+/* for detection of endless loops, caused by custom element programming */
+/* (using "MAX_PLAYFIELD_WIDTH" here is just a rough approximation...) */
+#define MAX_ELEMENT_CHANGE_RECURSION_DEPTH (MAX_PLAYFIELD_WIDTH)
+
+#define RECURSION_LOOP_DETECTION_START(e, rc) \
+{ \
+ if (recursion_loop_detected) \
+ return (rc); \
+ \
+ if (recursion_loop_depth > MAX_ELEMENT_CHANGE_RECURSION_DEPTH) \
+ { \
+ recursion_loop_detected = TRUE; \
+ recursion_loop_element = (e); \
+ } \
+ \
+ recursion_loop_depth++; \
+}
+
+#define RECURSION_LOOP_DETECTION_END() \
+{ \
+ recursion_loop_depth--; \
+}
+
+static int recursion_loop_depth;
+static boolean recursion_loop_detected;
+static boolean recursion_loop_element;
+