views/month: Rebuild layout blocks at once per frame

Instead of rebuilding them all every time an event is added or removed,
rebuild it once per frame. In case the month view isn't visible, don't
do anything, and wait until it's mapped to actually rebuild the event
blocks.

Related: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1381
Related: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1125

src/gui/views/gcal-month-view-row.c

@@ -51,6 +51,7 @@ struct _GcalMonthViewRow
 
   GListStore         *events;
   GHashTable         *layout_blocks;
+  gboolean            layout_blocks_valid;
 
   GcalContext        *context;
 };
@@ -62,6 +63,10 @@ static gint          compare_events_cb                           (gconstpointer
 static void          on_event_widget_activated_cb                (GcalEventWidget    *widget,
                                                                   GcalMonthViewRow   *self);
 
+static gboolean      widget_tick_cb                              (GtkWidget          *widget,
+                                                                  GdkFrameClock      *frame_clock,
+                                                                  gpointer            user_data);
+
 G_DEFINE_FINAL_TYPE (GcalMonthViewRow, gcal_month_view_row, GTK_TYPE_WIDGET)
 
 enum
@@ -173,6 +178,8 @@ prepare_layout_blocks (GcalMonthViewRow *self,
   guint weekday_heights[7] = { 0, };
   guint n_events;
 
+  g_assert (self->layout_blocks_valid);
+
   n_events = g_list_model_get_n_items (G_LIST_MODEL (self->events));
 
   for (guint i = 0; i < 7; i++)
@@ -274,6 +281,10 @@ recalculate_layout_blocks (GcalMonthViewRow *self)
   guint events_at_weekday[7] = { 0, };
   guint n_events;
 
+  GCAL_ENTRY;
+
+  g_assert (!self->layout_blocks_valid);
+
   range_start = gcal_range_get_start (self->range);
   n_events = g_list_model_get_n_items (G_LIST_MODEL (self->events));
 
@@ -363,6 +374,29 @@ recalculate_layout_blocks (GcalMonthViewRow *self)
 
       g_hash_table_insert (self->layout_blocks, event, g_steal_pointer (&blocks));
     }
+
+  self->layout_blocks_valid = TRUE;
+
+  GCAL_EXIT;
+}
+
+static void
+invalidate_layout_blocks (GcalMonthViewRow *self)
+{
+  GCAL_ENTRY;
+
+  if (!self->layout_blocks_valid)
+    GCAL_RETURN ();
+
+  if (gtk_widget_get_mapped (GTK_WIDGET (self)))
+    {
+      gtk_widget_add_tick_callback (GTK_WIDGET (self), widget_tick_cb, self, NULL);
+      gtk_widget_queue_allocate (GTK_WIDGET (self));
+    }
+
+  self->layout_blocks_valid = FALSE;
+
+  GCAL_EXIT;
 }
 
 
@@ -399,11 +433,40 @@ on_month_cell_show_overflow_cb (GcalMonthCell    *cell,
   g_signal_emit (self, signals[SHOW_OVERFLOW], 0, cell);
 }
 
+static gboolean
+widget_tick_cb (GtkWidget     *widget,
+                GdkFrameClock *frame_clock,
+                gpointer       user_data)
+{
+  GcalMonthViewRow *self = (GcalMonthViewRow *) widget;
+
+  GCAL_ENTRY;
+
+  g_assert (GCAL_IS_MONTH_VIEW_ROW (self));
+
+  recalculate_layout_blocks (self);
+
+  GCAL_RETURN (G_SOURCE_REMOVE);
+}
+
 
 /*
  * GtkWidget overrides
  */
 
+static void
+gcal_month_view_row_map (GtkWidget *widget)
+{
+  GcalMonthViewRow *self = (GcalMonthViewRow *) widget;
+
+  g_assert (GCAL_IS_MONTH_VIEW_ROW (self));
+
+  GTK_WIDGET_CLASS (gcal_month_view_row_parent_class)->map (widget);
+
+  if (!self->layout_blocks_valid)
+    recalculate_layout_blocks (self);
+}
+
 static void
 gcal_month_view_row_measure (GtkWidget      *widget,
                              GtkOrientation  orientation,
@@ -485,6 +548,7 @@ gcal_month_view_row_size_allocate (GtkWidget *widget,
     }
 
   /* Event widgets */
+  if (self->layout_blocks_valid)
     {
       gdouble cell_y[7];
       guint overflows[7] = { 0, };
@@ -610,6 +674,7 @@ gcal_month_view_row_class_init (GcalMonthViewRowClass *klass)
   object_class->get_property = gcal_month_view_row_get_property;
   object_class->set_property = gcal_month_view_row_set_property;
 
+  widget_class->map = gcal_month_view_row_map;
   widget_class->measure = gcal_month_view_row_measure;
   widget_class->size_allocate = gcal_month_view_row_size_allocate;
 
@@ -645,6 +710,7 @@ gcal_month_view_row_init (GcalMonthViewRow *self)
 {
   self->events = g_list_store_new (GCAL_TYPE_EVENT);
   self->layout_blocks = g_hash_table_new_full (g_direct_hash, g_direct_equal, NULL, (GDestroyNotify) g_ptr_array_unref);
+  self->layout_blocks_valid = TRUE;
 
   for (guint i = 0; i < 7; i++)
     {
@@ -712,6 +778,7 @@ gcal_month_view_row_set_range (GcalMonthViewRow *self,
   /* Preemptively remove all event widgets */
   g_list_store_remove_all (self->events);
   g_hash_table_remove_all (self->layout_blocks);
+  invalidate_layout_blocks (self);
 
   start = gcal_range_get_start (range);
   for (guint i = 0; i < 7; i++)
@@ -729,7 +796,7 @@ gcal_month_view_row_add_event (GcalMonthViewRow *self,
   g_assert (GCAL_IS_EVENT (event));
 
   g_list_store_insert_sorted (self->events, event, compare_events_cb, self);
-  recalculate_layout_blocks (self);
+  invalidate_layout_blocks (self);
 }
 
 void
@@ -753,7 +820,7 @@ gcal_month_view_row_remove_event (GcalMonthViewRow *self,
     }
 
   g_list_store_remove (self->events, position);
-  recalculate_layout_blocks (self);
+  invalidate_layout_blocks (self);
 
   GCAL_EXIT;
 }