event-widget: added compare function

This compare function is made to sort using the same two methods used
before but together, giving priority to the longer events.
The idea is sort event properly on year-view's sidebar.
This function will probably change later.

src/gcal-event-widget.c

@@ -1164,3 +1164,42 @@ gcal_event_widget_compare_by_start_date (GcalEventWidget *widget1,
 
   return icaltime_compare (*(priv1->dt_start), *(priv2->dt_start));
 }
+
+/**
+ * gcal_event_widget_compare_for_single_day:
+ * @widget1:
+ * @widget2:
+ *
+ * Compare widgets by putting those that span over a day before the rest, and between those
+ * who last less than a day by its start time/date
+ *
+ * Returns:
+ **/
+gint
+gcal_event_widget_compare_for_single_day (GcalEventWidget *widget1,
+                                          GcalEventWidget *widget2)
+{
+  GcalEventWidgetPrivate *priv1;
+  GcalEventWidgetPrivate *priv2;
+
+  time_t time_s1, time_s2;
+  time_t time_e1, time_e2;
+  time_t result;
+
+  priv1 = gcal_event_widget_get_instance_private (widget1);
+  priv2 = gcal_event_widget_get_instance_private (widget2);
+
+  time_e1 = time_s1 = icaltime_as_timet (*(priv1->dt_start));
+  time_e2 = time_s2 = icaltime_as_timet (*(priv2->dt_start));
+
+  if (priv1->dt_end != NULL)
+    time_e1 = icaltime_as_timet (*(priv1->dt_end));
+  if (priv2->dt_end)
+    time_e2 = icaltime_as_timet (*(priv2->dt_end));
+
+  result = (time_e2 - time_s2) - (time_e1 - time_s1);
+  if (result != 0)
+    return result;
+  else
+    return icaltime_compare (*(priv1->dt_start), *(priv2->dt_start));
+}