Add functions for cycling inside an enum.

src/core/enum_type.hpp

@@ -28,6 +28,19 @@
 	}
 
 
+/** Some enums need to have cycling through values */
+#define DECLARE_CYCLE(type, min_val, max_val) \
+	inline type CycleUp(type e) \
+	{ \
+		assert(!((int)e < min_val || (int)e > max_val)); \
+		return e == max_val ? (type)min_val : (type)((int)e + 1); \
+	} \
+	inline type CycleDown(type e) \
+	{ \
+		assert(!((int)e < min_val || (int)e > max_val)); \
+		return e == min_val ? (type)max_val : (type)((int)e - 1); \
+	}
+
 
 /** Operators to allow to work with enum as with type safe bit set in C++ */
 # define DECLARE_ENUM_AS_BIT_SET(mask_t) \