Index: trunk/src/libcschem/common_types.h
===================================================================
--- trunk/src/libcschem/common_types.h	(revision 493)
+++ trunk/src/libcschem/common_types.h	(revision 494)
@@ -13,7 +13,7 @@
 
 #define CSCH_COORD_MIN ((csch_color_t)-0x7fffffff)
 #define CSCH_COORD_MAX ((csch_color_t)+0x7fffffff)
-#define CSCH_COORD_INV CSCH_COORD_MIN
+#define CSCH_COORD_INV CSCH_COORD_MAX
 
 #define csch_pixelr(p) (((p) & 0xFF000000) >> 24)
 #define csch_pixelg(p) (((p) & 0x00FF0000) >> 16)
Index: trunk/src/libcschem/concrete.c
===================================================================
--- trunk/src/libcschem/concrete.c	(revision 493)
+++ trunk/src/libcschem/concrete.c	(revision 494)
@@ -39,6 +39,7 @@
 	csch_rtree_init(&sheet->rtree);
 	csch_cobj_init(&sheet->grp.hdr, sheet, oid, CSCH_CTYPE_GRP, CSCH_INVALID_OID);
 	sheet->next_id = oid+1;
+	csch_bbox_invalidate(&sheet->bbox);
 	return sheet;
 }
 
Index: trunk/src/libcschem/concrete.h
===================================================================
--- trunk/src/libcschem/concrete.h	(revision 493)
+++ trunk/src/libcschem/concrete.h	(revision 494)
@@ -84,6 +84,7 @@
 	char *dflt_font, *dflt_font_size, *dflt_font_style;
 
 	char *filename; /* original file name */
+	csch_rtree_box_t bbox;
 };
 
 /* Standard low level object operations; when int, return 0 for success */
Index: trunk/src/libcschem/concrete_obj.h
===================================================================
--- trunk/src/libcschem/concrete_obj.h	(revision 493)
+++ trunk/src/libcschem/concrete_obj.h	(revision 494)
@@ -46,11 +46,10 @@
 
 #define csch_obj_bbox_bump(obj, coord, value) \
 do { \
-	if (value < obj->hdr.bbox.coord ## 1) obj->hdr.bbox.coord ## 1 = value; \
-	if (value > obj->hdr.bbox.coord ## 2) obj->hdr.bbox.coord ## 2 = value; \
+	if (value < obj->hdr.bbox.coord ## 1) { obj->hdr.bbox.coord ## 1 = value; obj->hdr.sheet->bbox.x1 = CSCH_COORD_INV; } \
+	if (value > obj->hdr.bbox.coord ## 2) { obj->hdr.bbox.coord ## 2 = value; obj->hdr.sheet->bbox.x1 = CSCH_COORD_INV; } \
 } while(0)
 
-
 /* Initialize an object by setting the common header fields; the only purpose
    of this function is to get compiler warnings at every caller when the header
    is extended (because the number of args would be extended here) */
Index: trunk/src/libcschem/rtree.h
===================================================================
--- trunk/src/libcschem/rtree.h	(revision 493)
+++ trunk/src/libcschem/rtree.h	(revision 494)
@@ -14,4 +14,7 @@
 
 #include <genrtree/genrtree_api.h>
 
+#define csch_bbox_invalidate(bbox) (bbox)->x1 = CSCH_COORD_INV
+#define csch_bbox_is_invalid(bbox) ((bbox)->x1 == CSCH_COORD_INV)
+
 #endif /* CSCH_RTREE2_H */