polish!

Preview.cs

@@ -97,6 +97,7 @@ namespace PreviewToy
         private void render_area_Click(object sender, EventArgs e)
         {
             bring_client_to_foreground();
+            spawner.preview_did_switch();
         }
 
         public void set_render_area_size(Size size)

PreviewHandler.cs

@@ -137,7 +137,7 @@ namespace PreviewToy
         {
             try
             {
-                XElement rootElement = XElement.Load("config.xml");
+                XElement rootElement = XElement.Load("layout.xml");
                 foreach (var el in rootElement.Elements())
                 {
                     Dictionary<String, Point> inner = new Dictionary<String, Point>();
@@ -155,6 +155,11 @@ namespace PreviewToy
             }  
         }
 
+        public void preview_did_switch()
+        {
+            store_layout();
+        }
+
         private void store_layout()
         {
             XElement el = new XElement("layouts");
@@ -180,7 +185,7 @@ namespace PreviewToy
                 el.Add(layout);
             }
 
-            el.Save("config.xml");
+            el.Save("layout.xml");
         }
 
         private void handle_unique_layout(Preview preview, String last_known_active_window)