mg: fix space_to_tabstop

Since the import of mg in the tree, space_to_tabstop used curbp->w_doto
(the byte offset in the current line) as mean to deduce the current
column for indentation.  This is wrong because it doesn't account for
tab, control characters and octets > 127 (which are all rendered with
more than one column.)  Use instead getcolpos().

ok tb@

diff --git a/usr.bin/mg/util.c b/usr.bin/mg/util.c
index 6168f51..acb3714 100644 (file)
--- a/usr.bin/mg/util.c
+++ b/usr.bin/mg/util.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: util.c,v 1.48 2023/04/21 13:39:37 op Exp $    */
+/*     $OpenBSD: util.c,v 1.49 2023/04/21 14:14:13 op Exp $    */
 
 /* This file is in the public domain. */
 
@@ -482,17 +482,17 @@ backdel(int f, int n)
 int
 space_to_tabstop(int f, int n)
 {
-       int     c;
+       int     col, target;
 
        if (n < 0)
                return (FALSE);
        if (n == 0)
                return (TRUE);
 
-       c = curwp->w_doto;
+       col = target = getcolpos(curwp);
        while (n-- > 0)
-               c = ntabstop(c, curbp->b_tabw);
-       return (linsert(c - curwp->w_doto, ' '));
+               target = ntabstop(target, curbp->b_tabw);
+       return (linsert(target - col, ' '));
 }
 
 /*