core/range-tree: Add gcal_range_tree_has_entries_at_range

It checks if there's any entry in that range. It's a little faster
than gcal_range_tree_count_entries_at_range() because it stops at
the first entry that matches it.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/742>

src/core/gcal-range-tree.c

@@ -431,6 +431,34 @@ count_entries_at_range (GcalRange *range,
   return GCAL_TRAVERSE_CONTINUE;
 }
 
+static inline gboolean
+has_entries_at_range (GcalRange *range,
+                      gpointer   data,
+                      gpointer   user_data)
+{
+  GcalRangePosition position;
+  GcalRangeOverlap overlap;
+
+  struct {
+    GcalRange *range;
+    gboolean has_entries;
+  } *gather_data = user_data;
+
+  overlap = gcal_range_calculate_overlap (range, gather_data->range, &position);
+
+  if (overlap == GCAL_RANGE_NO_OVERLAP)
+    {
+      if (position == GCAL_RANGE_BEFORE)
+        return GCAL_TRAVERSE_CONTINUE;
+      if (position == GCAL_RANGE_AFTER)
+        return GCAL_TRAVERSE_STOP;
+    }
+
+  gather_data->has_entries = TRUE;
+
+  return GCAL_TRAVERSE_STOP;
+}
+
 static inline gboolean
 remove_data_func (GcalRange *range,
                   gpointer   data,
@@ -719,6 +747,23 @@ gcal_range_tree_get_data_at_range (GcalRangeTree *self,
   return data;
 }
 
+gboolean
+gcal_range_tree_has_entries_at_range (GcalRangeTree *self,
+                                      GcalRange     *range)
+{
+  struct {
+    GcalRange *range;
+    gboolean has_entry;
+  } gather_data = { range, FALSE };
+
+  g_return_val_if_fail (self, FALSE);
+  g_return_val_if_fail (range, FALSE);
+
+  gcal_range_tree_traverse (self, G_IN_ORDER, has_entries_at_range, &gather_data);
+
+  return gather_data.has_entry;
+}
+
 /**
  * gcal_range_tree_count_entries_at_range:
  * @self: a #GcalRangeTree

src/core/gcal-range-tree.h

@@ -79,6 +79,9 @@ GPtrArray*           gcal_range_tree_get_all_data                (GcalRangeTree
 GPtrArray*           gcal_range_tree_get_data_at_range           (GcalRangeTree      *self,
                                                                   GcalRange          *range);
 
+gboolean             gcal_range_tree_has_entries_at_range        (GcalRangeTree      *self,
+                                                                  GcalRange          *range);
+
 guint64              gcal_range_tree_count_entries_at_range      (GcalRangeTree      *self,
                                                                   GcalRange          *range);