Selectively refresh screen

When sync events produce results that modify the local db state,
record those events and have the screen widgets use that info
to decide whether to refresh (if relevant data are updated).

In practice this should mean far fewer screen refreshes (which
require costly db queries and manifest as UI pauses).

Change-Id: Iefca75ef3d727236b8e4d1199fd4301d25822fef

gertty/view/project_list.py

@@ -13,6 +13,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import logging
 import urwid
 
 from gertty import keymap
@@ -82,6 +83,7 @@ class ProjectListView(urwid.WidgetWrap):
 
     def __init__(self, app):
         super(ProjectListView, self).__init__(urwid.Pile([]))
+        self.log = logging.getLogger('gertty.view.project_list')
         self.app = app
         self.unreviewed = True
         self.subscribed = True
@@ -95,7 +97,17 @@ class ProjectListView(urwid.WidgetWrap):
         self._w.contents.append((self.listbox, ('weight', 1)))
         self._w.set_focus(3)
 
-    def refresh(self):
+    def refresh(self, event=None):
+        if event and not (isinstance(event, sync.ProjectAddedEvent)
+                          or
+                          isinstance(event, sync.ChangeAddedEvent)
+                          or
+                          (isinstance(event, sync.ChangeUpdatedEvent) and
+                           (event.status_changed or event.review_flag_changed))):
+            self.log.debug("Ignoring refresh project list due to event %s" % (event,))
+            return
+        self.log.debug("Refreshing project list due to event %s" % (event,))
+
         if self.subscribed:
             self.title = u'Subscribed projects'
             if self.unreviewed:
@@ -134,7 +146,7 @@ class ProjectListView(urwid.WidgetWrap):
         self.app.changeScreen(view_change_list.ChangeListView(
                 self.app,
                 "_project_key:%s %s" % (project_key, self.app.config.project_change_list_query),
-                project_name, unreviewed=True))
+                project_name, project_key=None, unreviewed=True))
 
     def keypress(self, size, key):
         r = super(ProjectListView, self).keypress(size, key)