s);
+              c1 = mb_cptr2char_adv((const char_u **)&s);
+              if (mb_char2cells(c1) > 1 || (c1len == 1 && c1 > 127)) {
+                return e_invarg;
+              }
+              multispace_len++;
+            }
+            if (multispace_len == 0) {
+              // lcs-multispace cannot be an empty string
+              return e_invarg;
+            }
+            p = s;
+          } else {
+            int multispace_pos = 0;
+            while (*s != NUL && *s != ',') {
+              c1 = mb_cptr2char_adv((const char_u **)&s);
+              if (p == last_multispace) {
+                wp->w_p_lcs_chars.multispace[multispace_pos++] = c1;
+              }
+            }
+            p = s;
+          }
+        } else {
+          return e_invarg;
+        }
       }
       if (*p == ',') {
         p++;

src/nvim/screen.c

@@ -2081,6 +2081,8 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
   int change_end = -1;                  // last col of changed area
   colnr_T trailcol = MAXCOL;            // start of trailing spaces
   colnr_T leadcol = 0;                  // start of leading spaces
+  bool in_multispace = false;           // in multiple consecutive spaces
+  int multispace_pos = 0;               // position in lcs-multispace string
   bool need_showbreak = false;          // overlong line, skip first x chars
   sign_attrs_T sattrs[SIGN_SHOW_MAX];   // attributes for signs
   int num_signs;                        // number of signs for line
@@ -2462,6 +2464,7 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
 
   if (wp->w_p_list && !has_fold && !end_fill) {
     if (wp->w_p_lcs_chars.space
+        || wp->w_p_lcs_chars.multispace != NULL
         || wp->w_p_lcs_chars.trail
         || wp->w_p_lcs_chars.lead
         || wp->w_p_lcs_chars.nbsp) {
@@ -3580,6 +3583,11 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
           }
         }
 
+        in_multispace = c == ' ' && ((ptr > line + 1 && ptr[-2] == ' ') || *ptr == ' ');
+        if (!in_multispace) {
+          multispace_pos = 0;
+        }
+
         // 'list': Change char 160 to 'nbsp' and space to 'space'.
         // But not when the character is followed by a composing
         // character (use mb_l to check that).
@@ -3591,10 +3599,18 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
                  && wp->w_p_lcs_chars.nbsp)
                 || (c == ' '
                     && mb_l == 1
-                    && wp->w_p_lcs_chars.space
+                    && (wp->w_p_lcs_chars.space
+                        || (in_multispace && wp->w_p_lcs_chars.multispace != NULL))
                     && ptr - line >= leadcol
                     && ptr - line <= trailcol))) {
-          c = (c == ' ') ? wp->w_p_lcs_chars.space : wp->w_p_lcs_chars.nbsp;
+          if (in_multispace && wp->w_p_lcs_chars.multispace != NULL) {
+            c = wp->w_p_lcs_chars.multispace[multispace_pos++];
+            if (wp->w_p_lcs_chars.multispace[multispace_pos] == NUL) {
+              multispace_pos = 0;
+            }
+          } else {
+            c = (c == ' ') ? wp->w_p_lcs_chars.space : wp->w_p_lcs_chars.nbsp;
+          }
           n_attr = 1;
           extra_attr = win_hl_attr(wp, HLF_0);
           saved_attr2 = char_attr;  // save current attr

src/nvim/testdir/test_listchars.vim

@@ -140,6 +140,93 @@ func Test_listchars()
 
   call assert_equal(expected, split(execute("%list"), "\n"))
 
+  " Test multispace
+  normal ggdG
+  set listchars=eol:$
+  set listchars+=multispace:yYzZ
+  set list
+
+  call append(0, [
+	      \ '    ffff    ',
+	      \ '  i i     gg',
+	      \ ' h          ',
+	      \ '          j ',
+	      \ '    0  0    ',
+	      \ ])
+
+  let expected = [
+	      \ 'yYzZffffyYzZ$',
+	      \ 'yYi iyYzZygg$',
+	      \ ' hyYzZyYzZyY$',
+	      \ 'yYzZyYzZyYj $',
+	      \ 'yYzZ0yY0yYzZ$',
+              \ '$'
+	      \ ]
+  redraw!
+  for i in range(1, 5)
+    call cursor(i, 1)
+    call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
+  endfor
+
+  call assert_equal(expected, split(execute("%list"), "\n"))
+
+  " the last occurrence of 'multispace:' is used
+  set listchars+=space:x,multispace:XyY
+
+  let expected = [
+	      \ 'XyYXffffXyYX$',
+	      \ 'XyixiXyYXygg$',
+	      \ 'xhXyYXyYXyYX$',
+	      \ 'XyYXyYXyYXjx$',
+	      \ 'XyYX0Xy0XyYX$',
+              \ '$'
+	      \ ]
+  redraw!
+  for i in range(1, 5)
+    call cursor(i, 1)
+    call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
+  endfor
+
+  call assert_equal(expected, split(execute("%list"), "\n"))
+
+  set listchars+=lead:>,trail:<
+
+  let expected = [
+	      \ '>>>>ffff<<<<$',
+	      \ '>>ixiXyYXygg$',
+	      \ '>h<<<<<<<<<<$',
+	      \ '>>>>>>>>>>j<$',
+	      \ '>>>>0Xy0<<<<$',
+              \ '$'
+	      \ ]
+  redraw!
+  for i in range(1, 5)
+    call cursor(i, 1)
+    call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
+  endfor
+
+  call assert_equal(expected, split(execute("%list"), "\n"))
+
+  " removing 'multispace:'
+  set listchars-=multispace:XyY
+  set listchars-=multispace:yYzZ
+
+  let expected = [
+	      \ '>>>>ffff<<<<$',
+	      \ '>>ixixxxxxgg$',
+	      \ '>h<<<<<<<<<<$',
+	      \ '>>>>>>>>>>j<$',
+	      \ '>>>>0xx0<<<<$',
+              \ '$'
+	      \ ]
+  redraw!
+  for i in range(1, 5)
+    call cursor(i, 1)
+    call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
+  endfor
+
+  call assert_equal(expected, split(execute("%list"), "\n"))
+
   " test nbsp
   normal ggdG
   set listchars=nbsp:X,trail:Y
@@ -189,20 +276,69 @@ func Test_listchars_unicode()
   set encoding=utf-8
   set ff=unix
 
-  set listchars=eol:⇔,space:␣,nbsp:≠,tab:←↔→
+  set listchars=eol:⇔,space:␣,multispace:≡≢≣,nbsp:≠,tab:←↔→
   set list
 
   let nbsp = nr2char(0xa0)
-  call append(0, ["a\tb c" .. nbsp .. "d"])
+  call append(0, ["        a\tb c" .. nbsp .. "d  "])
-  let expected = ['a←↔↔↔↔↔→b␣c≠d⇔']
+  let expected = ['≡≢≣≡≢≣≡≢a←↔↔↔↔↔→b␣c≠d≡≢⇔']
   redraw!
   call cursor(1, 1)
   call assert_equal(expected, ScreenLines(1, virtcol('$')))
+
+  set listchars+=lead:⇨,trail:⇦
+  let expected = ['⇨⇨⇨⇨⇨⇨⇨⇨a←↔↔↔↔↔→b␣c≠d⇦⇦⇔']
+  redraw!
+  call cursor(1, 1)
+  call assert_equal(expected, ScreenLines(1, virtcol('$')))
+
   let &encoding=oldencoding
   enew!
   set listchars& ff&
 endfunction
 
+func Test_listchars_invalid()
+  enew!
+  set ff=unix
+
+  set listchars=eol:$
+  set list
+  set ambiwidth=double
+
+  " No colon
+  call assert_fails('set listchars=x', 'E474:')
+  call assert_fails('set listchars=x', 'E474:')
+  call assert_fails('set listchars=multispace', 'E474:')
+
+  " Too short
+  call assert_fails('set listchars=space:', 'E474:')
+  call assert_fails('set listchars=tab:x', 'E474:')
+  call assert_fails('set listchars=multispace:', 'E474:')
+
+  " One occurrence too short
+  call assert_fails('set listchars=space:,space:x', 'E474:')
+  call assert_fails('set listchars=space:x,space:', 'E474:')
+  call assert_fails('set listchars=tab:x,tab:xx', 'E474:')
+  call assert_fails('set listchars=tab:xx,tab:x', 'E474:')
+  call assert_fails('set listchars=multispace:,multispace:x', 'E474:')
+  call assert_fails('set listchars=multispace:x,multispace:', 'E474:')
+
+  " Too long
+  call assert_fails('set listchars=space:xx', 'E474:')
+  call assert_fails('set listchars=tab:xxxx', 'E474:')
+
+  " Has non-single width character
+  call assert_fails('set listchars=space:·', 'E474:')
+  call assert_fails('set listchars=tab:·x', 'E474:')
+  call assert_fails('set listchars=tab:x·', 'E474:')
+  call assert_fails('set listchars=tab:xx·', 'E474:')
+  call assert_fails('set listchars=multispace:·', 'E474:')
+  call assert_fails('set listchars=multispace:xxx·', 'E474:')
+
+  enew!
+  set ambiwidth& listchars& ff&
+endfunction
+
 " Tests that space characters following composing character won't get replaced
 " by listchars.
 func Test_listchars_composing()