diff --git a/ncurses/base/lib_overlay.c b/ncurses/base/lib_overlay.c
new file mode 100644
index 0000000..669e8e7
--- /dev/null
+++ b/ncurses/base/lib_overlay.c
@@ -0,0 +1,206 @@
+/****************************************************************************
+ * Copyright (c) 1998-2007,2008 Free Software Foundation, Inc.              *
+ *                                                                          *
+ * Permission is hereby granted, free of charge, to any person obtaining a  *
+ * copy of this software and associated documentation files (the            *
+ * "Software"), to deal in the Software without restriction, including      *
+ * without limitation the rights to use, copy, modify, merge, publish,      *
+ * distribute, distribute with modifications, sublicense, and/or sell       *
+ * copies of the Software, and to permit persons to whom the Software is    *
+ * furnished to do so, subject to the following conditions:                 *
+ *                                                                          *
+ * The above copyright notice and this permission notice shall be included  *
+ * in all copies or substantial portions of the Software.                   *
+ *                                                                          *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
+ * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
+ * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
+ *                                                                          *
+ * Except as contained in this notice, the name(s) of the above copyright   *
+ * holders shall not be used in advertising or otherwise to promote the     *
+ * sale, use or other dealings in this Software without prior written       *
+ * authorization.                                                           *
+ ****************************************************************************/
+
+/****************************************************************************
+ *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
+ *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
+ ****************************************************************************/
+
+/*
+**	lib_overlay.c
+**
+**	The routines overlay(), copywin(), and overwrite().
+**
+*/
+
+#include <curses.priv.h>
+
+MODULE_ID("$Id: lib_overlay.c,v 1.27 2008/06/07 23:30:34 tom Exp $")
+
+static int
+overlap(const WINDOW *const src, WINDOW *const dst, int const flag)
+{
+    int rc = ERR;
+    int sx1, sy1, sx2, sy2;
+    int dx1, dy1, dx2, dy2;
+    int sminrow, smincol;
+    int dminrow, dmincol;
+    int dmaxrow, dmaxcol;
+
+    T((T_CALLED("overlap(%p,%p,%d)"), src, dst, flag));
+
+    if (src != 0 && dst != 0) {
+	_nc_lock_global(curses);
+
+	T(("src : begy %ld, begx %ld, maxy %ld, maxx %ld",
+	   (long) src->_begy,
+	   (long) src->_begx,
+	   (long) src->_maxy,
+	   (long) src->_maxx));
+	T(("dst : begy %ld, begx %ld, maxy %ld, maxx %ld",
+	   (long) dst->_begy,
+	   (long) dst->_begx,
+	   (long) dst->_maxy,
+	   (long) dst->_maxx));
+
+	sx1 = src->_begx;
+	sy1 = src->_begy;
+	sx2 = sx1 + src->_maxx;
+	sy2 = sy1 + src->_maxy;
+
+	dx1 = dst->_begx;
+	dy1 = dst->_begy;
+	dx2 = dx1 + dst->_maxx;
+	dy2 = dy1 + dst->_maxy;
+
+	if (dx2 >= sx1 && dx1 <= sx2 && dy2 >= sy1 && dy1 <= sy2) {
+	    sminrow = max(sy1, dy1) - sy1;
+	    smincol = max(sx1, dx1) - sx1;
+	    dminrow = max(sy1, dy1) - dy1;
+	    dmincol = max(sx1, dx1) - dx1;
+	    dmaxrow = min(sy2, dy2) - dy1;
+	    dmaxcol = min(sx2, dx2) - dx1;
+
+	    rc = copywin(src, dst,
+			 sminrow, smincol,
+			 dminrow, dmincol,
+			 dmaxrow, dmaxcol,
+			 flag);
+	}
+	_nc_unlock_global(curses);
+    }
+    returnCode(rc);
+}
+
+/*
+**
+**	overlay(win1, win2)
+**
+**
+**	overlay() writes the overlapping area of win1 behind win2
+**	on win2 non-destructively.
+**
+**/
+
+NCURSES_EXPORT(int)
+overlay(const WINDOW *win1, WINDOW *win2)
+{
+    T((T_CALLED("overlay(%p,%p)"), win1, win2));
+    returnCode(overlap(win1, win2, TRUE));
+}
+
+/*
+**
+**	overwrite(win1, win2)
+**
+**
+**	overwrite() writes the overlapping area of win1 behind win2
+**	on win2 destructively.
+**
+**/
+
+NCURSES_EXPORT(int)
+overwrite(const WINDOW *win1, WINDOW *win2)
+{
+    T((T_CALLED("overwrite(%p,%p)"), win1, win2));
+    returnCode(overlap(win1, win2, FALSE));
+}
+
+NCURSES_EXPORT(int)
+copywin(const WINDOW *src, WINDOW *dst,
+	int sminrow, int smincol,
+	int dminrow, int dmincol,
+	int dmaxrow, int dmaxcol,
+	int over)
+{
+    int rc = ERR;
+    int sx, sy, dx, dy;
+    bool touched;
+    attr_t bk;
+    attr_t mask;
+
+    T((T_CALLED("copywin(%p, %p, %d, %d, %d, %d, %d, %d, %d)"),
+       src, dst, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol, over));
+
+    if (src && dst) {
+	_nc_lock_global(curses);
+
+	bk = AttrOf(dst->_nc_bkgd);
+	mask = ~(attr_t) ((bk & A_COLOR) ? A_COLOR : 0);
+
+	/* make sure rectangle exists in source */
+	if ((sminrow + dmaxrow - dminrow) <= (src->_maxy + 1) &&
+	    (smincol + dmaxcol - dmincol) <= (src->_maxx + 1)) {
+
+	    T(("rectangle exists in source"));
+
+	    /* make sure rectangle fits in destination */
+	    if (dmaxrow <= dst->_maxy && dmaxcol <= dst->_maxx) {
+
+		T(("rectangle fits in destination"));
+
+		for (dy = dminrow, sy = sminrow;
+		     dy <= dmaxrow;
+		     sy++, dy++) {
+
+		    touched = FALSE;
+		    for (dx = dmincol, sx = smincol;
+			 dx <= dmaxcol;
+			 sx++, dx++) {
+			if (over) {
+			    if ((CharOf(src->_line[sy].text[sx]) != L(' ')) &&
+				(!CharEq(dst->_line[dy].text[dx],
+					 src->_line[sy].text[sx]))) {
+				dst->_line[dy].text[dx] =
+				    src->_line[sy].text[sx];
+				SetAttr(dst->_line[dy].text[dx],
+					((AttrOf(src->_line[sy].text[sx]) &
+					  mask) | bk));
+				touched = TRUE;
+			    }
+			} else {
+			    if (!CharEq(dst->_line[dy].text[dx],
+					src->_line[sy].text[sx])) {
+				dst->_line[dy].text[dx] =
+				    src->_line[sy].text[sx];
+				touched = TRUE;
+			    }
+			}
+		    }
+		    if (touched) {
+			touchline(dst, dminrow, (dmaxrow - dminrow + 1));
+		    }
+		}
+		T(("finished copywin"));
+		rc = OK;
+	    }
+	}
+	_nc_unlock_global(curses);
+    }
+    returnCode(rc);
+}