diff --git a/src/charset.c b/src/charset.c
index ef162e4..87ad303 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -839,14 +839,25 @@
 #endif
 
 /*
- * return the number of characters the string 's' will take on the screen,
- * taking into account the size of a tab
+ * Return the number of characters the string 's' will take on the screen,
+ * taking into account the size of a tab.
  */
     int
 linetabsize(s)
     char_u	*s;
 {
-    colnr_T	col = 0;
+    return linetabsize_col(0, s);
+}
+
+/*
+ * Like linetabsize(), but starting at column "startcol".
+ */
+    int
+linetabsize_col(startcol, s)
+    int		startcol;
+    char_u	*s;
+{
+    colnr_T	col = startcol;
 
     while (*s != NUL)
 	col += lbr_chartabsize_adv(&s, col);
diff --git a/src/eval.c b/src/eval.c
index a344cd2..3a0d85c 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -710,6 +710,7 @@
 static void f_strpart __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_strridx __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_strtrans __ARGS((typval_T *argvars, typval_T *rettv));
+static void f_strdisplaywidth __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_strwidth __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_submatch __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_substitute __ARGS((typval_T *argvars, typval_T *rettv));
@@ -7859,6 +7860,7 @@
 #endif
     {"str2nr",		1, 2, f_str2nr},
     {"strchars",	1, 1, f_strchars},
+    {"strdisplaywidth",	1, 2, f_strdisplaywidth},
 #ifdef HAVE_STRFTIME
     {"strftime",	1, 2, f_strftime},
 #endif
@@ -16805,6 +16807,23 @@
 }
 
 /*
+ * "strdisplaywidth()" function
+ */
+    static void
+f_strdisplaywidth(argvars, rettv)
+    typval_T	*argvars;
+    typval_T	*rettv;
+{
+    char_u	*s = get_tv_string(&argvars[0]);
+    int		col = 0;
+
+    if (argvars[1].v_type != VAR_UNKNOWN)
+	col = get_tv_number(&argvars[1]);
+
+    rettv->vval.v_number = (varnumber_T)(linetabsize_col(col, s));
+}
+
+/*
  * "strwidth()" function
  */
     static void
diff --git a/src/proto/charset.pro b/src/proto/charset.pro
index 1e6a708..472f1cd 100644
--- a/src/proto/charset.pro
+++ b/src/proto/charset.pro
@@ -15,6 +15,7 @@
 int vim_strnsize __ARGS((char_u *s, int len));
 int chartabsize __ARGS((char_u *p, colnr_T col));
 int linetabsize __ARGS((char_u *s));
+int linetabsize_col __ARGS((int startcol, char_u *s));
 int win_linetabsize __ARGS((win_T *wp, char_u *p, colnr_T len));
 int vim_isIDc __ARGS((int c));
 int vim_iswordc __ARGS((int c));