diff -urN cui21/Makefile cui22/Makefile
--- cui21/Makefile	Thu Jan 30 22:00:00 2014
+++ cui22/Makefile	Thu Jan 30 23:00:00 2014
@@ -1,7 +1,7 @@
 CC = gcc -Wall
 
 TARG = cui_test
-OBJS = cui.o dialog.o button.o label.o panel.o handler.o esc.o key.o
+OBJS = cui.o dialog.o button.o label.o panel.o handler.o esc.o key.o rect.o
 
 all: $(TARG)
 
diff -urN cui21/cui.c cui22/cui.c
--- cui21/cui.c	Thu Jan 30 22:40:00 2014
+++ cui22/cui.c	Thu Jan 30 23:00:00 2014
@@ -1,4 +1,5 @@
 #include "cui.h"
+#include "rect.h"
 #include "esc.h"
 #include "key.h"
 #include "handler.h"
@@ -56,10 +57,29 @@
 void
 cui_draw_str(cui obj, int x, int y, char *s, int attr)
 {
+	struct cui_rect t1, t2;
+	cui_rect r1 = &t1, r2 = &t2;
+	int n = strlen(s);
+	char *s2 = NULL;
+
+	if(!cui_visible_rect(obj, r1)) return;
+	cui_rect_init(r2, x, y, n, 1);
+	if(!cui_rect_and(r1, r2, r2)) return; /* r1 and r2 --> r2 */
+
+	s += r2->x - x;
+	if(r2->x + r2->w < x + n){
+		n = r2->w;
+		if((s2 = malloc(n + 1)) == NULL) ERR("No Mem");
+		memcpy(s2, s, n);
+		s2[n] = '\0';
+		s = s2;
+	}
+	x = r2->x;
 	cui_esc_loc(cui_gx(obj) + x, cui_gy(obj) + y);
 	cui_esc_attr(attr);
 	printf("%s", s);
 	fflush(stdout);
+	if(s2) free(s2);
 }
 
 void
@@ -225,6 +245,20 @@
 {
 	if(obj == NULL) return TRUE; /* root */
 	return !(obj->flags & CUI_FLG_HIDE) && cui_is_visible(obj->parent);
+}
+
+int
+cui_visible_rect(cui obj, cui_rect r)
+{
+	struct cui_rect tmp;
+	cui_rect t = &tmp;
+
+	cui_rect_init(r, 0, 0, obj->w, obj->h);
+	if(obj->parent == NULL) return !cui_rect_chk_empty(r); /* empty --> FALSE */
+	if(!cui_visible_rect(obj->parent, t)) return FALSE;
+	t->x -= obj->x;
+	t->y -= obj->y;
+	return cui_rect_and(r, t, r); /* r and t --> r */
 }
 
 void
diff -urN cui21/cui.h cui22/cui.h
--- cui21/cui.h	Thu Jan 30 22:30:00 2014
+++ cui22/cui.h	Thu Jan 30 23:00:00 2014
@@ -22,6 +22,8 @@
 
 typedef struct cui_handler_list *cui_handler_list;
 
+#include "rect.h"
+
 struct cui_base{
 	cui parent, children, next;
 	int x, y, w, h;
@@ -46,6 +48,8 @@
 void cui_hide(cui obj);
 void cui_show(cui obj);
 int cui_is_visible(cui obj);
+int cui_visible_rect(cui obj, cui_rect r);
+
 void cui_quit(void);
 void cui_main(cui top_obj);
 void cui_free(cui obj);
diff -urN cui21/rect.c cui22/rect.c
--- cui21/rect.c	Thu Jan  1 09:00:00 1970
+++ cui22/rect.c	Thu Jan 30 23:00:00 2014
@@ -0,0 +1,55 @@
+#include "rect.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void
+cui_rect_init(cui_rect r, int x, int y, int w, int h)
+{
+	r->x = x;
+	r->y = y;
+	r->w = w;
+	r->h = h;
+}
+
+void
+cui_rect_wh_to_x2y2(cui_rect r)
+{
+	r->w += r->x;
+	r->h += r->y;
+}
+
+void
+cui_rect_x2y2_to_wh(cui_rect r)
+{
+	r->w -= r->x;
+	r->h -= r->y;
+}
+
+int
+cui_rect_and(cui_rect a, cui_rect b, cui_rect r)
+{
+	struct cui_rect tmp;
+	cui_rect t = &tmp;
+
+	cui_rect_wh_to_x2y2(a);
+	cui_rect_wh_to_x2y2(b);
+	cui_rect_init(t,
+		a->x > b->x ? a->x : b->x,
+		a->y > b->y ? a->y : b->y,
+		a->w < b->w ? a->w : b->w,
+		a->h < b->h ? a->h : b->h);
+	cui_rect_x2y2_to_wh(t);
+	cui_rect_x2y2_to_wh(a);
+	cui_rect_x2y2_to_wh(b);
+	*r = *t;
+	return !cui_rect_chk_empty(r);
+}
+
+int
+cui_rect_chk_empty(cui_rect r)
+{
+	return r->w <= 0 || r->h <= 0;
+}
+
+/* EOF */
diff -urN cui21/rect.h cui22/rect.h
--- cui21/rect.h	Thu Jan  1 09:00:00 1970
+++ cui22/rect.h	Thu Jan 30 23:00:00 2014
@@ -0,0 +1,14 @@
+#ifndef __RECT_H__
+#define __RECT_H__
+
+typedef struct cui_rect{
+	int x, y, w, h;
+} *cui_rect;
+
+void cui_rect_init(cui_rect r, int x, int y, int w, int h);
+void cui_rect_wh_to_x2y2(cui_rect r);
+void cui_rect_x2y2_to_wh(cui_rect r);
+int cui_rect_and(cui_rect a, cui_rect b, cui_rect r);
+int cui_rect_chk_empty(cui_rect r);
+
+#endif