patch 8.0.0250: virtcol() does not work well for multi-byte characters

Problem:    When virtcol() gets a column that is not the first byte of a
            multi-byte character the result is unpredictable. (Christian
            Ludwig)
Solution:   Correct the column to the first byte of a multi-byte character.
            Change the utf-8 test to new style.

Author: brammool

src/Makefile

@@ -2058,7 +2058,6 @@ test1 \
 	test_listlbr \
 	test_listlbr_utf8 \
 	test_search_mbyte \
-	test_utf8 \
 	test_wordcount \
 	test3 test4 test5 test6 test7 test8 test9 \
 	test11 test12 test14 test15 test17 test18 test19 \
@@ -2183,6 +2182,7 @@ test_arglist \
 	test_undo \
 	test_unlet \
 	test_usercommands \
+	test_utf8 \
 	test_viminfo \
 	test_viml \
 	test_visual \

src/charset.c

@@ -1296,7 +1296,14 @@ getvcol(
     if (pos->col == MAXCOL)
 	posptr = NULL;  /* continue until the NUL */
     else
+    {
 	posptr = ptr + pos->col;
+#ifdef FEAT_MBYTE
+	if (has_mbyte)
+	    /* always start on the first byte */
+	    posptr -= (*mb_head_off)(line, posptr);
+#endif
+    }
 
     /*
      * This function is used very often, do some speed optimizations.

src/testdir/Make_all.mak

@@ -84,7 +84,6 @@ SCRIPTS_ALL = \
 	test_listchars.out \
 	test_listlbr.out \
 	test_search_mbyte.out \
-	test_utf8.out \
 	test_wordcount.out
 
 

src/testdir/test_alot_utf8.vim

@@ -9,3 +9,4 @@ source test_expr_utf8.vim
 source test_matchadd_conceal_utf8.vim
 source test_regexp_utf8.vim
 source test_source_utf8.vim
+source test_utf8.vim

src/testdir/test_utf8.in

@@ -0,0 +1,65 @@
+" Tests for Unicode manipulations
+if !has('multi_byte')
+  finish
+endif
+ 
+
+" Visual block Insert adjusts for multi-byte char
+func Test_visual_block_insert()
+  new
+  call setline(1, ["aaa", "あああ", "bbb"])
+  exe ":norm! gg0l\<C-V>jjIx\<Esc>"
+  call assert_equal(['axaa', 'xあああ', 'bxbb'], getline(1, '$'))
+  bwipeout!
+endfunc
+
+" Test for built-in function strchars()
+func Test_strchars()
+  let inp = ["a", "あいa", "A\u20dd", "A\u20dd\u20dd", "\u20dd"]
+  let exp = [[1, 1, 1], [3, 3, 3], [2, 2, 1], [3, 3, 1], [1, 1, 1]]
+  for i in range(len(inp))
+    call assert_equal(exp[i][0], strchars(inp[i]))
+    call assert_equal(exp[i][1], strchars(inp[i], 0))
+    call assert_equal(exp[i][2], strchars(inp[i], 1))
+  endfor
+endfunc
+
+" Test for customlist completion
+function! CustomComplete1(lead, line, pos)
+	return ['あ', 'い']
+endfunction
+
+function! CustomComplete2(lead, line, pos)
+	return ['あたし', 'あたま', 'あたりめ']
+endfunction
+
+function! CustomComplete3(lead, line, pos)
+	return ['Nこ', 'Nん', 'Nぶ']
+endfunction
+
+func Test_customlist_completion()
+  command -nargs=1 -complete=customlist,CustomComplete1 Test1 echo
+  call feedkeys(":Test1 \<C-L>\<C-B>\"\<CR>", 'itx')
+  call assert_equal('"Test1 ', getreg(':'))
+
+  command -nargs=1 -complete=customlist,CustomComplete2 Test2 echo
+  call feedkeys(":Test2 \<C-L>\<C-B>\"\<CR>", 'itx')
+  call assert_equal('"Test2 あた', getreg(':'))
+
+  command -nargs=1 -complete=customlist,CustomComplete3 Test3 echo
+  call feedkeys(":Test3 \<C-L>\<C-B>\"\<CR>", 'itx')
+  call assert_equal('"Test3 N', getreg(':'))
+
+  call garbagecollect(1)
+endfunc
+
+" Yank one 3 byte character and check the mark columns.
+func Test_getvcol()
+  new
+  call setline(1, "x\u2500x")
+  normal 0lvy
+  call assert_equal(2, col("'["))
+  call assert_equal(4, col("']"))
+  call assert_equal(2, virtcol("'["))
+  call assert_equal(2, virtcol("']"))
+endfunc

src/testdir/test_utf8.ok

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    250,
 /**/
     249,
 /**/