shown_projects is a dictionary

Window.py

@@ -15,7 +15,7 @@ class Window:
         self.mark = None
         if self.config.get('mark') is not None:
             self.mark = datetime.strptime(self.config.get('mark'), DT_FORMAT)
-        self.shown_projects = []
+        self.shown_projects = {}
         self.taskStart = datetime.now()
         self.monday = \
                 self.taskStart.date() - timedelta(self.taskStart.weekday())
@@ -296,7 +296,7 @@ class Window:
         else:
             pnum = 0
         if pnum:
-            self.shown_projects.append(pnum)
+            self.shown_projects[pnum] = 1
             self.project_select_event(pname)
             self.updateProjects()