Hob Cache for speed up switching

index fa79e0c..8c8d9e2 100644
@@ -99,7 +99,7 @@ class HobHandler(gobject.GObject):
             args.extend(argument)
             self.server.runCommand(args)
 
-    def handle_event(self, event, running_build, pbar):
+    def handle_event(self, event, running_build, pbar, hobprefs):
         if not event:
 	    return
 

@@ -161,11 +161,11 @@ class HobHandler(gobject.GObject):
             pbar.set_fraction(1.0)
         return
 
-    def event_handle_idle_func (self, eventHandler, running_build, pbar):
+    def event_handle_idle_func (self, eventHandler, running_build, pbar, hobrefs):
         # Consume as many messages as we can in the time available to us
         event = eventHandler.getEvent()
         while event:
-            self.handle_event(event, running_build, pbar)
+            self.handle_event(event, running_build, pbar, hobrefs)
             event = eventHandler.getEvent()
         return True
 

index f186410..05e8170 100644
@@ -143,7 +143,7 @@ class HobPrefs(gtk.Dialog):
             glib.idle_add(self.handler.reload_data)
 
     def __init__(self, configurator, handler, curr_sdk_mach, curr_distro, pclass,
-                 cpu_cnt, pmake, bbthread, image_types):
+                 cpu_cnt, pmake, bbthread, image_types, curr_mach):
         """
         """
         gtk.Dialog.__init__(self, "Preferences", None,

@@ -159,6 +159,7 @@ class HobPrefs(gtk.Dialog):
         self.configurator = configurator
 
         self.curr_sdk_mach = curr_sdk_mach
+        self.curr_mach = curr_mach
         self.curr_distro = curr_distro
         self.curr_package_format = pclass
         self.curr_output_type = None

index 06d936e..76cb294 100644
@@ -160,6 +160,7 @@ class MainWindow (gtk.Window):
         mach = combo.get_active_text()
         if mach != self.curr_mach:
             self.curr_mach = mach
+            self.prefs.curr_mach = mach
             # Flush this straight to the file as MACHINE is changed
             # independently of other 'Preferences'
             self.configurator.setLocalConfVar('MACHINE', mach)

@@ -887,7 +888,7 @@ def main (server, eventHandler):
     pkg, sep, pclass = pclasses[0].rpartition("_")
 
     prefs = HobPrefs(configurator, handler, sdk_mach, distro, pclass, cpu_cnt,
-                     pmake, bbthread, image_types)
+                     pmake, bbthread, image_types, mach)
     layers = LayerEditor(configurator, None)
     window = MainWindow(taskmodel, handler, configurator, prefs, layers, mach)
     prefs.set_parent_window(window)

@@ -918,7 +919,8 @@ def main (server, eventHandler):
                          handler.event_handle_idle_func,
                          eventHandler,
                          window.build,
-                         window.progress)
+                         window.progress,
+                         prefs)
 
     try:
         gtk.main()

index 8c8d9e2..c6d3bd5 100644
@@ -110,6 +110,19 @@ class HobHandler(gobject.GObject):
             self.emit("data-generated")
             self.generating = False
             if event._model:
+                # Currently, use these three property as the key, in the future
+                # more elements might be needed
+                mach = hobprefs.curr_mach
+                if mach == None:
+                    mach = ""
+                sdk_mach = hobprefs.curr_sdk_mach
+                if sdk_mach == None:
+                    sdk_mach = ""
+                distro = hobprefs.curr_distro
+                if distro == None:
+                    distro = ""
+                hash_key = mach + "," + sdk_mach + "," + distro
+                self.model.targetTreeCache[hash_key] = event._model 
                 self.model.populate(event._model)
         elif isinstance(event, bb.event.ConfigFilesFound):
             var = event._variable

index 5e979b7..bcd6328 100644
@@ -102,6 +102,11 @@ class TaskListModel(gtk.ListStore):
         self.packages = None
         self.images = None
         self.selected_image = None
+        # This var is used for caching target package dependency data. This
+        # data will be impacted by layers, distros, machine, sdk_machine value
+        # which is now all saved in HobPrefs data. For the hashset cache, it's
+        # obvious that the key will be those properties combination.
+        self.targetTreeCache = {}
         
         gtk.ListStore.__init__ (self,
                                 gobject.TYPE_STRING,

index 76cb294..5f6fdf5 100644
@@ -166,7 +166,23 @@ class MainWindow (gtk.Window):
             self.configurator.setLocalConfVar('MACHINE', mach)
             self.configurator.writeLocalConf()
             handler.set_machine(mach)
-            handler.reload_data()
+            mach = self.prefs.curr_mach
+            if mach == None:
+                mach = ""
+            sdk_mach = self.prefs.curr_sdk_mach
+            if sdk_mach == None:
+                sdk_mach = ""
+            distro = self.prefs.curr_distro
+            if distro == None:
+                distro = ""
+            hash_key = mach + "," + sdk_mach + "," + distro
+            # Only when this target tree has not been cached, need we reload
+            # the target tree data
+            if (self.model.targetTreeCache.has_key(hash_key) == False):
+                handler.reload_data()
+            # Otherwise, simply reload the cache data
+            else:
+                handler.model.populate(self.model.targetTreeCache[hash_key])
 
     def update_machines(self, handler, machines):
         active = 0