vim-patch:8.1.0116: display problem with 'vartabstop' and 'linebreak'

Problem:    Display problem with 'vartabstop' and 'linebreak'. (Chauca
            Fuentes)
Solution:   Call tabstop_padding(). (Christian Brabandt, closes vim/vim#3076)
a87b72cc31

src/nvim/screen.c

@@ -3441,8 +3441,8 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow,
           // TODO: is passing p for start of the line OK?
           n_extra = win_lbr_chartabsize(wp, line, p, (colnr_T)vcol, NULL) - 1;
           if (c == TAB && n_extra + col > grid->Columns) {
-            n_extra = (int)wp->w_buffer->b_p_ts
-                      - vcol % (int)wp->w_buffer->b_p_ts - 1;
+            n_extra = tabstop_padding(vcol, wp->w_buffer->b_p_ts,
+                                      wp->w_buffer->b_p_vts_array) - 1;
           }
           c_extra = mb_off > 0 ? MB_FILLER_CHAR : ' ';
           c_final = NUL;

src/nvim/testdir/test_vartabs.vim

@@ -4,6 +4,11 @@ if !has("vartabs")
   finish
 endif
 
+source view_util.vim
+function! s:compare_lines(expect, actual)
+  call assert_equal(join(a:expect, "\n"), join(a:actual, "\n"))
+endfunction
+
 func! Test_vartabs()
   new
   %d
@@ -255,3 +260,23 @@ func! Test_vartabs_breakindent()
 
   bwipeout!
 endfunc
+
+func! Test_vartabs_linebreak()
+  if winwidth(0) < 80
+    return
+  endif
+  new
+  70vnew
+  %d
+  setl linebreak vartabstop=10,15,20,40
+  call setline(1, "\tx\tx\tx\tx")
+
+  let lines = ScreenLines([1, 2], winwidth(0))
+  let expect = ['          x              x                   x                        ',
+        \       '               x                                                      ']
+  call s:compare_lines(expect, lines)
+
+  " cleanup
+  bw!
+  bw!
+endfunc