window: Delegate changing dates to GcalView

The view knows its time range, and knows what the
next or previous dates should be. So instead of
calculating the next date manually, ask the views
for that.

src/views/gcal-month-view.c

@@ -1220,6 +1220,25 @@ gcal_month_view_update_subscription (GcalView *view)
                                range_end);
 }
 
+static GDateTime*
+gcal_month_view_get_next_date (GcalView *view)
+{
+  GcalMonthView *self = GCAL_MONTH_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_months (self->date, 1);
+}
+
+
+static GDateTime*
+gcal_month_view_get_previous_date (GcalView *view)
+{
+  GcalMonthView *self = GCAL_MONTH_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_months (self->date, -1);
+}
+
 static void
 gcal_view_interface_init (GcalViewInterface *iface)
 {
@@ -1228,6 +1247,8 @@ gcal_view_interface_init (GcalViewInterface *iface)
   iface->clear_marks = gcal_month_view_clear_marks;
   iface->get_children_by_uuid = gcal_month_view_get_children_by_uuid;
   iface->update_subscription = gcal_month_view_update_subscription;
+  iface->get_next_date = gcal_month_view_get_next_date;
+  iface->get_previous_date = gcal_month_view_get_previous_date;
 }
 
 

src/views/gcal-view.c

@@ -210,3 +210,66 @@ gcal_view_update_subscription (GcalView *self)
 
   GCAL_VIEW_GET_IFACE (self)->update_subscription (self);
 }
+
+/**
+ * gcal_view_get_next_date:
+ * @self: a #GcalView
+ *
+ * Retrieves the next date from @self. Different views have
+ * different time ranges (e.g. day view ranges 1 day, week
+ * view ranges 1 week, etc) and pressing the next button
+ * of the main window may advance the time in different steps.
+ *
+ * Returns: (transfer full): a #GDateTime
+ */
+GDateTime*
+gcal_view_get_next_date (GcalView *self)
+{
+  g_autoptr (GDateTime) next_date = NULL;
+
+  g_return_val_if_fail (GCAL_IS_VIEW (self), NULL);
+  g_return_val_if_fail (GCAL_VIEW_GET_IFACE (self)->get_next_date, NULL);
+
+  next_date = GCAL_VIEW_GET_IFACE (self)->get_next_date (self);
+
+#ifdef GCAL_ENABLE_TRACE
+    {
+      g_autofree gchar *str = NULL;
+
+      str = g_date_time_format (next_date, "%x %X %z");
+      g_debug ("%s's next date: %s", G_OBJECT_TYPE_NAME (self), str);
+    }
+#endif
+
+  return g_steal_pointer (&next_date);
+}
+
+/**
+ * gcal_view_get_previous_date:
+ * @self: a #GcalView
+ *
+ * Retrieves the previous date from @self.
+ *
+ * Returns: (transfer full): a #GDateTime
+ */
+GDateTime*
+gcal_view_get_previous_date (GcalView *self)
+{
+  g_autoptr (GDateTime) previous_date = NULL;
+
+  g_return_val_if_fail (GCAL_IS_VIEW (self), NULL);
+  g_return_val_if_fail (GCAL_VIEW_GET_IFACE (self)->get_previous_date, NULL);
+
+  previous_date = GCAL_VIEW_GET_IFACE (self)->get_previous_date (self);
+
+#ifdef GCAL_ENABLE_TRACE
+    {
+      g_autofree gchar *str = NULL;
+
+      str = g_date_time_format (previous_date, "%x %X %z");
+      g_debug ("%s's previous date: %s", G_OBJECT_TYPE_NAME (self), str);
+    }
+#endif
+
+  return g_steal_pointer (&previous_date);
+}

src/views/gcal-view.h

@@ -50,6 +50,10 @@ struct _GcalViewInterface
 
   void               (*update_subscription)                      (GcalView           *self);
 
+  GDateTime*         (*get_next_date)                            (GcalView           *self);
+
+  GDateTime*         (*get_previous_date)                        (GcalView           *self);
+
   /* Marks related API */
   void               (*clear_marks)                              (GcalView           *view);
 
@@ -73,6 +77,9 @@ GList*               gcal_view_get_children_by_uuid              (GcalView
 
 void                 gcal_view_update_subscription               (GcalView              *self);
 
+GDateTime*           gcal_view_get_next_date                     (GcalView              *self);
+
+GDateTime*           gcal_view_get_previous_date                 (GcalView              *self);
 
 G_END_DECLS
 

src/views/gcal-week-view.c

@@ -248,6 +248,25 @@ gcal_week_view_update_subscription (GcalView *view)
                                range_end);
 }
 
+static GDateTime*
+gcal_week_view_get_next_date (GcalView *view)
+{
+  GcalWeekView *self = GCAL_WEEK_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_weeks (self->date, 1);
+}
+
+
+static GDateTime*
+gcal_week_view_get_previous_date (GcalView *view)
+{
+  GcalWeekView *self = GCAL_WEEK_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_weeks (self->date, -1);
+}
+
 static void
 gcal_view_interface_init (GcalViewInterface *iface)
 {
@@ -256,6 +275,8 @@ gcal_view_interface_init (GcalViewInterface *iface)
   iface->get_children_by_uuid = gcal_week_view_get_children_by_uuid;
   iface->clear_marks = gcal_week_view_clear_marks;
   iface->update_subscription = gcal_week_view_update_subscription;
+  iface->get_next_date = gcal_week_view_get_next_date;
+  iface->get_previous_date = gcal_week_view_get_previous_date;
 }
 
 static void

src/views/gcal-year-view.c

@@ -1609,6 +1609,25 @@ gcal_year_view_update_subscription (GcalView *view)
                                range_end);
 }
 
+static GDateTime*
+gcal_year_view_get_next_date (GcalView *view)
+{
+  GcalYearView *self = GCAL_YEAR_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_years (self->date, 1);
+}
+
+
+static GDateTime*
+gcal_year_view_get_previous_date (GcalView *view)
+{
+  GcalYearView *self = GCAL_YEAR_VIEW (view);
+
+  g_assert (self->date != NULL);
+  return g_date_time_add_years (self->date, -1);
+}
+
 static void
 gcal_view_interface_init (GcalViewInterface *iface)
 {
@@ -1617,6 +1636,8 @@ gcal_view_interface_init (GcalViewInterface *iface)
   iface->set_date = gcal_year_view_set_date;
   iface->get_children_by_uuid = gcal_year_view_get_children_by_uuid;
   iface->update_subscription = gcal_year_view_update_subscription;
+  iface->get_next_date = gcal_year_view_get_next_date;
+  iface->get_previous_date = gcal_year_view_get_previous_date;
 }
 
 static void