patch 9.0.1223: cannot use setcellwidths() below 0x100

Problem:    Cannot use setcellwidths() below 0x100.
Solution:   Also accept characters between 0x80 and 0x100. (Ken Takata,
            closes #11834)

runtime/doc/builtin.txt

@@ -7966,7 +7966,7 @@ setcellwidths({list})					*setcellwidths()*
 		{low} and {high} can be the same, in which case this refers to
 		one character.  Otherwise it is the range of characters from
 		{low} to {high} (inclusive).		*E1111* *E1114*
-		Only characters with value 0x100 and higher can be used.
+		Only characters with value 0x80 and higher can be used.
 
 		{width} must be either 1 or 2, indicating the character width
 		in screen cells.			*E1112*

src/errors.h

@@ -2841,8 +2841,8 @@ EXTERN char e_list_item_nr_cell_width_invalid[]
 	INIT(= N_("E1112: List item %d cell width invalid"));
 EXTERN char e_overlapping_ranges_for_nr[]
 	INIT(= N_("E1113: Overlapping ranges for 0x%lx"));
-EXTERN char e_only_values_of_0x100_and_higher_supported[]
-	INIT(= N_("E1114: Only values of 0x100 and higher supported"));
+EXTERN char e_only_values_of_0x80_and_higher_supported[]
+	INIT(= N_("E1114: Only values of 0x80 and higher supported"));
 EXTERN char e_assert_fails_fourth_argument[]
 	INIT(= N_("E1115: \"assert_fails()\" fourth argument must be a number"));
 EXTERN char e_assert_fails_fifth_argument[]

src/mbyte.c

@@ -1589,19 +1589,26 @@ utf_char2cells(int c)
 #endif
     };
 
-    if (c >= 0x100)
-    {
-#if defined(FEAT_EVAL) || defined(USE_WCHAR_FUNCTIONS)
-	int	n;
-#endif
-
 #ifdef FEAT_EVAL
-	n = cw_value(c);
+    // Use the value from setcellwidths() at 0x80 and higher, unless the
+    // character is not printable.
+    if (c >= 0x80 &&
+# ifdef USE_WCHAR_FUNCTIONS
+	    wcwidth(c) >= 1 &&
+# endif
+	    vim_isprintc(c))
+    {
+	int n = cw_value(c);
 	if (n != 0)
 	    return n;
+    }
 #endif
 
+    if (c >= 0x100)
+    {
 #ifdef USE_WCHAR_FUNCTIONS
+	int	n;
+
 	/*
 	 * Assume the library function wcwidth() works better than our own
 	 * stuff.  It should return 1 for ambiguous width chars!
@@ -5661,9 +5668,9 @@ f_setcellwidths(typval_T *argvars, typval_T *rettv UNUSED)
 	    if (i == 0)
 	    {
 		n1 = lili->li_tv.vval.v_number;
-		if (n1 < 0x100)
+		if (n1 < 0x80)
 		{
-		    emsg(_(e_only_values_of_0x100_and_higher_supported));
+		    emsg(_(e_only_values_of_0x80_and_higher_supported));
 		    vim_free(ptrs);
 		    return;
 		}

src/testdir/test_utf8.vim

@@ -167,6 +167,39 @@ func Test_setcellwidths()
   call assert_equal(2, strwidth("\u1339"))
   call assert_equal(1, strwidth("\u133a"))
 
+  for aw in ['single', 'double']
+    exe 'set ambiwidth=' . aw
+    " Handle \u0080 to \u009F as control chars even on MS-Windows.
+    set isprint=@,161-255
+
+    call setcellwidths([])
+    " Control chars
+    call assert_equal(4, strwidth("\u0081"))
+    call assert_equal(6, strwidth("\uFEFF"))
+    " Ambiguous width chars
+    call assert_equal((aw == 'single') ? 1 : 2, strwidth("\u00A1"))
+    call assert_equal((aw == 'single') ? 1 : 2, strwidth("\u2010"))
+
+    call setcellwidths([[0x81, 0x81, 1], [0xA1, 0xA1, 1],
+                      \ [0x2010, 0x2010, 1], [0xFEFF, 0xFEFF, 1]])
+    " Control chars
+    call assert_equal(4, strwidth("\u0081"))
+    call assert_equal(6, strwidth("\uFEFF"))
+    " Ambiguous width chars
+    call assert_equal(1, strwidth("\u00A1"))
+    call assert_equal(1, strwidth("\u2010"))
+
+    call setcellwidths([[0x81, 0x81, 2], [0xA1, 0xA1, 2],
+                      \ [0x2010, 0x2010, 2], [0xFEFF, 0xFEFF, 2]])
+    " Control chars
+    call assert_equal(4, strwidth("\u0081"))
+    call assert_equal(6, strwidth("\uFEFF"))
+    " Ambiguous width chars
+    call assert_equal(2, strwidth("\u00A1"))
+    call assert_equal(2, strwidth("\u2010"))
+  endfor
+  set ambiwidth& isprint&
+
   call setcellwidths([])
 
   call assert_fails('call setcellwidths(1)', 'E1211:')

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1223,
 /**/
     1222,
 /**/