eo2: add eo2_call_stack_depth

src/lib/eo/Eo.h

@@ -680,6 +680,8 @@ EAPI Eina_Bool eo2_do_start(Eo *obj_id, Eina_Bool do_super);
 // end of the eo2_do barrier, unref the obj, move the stack pointer
 EAPI void eo2_do_end();
 
+EAPI int eo2_call_stack_depth();
+
 // eo object method calls batch,
 // DO NOT use return statement in it, use break if necessary
 #define eo2_do(objid, ...)                            \

src/lib/eo/eo.c

@@ -300,6 +300,13 @@ static Eo2_Call_Stack eo2_call_stack = {
        },
        NULL };
 
+EAPI int
+eo2_call_stack_depth()
+{
+   return ((eo2_call_stack.frame_ptr == NULL) ? 0 :
+           1 + (eo2_call_stack.frame_ptr - eo2_call_stack.stack));
+}
+
 EAPI Eina_Bool
 eo2_do_start(Eo *obj_id, Eina_Bool do_super)
 {