+/* Returns true if SUPER is a histogram_chart, otherwise false. */
+static inline bool
+is_histogram_chart (const struct chart_item *super)
+{
+ return super->class == &histogram_chart_class;
+}
+
+/* Returns SUPER converted to histogram_chart. SUPER must be a histogram_chart, as
+ reported by is_histogram_chart. */
+static inline struct histogram_chart *
+to_histogram_chart (const struct chart_item *super)
+{
+ assert (is_histogram_chart (super));
+ return UP_CAST (super, struct histogram_chart, chart_item);
+}
+
+/* Returns INSTANCE converted to chart_item. */
+static inline struct chart_item *
+histogram_chart_super (const struct histogram_chart *instance)
+{
+ return CONST_CAST (struct chart_item *, &instance->chart_item);
+}
+
+/* Increments INSTANCE's reference count and returns INSTANCE. */
+static inline struct histogram_chart *
+histogram_chart_ref (const struct histogram_chart *instance)
+{
+ return to_histogram_chart (chart_item_ref (&instance->chart_item));
+}
+
+/* Decrements INSTANCE's reference count, then destroys INSTANCE if
+ the reference count is now zero. */
+static inline void
+histogram_chart_unref (struct histogram_chart *instance)
+{
+ chart_item_unref (&instance->chart_item);
+}
+
+/* Returns true if INSTANCE's reference count is greater than 1,
+ false otherwise. */
+static inline bool
+histogram_chart_is_shared (const struct histogram_chart *instance)
+{
+ return chart_item_is_shared (&instance->chart_item);
+}
+
+static inline void
+histogram_chart_submit (struct histogram_chart *instance)
+{
+ chart_item_submit (&instance->chart_item);
+}
+\f
+#endif /* output/plot-hist.h */