--- a/src/net/kryshen/indyvon/component.clj	Fri Aug 27 01:24:31 2010 +0400
+++ b/src/net/kryshen/indyvon/component.clj	Fri Aug 27 19:47:28 2010 +0400
@@ -31,6 +31,6 @@
                 (let [s (root-size layer (font-context this) this)]
                   (Dimension. (:width s) (:height s)))))]
        (.setBackground panel (:back-color *theme*))
-       (add-observer layer (fn [_] (.repaint panel)))
+       (add-observer panel layer (fn [_] (.repaint panel)))
        (listen! event-dispatcher panel)
        panel)))

--- a/src/net/kryshen/indyvon/core.clj	Fri Aug 27 01:24:31 2010 +0400
+++ b/src/net/kryshen/indyvon/core.clj	Fri Aug 27 19:47:28 2010 +0400
@@ -113,28 +113,29 @@
 
 (def observers (atom nil))
 
+;; TODO: groups should be weakly referenced.
+;; Need persistent analog to java.util.WeakHashMap.
 (defn add-observer
-  ([target f]
-     (add-observer target f :default))
-  ([target f group-id]
-     (swap! observers assoc-in-cons [group-id target] f)
-     nil))
-
-(defn remove-group
-  "Remove group of observers."
-  [group-id]
-  (swap! observers dissoc group-id)
+  "Add observer fn for the target to the specified group."
+  [group target f]
+  (swap! observers assoc-in-cons [group target] f)
   nil)
 
-(defn- change-group-id*
-  [observers old-id new-id]
-  (let [group (get observers old-id)]
-    (assoc (dissoc observers old-id)
-      new-id group)))
+(defn remove-observer-group
+  "Remove group of observers."
+  [group]
+  (swap! observers dissoc group)
+  nil)
 
-(defn- change-group-id
-  [old-id new-id]
-  (swap! observers change-group-id* old-id new-id))
+;; (defn- replace-observer-group*
+;;   [observers old-id new-id]
+;;   (let [group (get observers old-id)]
+;;     (assoc (dissoc observers old-id)
+;;       new-id group)))
+
+;; (defn- replace-observer-group
+;;   [old-id new-id]
+;;   (swap! observers replace-observer-group* old-id new-id))
 
 (defn update
   "Notify observers."
@@ -152,13 +153,14 @@
   removed after the next frame rendering is complete."
   [target f]
   (let [root *root*]
-    (add-observer target f root)))
+    (add-observer root target f)))
 
 (defn repaint-on-update
   "Trigger repaint of the current scene when the target updates."
   [target]
   (let [root *root*]
-    (add-observer target (fn [_] (update root)) root)))
+    (if (not= root target)
+      (add-observer root target (fn [_] (update root))))))
 
 ;;
 ;; Rendering
@@ -326,15 +328,14 @@
                *width* width
                *height* height
                *clip* (Rectangle2D$Double. 0 0 width height)]
-       (let [tmp-group (Object.)]
-         (apply-theme)
-         (.clearRect graphics 0 0 width height)
-         (change-group-id layer tmp-group)
-         (try
-           (render! layer)
-           (finally
-            (remove-group tmp-group)
-            (commit event-dispatcher)))))))
+       (apply-theme)
+       (with-color (:back-color *theme*)
+         (.fillRect graphics 0 0 width height))
+       (remove-observer-group layer)
+       (try
+         (render! layer)
+         (finally
+          (commit event-dispatcher))))))
 
 (defn root-size
   ([layer font-context]

--- a/src/net/kryshen/indyvon/demo.clj	Fri Aug 27 01:24:31 2010 +0400
+++ b/src/net/kryshen/indyvon/demo.clj	Fri Aug 27 19:47:28 2010 +0400
@@ -13,8 +13,6 @@
    (java.awt Color)
    (javax.swing JFrame)))
 
-(def frame (JFrame. "Test"))
-
 (def layer1
      (reify
       Layer
@@ -86,11 +84,17 @@
          (draw! fps))
       (layer-size [layer] (Size. 400 300))))
 
-(defn -main []
-  (doto frame
+(def root (viewport layer))
+
+(defn show-frame [layer]
+  (doto (JFrame. "Test")
     (.addWindowListener
      (proxy [java.awt.event.WindowAdapter] []
        (windowClosing [event] (.dispose frame))))
-    (.. (getContentPane) (add (make-jpanel (viewport layer))))
+    (.. (getContentPane) (add (make-jpanel layer)))
     (.pack)
     (.setVisible true)))
+
+(defn -main []
+  (show-frame root)
+  (show-frame (miniature root 80 60)))

--- a/src/net/kryshen/indyvon/layers.clj	Fri Aug 27 01:24:31 2010 +0400
+++ b/src/net/kryshen/indyvon/layers.clj	Fri Aug 27 19:47:28 2010 +0400
@@ -271,6 +271,7 @@
     (reify
      Layer
      (render! [layer]
+        (repaint-on-update layer)
         (with-handlers layer
           (let [anchor (anchor content h-align v-align)]
             (dosync
@@ -294,7 +295,7 @@
             (alter y + (- @fix-y (:y-on-screen e)))
             (ref-set fix-x (:x-on-screen e))
             (ref-set fix-y (:y-on-screen e)))
-           (repaint))))
+           (update layer))))
      (layer-size [layer] (layer-size content))))))
 
 ;;