vim-patch:8.2.5019: cannot get the first screen column of a character (#23312)

Problem:    Cannot get the first screen column of a character.
Solution:   Let virtcol() optionally return a list. (closes vim/vim#10482,
            closes vim/vim#7964)

0f7a3e1de6

Co-authored-by: LemonBoy <thatlemon@gmail.com>

runtime/doc/builtin.txt

@@ -546,7 +546,8 @@ undotree()			List	undo file tree
 uniq({list} [, {func} [, {dict}]])
 				List	remove adjacent duplicates from a list
 values({dict})			List	values in {dict}
-virtcol({expr})			Number	screen column of cursor or mark
+virtcol({expr} [, {list}])	Number or List
+					screen column of cursor or mark
 virtcol2col({winid}, {lnum}, {col})
 				Number  byte index of a character on screen
 visualmode([expr])		String	last visual mode used
@@ -637,6 +638,7 @@ add({object}, {expr})					*add()*
 and({expr}, {expr})					*and()*
 		Bitwise AND on the two arguments.  The arguments are converted
 		to a number.  A List, Dict or Float argument causes an error.
+		Also see `or()` and `xor()`.
 		Example: >
 			:let flag = and(bits, 0x80)
 <		Can also be used as a |method|: >
@@ -9070,7 +9072,7 @@ values({dict})						*values()*
 		Can also be used as a |method|: >
 			mydict->values()
 
-virtcol({expr})						*virtcol()*
+virtcol({expr} [, {list}])				*virtcol()*
 		The result is a Number, which is the screen column of the file
 		position given with {expr}.  That is, the last screen position
 		occupied by the character at that position, when the screen
@@ -9079,13 +9081,17 @@ virtcol({expr})						*virtcol()*
 		the <Tab>.  For example, for a <Tab> in column 1, with 'ts'
 		set to 8, it returns 8. |conceal| is ignored.
 		For the byte position use |col()|.
+
 		For the use of {expr} see |col()|.
-		When 'virtualedit' is used {expr} can be [lnum, col, off], where
-		"off" is the offset in screen columns from the start of the
-		character.  E.g., a position within a <Tab> or after the last
-		character.  When "off" is omitted zero is used.
-		When Virtual editing is active in the current mode, a position
-		beyond the end of the line can be returned. |'virtualedit'|
+
+		When 'virtualedit' is used {expr} can be [lnum, col, off],
+		where "off" is the offset in screen columns from the start of
+		the character.  E.g., a position within a <Tab> or after the
+		last character.  When "off" is omitted zero is used.  When
+		Virtual editing is active in the current mode, a position
+		beyond the end of the line can be returned.  Also see
+		|'virtualedit'|
+
 		The accepted positions are:
 		    .	    the cursor position
 		    $	    the end of the cursor line (the result is the
@@ -9097,11 +9103,22 @@ virtcol({expr})						*virtcol()*
 			    cursor is the end).  When not in Visual mode
 			    returns the cursor position.  Differs from |'<| in
 			    that it's updated right away.
+
+		If {list} is present and non-zero then virtcol() returns a List
+		with the first and last screen position occupied by the
+		character.
+
 		Note that only marks in the current file can be used.
 		Examples: >
-  virtcol(".")	   with text "foo^Lbar", with cursor on the "^L", returns 5
-  virtcol("$")	   with text "foo^Lbar", returns 9
-  virtcol("'t")    with text "	  there", with 't at 'h', returns 6
+			" With text "foo^Lbar" and cursor on the "^L":
+
+			virtcol(".")	" returns 5
+			virtcol(".", 1)	" returns [4, 5]
+			virtcol("$")	" returns 9
+
+			" With text "	  there", with 't at 'h':
+
+			virtcol("'t")	" returns 6
 <		The first column is 1.  0 is returned for an error.
 		A more advanced example that echoes the maximum length of
 		all lines: >

src/nvim/eval.lua

@@ -436,7 +436,7 @@ return {
     undotree={},
     uniq={args={1, 3}, base=1},
     values={args=1, base=1},
-    virtcol={args=1, base=1},
+    virtcol={args={1, 2}, base=1},
     virtcol2col={args=3, base=1},
     visualmode={args={0, 1}},
     wait={args={2,3}},

src/nvim/eval/funcs.c

@@ -9275,10 +9275,11 @@ static void f_undotree(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   tv_dict_add_list(dict, S_LEN("entries"), u_eval_tree(curbuf->b_u_oldhead));
 }
 
-/// "virtcol(string)" function
+/// "virtcol(string, bool)" function
 static void f_virtcol(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
-  colnr_T vcol = 0;
+  colnr_T vcol_start = 0;
+  colnr_T vcol_end = 0;
   int fnum = curbuf->b_fnum;
 
   pos_T *fp = var2fpos(&argvars[0], false, &fnum, false);
@@ -9293,11 +9294,18 @@ static void f_virtcol(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
         fp->col = (colnr_T)len;
       }
     }
-    getvvcol(curwin, fp, NULL, NULL, &vcol);
-    vcol++;
+    getvvcol(curwin, fp, &vcol_start, NULL, &vcol_end);
+    vcol_start++;
+    vcol_end++;
   }
 
-  rettv->vval.v_number = vcol;
+  if (argvars[1].v_type != VAR_UNKNOWN && tv_get_bool(&argvars[1])) {
+    tv_list_alloc_ret(rettv, 2);
+    tv_list_append_number(rettv->vval.v_list, vcol_start);
+    tv_list_append_number(rettv->vval.v_list, vcol_end);
+  } else {
+    rettv->vval.v_number = vcol_end;
+  }
 }
 
 /// "visualmode()" function

test/old/testdir/test_functions.vim

@@ -2607,4 +2607,15 @@ func Test_builtin_check()
 endfunc
 
 
+" Test for virtcol()
+func Test_virtcol()
+  enew!
+  call setline(1, "the\tquick\tbrown\tfox")
+  norm! 4|
+  call assert_equal(8, virtcol('.'))
+  call assert_equal(8, virtcol('.', v:false))
+  call assert_equal([4, 8], virtcol('.', v:true))
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab