--- a/include/mb_types.h	Mon Sep 20 22:43:43 2010 +0800
+++ b/include/mb_types.h	Mon Sep 20 22:43:43 2010 +0800
@@ -178,6 +178,9 @@
     co_aix cache_2_pdev[6];	/*!< Transfrom matrix from space of
 				 * cached one to its parent. */
     co_aix cache_2_pdev_rev[6];	/*!< Reverse of cache_2_pdev. */
+    co_aix aggr_2_pdev[6];	/*!< Aggregation of cache_2_pdev from root  */
+    co_aix aggr_2_pdev_rev[6];	/*!< Aggregation of cache_2_pdev_rev
+				 * from root  */
 } coord_canvas_info_t;
 
 /*! \brief A coordination system.
@@ -372,6 +375,8 @@
     ((coord)->canvas_info->aggr_dirty_areas)
 #define coord_get_2pdev(coord) ((coord)->canvas_info->cache_2_pdev)
 #define coord_get_2pdev_rev(coord) ((coord)->canvas_info->cache_2_pdev_rev)
+#define coord_get_aggr2pdev(coord) ((coord)->canvas_info->aggr_2_pdev)
+#define coord_get_aggr2pdev_rev(coord) ((coord)->canvas_info->aggr_2_pdev_rev)
 
 /* @} */
 

--- a/src/redraw_man.c	Mon Sep 20 22:43:43 2010 +0800
+++ b/src/redraw_man.c	Mon Sep 20 22:43:43 2010 +0800
@@ -612,6 +612,7 @@
 coord_canvas_info_new(redraw_man_t *rdman, coord_t *coord,
 		      mbe_t *canvas) {
     coord_canvas_info_t *info;
+    static co_aix id[6] = {1, 0, 0, 0, 1, 0};
 
     info = (coord_canvas_info_t *)elmpool_elm_alloc(rdman->coord_canvas_pool);
     if(info == NULL)
@@ -624,6 +625,10 @@
     bzero(info->pcache_areas, sizeof(area_t) * 2);
     info->pcache_cur_area = &info->pcache_areas[0];
     info->pcache_last_area = &info->pcache_areas[1];
+    memcpy(info->cache_2_pdev, id, sizeof(co_aix) * 6);
+    memcpy(info->cache_2_pdev_rev, id, sizeof(co_aix) * 6);
+    memcpy(info->aggr_2_pdev, id, sizeof(co_aix) * 6);
+    memcpy(info->aggr_2_pdev_rev, id, sizeof(co_aix) * 6);
 
     return info;
 }
@@ -1751,6 +1756,34 @@
     return OK;
 }
 
+/*! \brief Update aggregated cache_2_pdev matrix for cached coords.
+ *
+ * This is perfromed from root to leaves.  Aggregated cache_2_pdev is
+ * named as aggr_2_pdev field of canvas_info_t.  It is the matrix to
+ * transform a point from space of a cached coord to the space of root
+ * coord.
+ */
+static int
+update_aggr_pdev(redraw_man_t *rdman) {
+    int i;
+    coords_t *all_zeroing;
+    coord_t *coord, *parent_cached;
+
+    all_zeroing = &rdman->zeroing_coords;
+    for(i = 0; i < all_zeroing->num; i++) {
+	coord = all_zeroing->ds[i];
+	parent_cached = coord_get_cached(coord_get_parent(coord));
+	matrix_mul(coord_get_2pdev(parent_cached),
+		   coord_get_2pdev(coord),
+		   coord_get_aggr2pdev(coord));
+	matrix_mul(coord_get_2pdev_rev(coord),
+		   coord_get_2pdev_rev(parent_cached),
+		   coord_get_aggr2pdev_rev(coord));
+    }
+
+    return OK;
+}
+
 /*! \brief Add aggregated dirty areas to ancestor.
  *
  * Dirty areas are aggregated into two areas.  It assumes that even or odd
@@ -2008,6 +2041,10 @@
     if(r != OK)
 	return ERR;
 
+    r = update_aggr_pdev(rdman);
+    if(r != OK)
+	return ERR;
+
     /*
      * Clear all flags setted by zeroing.
      */