patch 8.1.1868: multi-byte chars in 'listchars' fail with 'linebreak' set

Problem:    Multibyte characters in 'listchars' don't work correctly if
            'linebreak' is also enabled. (Martin Tournoij)
Solution:   Make it work correctly. (Christian Brabandt, closes #4822,
            closes #4812)

src/screen.c

@@ -4891,7 +4891,7 @@ win_line(
 		    if (*p_sbr != NUL && vcol == vcol_sbr && wp->w_p_wrap)
 			vcol_adjusted = vcol - MB_CHARLEN(p_sbr);
 #endif
-		    /* tab amount depends on current column */
+		    // tab amount depends on current column
 #ifdef FEAT_VARTABS
 		    tab_len = tabstop_padding(vcol_adjusted,
 					      wp->w_buffer->b_p_ts,
@@ -4904,7 +4904,7 @@ win_line(
 #ifdef FEAT_LINEBREAK
 		    if (!wp->w_p_lbr || !wp->w_p_list)
 #endif
-		    /* tab amount depends on current column */
+			// tab amount depends on current column
 			n_extra = tab_len;
 #ifdef FEAT_LINEBREAK
 		    else
@@ -4916,18 +4916,17 @@ win_line(
 
 #ifdef FEAT_CONCEAL
 			if (vcol_off > 0)
-			    /* there are characters to conceal */
+			    // there are characters to conceal
 			    tab_len += vcol_off;
-			/* boguscols before FIX_FOR_BOGUSCOLS macro from above
+			// boguscols before FIX_FOR_BOGUSCOLS macro from above
-			 */
 			if (wp->w_p_list && lcs_tab1 && old_boguscols > 0
 							 && n_extra > tab_len)
 			    tab_len += n_extra - tab_len;
 #endif
 
-			/* if n_extra > 0, it gives the number of chars, to
+			// if n_extra > 0, it gives the number of chars, to
-			 * use for a tab, else we need to calculate the width
+			// use for a tab, else we need to calculate the width
-			 * for a tab */
+			// for a tab
 			len = (tab_len * mb_char2len(lcs_tab2));
 			if (n_extra > 0)
 			    len += n_extra - tab_len;
@@ -4939,20 +4938,27 @@ win_line(
 			p_extra_free = p;
 			for (i = 0; i < tab_len; i++)
 			{
+			    int lcs = lcs_tab2;
+
 			    if (*p == NUL)
 			    {
 				tab_len = i;
 				break;
 			    }
-			    mb_char2bytes(lcs_tab2, p);
+
-			    p += mb_char2len(lcs_tab2);
+			    // if lcs_tab3 is given, need to change the char
-			    n_extra += mb_char2len(lcs_tab2)
+			    // for tab
+			    if (lcs_tab3 && i == tab_len - 1)
+				lcs = lcs_tab3;
+			    mb_char2bytes(lcs, p);
+			    p += mb_char2len(lcs);
+			    n_extra += mb_char2len(lcs)
 						  - (saved_nextra > 0 ? 1 : 0);
 			}
 			p_extra = p_extra_free;
 #ifdef FEAT_CONCEAL
-			/* n_extra will be increased by FIX_FOX_BOGUSCOLS
+			// n_extra will be increased by FIX_FOX_BOGUSCOLS
-			 * macro below, so need to adjust for that here */
+			// macro below, so need to adjust for that here
 			if (vcol_off > 0)
 			    n_extra -= vcol_off;
 #endif

src/testdir/test_listchars.vim

@@ -58,6 +58,26 @@ func Test_listchars()
     call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
   endfor
 
+  " tab with 3rd character and linebreak set
+  set listchars-=tab:<=>
+  set listchars+=tab:<·>
+  set linebreak
+  let expected = [
+	      \ '<······>aa<····>$',
+	      \ '..bb<··>--$',
+	      \ '...cccc>-$',
+	      \ 'dd........ee--<>$',
+	      \ '-$'
+	      \ ]
+  redraw!
+  for i in range(1, 5)
+    call cursor(i, 1)
+    call assert_equal([expected[i - 1]], ScreenLines(i, virtcol('$')))
+  endfor
+  set nolinebreak
+  set listchars-=tab:<·>
+  set listchars+=tab:<=>
+
   set listchars-=trail:-
   let expected = [
 	      \ '<======>aa<====>$',

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1868,
 /**/
     1867,
 /**/